Unit on Sailboats

Types of Boats

Types of Sailboats

Modern SloopRacing SloopFractional Sloop RigCat RigCat-Rigged Racing DinghyKetchYawlSchoonerSchooner with Top Mast and Flying JibsSquare-Rigged Tall Ship

Vocabulary – Parts of Sailboat

RudderMastBoomHullSail

Vocabulary – Around the Water

BeachSandSalt waterFresh

waterSunburnWindWavesCurrent

•Playa•Arena •de agua salada•Agua dulce•Quemadura del sol•Viento•Ondas•corriente

شاطئرمل

المالحة المياهعذبة مياه

الشمس حروقرياحأمواجالحالي

Vocabulary – Water Sports

SkiingSurfingSwimmingSnorkelingScuba divingBoating Sailing Diving Fishing

HOW STUFF FLOATS…

Buoyancy

BUOYANCY

CE 3250JOE ECKHARDT, MIKE FIRESTONE,

CHRISTOS MELISTAS, MEGHAN VOHS

What is Buoyancy?

In simple terms, buoyancy is the ability of an object to float.

Whether or not a given object will float is determined by the buoyant force on the object.

This force is caused by the difference between the pressure at the top of the object, which pushes it downward and the pressure at the bottom of the object which pushes it upward. Because the pressure at the bottom of the object is always greater than the pressure at the top, every submerged object feels an upward buoyant force.

The magnitude of this buoyant force is equal to the weight of the fluid that is displaced by the submerged object.

The weight of the water that is displaced by this block of wood is equal to the buoyant force acting on the block. (excerpt from http://www.pbs.org)

What is Buoyancy? (cont.)

The difference between the buoyant force acting up on the object and the force due to gravity acting downward on the object will determine whether or not the object will float or sink.

If the buoyant force is greater than the gravitational force, the object will float, but if the opposite is true, the object will sink.

Buoyancy kept the S.S. Edmund Fitzgerald afloat in the Great Lakes until water filled its hull causing the ships weight to exceed the buoyant force acting upward on it. The rest is history.

How to Calculate BuoyancyThe buoyant force (FB)

is equal to the weight of fluid the object displaces. If an object is submerged

it displaces its total volume of fluid.

If it is partially submerged it displaces the volume of fluid equal to its submerged volume.

The weight of the fluid it displaces is the volume of fluid multiplied by the fluid’s specific weight.

How to Calculate BuoyancyTotally Submerged Object in Water

Object’s Volume = 1ft3

Specific Weight of Water (γWater) = 62.4lb/ft3

FB = 1ft3 x 62.4lb/ft3 = 62.4lb

How to Calculate BuoyancyObject 50% Submerged in Water

Object’s Volume = 1ft3

Submerged volume = 0.5ft3

Specific Weight of Water (γWater) = 62.4lb/ft3

FB = 0.5ft3 x 62.4lb/ft3 = 31.2lb

Understanding Buoyancy

Q: An inverted spherical shell of diameter, d = 1m is used to cover a tank filled with water. What is the minimum weight the shell must be to hold itself in place?

Understanding Buoyancy (cont.)A: Since only half the sphere is covering the tank,

we only need to account for half the volume. So, V = 4/3 pr3. Since only half the volume is to be accounted for, the volume that is to be used is V = 4/6 pr3. So, the volume of the sphere will be 4/6 p*(.5m)3 = .262m3. Then, the forces in the y-direction must be summed and set equal to zero. Our equation will be FB – W = 0. FB = Specific weight of water (gW) * volume of sphere. So, our equation to solve for W will be (9,806 N/m3)*(.262m3) – W = 0. Solving for W, the minimum weight the shell must be to hold itself in place is 2,569.17N.

Who Needs Buoyancy?

Everyone needs buoyancy!

If you swim, boat, scuba dive, or float; you need buoyancy!!!

Buoyancy and Swimming Buoyancy is why most

people float. Your body displaces water. When the weight of the water you displace is more than your weight you float.

Because of buoyancy you weigh very little in water.

You can put most of your energy into movement because you need very little to carry yourself

CHEAP, CREATIVE, AND HAVING FUN ON THE WATER

The Puddle Duck Racer

The Hull

Launching the class When creating a new sailboat class, there are a lot of possibilities for the

types of hull shapes that can be used. After a lot of thought, a box boat type hull was clearly the best solution. For more info, see designing the PDRacer. In July 2002, I built the flats rat and spent a year a testing it out. For the rat, instead of using the mouseboat rocker, I used design concepts presented in the Moth class to create my own hybrid rocker shape. Later this same rocker shape would be used for the PDRacer. In July of 2003, I released the rocker for the Puddle Duck and the first set of rules, of which there were only 4:

1 - All boats must use the above section for the sides2 - All boats must be atleast 48" wide across the bottom3 - All boats must have enough emergency floatation to be self rescued4 - All boats must have flat parallel sides

I was still deep in other boat projects, and was going to build the first pdracer, right after finishing a previous boat which was almost done. My friend Doug Day decided he couldn't wait, and built the first PD and announced it was 3D on Jan 8, 2004. I was still finishing up the other boat, tempted to stop and build a PD, but just wanted to finish up the other project first. Ken Abrahams, another one of my friends, saw that Doug built a PD and so built one also, announcing it went 3D on Jan 14, 2004. Kicking myself for not building the first one, and even missing the 2nd hull number, I dropped everything and built hull #3, which went 3D on Feb 5th, 2004. Here is what happened to the first three PDRacers.

As you can see from above, there were only 4 original rules and today we have more. So obviously I have made changes along the way, but if you read our current rules and compare with the original 4 above, hopefully you will agree with me that they mean the same thing. I have only added or re-worded rules to clarify their explanation and resolve issues to further protect the original hull shape and concept of our class. I am the only one that controls and can modify the rules, and when I die, my kid is ready to pickup and carry on the task of defending the rules & simple concept of our class: we all use the same shaped hulls and modify the other stuff, and go play with them in fun ways and also for serious racing. It says it right there in our class motto: Cheap, Creative, and Having Fun On The Water

We had our first puddle duck race between the three of us on Feb 28th, 2004, we even crossed the start line in that order. The home page picture (with the big duck on the side of the boat) was taken just as Ken in #2 was crossing the start line, you can just barely see a chlorox bottle just ahead of the luff of his sail. That was the other marker for the start line.