Energy-Appropriate Personal Watercraft

Team 4 ndash Hocking River Pirates

Michelle Barwacz Eric Carlson

Daniel Edwartoski Michael Graham

Kevin Hardin Alicia Konczol

Matthew Schuenke Ross Scoular

Matthew Smith

June 1 2007

Abstract The problem of pollution in marine environments clearly indicates a need for more environmentally friendly recreational watercraft Through customer interviews external research and benchmarking a niche market of the recreational fisherman was determined to be an adequate customer base to develop a project A list of target specifications and design criteria was developed the conceptual design process was completed and concept was selected A final design was developed incorporating collapsibility and an electric motor as the propulsion system The collapsibility features allow the watercraft to be separated into lightweight components that can be easily transported and assembled by a single user

2

Table of Contents 10 Introduction 3

11 Initial Needs Statement 3 20 Customer Needs Assessment 3

21 Weighting of Customer Needs 4 30 Revised Needs Statement 6

31 Target Specifications 7 32 Design Criteria 8

40 External Search 9 41 Benchmarking 10

50 Concept Generation 13 51 Problem Clarification 13 52 Concept Generation 14

521 Power Plant Options 15 522 Hull Configurations 18 523 Delighters 19

60 Concept Selection 19 61 Data and Calculations for Feasibility and Effectiveness Analysis 19

611 Power Calculations and Analysis 19 612 Electric Motor Analysis 26 613 DC Battery Analysis 28 614 Human Power Analysis 33 615 Buoyancy Analysis 35

62 Concept Screening 35 621 Customer Feedback Process 35 622 Concept Screening Process 37 63 Concept Development Scoring and Selection 39 631 Human Power Selection 39 632 Hull Selection 39 633 Selected Concept 40 634 Cost Feasibility 41 70 Final Design 42 701 Propulsion System 47 702 Hull System 55 703 Transportation 70 71 Design Drawings Parts List and Bill of Materials 71 72 How Does it Work 71 721 Storage and Transportation 71 722 Assembly 73 723 Propulsion System 76 73 How is it Made 81 80 Conclusion 91 References 100 Appendix A Customer Survey 103 Appendix B Business Opportunity Statement 104 Appendix C FMEA Worksheets 106 Appendix D Individual Component Analyses 117

3

10 Introduction Marine pollution by personal watercraft is often overlooked when discussing pollution However one 2-stroke outboard motor running for seven hours can pollute more than an average car driven 100000 miles (Better Boating) When considering the fact that 713 million Americans participate in recreational boating (National Marine Manufacturer 2006) 75 of which using 2-stroke motors (Blue Water Network 2006) the pollution produced due to these engines becomes a serious problem Oil spill dispersants are toxic to marine plants and animals They impair breathing in fish and reduce the amount of oxygen in water (University of California) Conventional 2-stroke motors allow 20-30 of their fuel to go directly to the air or water (Massachusetts 2006) One quart of oil can form a film over a body of water 2 acres in size (California Department of Waterways) Looking at these facts it is not difficult to see that recreational boating causes serious harm to marine environments Due to the environmental hazards recreational boating creates it is logical to pursue a development in this area that addresses the issue of pollution and fuel efficiency With the proper design a personal watercraft could be produced that is attractive to anglers and other recreational boaters 11 Initial Needs Statement With the steady increase in recreational boating the goal of decreasing Americarsquos oil dependency and the current efficiency and environmental deficiencies for watercraft there is a need to make watercraft more environmentally-friendly and energy-efficient To reach this goal there is a need for a 1-seat demonstration watercraft that could fill a niche market and be used to demonstrate the technology to watercraft manufacturing companies This scaled demonstration watercraft must be safe energy efficient environmentally friendly and reliable while demonstrating appropriate speed endurance and payload capacity 20 Customer Needs Assessment Multiple interviewing and observing methods were used to assess the customer needs These methods were aimed at finding information from two different groups of users recreational boaters and fishermen Forty-three interviews and surveys were compiled to obtain information on customer needs Sample interview questions can be seen in Appendix A Data was collected as individuals and reviewed as a team to create the initial customer needs list shown in Table 1

4

Table 1 Initial Customer Needs List Obtained from Interviews and Observations

21 Weighting of Customer Needs Weighting can help in making design decisions by determining what needs are more important than others If one need conflicts with another the need that carries the most weight will supersede the other either partially or fully in the design Table 2 shows the generic needs list and their weights relative to one another The analytical hierarchy process (AHP) was used to weight the needs Table 3 shows the needs and their AHP rankings in this hierarchy Although the purpose of this project is to address the environmental and energy issues related to recreational boating that issue received a lower rating than performance reliability and safety This is due to the fact that the customer research showed environmental impact and energy efficiency to be less important to the customer than performance reliability and safety This makes sense in that if a watercraft is not safe and cannot perform the duties required by the customer energy efficiency will not weigh into their purchasing decision However most customers did state that as long as the desired performance was achieved a more environmentally friendly and energy efficient watercraft would be desirable In Table 3 each general need was divided up into components that are used to accomplish the task of fulfilling the general need These needs were then ranked on a one to five scale based on importance one being very important and five being the least important These rankings can be seen in Table 4 The rankings were determined by the team members coming to a consensus on each ranking based on customer interviews and engineering experience

Transport one person Sufficient storage space Functional in multiple environments Easy to Operate Operate for duration of a typical fishing outing Mechanically driven propeller Human power as back-up power source Reliable Portable by one person Easy of load on and off truck Durable Easy to maintain Resist damage to water-born debris Meet Federal and Ohio state laws and regulations Low noise Safe

5

Table 2 AHP Pair-wise Comparison Chart to Determine Weighting for Main Objective Categories

Table 3 Hierarchal Customer Needs List

1 Performance (023) 11 Transport one passenger 12 Sufficient storage space and capacity 13 Function in a variety of environments 14 Easy to Operate 15 Operate at sufficient speeds 16 Operate for a duration of a typical outing

2 Environmental Impact and Energy Efficiency (013) 21 Environmentally friendly and energy efficient 22 Utilize human power as back-up source

3 Portability (008) 31 Deployable by one person 32 Transported without the use of a trailer

4 Reliability (026) 41 Durable 42 Easy to maintain 43 Resist damage caused by water-born debris

5 Safety (030) 51 Comply with all federal and Ohio state laws and regulations

6

Table 4 Ranking of Specific Needs Based on Importance

Need Need Importance

11 The watercraft should transport one passenger 1 12 The watercraft should have sufficient storage space and capacity 3 13 The watercraft should be able to function in a variety of environments 3 14 The watercraft should be easy to operate 1 15 The watercraft should operate at speeds similar to existing watercraft 2

16 The watercraft should be able to operate for the duration of a typical fishing outing 1

21 The watercraft should have an environmentally friendly and energy efficient propulsion system 1

22 The watercraft should utilize human power as a back-up power source 4 31 The watercraft should be able to be deployed by one person 2

32 The watercraft should be able to be transported without the use of a trailer 2

41 The watercraft should be durable 2 42 The watercraft should be easy to maintain 2 43 The watercraft should resist damage caused by water-born debris 2

30 Revised Needs Statement With continued research customer feedback and benchmarking a revised needs statement was proposed

With fossil fuel dependency and environmental impact at the forefront of current societal issues a goal for a more energy-efficient and environmentally-friendly propulsion system for watercraft has been recognized In following this goal as well as the current trend of personal watercraft for anglers there is a need for a one-person watercraft that is tailored toward anglers and utilizes both mechanical and human power This watercraft must be safe energy efficient environmentally friendly reliable and lightweight while demonstrating appropriate speed endurance and utility

Conducting preliminary interviews pertaining to the original needs statement allowed a specific group to be targeted as the users of this watercraft Based on these findings new interview questions were written to target the angling community The interviews also provided vital information about what customers expect in a product Benchmarking provided basic input on existing watercraft and energy alternatives that are applicable toward the need From here the original needs statement was revised and target specifications were determined

7

31 Target Specifications Energy Efficiency amp Environmental Impact The watercraft should demonstrate an efficient use of energy and minimal environmental impact

o Based on the course-wide consensus to address the current energy situation Capacity The watercraft should comfortably fit one passenger with the dimensions of a 95th percentile male as well as have a total weight capacity of 300 lbs

o Based on the 95th percentile male described as being 6rsquo 2rdquo tall and 267 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Based on the customer survey with 30 lbs being the highest of the top three survey results for cargo capacity

o A ldquocomfortable fitrdquo will be determined by testing a broad range of body types Speed The watercraft should be able to achieve a maximum speed of 5 mph in calm conditions

o Based on the customer survey that had 5-10 mph the highest range of speeds

o Electric trolling motor benchmarks had similar speed ranges

o ldquoCalm conditionsrdquo is defined as negligible wind and waves Duration of Usage The propulsion system should be able to propel the watercraft at 5 mph for a minimum of 2 hrs without refueling or recharging

o Varying weather and water conditions make any specified range for the watercraft impractical Consequently the duration of usage will be the specification that dictates the energy supply required

o Customer interviews resulted in run times ranging between 2 and 6 hours Deployment The watercraft should be able to be deployed from the transportation medium to the water by one person without the use of a boat ramp In addition the design of the watercraft should make allowances for the limited physical strength and endurance of the user to deploy the watercraft

o Based on the assumption that the watercraft will have warning labels that depict lifting assembly hazards recommend lifting assembly procedures and recommend that smaller users have help assembling the watercraft components

8

o Based on the assumption developed from experimentation by the female team members that a 50th percentile female can safely and repeatedly carry approximately 50 lbs for a distance of 100 ft

o Based on the 50th percentile female described as being 5rsquo 4rdquo tall and 155 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Benchmarked watercrafts accommodate one passenger and are less than 100 lbs

o Benchmarked watercrafts have removable motors and batteries to help decrease the weight that must be lifted

Size All of the separable components of the watercraft should fit within a volume that is 4rsquoW x 8rsquoL x 4rsquoH

o Customer survey results showed widths between the wheel wells of truck beds ranging between 3 frac12 ft and 4 frac12 ft

o Building or buying a trailer is not feasible due to the constraints of laboratory space and additional costs incurred

Laws amp Regulations The watercraft should comply with all federal and Ohio state laws and regulations

o Based on the Ohio Revised Code the watercraft must

be inspected by a watercraft officer to receive a HIN display accordingly

have a valid registration display tags accordingly

display identification number accordingly

have one Type I II or III personal floatation device per watercraft occupant

o Based on US Code and Ohio Revised Code the watercraft should

carry a US coast guard approved distress flag and daynight distress signals

incorporate a lanyard-type engine cutoff switch 32 Design Criteria The watercraft must not only meet the target specifications but also fulfill the following design criteria

bull The watercraftrsquos propulsion system should be less than or equal to 10 Hp such that Ohiorsquos training and title requirements are not applicable

bull The watercraft should be less than 14 ft long such that Ohiorsquos training and title requirements are not applicable

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

4

Table 1 Initial Customer Needs List Obtained from Interviews and Observations

21 Weighting of Customer Needs Weighting can help in making design decisions by determining what needs are more important than others If one need conflicts with another the need that carries the most weight will supersede the other either partially or fully in the design Table 2 shows the generic needs list and their weights relative to one another The analytical hierarchy process (AHP) was used to weight the needs Table 3 shows the needs and their AHP rankings in this hierarchy Although the purpose of this project is to address the environmental and energy issues related to recreational boating that issue received a lower rating than performance reliability and safety This is due to the fact that the customer research showed environmental impact and energy efficiency to be less important to the customer than performance reliability and safety This makes sense in that if a watercraft is not safe and cannot perform the duties required by the customer energy efficiency will not weigh into their purchasing decision However most customers did state that as long as the desired performance was achieved a more environmentally friendly and energy efficient watercraft would be desirable In Table 3 each general need was divided up into components that are used to accomplish the task of fulfilling the general need These needs were then ranked on a one to five scale based on importance one being very important and five being the least important These rankings can be seen in Table 4 The rankings were determined by the team members coming to a consensus on each ranking based on customer interviews and engineering experience

Transport one person Sufficient storage space Functional in multiple environments Easy to Operate Operate for duration of a typical fishing outing Mechanically driven propeller Human power as back-up power source Reliable Portable by one person Easy of load on and off truck Durable Easy to maintain Resist damage to water-born debris Meet Federal and Ohio state laws and regulations Low noise Safe

5

Table 2 AHP Pair-wise Comparison Chart to Determine Weighting for Main Objective Categories

Table 3 Hierarchal Customer Needs List

1 Performance (023) 11 Transport one passenger 12 Sufficient storage space and capacity 13 Function in a variety of environments 14 Easy to Operate 15 Operate at sufficient speeds 16 Operate for a duration of a typical outing

2 Environmental Impact and Energy Efficiency (013) 21 Environmentally friendly and energy efficient 22 Utilize human power as back-up source

3 Portability (008) 31 Deployable by one person 32 Transported without the use of a trailer

4 Reliability (026) 41 Durable 42 Easy to maintain 43 Resist damage caused by water-born debris

5 Safety (030) 51 Comply with all federal and Ohio state laws and regulations

6

Table 4 Ranking of Specific Needs Based on Importance

Need Need Importance

11 The watercraft should transport one passenger 1 12 The watercraft should have sufficient storage space and capacity 3 13 The watercraft should be able to function in a variety of environments 3 14 The watercraft should be easy to operate 1 15 The watercraft should operate at speeds similar to existing watercraft 2

16 The watercraft should be able to operate for the duration of a typical fishing outing 1

21 The watercraft should have an environmentally friendly and energy efficient propulsion system 1

22 The watercraft should utilize human power as a back-up power source 4 31 The watercraft should be able to be deployed by one person 2

32 The watercraft should be able to be transported without the use of a trailer 2

41 The watercraft should be durable 2 42 The watercraft should be easy to maintain 2 43 The watercraft should resist damage caused by water-born debris 2

30 Revised Needs Statement With continued research customer feedback and benchmarking a revised needs statement was proposed

With fossil fuel dependency and environmental impact at the forefront of current societal issues a goal for a more energy-efficient and environmentally-friendly propulsion system for watercraft has been recognized In following this goal as well as the current trend of personal watercraft for anglers there is a need for a one-person watercraft that is tailored toward anglers and utilizes both mechanical and human power This watercraft must be safe energy efficient environmentally friendly reliable and lightweight while demonstrating appropriate speed endurance and utility

Conducting preliminary interviews pertaining to the original needs statement allowed a specific group to be targeted as the users of this watercraft Based on these findings new interview questions were written to target the angling community The interviews also provided vital information about what customers expect in a product Benchmarking provided basic input on existing watercraft and energy alternatives that are applicable toward the need From here the original needs statement was revised and target specifications were determined

7

31 Target Specifications Energy Efficiency amp Environmental Impact The watercraft should demonstrate an efficient use of energy and minimal environmental impact

o Based on the course-wide consensus to address the current energy situation Capacity The watercraft should comfortably fit one passenger with the dimensions of a 95th percentile male as well as have a total weight capacity of 300 lbs

o Based on the 95th percentile male described as being 6rsquo 2rdquo tall and 267 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Based on the customer survey with 30 lbs being the highest of the top three survey results for cargo capacity

o A ldquocomfortable fitrdquo will be determined by testing a broad range of body types Speed The watercraft should be able to achieve a maximum speed of 5 mph in calm conditions

o Based on the customer survey that had 5-10 mph the highest range of speeds

o Electric trolling motor benchmarks had similar speed ranges

o ldquoCalm conditionsrdquo is defined as negligible wind and waves Duration of Usage The propulsion system should be able to propel the watercraft at 5 mph for a minimum of 2 hrs without refueling or recharging

o Varying weather and water conditions make any specified range for the watercraft impractical Consequently the duration of usage will be the specification that dictates the energy supply required

o Customer interviews resulted in run times ranging between 2 and 6 hours Deployment The watercraft should be able to be deployed from the transportation medium to the water by one person without the use of a boat ramp In addition the design of the watercraft should make allowances for the limited physical strength and endurance of the user to deploy the watercraft

o Based on the assumption that the watercraft will have warning labels that depict lifting assembly hazards recommend lifting assembly procedures and recommend that smaller users have help assembling the watercraft components

8

o Based on the assumption developed from experimentation by the female team members that a 50th percentile female can safely and repeatedly carry approximately 50 lbs for a distance of 100 ft

o Based on the 50th percentile female described as being 5rsquo 4rdquo tall and 155 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Benchmarked watercrafts accommodate one passenger and are less than 100 lbs

o Benchmarked watercrafts have removable motors and batteries to help decrease the weight that must be lifted

Size All of the separable components of the watercraft should fit within a volume that is 4rsquoW x 8rsquoL x 4rsquoH

o Customer survey results showed widths between the wheel wells of truck beds ranging between 3 frac12 ft and 4 frac12 ft

o Building or buying a trailer is not feasible due to the constraints of laboratory space and additional costs incurred

Laws amp Regulations The watercraft should comply with all federal and Ohio state laws and regulations

o Based on the Ohio Revised Code the watercraft must

be inspected by a watercraft officer to receive a HIN display accordingly

have a valid registration display tags accordingly

display identification number accordingly

have one Type I II or III personal floatation device per watercraft occupant

o Based on US Code and Ohio Revised Code the watercraft should

carry a US coast guard approved distress flag and daynight distress signals

incorporate a lanyard-type engine cutoff switch 32 Design Criteria The watercraft must not only meet the target specifications but also fulfill the following design criteria

bull The watercraftrsquos propulsion system should be less than or equal to 10 Hp such that Ohiorsquos training and title requirements are not applicable

bull The watercraft should be less than 14 ft long such that Ohiorsquos training and title requirements are not applicable

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

5

Table 2 AHP Pair-wise Comparison Chart to Determine Weighting for Main Objective Categories

Table 3 Hierarchal Customer Needs List

1 Performance (023) 11 Transport one passenger 12 Sufficient storage space and capacity 13 Function in a variety of environments 14 Easy to Operate 15 Operate at sufficient speeds 16 Operate for a duration of a typical outing

2 Environmental Impact and Energy Efficiency (013) 21 Environmentally friendly and energy efficient 22 Utilize human power as back-up source

3 Portability (008) 31 Deployable by one person 32 Transported without the use of a trailer

4 Reliability (026) 41 Durable 42 Easy to maintain 43 Resist damage caused by water-born debris

5 Safety (030) 51 Comply with all federal and Ohio state laws and regulations

6

Table 4 Ranking of Specific Needs Based on Importance

Need Need Importance

11 The watercraft should transport one passenger 1 12 The watercraft should have sufficient storage space and capacity 3 13 The watercraft should be able to function in a variety of environments 3 14 The watercraft should be easy to operate 1 15 The watercraft should operate at speeds similar to existing watercraft 2

16 The watercraft should be able to operate for the duration of a typical fishing outing 1

21 The watercraft should have an environmentally friendly and energy efficient propulsion system 1

22 The watercraft should utilize human power as a back-up power source 4 31 The watercraft should be able to be deployed by one person 2

32 The watercraft should be able to be transported without the use of a trailer 2

41 The watercraft should be durable 2 42 The watercraft should be easy to maintain 2 43 The watercraft should resist damage caused by water-born debris 2

30 Revised Needs Statement With continued research customer feedback and benchmarking a revised needs statement was proposed

With fossil fuel dependency and environmental impact at the forefront of current societal issues a goal for a more energy-efficient and environmentally-friendly propulsion system for watercraft has been recognized In following this goal as well as the current trend of personal watercraft for anglers there is a need for a one-person watercraft that is tailored toward anglers and utilizes both mechanical and human power This watercraft must be safe energy efficient environmentally friendly reliable and lightweight while demonstrating appropriate speed endurance and utility

Conducting preliminary interviews pertaining to the original needs statement allowed a specific group to be targeted as the users of this watercraft Based on these findings new interview questions were written to target the angling community The interviews also provided vital information about what customers expect in a product Benchmarking provided basic input on existing watercraft and energy alternatives that are applicable toward the need From here the original needs statement was revised and target specifications were determined

7

31 Target Specifications Energy Efficiency amp Environmental Impact The watercraft should demonstrate an efficient use of energy and minimal environmental impact

o Based on the course-wide consensus to address the current energy situation Capacity The watercraft should comfortably fit one passenger with the dimensions of a 95th percentile male as well as have a total weight capacity of 300 lbs

o Based on the 95th percentile male described as being 6rsquo 2rdquo tall and 267 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Based on the customer survey with 30 lbs being the highest of the top three survey results for cargo capacity

o A ldquocomfortable fitrdquo will be determined by testing a broad range of body types Speed The watercraft should be able to achieve a maximum speed of 5 mph in calm conditions

o Based on the customer survey that had 5-10 mph the highest range of speeds

o Electric trolling motor benchmarks had similar speed ranges

o ldquoCalm conditionsrdquo is defined as negligible wind and waves Duration of Usage The propulsion system should be able to propel the watercraft at 5 mph for a minimum of 2 hrs without refueling or recharging

o Varying weather and water conditions make any specified range for the watercraft impractical Consequently the duration of usage will be the specification that dictates the energy supply required

o Customer interviews resulted in run times ranging between 2 and 6 hours Deployment The watercraft should be able to be deployed from the transportation medium to the water by one person without the use of a boat ramp In addition the design of the watercraft should make allowances for the limited physical strength and endurance of the user to deploy the watercraft

o Based on the assumption that the watercraft will have warning labels that depict lifting assembly hazards recommend lifting assembly procedures and recommend that smaller users have help assembling the watercraft components

8

o Based on the assumption developed from experimentation by the female team members that a 50th percentile female can safely and repeatedly carry approximately 50 lbs for a distance of 100 ft

o Based on the 50th percentile female described as being 5rsquo 4rdquo tall and 155 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Benchmarked watercrafts accommodate one passenger and are less than 100 lbs

o Benchmarked watercrafts have removable motors and batteries to help decrease the weight that must be lifted

Size All of the separable components of the watercraft should fit within a volume that is 4rsquoW x 8rsquoL x 4rsquoH

o Customer survey results showed widths between the wheel wells of truck beds ranging between 3 frac12 ft and 4 frac12 ft

o Building or buying a trailer is not feasible due to the constraints of laboratory space and additional costs incurred

Laws amp Regulations The watercraft should comply with all federal and Ohio state laws and regulations

o Based on the Ohio Revised Code the watercraft must

be inspected by a watercraft officer to receive a HIN display accordingly

have a valid registration display tags accordingly

display identification number accordingly

have one Type I II or III personal floatation device per watercraft occupant

o Based on US Code and Ohio Revised Code the watercraft should

carry a US coast guard approved distress flag and daynight distress signals

incorporate a lanyard-type engine cutoff switch 32 Design Criteria The watercraft must not only meet the target specifications but also fulfill the following design criteria

bull The watercraftrsquos propulsion system should be less than or equal to 10 Hp such that Ohiorsquos training and title requirements are not applicable

bull The watercraft should be less than 14 ft long such that Ohiorsquos training and title requirements are not applicable

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

6

Table 4 Ranking of Specific Needs Based on Importance

Need Need Importance

11 The watercraft should transport one passenger 1 12 The watercraft should have sufficient storage space and capacity 3 13 The watercraft should be able to function in a variety of environments 3 14 The watercraft should be easy to operate 1 15 The watercraft should operate at speeds similar to existing watercraft 2

16 The watercraft should be able to operate for the duration of a typical fishing outing 1

21 The watercraft should have an environmentally friendly and energy efficient propulsion system 1

22 The watercraft should utilize human power as a back-up power source 4 31 The watercraft should be able to be deployed by one person 2

32 The watercraft should be able to be transported without the use of a trailer 2

41 The watercraft should be durable 2 42 The watercraft should be easy to maintain 2 43 The watercraft should resist damage caused by water-born debris 2

30 Revised Needs Statement With continued research customer feedback and benchmarking a revised needs statement was proposed

With fossil fuel dependency and environmental impact at the forefront of current societal issues a goal for a more energy-efficient and environmentally-friendly propulsion system for watercraft has been recognized In following this goal as well as the current trend of personal watercraft for anglers there is a need for a one-person watercraft that is tailored toward anglers and utilizes both mechanical and human power This watercraft must be safe energy efficient environmentally friendly reliable and lightweight while demonstrating appropriate speed endurance and utility

Conducting preliminary interviews pertaining to the original needs statement allowed a specific group to be targeted as the users of this watercraft Based on these findings new interview questions were written to target the angling community The interviews also provided vital information about what customers expect in a product Benchmarking provided basic input on existing watercraft and energy alternatives that are applicable toward the need From here the original needs statement was revised and target specifications were determined

7

31 Target Specifications Energy Efficiency amp Environmental Impact The watercraft should demonstrate an efficient use of energy and minimal environmental impact

o Based on the course-wide consensus to address the current energy situation Capacity The watercraft should comfortably fit one passenger with the dimensions of a 95th percentile male as well as have a total weight capacity of 300 lbs

o Based on the 95th percentile male described as being 6rsquo 2rdquo tall and 267 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Based on the customer survey with 30 lbs being the highest of the top three survey results for cargo capacity

o A ldquocomfortable fitrdquo will be determined by testing a broad range of body types Speed The watercraft should be able to achieve a maximum speed of 5 mph in calm conditions

o Based on the customer survey that had 5-10 mph the highest range of speeds

o Electric trolling motor benchmarks had similar speed ranges

o ldquoCalm conditionsrdquo is defined as negligible wind and waves Duration of Usage The propulsion system should be able to propel the watercraft at 5 mph for a minimum of 2 hrs without refueling or recharging

o Varying weather and water conditions make any specified range for the watercraft impractical Consequently the duration of usage will be the specification that dictates the energy supply required

o Customer interviews resulted in run times ranging between 2 and 6 hours Deployment The watercraft should be able to be deployed from the transportation medium to the water by one person without the use of a boat ramp In addition the design of the watercraft should make allowances for the limited physical strength and endurance of the user to deploy the watercraft

o Based on the assumption that the watercraft will have warning labels that depict lifting assembly hazards recommend lifting assembly procedures and recommend that smaller users have help assembling the watercraft components

8

o Based on the assumption developed from experimentation by the female team members that a 50th percentile female can safely and repeatedly carry approximately 50 lbs for a distance of 100 ft

o Based on the 50th percentile female described as being 5rsquo 4rdquo tall and 155 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Benchmarked watercrafts accommodate one passenger and are less than 100 lbs

o Benchmarked watercrafts have removable motors and batteries to help decrease the weight that must be lifted

Size All of the separable components of the watercraft should fit within a volume that is 4rsquoW x 8rsquoL x 4rsquoH

o Customer survey results showed widths between the wheel wells of truck beds ranging between 3 frac12 ft and 4 frac12 ft

o Building or buying a trailer is not feasible due to the constraints of laboratory space and additional costs incurred

Laws amp Regulations The watercraft should comply with all federal and Ohio state laws and regulations

o Based on the Ohio Revised Code the watercraft must

be inspected by a watercraft officer to receive a HIN display accordingly

have a valid registration display tags accordingly

display identification number accordingly

have one Type I II or III personal floatation device per watercraft occupant

o Based on US Code and Ohio Revised Code the watercraft should

carry a US coast guard approved distress flag and daynight distress signals

incorporate a lanyard-type engine cutoff switch 32 Design Criteria The watercraft must not only meet the target specifications but also fulfill the following design criteria

bull The watercraftrsquos propulsion system should be less than or equal to 10 Hp such that Ohiorsquos training and title requirements are not applicable

bull The watercraft should be less than 14 ft long such that Ohiorsquos training and title requirements are not applicable

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

7

31 Target Specifications Energy Efficiency amp Environmental Impact The watercraft should demonstrate an efficient use of energy and minimal environmental impact

o Based on the course-wide consensus to address the current energy situation Capacity The watercraft should comfortably fit one passenger with the dimensions of a 95th percentile male as well as have a total weight capacity of 300 lbs

o Based on the 95th percentile male described as being 6rsquo 2rdquo tall and 267 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Based on the customer survey with 30 lbs being the highest of the top three survey results for cargo capacity

o A ldquocomfortable fitrdquo will be determined by testing a broad range of body types Speed The watercraft should be able to achieve a maximum speed of 5 mph in calm conditions

o Based on the customer survey that had 5-10 mph the highest range of speeds

o Electric trolling motor benchmarks had similar speed ranges

o ldquoCalm conditionsrdquo is defined as negligible wind and waves Duration of Usage The propulsion system should be able to propel the watercraft at 5 mph for a minimum of 2 hrs without refueling or recharging

o Varying weather and water conditions make any specified range for the watercraft impractical Consequently the duration of usage will be the specification that dictates the energy supply required

o Customer interviews resulted in run times ranging between 2 and 6 hours Deployment The watercraft should be able to be deployed from the transportation medium to the water by one person without the use of a boat ramp In addition the design of the watercraft should make allowances for the limited physical strength and endurance of the user to deploy the watercraft

o Based on the assumption that the watercraft will have warning labels that depict lifting assembly hazards recommend lifting assembly procedures and recommend that smaller users have help assembling the watercraft components

8

o Based on the assumption developed from experimentation by the female team members that a 50th percentile female can safely and repeatedly carry approximately 50 lbs for a distance of 100 ft

o Based on the 50th percentile female described as being 5rsquo 4rdquo tall and 155 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Benchmarked watercrafts accommodate one passenger and are less than 100 lbs

o Benchmarked watercrafts have removable motors and batteries to help decrease the weight that must be lifted

Size All of the separable components of the watercraft should fit within a volume that is 4rsquoW x 8rsquoL x 4rsquoH

o Customer survey results showed widths between the wheel wells of truck beds ranging between 3 frac12 ft and 4 frac12 ft

o Building or buying a trailer is not feasible due to the constraints of laboratory space and additional costs incurred

Laws amp Regulations The watercraft should comply with all federal and Ohio state laws and regulations

o Based on the Ohio Revised Code the watercraft must

be inspected by a watercraft officer to receive a HIN display accordingly

have a valid registration display tags accordingly

display identification number accordingly

have one Type I II or III personal floatation device per watercraft occupant

o Based on US Code and Ohio Revised Code the watercraft should

carry a US coast guard approved distress flag and daynight distress signals

incorporate a lanyard-type engine cutoff switch 32 Design Criteria The watercraft must not only meet the target specifications but also fulfill the following design criteria

bull The watercraftrsquos propulsion system should be less than or equal to 10 Hp such that Ohiorsquos training and title requirements are not applicable

bull The watercraft should be less than 14 ft long such that Ohiorsquos training and title requirements are not applicable

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

8

o Based on the assumption developed from experimentation by the female team members that a 50th percentile female can safely and repeatedly carry approximately 50 lbs for a distance of 100 ft

o Based on the 50th percentile female described as being 5rsquo 4rdquo tall and 155 lbs in the Anthropometric Reference Data for Children and Adults US Population 1999-2002 published by the National Center for Health Care Statistics

o Benchmarked watercrafts accommodate one passenger and are less than 100 lbs

o Benchmarked watercrafts have removable motors and batteries to help decrease the weight that must be lifted

Size All of the separable components of the watercraft should fit within a volume that is 4rsquoW x 8rsquoL x 4rsquoH

o Customer survey results showed widths between the wheel wells of truck beds ranging between 3 frac12 ft and 4 frac12 ft

o Building or buying a trailer is not feasible due to the constraints of laboratory space and additional costs incurred

Laws amp Regulations The watercraft should comply with all federal and Ohio state laws and regulations

o Based on the Ohio Revised Code the watercraft must

be inspected by a watercraft officer to receive a HIN display accordingly

have a valid registration display tags accordingly

display identification number accordingly

have one Type I II or III personal floatation device per watercraft occupant

o Based on US Code and Ohio Revised Code the watercraft should

carry a US coast guard approved distress flag and daynight distress signals

incorporate a lanyard-type engine cutoff switch 32 Design Criteria The watercraft must not only meet the target specifications but also fulfill the following design criteria

bull The watercraftrsquos propulsion system should be less than or equal to 10 Hp such that Ohiorsquos training and title requirements are not applicable

bull The watercraft should be less than 14 ft long such that Ohiorsquos training and title requirements are not applicable

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

9

bull The watercraft should be easy to operate

bull The watercraft should accelerate from rest to the maximum speed in a time duration that would be acceptable to the customers (approximately 10 seconds)

bull The watercraft should have an alternative method of propulsion in the event of the mechanical propulsion systemrsquos failure

bull The watercraft should be safe with sufficient stability to reduce the chance that the passenger fall overboard

bull The watercraft should be weather resistant for both storage and transportation purposes

bull The watercraft should resist damage from water-born debris and partially-to-fully-submerged obstacles as well as resist damage during transportation

bull The watercraft should be aesthetically pleasing

bull The watercraft should be designed and manufactured such that a full production version of the watercraft could be priced competitively

40 External Search The process of developing a product involves research and insight into the needs of customers and similar products currently on the market Therefore research was done on the environmental impact of traditional outboard motors as well as on similar alternatively fueled watercraft Hull design powering and propulsion methods were also researched Several patents were found pertaining to the specific needs statements and are shown below with a brief description Research was also performed on Ohio state regulations and will be performed on other statersquos regulations involving safety and licensing of watercraft Regulations depend on the size and power of the watercraft being used so further research will be performed into regulations as the process continues The following is the list of similar product patents US 7047901

Hydrofoil boat large enough for one person to sit or stand on and powered by an electric motor and a battery system The one person watercraft as well as the electric motor and battery system are ideas being considered in this project US 6855016

Incorporates solar power and human kinetic power for electrical power generation and storage for the propulsion system This watercraft illustrates different power sources that may be useful to this project

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

10

US 7047902 Electrically driven solar charged watercraft which provides an innovative solar canopy ventilation system Again the power sources might be relevant to the scope of the project US 6868938 Noise-reducing engine with noise-reducing insulation layer The noise-reducing engine could be beneficial to the project in that the low noise level avoids disturbing wildlife US 6837176 Hull designed to hydroplane on top of the water when the vessel is moving at high speeds and displace the water surface at low speeds This design could be applicable but is most likely infeasible for the scope of this project 41 Benchmarking Benchmarking was performed to find watercraft that closely fit the needs statement and desired market This process allows the design team to see similar products for ideas as well as to avoid potential pitfalls The benchmarks were then compared to each other based on their fulfillment of the customer requirements This comparison can be seen in Table 5 where one dot represents the lowest rating and five dots represent a good fulfillment of customer requirements

The Bobcat Mag II (Bobcat Boats 2007) can be seen in Figure 1 This boat is a single passenger electric fishing boat that is 12 ft 4 in long 40 in wide and 105 in deep It weighs 95 pounds and includes an electric motor which supplies 30 pounds of thrust and also has either a 100 amp or 130 amp deep cycle battery The boat has a maximum speed of 8 mph and a cruising speed of 5 mph

Figure 1 Bobcat Mag II

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

11

Figure 2 The Trout Unlimited Rogue River Pontoon Boat

The Trout Unlimited Rogue River Pontoon Boat (Cabelas 2007) is a one passenger oar rowed pontoon boat with adjustable foot rests It has a weight of 90 lbs at 108 in long 56 in wide and 30 in tall It has a carrying capacity of 400 lbs and has a fold down wheel for easy transportation

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

12

Table 5 Benchmark Comparisons to Customer Requirements

Need Need Imp

Bob

cat M

ag II

The

Blu

e R

ibbo

n

Bas

s H

unte

r EX

Boa

t w M

inn

Kot

a En

dura

30

Mot

or

Trou

t Unl

imite

d R

ogue

Riv

er

Pont

oon

Boa

t

The

Dec

avita

tor

11 The watercraft should transport one passenger 1 bullbullbullbullbull bullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull12 The watercraft should have sufficient storage

space and capacity 3 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbull bull 13 The watercraft should be able to function in a

variety of environments 3 bullbullbullbullbull bullbullbull bullbullbullbullbull bullbullbullbullbull bullbull 14 The watercraft should be easy to operate 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 15 The watercraft should operate at speeds similar

to existing watercraft 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull16 The watercraft should be able to operate for the

duration of a typical fishing outing 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bull 21 The watercraft should have an environmentally

friendly and energy efficient propulsion system 1 bullbullbullbull bullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull22 The watercraft should utilize human power as a

back-up power source 4 bullbull bull bull bullbullbullbullbull bullbullbullbullbull31 The watercraft should be able to be deployed

by one person 2 bullbullbullbull bull bull bullbullbullbullbull bullbullbull 32 The watercraft should be able to be transported

without the use of a trailer 2 bullbullbull bull bull bullbullbullbullbull bull 41 The watercraft should be durable 2 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbull bullbullbull 42 The watercraft should be easy to maintain 2 bullbullbullbullbull bullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbull 43 The watercraft should resist damage caused by

water-born debris 2 bullbullbullbull bullbullbull bullbullbullbull bullbullbullbull bull 51 The watercraft should comply with all federal

and Ohio state laws and regulations 1 bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull bullbullbullbullbull

The Decavitator (Decavitator 2007) is a one passenger human powered watercraft with a pontoon hull hydrofoils 10 ft diameter propeller (air) bicycle-style pedals and semi-recumbent seat This watercraft set the world record for speed at 185 knots for a human powered watercraft It has a weight of 48 lbs at 20ft long 8 ft wide and 6 ft tall

The Bass Hunter EX Boat (Bass Hunter 2007) is a two person fishing boat that is 114 in long and 48 in wide It has a 550 lb capacity and is adaptable for either a 5 hp motor or an electric trolling motor It has foam-filled pontoons that provide excellent stability

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

13

50 Concept Generation 51 Problem Clarification A power-flow model was utilized in this project to describe the inputs outputs and variables of the watercraft being designed Figure 3 is a generic power-flow model that focuses on the source-to-thrust power delivery of the propulsion system Following the target specifications described in the pervious section both a general power source and human power are represented in the model as the sources of power for the watercraft However the two power sources are not necessarily in parallel as they appear in the figure User input dictates the use of power to develop the thrust needed to move the watercraft The external loads include the drag caused by the water and the air as well as the weight of the watercraft passenger and cargo The internal loads include mechanical losses and the efficiency of the power distribution throughout all aspects of the propulsion system Federal and Ohio laws and regulations will dictate the maximum size of the power source to be 10 Hp Furthermore the overall efficiency and environmental impact of the watercraft must be considered

Figure 3 Power-Flow Model for Problem Clarification 52 Concept Generation The concept generation process involved brainstorming and screening performed as both individuals and as a team Individual concepts for overall design and sub level

Power Source

Power Converters

Transmissions and Drive Trains

User Inputs System Controls

External and Internal Loads

Efficiency Environmental

Impact

Safety Laws and

Regulations

Human Power

Thrust

Auxiliaries and Accessories

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

14

components were formed and then brought to the team to allow for improvements and integration of feasible ideas After initial system level concepts were generated the team was divided into hull mechanical power and human power groups to gain specialized knowledge about these specific subsystems The hull group explored different hull types and noted advantages and disadvantages of each design The mechanical power group looked into potential power sources to drive the propeller of the watercraft The human power group looked into the pros and cons of series or parallel power generation and human power generation capabilities Ideas and explanations were then brought to the main team to select the best concepts for each subsystem This collaboration process then resulted in the selection of a final concept Figure 4 shows the process used for selecting the best concepts The key steps in the process were Enhance amp Merge and Reflection In the Enhance amp Merge step of the process the team made ideas more feasible and creative by improving and integrating individual ideas The reflection step of the process was necessary to ensure the generated solutions were well received by the customers and met the target specifications and design criteria for the project This step was also critical in ensuring each idea was feasible within the scope of this project Once the final design is generated and positive customer feedback is received the process moves towards prototyping and manufacturing

Figure 4 Conceptual Design Process

Individual Brainstorming

Group Discussion

Individual Rating

Detail Design

Prototype

Manufacture

Group Screening

Enhance amp Merge

Best Concept

Reflection

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted

15

521 Power Plant Options Internal Combustion Engine

Gasoline Gasoline is a reliable power source but is a large contributor of pollution in marine environments Using a gasoline engine does not address the energy situation and defeats the purpose of making an energy efficient vehicle E85 E85 is a mixture of 85 ethanol and 15 gasoline and is considered an alternative fuel While E85 burns cleaner than gasoline it ultimately will not solve the environmental issues associated with boating As with the gasoline outboard motor exhaust goes directly into the water and the issue of noise pollution is not addressed Also the infrastructure for E85 is not prevalent enough to be a feasible alternative fuel for this watercraft

Due to the fact that neither an internal combustion engine burning gasoline nor E85 will address the target specification concerning environmental impact the watercraft power plant was defaulted to an electric motor Later sections in this report will not contain information calculations or analysis relating to internal combustion engines because that power plant option was eliminated at this stage in conceptual design Electric Motor

Batteries Batteries provide a reliable power source to drive the motor Batteries also help to reduce noise pollution and eliminate exhaust and fuel spillage when used to power an electric motor that drives the propeller They are heavy relative to other power sources and are typically recharged with electricity produced by burning fossil fuels Solar Solar energy is free but cannot provide enough energy to power the watercraft directly Solar panels are also expensive and are typically only reliable in sunny climates

Human Power

Paddle Power Paddles or oars are the first form of human power that comes to mind when personal watercraft are being discussed Oars are a good option for reliability reasons but can sometimes be difficult to manage when fishing Series Hybrid The human-electric series hybrid incorporates both human power and electric power Figure 5 shows a conceptual drawing of the series hybrid system In a series hybrid the human pedals to power an electric generator that charges a battery system which in turn powers the motor The advantages of this system are the ability to pedal while the watercraft is at rest in order to store energy for use during movement the ability to deliver power at a more constant rate and reduced mechanical complications The disadvantage of the series hybrid is the loss of efficiency due to energy conversion from human to battery to motor Figure 6 shows a diagram of the power flow for the human-electric series hybrid

16

Figure 5 Series Hybrid

Figure 6 Human-Electric Series Hybrid Power Flow

Integrated Parallel Hybrid The integrated parallel hybrid allows the use of human power whenever needed Figure 7 shows a conceptual drawing of the integrated parallel system The integrated parallel hybrid connects the human power output and the motor directly to the same propeller via a driveshaft This is advantageous because the watercraft can be propelled even after the batteries have been depleted The disadvantage is that propellers are designed differently for human power than motor power As a result it will be difficult to maximize the performance of both power sources Figure 8 shows the power flow diagram for the human-electric parallel hybrid

Battery

Controller

Electric Motor

Human Power

Generator

Driveshaft Propeller

17

Figure 7 Integrated Parallel Hybrid

Figure 8 Human-Electric Integrated Parallel Hybrid Power Flow

Independent Parallel Hybrid The independent parallel hybrid consists of human power element that is completely separate of the electric motor Figure 9 shows a conceptual drawing of this system This design involves two separate propellers The human power system will be able to fold up to reduce extra drag in the water The advantages of this system are that the separate propellers allow for both systems to be maximized and that the power system that is not in use will fold up out of the water do reduce drag The disadvantage is that the human power system could crowd the deck of the watercraft Figure 10 shows the power flow diagram for the separated parallel hybrid

Human Power

Transmission

Battery

Driveshaft Propeller

Electric Motor

Controller

18

Figure 9 Independent Parallel Hybrid

Figure 10 Human-Electric Separated Parallel Hybrid Power Flow

522 Hull Configurations Mono-hull Mono-hull designs offer high buoyancy plenty of on board storage and the ability to cut through waves However a mono-hull would require a trailer and limits collapsibility both detrimental to one person deployment Dual-hull Dual-hull designs offer increased stability and can enter shallow waters Pontoons the typical form of a dual-hull are much easier to build and aid the implementation of collapsibility and the application of both mechanical and human power The pontoon design will allow attached propulsion systems to be put in the water without having to make holes in the hull of the watercraft Listed below are different pontoon designs that were considered

Human Power

DriveshaftPropeller

Battery

Driveshaft Propeller

Electric Motor

Controller

19

Plain Cylinder This design is the most common pontoon in the boating industry The plain cylinder design has the shape of a circle when looking at a section view When size and space are not an issue this design works well providing plenty of buoyancy as long as the pontoon keeps its upper half out of the water Catamaran This designrsquos goal is to cut through the water with ease and reach high speeds with minimal drag The downside of the catamaran design is the limited buoyancy provided by each pontoon Due to the more narrow design for cutting through waves the surface area in contact with the water is limited on the bottom side of the pontoon U-Shaped This is a new design in pontoon technology which is meant to supply extra buoyancy per pontoon Instead of a complete cylinder the pontoon has a cylindrical bottom up to the mid-point where it meets vertical walls going straight up forming a U shape The U-shaped pontoon provides a larger volume creating more buoyancy per pontoon (JC Pontoon 2006)

523 Delighters Many aspects of this project are unique to the market and will distinguish this product from other similar products These include

Collapsibility Incorporating collapsibility into the product design has the potential to increase marketability without necessarily increasing product cost This is also a key feature in transportation and storage as the product can be transported without a trailer and will take up less room in storage than other products Individual Deployment Since this watercraft is made for one person it makes sense that it be easily deployed by one person At a manageable weight a collapsible watercraft is maneuverable and can access bodies of water without conventional launch sites Incorporating wheels into the design could be a key feature for maneuverability and deployment of the watercraft

60 Concept Selection

61 Data and Calculations for Feasibility and Effectiveness Analysis 611 Power Calculations and Analysis Power calculations for the watercraft were performed to determine the amount of power required to meet the target specifications and design criteria of this project The calculations assumed the overall weight to be 600 lbs which accounted for 300 lbs of watercraft hull and 300 lbs for both the passenger and cargo As stated in the target specifications and design criteria the power calculations were performed for the watercraft accelerating to a 5 mph cruising speed in 10 seconds According to Newtonrsquos Second Law the sum of the forces is equal to the mass times acceleration Figure 11

20

shows the free body diagram of the watercraft with the positive direction of movement indicated to the left

Watercraft Hull

Passenger

FD Water

FD Air

FB

FD Air

FD Water FTH

WTotal

ma

PropellerAssembly

Figure 11 Free Body Diagram for the Watercraft

The force moving the watercraft forward is the thrust Fth generated by the propulsion system The water and air acting against the forward motion of the watercraft are represented by the drag forces Fd as indicated The drag force was calculated using Equation 1 where ρ is density of the fluid medium CD is the coefficient of drag A is the reference area of the object and U is the velocity

2

21 AUCF DD ρ= (Equation 1)

The drag force due to the air was a combination of the drag due to the passenger and the watercraft hull In the case of the passenger the coefficient of drag was assumed to be 110 and the reference area was assumed to be 55 ft2 (Fundamentals of Fluid Mechanics 2006) The coefficients of drag used to calculate the drag force due to the air on the watercraft hull was determined from a coefficient of drag chart using a calculated Reynolds number The Reynolds number was calculated using Equation 2 where U is the velocity D is the characteristic dimension (typically diameter) and ν is the kinematic viscosity of the fluid medium

21

υUD

=Re (Equation 2)

Figure 12 shows the relationship between the coefficient of drag and Reynolds number for various shapes ranging from a flat plate perpendicular to the flow of the fluid to a flat plate parallel to the flow The pontoons were assumed to be cylindrical in shape 8 feet long and 15 feet in diameter with a corresponding diameter-to-length ratio of 01875 As shown in Figure 12 an ellipse is considered to have a diameter-to-length ratio of 05 and an airfoil is considered to have a diameter-to-length ratio of 018 Thus the pontoons were assumed to have a curve similar in shape to that of the ellipse but shifted downward and flattened to resemble that of the airfoil The red drag line in Figure 12 is the hand drawn estimation of the pontoonrsquos characteristics and all coefficients of drag for the watercraft hull were determined graphically from that line

Figure 12 Coefficients of Drag According to Reynolds Number for

Various Shapes with Estimated Drag Line for the Pontoon Shape (Munson Young and Okiishi)

The drag force due to the water was a combination of the drag due to the watercraft hull and the submerged propeller assembly The coefficient of drag was determined by the same method as for the air and the drag force was determined using Equation 1 The

22

drag forces when totaled together were then used to calculate the thrust according to Equation 3 which was derived from Newtonrsquos Second Law

maFFTotalDTH =minus (Equation 3)

The thrust requirements were determined for a range of speeds as listed in Table 6

Table 6 Total Thrust Requirements of the Watercraft for Various Speeds

Velocity Thrust Required to Overcome Drag Forces and Accelerate to the

Specified Velocity

[mph] [N] [lbf] 3 11180 2513

4 16629 3738

5 22939 5157

6 30111 6769

7 38143 8575

8 47037 10574

9 56792 12767

10 67408 15154

The power requirements of achieving the calculated thrusts were a function of the propellerrsquos ability to convert rotational motion into a force Thus the power requirements must take into account both the torque created by centrifugal force and the torque created by the thrust Figure 13 depicts the forces that contribute to the total torque of the propulsion system (HydroComp Technical Report 2007)

23

Figure 13 Force Diagram of a Typical Propeller The propeller was assumed to have geometry similar to that of trolling motor propeller which is flat in shape However to allow the propeller to be representative of both trolling motor propellers and regular propellers the rake and pitch angles were assumed to be 10deg The rake angle describes the tilt of the propeller blades away from the gear case The pitch angle describes the orientation of the propeller blades with respect to the rotational axis of the gear case Trolling motor propellers being flat in their geometry would have a rake and pitch angles of 0deg The rotational speed of the propeller was assumed to be 1750 rpm and accounted for a gear reduction of 20 between the motor and the propeller The centrifugal force was calculated using Equation 4 where m is the mass of the water displaced by the propeller blades and at is the centripetal acceleration

tlCentrifuga maF = (Equation 4) The mass of the water displaced by the propeller blades was estimated by assuming that the propeller is a cylinder with a smaller cylinder representing the gear case removed from the center The interrupted nature of the propeller blade arrangement led to the volume of the aforementioned cylinder being multiplied by ⅓ Thus the mass of the displaced water was assumed to be the calculated volume multiplied by the density of water or 000176 slugs The centripetal acceleration was calculated using Equation 5 where vt is the tangential velocity and r is the radius of the propeller (3 inches)

24

rv

a tt

2

= (Equation 5)

The tangential velocity was calculated using Equation 6 where ω is the angular velocity (18326 rads equiv 1750 rpm) and r is radius mentioned above

ωrvt = (Equation 6) The centrifugal force was determined to be 1479 lbs The horizontal component of this force determined to be 257 lbs was then used in the torque calculations The torque was calculated using Equation 7 where FCentrifugal is the centrifugal force and l is the length of the lever arm where the force is acting (225 inches equiv frac34middotr) The lever arm length was used instead of the propeller radius because the ldquotear droprdquo shape of the propeller blades means that the force does not act at the very tip

lFT lCentrifugalCentrifuga = (Equation 7) The torque due to the centrifugal force was determined to be 578 in-lbs Similarly to the torque due to the centrifugal force the torque due to the thrust was calculated using Equation 7 The power required to overcome the torque of the propulsion system was then calculated using Equation 8 where T is either the torque due to the centrifugal force or the torque due to the thrust and ω is the angular velocity from above

ωTP = (Equation 8) Table 7 shows the power requirements associated with the both the centrifugal force and the thrust as well as the total power requirements These power requirements were determined for a range of speeds

25

Table 7 Total Power Requirements of the Watercraft for Various Speeds

Velocity Power Due to the Thrust Torque

Power Due to the Centrifugal Torque

Total Power

[mph] [W] [Hp] [W] [Hp] [W] [Hp] 3 20647 0277 11968 0160 32615 0437

4 30709 0412 11968 0160 42678 0572

5 42363 0568 11968 0160 54331 0729

6 55606 0746 11968 0160 67575 0906

7 70440 0945 11968 0160 82409 1105

8 86865 1165 11968 0160 98833 1325

9 104880 1406 11968 0160 116848 1567

10 124485 1669 11968 0160 136453 1830

Table 8 shows the power requirements taking into account the overall system efficiency The efficiency of the electric motor was estimated at 90 which is typical of brush-less electric motors The system losses were estimated at 10 taking into account the mechanical power transmission losses and the electrical power transmission losses Thus the overall efficiency was 80 Figure 14 depicts the power requirements and thrust requirements of the watercraft propulsion system according the watercraft speed

Table 8 Total Power Requirements of the Watercraft at 80 Efficiency for Various Speeds

Velocity Total Power at 80

Efficiency

[mph] [W] [Hp] 3 40768 0547 4 53347 0715 5 67914 0911 6 84468 1133 7 103011 1381 8 123541 1657 9 146060 1959

10 170566 2287

26

000

025

050

075

100

125

150

175

200

225

250

3 4 5 6 7 8 9 10

Watercraft Velocity U [mph]

Pow

er R

equi

red

P [

hp]

0

20

40

60

80

100

120

140

160

Thru

st R

equi

red

FTH

[lb

s]

Power Thrust

Figure 14 Power and Thrust Required as a Function of the Watercraft Velocity

To achieve a velocity of 5 mph with in an acceleration period of 10 seconds starting from rest the propulsion system requires 52 lbs of thrust and 0911 hp When sizing the propulsion system it would appropriate to examine 10 hp electric motors that are sufficient to be coupled with a propeller assembly that is capable of generating approximately 55 lbs of thrust 612 Electric Motor Analysis Before looking into different types of power supplies electric motors needed to be researched to determine the voltage and current requirements needed to meet our power output requirements Table 9 compares the key aspects of four electric motors that fit the needs of the project The table looks at the weight voltage requirements max current draw and the max power output of each particular motor

27

Table 9 Electric Motor Comparison (Robot Marketplace 2006) (Electric Vehicles 2006)

Etek ADC Perm DampDVoltage 24 ndash 48 V 24 ndash 48 V 24 ndash 48 V 36 ndash 48 VCurrent Draw 330 Amps ------ 200 Amps 125 Amps

Weight 208 lbs ------ 248 lbs 540 lbsCost $500 $520 $956 $590Max HP 15 38 151 61Efficiency ------ ------ 886 ------ When initially comparing the given motors it is easy to see that the Etek electric motor best fits the needs of this project It has the highest power output and is very light weight which meets two of the important design specifications for any watercraft The power output of an electric motor is a function of current and voltage The angular velocity of a DC motor is proportional to the voltage of the system and the torque output of the motor is proportional to the current draw Drawing a large current from the voltage supply will produce the most power from an electric motor since the voltage is usually fixed to 12 24 36 or 48 volt configurations (Electric Motor 2006) The power of an electric motor is given by Equation 9

P = IV (Equation 9)

Table 10 shows how the relation between current and voltage can change the power output of an electric motor

28

Table 10 Power Output of Motor Depending on Voltage and Current

Current

Draw [A]

24 V 36 V 48 V

30 087 HP 130 HP 174 HP 40 116 174 232 50 145 217 290 60 174 261 348 70 203 304 406 80 232 348 463 90 261 391 521 100 290 434 579 110 319 478 637 120 348 521 695 130 377 565 753 140 406 608 811 150 434 652 869

613 DC Battery Analysis Lead Acid Deep Cycle Batteries Lead-Acid batteries are electrical storage devices made from a combination of lead plates and an electrolyte The electrolyte is a diluted sulfuric acid and is used to convert electrical energy into potential energy and vise-versa The battery uses a reversible chemical reaction in order to store energy Deep Cycle batteries have thicker lead plates that help them to handle larger amounts of discharge This doesnrsquot allow them to dispense charge as quickly but it does allow it for longer periods of time (How Lead Acid 2007) NIMH Deep Cycle Batteries

Nickel metal hydride (NiMH) batteries are made up of nickel for the cathode and a hydrogen absorbing alloy for the anode The reaction that occurs in a NiMH battery is explained by the following equation

H2O + Mm + 2eminus harr OHminus + 05H2 (stored as Mm-Hx)

The battery is charged in the right direction and discharged in the left direction With NiMH batteries overcharge is not as much of a safety concern as Lead-Acid batteries but it can diminish the long term life of the battery (Nickel Metal Hydride 2007) Table 11 looks at the comparison between the two types of batteries previously discussed

29

Table 11 Battery Property Comparison

Properties Lead Acid NIMH Energy-to-weight 30-40 Whrkg 30-80 Whrkg Power-to-weight 180 Wkg 250-1000 Wkg ChargeDischarge Efficiencies 70-92 66 Cycle Durability 500-800 Cycles 500-1000 Cycles Nominal Cell Voltage 20 V 12 V

A decision matrix was used in order to choose which battery type to use to supply power to our electric motor The key arearsquos looked at when choosing a battery type were weight energy density cost efficiency and cycle durability Table 12 shows the results that were concluded from this method

Table 12 Battery Type Decision Matrix

It was determined that the watercraft will use lead-acid batteries to supply power to the motor The specific battery brand and configuration will be selected later on in the design process Voltage amp hours weight and cost are the key aspects of DC batteries in the scope of this project The key drivers used in the selection process of DC batteries were amp hours and cost After initial battery research was completed nickel metal hydride batteries were eliminated as an option Table 13 compares 4 batteries that meet the teamrsquos cost and amp hour restrictions Please note that these batteries were only chosen to perform preliminary calculations showing runtime in relation to current draw Section 701 shows further battery selection

30

Table 13 Battery Comparison (Apex Battery 2006)

Deka 8AU1 Deka 8GU1 Odyssey 8GU-1HW Amp Hr 325 361 27 31 Voltage 12 12 12 12 Weight 24 lbs 24 lbs 24 lbs 24 lbs Cost $8695 $10995 $18999 $10995 The key aspect of the motor that different types of batteries affect is the runtime Batteries are designed with a specific amp hour capacity which is the amount of current that can be drawn from the battery in one hour before the stored energy is completely drained Equation 10 was used to calculate the run time an electric motor

wCurrentDrasofBatterieAmpHrRunTime )()(

= (Equation 10)

Figure 15 demonstrates the affect that current draw has on the run times for the same batteries compared in Table 11 It is important to note that the figure is created to demonstrate the situation of four 12 volt batteries connected in series This allows for the most current to be drawn from the system because it makes the total voltage 48 volts where with 4 batteries in parallel would only make the total voltage 12 volts The graph also shows the run time for each battery run until 100 discharge this should not be done when actually running the motor because the life cycles of the battery is dictated by the percent of the batteryrsquos capacity that was depleted