Voith Turbo

The Voith Schneider PropellerCurrent Applications and New Developments

Dr.-Ing. Jens-Erk Bartels, Dr.-Ing. Dirk Jürgens

2 Introduction

3 Design of the

Voith Schneider Propeller

5 The hydrodynamic principle of

thrust generation

9 Hydrodynamic characteristics

of Voith Schneider Propellers

12 Hydrodynamic calculation

methods for Voith Schneider

Propellers

13 Ships with Voith Schneider

Propellers

16 Ship Assistance with Voith

Water Tractors

18 Voith Water Tractors as

escort ships

19 Voith Turbo Fin (VTF)

21 Mine Countermeasure Vessels

(MCMV) with VSP

22 Voith Cycloidal Rudder (VCR)

26 Bibliography

122

Voith Schneider Propellers (VSP)

are used primarily for ships that

have to satisfy particularly demand-

ing safety and manoeuvrability

requirements. Unique to the Voith

Schneider Propeller is its vertical

axis of rotation. The thrust is gener-

ated by separately oscillating,

balanced propeller blades. Due to

its physical operating principle and

its design, thrust adjustments can

be done very quickly. The VSP, a

controllable-pitch propeller, permits

continuously variable thrust adjust-

ment through 360°. Combining

steering and propulsion. Rapid,

step-less thrust variation according

to X/Y coordinates improves ship

handling.

Voith Schneider Propellers operate

at a comparatively low revolutional

speed and are therefore notable for

their long service life and very low

maintenance requirements. Cur-

rently, VSPs are used primarily on

Voith Water Tractors (VWT), double-

ended ferries (DEF), mine counter-

measure vessels (MCMV), passen-

ger ships, buoy layers and floating

cranes. The development of the

Voith Water Tractor (VWT) is

significant and has dramatically in-

creased the safety of tug opera-

tions. When escorting ships carry-

ing hazardous cargo, the Voith

Water Tractor achieves the highest

assistance forces for a wide speed

range due to its optimum design.

Specifically designed VWT´s enable

escort duties to be carried out saf-

ely, even at high speeds. The Voith

Water Tractor marked the introduc-

tion of indirect steering to ship

assistance.

Recently, the systematic use of

Computational Fluid Dynamics

(CFD) has provided a more detailed

understanding of the flow physics of

the Voith Schneider Propeller.

Combined with the use of modern

development tools (3D-CAD, FEM),

CFD is opening up new prospects

for accelerated development work.

Continuous improvements in the

VSP´s hydromechanical properties

Introduction

Figure 1: Voith Schneider Propeller incorporated into a ship’s hull

Design of the Voith Schneider Propeller

Figure 2: General comparison between VoithSchneider Propeller and screw propeller

will bring in new applications for

this type of propeller. The Voith

Schneider Propeller is based on an

invention by Ernst Schneider dating

from 1925. The Voith company took

up the idea and, working with the

inventor, brought it to maturity. By

1927, the propeller was sufficiently

advanced for a test boat to be

produced. The idea behind the Voith

Water Tractor and its practical

implementation are associated with

Voith engineer Wolfgang Baer.

Development of the VWT started in

1952.

The following sections describe the

construction of the Voith Schneider

Propeller, the physical principle

behind its operation and examples

of its application. They also de-

scribe recent developments such as

the Voith Cycloidal Rudder and the

Voith Turbo Fin.

The Voith Schneider Propeller

generates thrust by means of pro-

filed blades that project from the

bottom of the ship and rotate about

a vertical axis. The blades are

mounted in a rotor casing that is

flush with the bottom of the ship

(Figure 1).

Superimposed on the rotary motion

of the blades about the common

vertical axis is a local oscillating

motion about the respective axis of

each blade's shaft. To generate the

oscillating motion, a kinematic

mechanism is used to control the

blades relative to the blade circle

tangent as they revolve as a result,

directional thrust is obtained.

Since the VSP simultaneously

generates propulsion and steering

forces, there is no need for addi-

tional appendages such as pro-

peller brackets, rudders, pods,

shafts etc.

A significant difference between

the Voith Schneider Propeller and

the screw propeller is the direction

of the axis of rotation relative to the

direction of thrust. In the case of

screw propellers, the axis of rota-

tion and the direction of thrust are

identical with the VSP they are

perpendicular to one another

(Figure 2).

Thus the Voith Schneider Propeller,

has no preferential direction of

thrust and allows infinite variation in

the magnitude and direction of

thrust.

Figure 3 shows a 3D-CAD illustration

of a type R5 Voith Schneider Pro-

peller. The sectioned view (Figure 4)

illustrates its construction.The en-

ergy required to generate the thrust

is supplied to the rotor casing (1) via

the flanged-on reduction gear (7) and

the bevel gear (6). Gland bearings

or special roller bearings are used

to support the blade shaft. The rotor

casing is axially supported by the

thrust plate (10) and centered radi-

ally by the roller bearing (11). Due

to the kinematic system (3), the

blades (2) perform an oscillating

344

motion. The amplitude and phase

of the blades' motion is determined

by the position of the steering cen-

ter and hence the magnitude and

direction of thrust are varied by

means of the control rod (4).

The control rod is actuated by two

orthogonally arranged servo motors

(5). The propulsion servo motor is

used to adjust the pitch for longitu-

dinal thrust (forward and reverse

motion of the ship). The rudder

servo motor is used for transverse

thrust (motion to port and starboard).

The two servo motors permit steer-

ing according to Cartesian X/Y coor-

dinates (identical with the principal

axes of the ship), controlled changes

in thrust are possible via the thrust-

free condition ("from zero"). For ex-

ample, its direction can be changed

from full ahead to full astern at a

constant speed of rotation without

creating disturbing transverse

forces.

The division into propulsion thrust

and steering forces, i.e. steering

according to Cartesian coordinates,

makes handling the ship an easily

understood and user-friendly pro-

cess for the helmsman.

Fitting the Voith Schneider Propeller

with mechanical controls for the

servo motors and an oil pump (12)

flanged to the input gear results in

a self-contained propulsion and

manoeuvring system which, apart

from the torque input, requires no

other source of power.

The step-less nature of the con-

trollable pitch Voith Schneider

Propeller, which is not direction-

dependent, is made possible by a

technically sophisticated kinematic

system. Various mechanical kine-

matic systems and hydraulic blade

actuating systems were developed

and used in the course of develop-

ment [1]. The current generation of

VSPs is fitted exclusively with the

robust crank-type kinematic system.

Figure 5 illustrates the kinematic

principle of the VSP.

If the centre of the lower spherical

bearing (steering centre) is at

the centre of the rotor casing, the

blades are not angled relative to

the tangent to the blade circle

(Figure 6a). If the lower spherical

bearing is moved away from the

centre of the rotor casing by the

actuation of one or both servo mo-

tors and the lever action of the

control rod, the blades are set at

an adjustable angle to the tangent

of the path as they revolve.

The maximum angle of attack of the

blades increases with the excentric-

ity. Since the blades are very largely

balanced, that is to say the result-

ant force due to the hydrodynamic

effect and inertia acts in the region

of the extended shaft axis, the

excentricity can be varied very

quickly and with little power from

the servo motors, thanks to the

considerable leverage effect of the

control rod (Figure 5).

Figure 3: VSP type R5, (3D-CAD drawing)

Figure 4: Sectioned view of type R5 Voith Schneider Propeller

Figure 5: Kinematic principle of theVoith Schneider Propeller

This technical solution is the basis

for the rapid and sensitive variation

in thrust of Voith Schneider Pro-

pellers. For reasons of design, the

mechanical excentricity, i.e. the

position of the lower spherical

bearing (Figure 5) is very much

less than that of the position of the

hydrodynamic steering centre N

or N', which will be explained below

(Figure 7).

Due to the controllable pitch of the

Voith Schneider Propeller, it can be

operated at a constant speed.

However, it is customary to vary the

speed and pitch to optimize energy

utilization. Voith Schneider Pro-

pellers are currently available for

input power up to 4 100 kW. The

blade orbit diameter varies within

a range from 1.2 m to 3.8 m. VSPs

are manufactured with four, five or

six blades.

The blades of the Voith Schneider

Propeller move along a circular

path while simultaneously perform-

ing a superimposed pivoting mo-

tion.

The perpendiculars of the chords

of the profiles intersect at a single

point, the steering centre N, as the

blades revolve. Figure 8 shows the

movements of the blades a) for an

observer standing on the propeller

and moving with it and b) for a sta-

tionary observer.

The excentricity e – also referred to

as pitch – of the Voith Schneider

Propeller is defined as:

The pitch of the Voith Schneider

Propeller can be varied within a

range e _< 0.8. Propellers with a

pitch e > 1 are known as trochoidal

propellers. The Kirsten-Boeing

propeller is a special case, with

a pitch of e = 1.

e = OND/2

Figure 7: Velocities at the blade in zero-thrust condition

The hydrodynamic principle of thrust generation

Figure 6: a) Centre of the kinematic system is identical to the centre of the rotor casingb) Excentricity between the centre of the kinematic system and the centre

of the rotor casing

a) b)

The advance coefficient (λ) of the

VSP is the ratio of the inflow veloc-

ity of the propeller (VA) to the circum-

ferential velocity u of the blades (u):

The circumferential velocity u at the

blade circle, with rotor speed (n) and

blade orbit diameter (D), is given by:

The motion of the blade relative to

a stationary observer, as illustrated

in Figure 8 right, arises from the

superimposition of the rotary move-

ment and a straight line represent-

ing the forward motion of the ves-

sel. The blade follows a curve of a

cycloid. The rolling radius of the

cycloid is λ*D/2. In one revolution,

the propeller travels a distance

λ*D*π in the direction of motion of

the ship. Because the blades travel

along a cycloidal path, the Voith

Schneider Propeller is also referred

to as a cycloidal propeller.

Figures 7 and 8 illustrate the inflow

conditions in the zero thrust condi-

tion. In each angular position, the

water flows in at a zero lift angle,

i.e. there is no hydrodynamic lift.

The drag for the profiles are negli-

gible in these analyses.

To generate thrust, the blades are

set at an angle λ relative to their

path. To achieve this, the steering

centre is adjusted from N to N'.

Because the water flows in at an

angle of attack λ, there is a hydro-

dynamic lift force (A) and drag force

(W) on the blade. The drag force

has two components: the induced

drag and the profile drag. Figure 9

illustrates the generation of thrust.

The steering centre is varied by

means of the kinematic system

(Figure 5).

The VSP employs a two-stage

thrust generation. As they revolve,

the blades produce forces in the

desired direction of thrust both in

the forward and rearward half of the

rotor. Figure 10 shows individual

blade positions that contribute to

thrust generation. Since the profiles

are moving in opposite directions

in the front and rear halves of the

rotor, the VSP gives rise to hydro-

dynamic effects comparable to the

interactions familiar from contra-

rotating propellers [3].

Figure 11 shows the forces acting

on the propeller in selected blade

positions. There is continuous vari-

ation in the lift during each revolu-

tion owing to the non-stationary

inflow to the propeller blades. The

force-components acting trans-

versely to the desired direction of

thrust cancel each other out, while

the force-components in the direc-

tion of thrust add up over the cir-

cumference of the propeller.566

Figure 8: Illustration of law of intersecting perpendicularsand the cycloidal path of the VSP

Figure 9: Forces on the blade for two angular positions

λ =VA

u

u = π . D . n

a) b)

Figure 12 shows the lift conditions

as a function of the cycloidal path

for a stationary observer.

The physical principle involved in

the generation of thrust by the Voith

Schneider Propeller is that of hy-

drodynamic lift. Thrust generation

differs in a fundamental way from

that represented by the flow con-

ditions of a paddle-wheel blade,

where resistance forces are the

decisive factor in thrust generation.

The thrust of the propeller is per-

pendicular to the line ON (in bollard

pull conditions) or to the line NN'

(in open water condition). By shift-

ing the steering centre N or N' it is

possible to produce thrust in any

direction.

Figure 13 shows the effect of

changing the steering centre N'.

If it is moved toward the centre of

the rotor from one particular ob-

served starting point (Figure 13a),

for example, the thrust is reduced

(Figure 13b). Giving the steering

centre a negative value x reverses

the direction of thrust (Figure 13c).

Simply by adjusting the steering

centre, it is thus possible to reverse

the thrust – without suffering the

effects of unwanted transverse

forces.

The zero-thrust condition can be

selected at any time, making the

ship very safe to handle.

Voith Schneider Propellers operate

at very low number of revolutions –

only about 25 % of the number of

revolutions of screw propellers of

comparable size and power. The

reasons for the low speeds can be

summarized as follows:

� In certain installation conditions,

the rectangular swept area of a

VSP is approximately twice as

large as that of a screw propeller

(Figure 14).

Figure 10: Blade positionsfor thrust generation

Figure 11: Forces on the blade in various angular positions

Figure 12: Lift generation at a blade as a function of the cycloidal path

788

N’

N’ N’

Figure 13: Influence of the position of the steering centre N’on the direction and magnitude of thrust (a-f)

a) b) c)

N’

N’N’

d) e) f)

� The blades are arranged at the

outer periphery of the rotor. The

resulting inflow due to the rota-

tion of the rotor and the speed

of the ship is constant over the

vertical length of the blades. With

screw propellers, the inflow in-

creases with the radius of the

propeller.

� The flow conditions at the blade

are non-stationary. They permit

larger effective angles of attack

without flow separation [4].

� The VSP generates the thrust

in two stages – in the front and

rear half of the rotor – in a man-

ner similar to contra-rotating

propellers (Figure 10).

The low speed is associated with

high torques, which call for robust

design, although there is the disad-

vantage of greater weight.

The advantages of the low speeds

are:� Long service life, especially for

the bearings and seals.

� Reduced vulnerability to obsta-

cles such as driftwood and ice.

The blade generally strikes such

obstacles with its leading edge,

which means that the blade then

has the maximum moment of

resistance relative to the direc-

tion of attack of the applied

force.

� Low hydroacoustic signatures.

� Components with very high

safety factors.

Figure 14: Comparison of the swept areafrom a Voith Schneider Propeller and froma screw propeller at a given draught

. λ

T0,5.ρ.D.L.u2kS =

kD

4.Mρ.D2.L.u2kD =

T

ρ.n2.D3.LkT =

Mρ.n2.D4.L

kQ =

kS

λ . πJ =

kT = 0,5.π2.kS

kQ = kD .π2

4

ηO =2.π

. JkD kS

ηO =

Voith definition Coefficients byanalogy with screwpropellers

Conversion

Advance coefficient

Thrust coefficient

Torque coefficient

Open-water efficiency

Circumferential velocity of VSP blades

VAπ.n.D

λ =n.D

J =VA

u = π . n . D

Table 1: Hydrodynamic coefficients for the VSP

To illustrate the effect of rotational

speed on the characteristics of the

VSP, an analogy may be drawn with

the diesel engine (low-speed, medi-

um-speed and high-speed). There

too, rotational speed has a decisive

effect on the technical parameters.

The hydrodynamic characteristics

of Voith Schneider Propellers are

represented by dimensionless coef-

ficients which, as a result of the

historical development of the sys-

tem, differ by constant factors from

those of screw propellers. A brief

summary and corresponding con-

version factors to the coefficients

for the VSP, based on a comparison

with screw propellers, are given in

Table 1. In the dimensionless repre-

sentation, it is useful to incorporate

the blade length L into the corre-

sponding coefficients for thrust and

torque.

The Reynolds number for Voith

Schneider Propellers, based on the

mean chord length c of a profile, is

defined as follows:

where n is the kinematic viscosity.

Owing to the low number of revo-

lutions of Voith Schneider Pro-

pellers, the Reynolds number ob-

tained for a model propeller in pro-

pulsion tests is relatively low. It is

therefore necessary to correct the

results obtained with the model,

and this can be done with meas-

ured values obtained by the Ham-

burg Ship Model Basin (HSVA) [5]

or with validated correction factors

obtained more recently by Compu-

tational Fluid Dynamics (CFD).

The hydrodynamic properties of

Voith Schneider Propellers are

primarily influenced by the following

parameters:

� Blade angle of attack during

revolution� Profile geometry� Ratio of chord length c to blade

circle diameter D, (c/D)� Relative thickness of the profile� Blade shaft position� Ratio of blade length L to blade

orbit diameter D, (L/D)� Shape of blade outline� Design of the blade ends

With Voith Schneider Propellers,

the ends of the blades can be op-

timized in a technically simple and

very effective way (by using end

plates or making the ends elliptical

or swept back for example) to re-

duce the induced drag. Figure 15

shows a VSP blade with an end

plate.

Figure 16 shows as example an

open water diagram for a modern

Voith Schneider Propeller. The

propeller has been optimized for

these conditions.

. VA2 + u2Re =

cν

Hydrodynamic characteristics of Voith Schneider Propellers

Figure 15: VSP bladewith end plate

91100

0,8

0,6

0,4

0,2

00 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9

λ

k S, k

D, η

ο

ηο

KD

KS

Selected results from model scale

tests are shown in Figures 17, 18

and 19 [6]. The measurements

were obtained with a model pro-

peller on which the ratio of blade

length to blade orbit diameter is just

L/D = 0.5 and the ratio of chord

length c to blade circle diameter is

c/D = 0.176. The major differences

between this model propeller and

the modern VSP are in the adjust-

ment of the blades, the blade pro-

file, the relative blade length and

the relative profile thickness. Higher

efficiency is achieved with modern

VSPs.

The thrust coefficients (Figure 17)

and figures for efficiency (Figure

18) are a function of the advance

coefficient λ and pitch e. There is

a qualitative shift in the coefficients

as a function of λ and e, as is famil-

iar from screw propellers with vari-

able pitch. As the pitch increases,

so does efficiency.

The effect of the number of blades

is illustrated in Figure 19. The

smaller the number, the higher the

efficiency. On today's VSPs, the

number of blades is much less

significant since the hydrodynamic

interactions between the blades

on the front and rear halves of the

rotor are reduced by modification

of the blade angle curve.

The profiles of Voith Schneider

Propellers are optimized for each

particular application. On a VWT,

the bollard pull is optimized. High-

lift profiles are therefore used on

these ships. These correspond

very largely to HSVA profiles [7]

but have a modified leading and

trailing edge. On VSPs optimized

for conditions in open waters, con-

vex blades are often used. On

these propellers, the relative profile

thickness is less than on tugs.

0 0.2 0.4 0.6 0.8 1.0

0.8

0.6

0.4

0.2

0

λ

ηο

e = 0.4

e = 0.6e = 0.5

e = 0.7e = 0.8

e = 0.9

e = pitch

Figure 16: Open-water diagram of a modern5-blade Voith Schneider Propeller; Re = 5.9106 to 7.3 106; L/D =1.0; c/D =0.18

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0.70.60.50.40.30.20.1

0

λ

ηο

e = 0.4

e = 0.5e = 0.6

e = 0.7e = 0.8

e = 0.9

e = pitch

Figure 17: Thrust coefficient of a 6-blade model propeller as a function ofpitch e, Re = 1.2 105-2.1 105 [6]

Figure 18: Open water efficiency of a6-blade model propeller as a functionof pitch e, Re = 1.2 105-2.1 105 [6]

VA/U = 0,8 VA/U = 1,0

VA/U = 0,0 VA/U = 0,4

KSy

KS

x

-2,0 -1,5 -1,0 -0,5 0 0,5 1,0 1,5 2,0

1,0

0,5

0,5

1,0

1,5

2,0

0,90,80,70,60,50,40,30,20,1

00 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9

λ

k S, η

ο

ηο (2-blade)

ηο (6-blade)

ηο (3-blade)kS (6-blade)

kS (3-blade)

kS (2-blade)

The side thrust of Voith Schneider

Propellers increases with the in-

crease of the advance coefficient.

Figure 20 shows a corresponding

diagram for various advance coeffi-

cient and steering angles. As the

advance ratio increases, that is to

say as the speed of the ship in-

creases and the propeller speed

remains the same, the steering

forces also increase, as do the

torques. Because the VSP is ad-

justable, it is possible to achieve

a high steering force by means of

a very rapid change in pitch.

For tests with models at towing

tanks, Voith Turbo Marine can sup-

ply model propellers with 5 or 6

blades and diameters of 160 mm

and 200 mm.

As with the calculation of flows

around screw propellers, various

methods have been developed

for Voith Schneider Propellers:

� Simple calculation methods

based on the theorem of mo-

mentum and simple, steady-state

methods of hydrofoil theory [8].

These methods are simple to

manipulate but yield inaccurate

values when the pitch is rela-

tively large and do not allow

assessments of local hydrody-

namic values, such as pressures

and forces as a function of the

angle of revolution.

� Methods based on the extended

lifting line theory [9],[10], with all

the free vortices moving at a

constant velocity and exclusively

in the direction of inflow. Variable

inflow in the direction of the

chord is not taken into account.

It is possible to calculate local

forces and torques.

� Discrete-time vortex lattice meth-

ods make it possible to allow for

variable inflow in the direction of

the chord and for the steady-state

nature of the flow [11]. The posi-

tion of the free vortices is calcu-

lated for each time step.Accuracy

is comparable with that of vortex-

lattice methods for screw propel-

lers [12]. One ad vantage is the

small amount of computing time

required, relative to the capacity

of today's computers. On the

other hand, there is the disad-

vantage that viscous effects can

only be taken into account by us-

ing the outflow condition formu-

lated by Kutta and Joukowski,

with global corrections.

� Calculation methods which in

volve solving the Reynolds-aver-

aged Navier-Stokes equations

(RANSE). By adapting commer-

cial codes for solving the RANSE,

it is possible to calculate flows

around Voith Schneider Pro-

Figure 20: Effect of advance ratio λ on the steeringforces of a Voith Schneider Propeller

Figure 19: Thrust coefficient and efficiency of aVSP model propeller as a function of the numberof blades, Re = 1.2*105-2.1*105 [6]

111122

pellers very accurately. There is

very good agreement between

the calculations and measure-

ments. This method is also re

ferred to as CFD (Computational

Fluid Dynamics).

A brief description of how the flow

around Voith Schneider Propellers

is calculated by solving the Reyn-

olds-averaged Navier Stokes equa-

tions is given below. The flow

around Voith Schneider Propellers

is calculated by solving the Reyn-

olds-averaged Navier-Stokes equa-

tions. Turbulent effects are taken

into consideration by using state

of the art turbulence models. Voith

uses the COMET Software.

It is based on the Finite Volume

Method, which ensures conserva-

tive handling of all flow variables.

A detailed description of the theory

is given in [13]. Figure 21 shows

one example of a mesh for solving

the RANSE. It divides the flow

volume around a Voith Schneider

Propeller into discrete elements.

Figure 22 shows a calculated pres-

sure distribution. This shows that

high levels of thrust are generated,

especially in the second half of the

rotor. Although the effective angles

of attack should be smaller in the

second half of the rotor owing to

the induced velocities of the first

half, the pressure distributions tell

a different story. The reason for this

is to be found in the approximately

30 % shaft position of the VSP

blade.

The higher velocities in the region

of the profile's trailing edge in the

second half of the rotor give rise to

high lift and even pressure distribu-

tion, as can be seen especially in

Figure 23. It shows the calculated

pressure distribution for a Voith

Schneider Propeller with a nozzle

plate. Like the nozzle for screw

propellers, the nozzle plate has the

effect of increasing thrust at bollard

pull conditions.

This section describes examples

of the use of Voith Schneider Pro-

pellers on VWT´s, double-ended

ferries and mine countermeasure

vessels. Examples of other applica-

tions are given in [1].

Hydrodynamic calculation methods for Voith Schneider Propellers

Figure 21: Global calculation mesh and detail of the profile meshfor solving the RANSE, applied to a Voith Schneider Propeller

Figure 22: Calculated pressure distribution at the blades of a VSP

Ships with Voith Schneider Propellers

Figure 24: Speeds in which assistance may be required

6.1 Voith Water Tractor (VWT)

Ship-handling operations are an

important link between land and

sea transportation.

Ship-handling tugs are increasingly

playing a key role in ensuring the

safety of incoming merchant ves-

sels right up until they are able to

tie up at the terminal jetty. New dan-

gers and risks due to the increasing

size of seagoing ships, the huge in-

crease in the transportation of haz-

ardous substances such as crude

oil, LNG and chemicals, and narrow

channels in many harbors have

made safety in ship assistance a

decisive factor in risk assessment

as applied to terminals and the en-

vironment.

In the currently understood sense,

assistance to ships is necessary

when a freighter's own systems

cannot provide sufficient manoeu-

vrability at low speed. It is also re-

quired in emergencies when, due

possibly to the failure of the steer-

ing or propulsion system, a seago-

ing ship goes out of control and

poses a risk to itself, to other ship-

ping, to installations on land and to

the environment.

Figure 24 illustrates when and

where assistance from the ship-

handling tug may be necessary.

The efficiency of a ship's rudder in-

creases approximately in proportion

to the square of the speed. Con-

versely, its steering capacity falls

very rapidly as the speed of the ship

decreases. Depending on the size

and type of ship and on wind, and

current conditions or conditions in

a particular area, it may be neces-

sary to provide assistance at rela-

tively high speeds of as much as

6-8 knots. The Voith Water Tractor

(Figure 25) covers all the above

aspects. Thanks to the two possible

methods of operation – direct and

indirect – the VWT can assist a ship

safely over a wide range of speeds.

Its introduction has fundamentally

eliminated the dangers associated

with stern-propulsion tugs when used

to assist ships. The distinguishing

feature of the Voith Water Tractor

is that the propellers are located in

the bow section, where they are

protected by an integrated nozzle

plate. Other important elements are

the aft stabilising fin with the towing

gear mounted above it, and the cen-

trally mounted, logical controls

(Figure 26).

Bow steering – i.e. location of the

propellers in the bow section – was

chosen for the Voith Water Tractor

� to enable the interactive hydro-

dynamic forces between the tow

and the tractor to be counter-

acted, even at high speeds� to obtain a stable equilibrium

between the two forces acting on

the tractor – propeller thrust and

towing force

Tugs fast forward have a relatively

low efficiency, and this falls as the

speed at which assistance is pro-

vided increases. One reason for this

Figure 23: Pressures at a VSPwith guard plate

131144

is that a considerable proportion of

the tug's power output is required to

maintain its own speed. Another rea-

son is that the force supplied by the

tug is applied at or close to the hy-

dro-dynamic centre of gravity of the

seagoing ship, without any effective

leverage. However, in some ship-

ping areas it is impossible to avoid

using a tug fast forward. When

making fast, the interactive forces

between the seagoing vessel and

the ship-handling vessel are ex-

tremely critical.

There can be significant negative

pressure due to the hydrodynamic

interactions between the ships'

hulls, especially when the two ves-

sels are close together. In addition,

there is a risk to the stability of the

ship-handling vessel from the trans-

verse component of the tow-rope

pull. With its propulsion arranged

forward, a Voith Water Tractor can

carry out this assistance manoeu-

vre safely. This was demonstrated

by systematic tests on models car-

ried out in the 1960s by the Ham-

burger Ship Model Basin

(HSVA) [14].

An important consideration when

providing assistance to a ship is

the protection afforded to the pro-

pellers from unwanted contact at

the side and from bottom contact.

The nozzle plate arranged under

the tips of the propeller blades to

increase propeller thrust under

bollard pull conditions serves si-

multaneously to provide them with

reliable protection.

Another important aspect is the

redundancy of the propulsion sys-

tem, which is intended to eliminate

the need to break off assistance im-

mediately if one of the drivelines

fails. In this context, system redun-

dancy means not just the presence

of two propulsion systems but also

requires independent operation of

these systems.

It is the special feature of the Voith

Schneider Propeller with its ability

to supply variable thrust according

to X/Y coordinates that are identical

with the ship's coordinate system

which opens up this option.

The steering characteristics of the

Voith Schneider Propellers ensure

that the Voith Water Tractor can be

steered in an equivalent way with

one or two propellers, i.e. there is

a fall-back option but no change in

the handling characteristics.

Thanks to the forward position of

the propulsion system, the towing

gear on the Voith Water Tractor can

be positioned well aft so that the

two main forces – propeller thrust

and tow-rope pull – acting on the

ship are directed away from its cen-

tre of rotation, and a constant sta-

ble equilibrium is established be-

tween these forces – a significant

safety feature compared with stern-

propulsion tugs.

Figure 25: Escort Voith Water Tractor "Tan‘erliq", 2 VSP 36 GII/270, P = 2 x 3460 kW

Figure 26: Characteristic features of the Voith Water Tractor

People are a significant component

in any safety system. Experience

shows that a very high percentage

of accidents are due to human er-

ror. The way in which people oper-

ate safety systems is therefore very

important. The steering provided by

the Voith Schneider Propeller meets

this safety requirement. The logical

arrangement of the control on the

bridge permits intuitive steering in

any situation. There is no need for a

change in approach when switching

from operation fast forward to oper-

ation fast aft, from the direct to the

indirect method or from one to two

propellers. This prevents serious

errors due to stress

in emergency situations.

With its relatively large skeg pro-

peller guard and nozzle plate, the

Voith Water Tractor is equipped with

two hydrofoil systems that have a

damping effect on its movements

due to swell. The skeg reduces the

rolling motion and the guard plate

damps pitching and heave motions.

The vertically arranged, rotating

VSP blades likewise have a damp-

ing effect on the swell-induced

motion of the ship.

The skeg and the active VSP

blades of the Voith Water Tractor

ensure good directional stability.

Since all seagoing ships are driven

and steered from the stern, it

makes the most sense to place

an assistance vessel at the ship's

stern when replacing or supple-

menting these systems. Thanks to

the equilibrium between the tow-

rope pull and the propeller thrust,

the Voith Water Tractor can operate

behind the ship while secured to

the tow-rope.

If the VWT has to produce forces

opposed to the direction of motion

of the seagoing ship while in this

position, the VSPs are subjected

to a negative approach flow. They

then operate with a negative ad-

vance coefficient. The propellers

may also be subjected to severe

additional loads by the propeller

wash of the ship to be manoeu-

vered. Such complex flow condi-

tions pose relatively few problems

for the VSP because:

� the VSP has a vertical axis, and

the rotating propeller wash has

less effect on the inflow to the

blades than in the case of inter-

action between two screw

propellers

� the VSP’s large wash area evens

out such effects

� the pitch control allows precise

adaptation to a variable

approach flow and thus prevents

overloading of the propulsion

system

This enables engine power to be

converted immediately into active

braking force in any phase. Here

too, the operating redundancy of

the systems guarantees safety,

QK

V [kn]

PQ

e2

e1

GB

V [kn]

FPPQQ

PLLLWQ

Ib Ia

FQ FenderAP

C

FS

L

Figure 27: Forces in the direct method - pushing a seagoing vessel

151166

Figure 29: Stability and remaining freeboard in the direct method

1,50

1,45

1,40

1,35

1,30

1,25

1,200 5 15 25 35 45 55 65 75 85

Free

boar

d [m

]

Alpha [*]

1,55

0 10 20 30 40 50 60 70 80 90

70

60

50

40

30

20

10

0

Alpha [*]

FS-total [t]-0.00knFS-total [t]-1.00knFS-total [t]-2.00knFS-total [t]-3.00knFS-total [t]-4.00knFS-total [t]-5.00knFS-total [t]-6.00kn

For

ces

[t]

ensuring that assistance operations

are not put at risk if one of the pro-

pulsion systems fails, even at high

speeds.

For steering at low speed, i.e. to

supplement the rudder force of

the seagoing ship, the installed

power of the Voith Water Tractor

is employed via the thrust of the

propellers – the direct method.

The forces that arise while pushing

a seagoing ship are illustrated in

Figure 27.

While the optimum position of the

Voith Water Tractor for pushing at a

speed of 0 is 90° to the axis of the

seagoing ship, as would be ex-

pected, this changes with increas-

ing speed, and the angles of inci-

dence become smaller (Figure 28).

The diagrams in Figures 28 and 29

are based on the following ship's

parameters:

� Lwl = 33.50 m

B = 10.50 m

Thull = 2,8 m

D = 4,2 m

Disp. = 598 t

GM = 210 m

� 2*VSP 32R6/210

PB = 2*2450 kW

Due to the hydrodynamic action of

the fin, the Voith Water Tractor is ca-

pable of maintaining the maximum

steering force from a speed of zero

to about 6 kn, the maximum practi-

cable speed for the direct method.

Whereas the Voith Water Tractor

leans into the flow initially with in-

creasing speed, as would be ex-

pected, leading to a reduction in

the freeboard, the ship is already

beginning to right itself at a speed

of about 4 kn (Figure 29). This ef-

fect is governed by the high trans-

verse propeller thrust required. At

higher speeds in the direct method,

therefore, the freeboard increases

to beyond that when the ship is

Figure 28: Steering forces in the direct method

Ship Assistance with Voith Water Tractor

C

FS

LC

FS

LV = 0 - 2 : kn

C

FS

L α = 90°

V = 0 - 2 : knC

FS

L

α = 60°V = 0 - 2 : kn

C

FS

L

α = 50°

α

α C

FS

LC

FS

LV = 0 - 2 : kn

C

FS

L α = 80°α

floating upright. The assistance ma-

noeuvres can therefore be carried

out with a high degree of safety

within the speed range outlined.

Figure 30 shows the optimum push

positions of a Voith Water Tractor

as a function of speed.

The direct method cannot be used

at higher speeds because the force

required to drive the tractor itself

reduces the tow-rope pull accord-

ingly and, depending on the speed,

there is only a reduced tow-rope

force available. The Voith Water

Tractor therefore marked the intro-

duction of the indirect method.

In this method, the hydrodynamic

lift forces of the ship's hull and the

fin are introduced into the ship via

the towing rope (Figure 31). In the

indirect operating method, the pro-

pellers are essentially used only as

steering gear to position the Voith

Water Tractor's hull at the correct

optimum angle of attack and to

adjust the port- or starboard-side

steering position relative to the

ship. As a result, the maximum

steering or braking forces are ef-

fectively generated to meet the re-

quirements for assistance [15]. In

this application, a heeling moment

on the Voith Water Tractor is con-

sciously accepted and increases as

the square of the speed. The design

of a Voith Water Tractor must take

account of this moment-related re-

quirement by optimizing the princi-

pal dimensions, the shape parame-

ters, weight distribution, dynamic

stability and arrangement of the

towing winch.

Serious accidents with tankers have

led to a demand for safe escort

vessels.

Following the most severe tanker

accident to date, that of the "Exxon

Valdez" off Alaska, safe escort

ships were prescribed by law in

hazardous waters such as Prince

William Sound, the Strait of Juan

de Fucca, San Francisco Bay

etc. All tankers with a dead weight

of above 5,000 tDW must be es-

corted by a suitable tug [16].

In many sea areas where escort

ships are required, such as Valdez,

Alaska and Placentia Bay, New-

foundland, Canada, attempts have

been made to describe the complex

behavior of the Voith Water Tractor

escort together with a tanker. In

various risk scenarios involving the

parameters of the largest tankers

entering these areas and extreme

weather conditions, permitted turn-

ing circles were laid down as limits

within which the tanker had to be

brought under control if the steering

or main engines of the tanker failed

[17], [18].

In Scandinavia, on the other hand,

the maximum steering forces to be

produced by an escort tug to se-

cure an at-risk tanker are defined

in complex risk assessments for

individual terminals. Tugs designed

for such escort duties are given an

"Escort Rating Number (n, v)",

Figure 30: Optimum push positions of a Voith Water Tractor as a function of speed

v [kn]

FB

FS

Fy

FT

FTy

FTxFx

Tx

Ty

T

α

Figure 31: Forces acting on a Voith Water Tractor in indirect method

171188

which expresses the maximum

steering force (n) in tonnes at an

escort speed (v) in knots [19]. As

with the requirement for the maxi-

mum time to put the helm over from

hard to port to hard to starboard,

the escort tug must be able to

change position within 31 seconds.

If the actual manoeuvring time from

one position to the opposite one

exceeds the prescribed value, the

"Escort Rating Number" is reduced

accordingly. The area criterion of

the leverarm curve is decisive for

the assessment of stability. Be-

tween equilibrium and the maxi-

mum heel of 20°, the area of the

leverarm curve under the righting to

heeling lever must be at least 25%

above the value for the area of the

heeling lever. Moreover, the total

area of the righting levers up to the

critical inflow opening, or at most

40%, must be 40% greater than the

area of the heeling levers [19].

The escort tug must also have a

"self-tension" towing winch so that

it can handle the considerable over-

loads during dynamic oscillation of

the tow-rope forces at sea. If the

tow-rope force is more than 50%

of the breaking strength of the tow-

rope, the towing winch must auto-

matically release it. If the force falls

below this value again, the winch

must draw in the rope to its original

length. The breaking strength of the

tow-rope must be at least 2.2 times

the average maximum measured

tow-rope force.

There are many different ways of

optimizing the system to increase

the maximum steering forces, by

maximizing the under water lateral

area and the transverse force coef-

ficient of the tug through variation

of its shape [20].

The steering forces of a Voith Water

Tractor can be maximized by:

� choosing high-lift profiles for

the fin

� using hydrodynamically

optimized appendages on the

ship's hull and end plates on

the fin

� the position of the A-frame rela-

tive to the hydrodynamic point of

action of force

� the angle of attack of the ship

relative to the towing direction

� balancing the moments about

the A-frame [21].

v = 0 knv = 2 kn

v = 4 kn v = 5 kn

v = 6 knv = 8 kn v = 10 kn

Forces transverse [t]

For

ces

long

itudi

nal [

t]

-160 -120 -80 -40 0 40 80 120 160

100

50

-50

-100

-150

-200

Figure 32: "Butterfly" diagram for Voith Water Tractorescort "Ajax", Østensjø Reederi A/S, Norway

Escort Voith Water Tractors

VTF

without VTF

0 50 100 150 200

50

0

-50

-100

-150

FB

[kN

]

FB [kN]

The transverse thrust component

of the Voith Schneider Propeller re-

quired to ensure equilibrium should

be as small as possible. The ship's

design must provide the Voith Water

Tractor with sufficient stability and

freeboard to enable it to safely

accept the maximum tow-rope

forces. The results of optimizing the

ship in this way can be depicted by

a "butterfly" diagram [22]. Figure 32

shows by way of example the steer-

ing and braking forces that can be

achieved over the entire speed

range of the Escort Voith Water

Tractor "Ajax" [21]. The principal

data for this ship are as follows:

� Lwl = 38.20 m

B = 14.20 m

Thull = 3.8 m

D = 6.25 m

Disp. = 1276 t� GM = 2.98 m

2*VSP 36GII/270

PB = 2*3460 kW

The serious accident involving the

nker "Aegean Sea" at the entrance

to the Spanish port of La Coruna

was one of the reasons why the

Voith Water Tractors used in Spain

are designed for escort duties. The

same applies to the water tractors

used at Southampton, Cork, Ant-

werp, Ravenna and Venice. To meet

the requirements for high steering

forces while retaining the compact

dimensions of a harbor tug, Voith

has developed the Voith Turbo

Fin (VTF). For this purpose, the

familiar rotor rudder system [7] was

adapted to the fin on the Voith

Water Tractor. On the nose of the

fin profile there is a rotating cylinder

which can be activated by the

captain as and when required in

indirect operations. By selectively

altering the boundary layer, flow

separation is delayed and the steer-

ing force of the entire VWT is in-

creased by up to 18%, allowing it

to be positioned at greater angles

of attack (Figure 33a, b). The diam-

eter of the rotating cylinder is about

50% of the maximum thickness of

the fin profile. To get the best re-

sults from the VTF, the velocity of

the cylinder's circumference should

be about 4 times the ship's speed.

The captain activates the Voith

Turbo Fin by means of a pushbut-

ton at the helm. When he turns the

wheel to generate steering forces

to port or starboard, the cylinder

begins to turn in the corresponding

direction of rotation. With the Voith

Turbo Fin, Voith Water Tractors cor-

responding in size to conventional

harbor assistance tugs for escort

duties can generate steering forces

of over 100 t. This considerably

enhances the multipurpose charac-

ter of these ships.

Figure 33a: Steering and braking forcesat V=10kn with and without VTF

Voith Turbo Fin (VTF)

Figure 33b: Escort Voith Water Tractorwith Voith Turbo Fin

192200

Delta V [%]v-DEF/v-SIN [%]

Fuel-DEF/F-SIN [%]Pb-DEF/Pd-SIN [%]

v, P

b, F

uel [

%]

distance [sm]0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5

100

90

80

70

60

50

40

30

20

"Schlupengat" 4 VSP's, displ.= 4 285 t"Prinses Juliana" 2 Screws, displ.= 4 270 t

Fb

[kN

]

v [kn]0 2 4 6 8 10 12 14

1200

1000

800

600

400

200

0

6.2 VSP Double-Ended Ferries

The steady increase in the propor-

tion of the total costs of a product

accounted for by transportation,

storage and handling has always

exerted enormous economic pres-

sure on the productivity of trans-

portation by water. At an early

stage, seasonal fluctuations in

passenger numbers led to great

interest in carrying commercial

loads such as cars, trucks, heavy

goods and railway wagons.

Transporting such commercial

loads rapidly became a factor in

the profitability of ferry links.

In recent years, in particular, ferries

have become an efficient element

in complex integrated transport

systems. In contrast to the require-

ments of other types of shipping,

ferry links over short distances are

of a completely dynamic nature.

Operations thus have to flow as

continuously as possible, with short

journey times and economically

acceptable propulsion power. The

shorter the distance between ferry

ports, the more significant the

following factors:

� loading and unloading times� the berthing and unberthing of

the ferry� acceleration and deceleration

of the ship in the ferry port

and the less significant the achiev-

able speed in open waters. To keep

to the fixed timetable for every

modern short-distance ferry, every

minute that can be saved in loading

and unloading and manoeuvring at

the ferry port means a reduction in

the required speed in open waters

and a corresponding reduction in

the required propulsion power and

significantly reduced operating

costs. Figure 34 shows the fuel

consumption, installed power and

required speed of a double-ended

ferry in comparison with single-

ended ferries. The comparison is

based on the following parameters:

� loading time: 15 min� manoeuvring time: 2 min� additional manoeuvring time

for single enders: 1 min

Principal data of the double-ended

ferry:

� Lwl = 31.5 m

B = 15.0 m

Thull = 1.6 m

D = 2.60 m

Disp. = 700 t

v = 12 kn� 2*VSP 16KG

PB = 2*470 kW

With their "roll-through" load-han-

dling capability and minimal ma-

noeuvring at the ferry port, double-

ended ferries undoubtedly offer the

best foundation for economic short-

haul ferry operations. The compro-

mise that the shipbuilding engineer

has to make with regard to resist-

ance and somewhat higher power

requirements when designing a

Figure 34: Economic viability of a double-endedferry in comparison with a single ender

Figure 35: Braking forces of a double-endedferry with Voith Schneider Propellers

ship with a double-symmetrical hull

in comparison with a ship that has

conventional stern propulsion is

made good by savings on time and

power during manoeuvring [23]. The

first double-ended ferry with propul-

sion systems that could be rotated

through 360° was the VSP ferry

"Lymington" built in 1938, which was

later rechristened "Sound of Sanda"

and served for more than 50 years

on the River Clyde in Great Britain.

Double-ended ferries with screw

propellers have to compensate for

transverse forces due to wind and

currents during crossings by means

of a drift angle, which leads to

higher drag and the requirement

for additional power. With its spe-

cific thrust characteristic, the Voith

Schneider Propeller is capable of

generating sufficient transverse-

thrust components and compensat-

ing for wind and currents over vir-

tually the entire speed range with-

out the need for the ferry to adopt

a drift angle [23], [24].

The large swept area of the Voith

Schneider Propeller means that the

thrust loading on the propeller is

low and, coupled with its control-

lable pitch characteristic, enables it

to produce extremely high braking

forces (Figure 35).

6.3 Mine Countermeasure

Vessels (MCMV) with VSP

The Voith Schneider Propeller was

first used for military applications in

the early Thirties on the first Type

M1 and M2 minesweepers. By the

end of the Second World War al-

most 120 minesweepers had been

built. The aircraft catapult ships

"Falke" and "Bussard" likewise had

Voith Schneider Propellers as their

main means of propulsion. Thanks

to the positive experience with

minesweepers, military use of Voith

Schneider Propellers in the post-

war period was focused on modern

mine-hunters – mine countermea-

sure vessels (MCMVs).

Owing to the enormous technologi-

cal progress in the effectiveness

and disguising of modern and very

cost-effective sea mines, mine

hunting has become a very danger-

ous and complicated defensive

military operation. MCMVs fitted

with VSPs have a single propulsion

system for operations mine hunting,

for clearing sea mines with me-

chanical, magnetic or acoustic

sweeping equipment and for travel-

ing in open waters to the area of

operations. To clear designated sea

areas, high directional stability

combined with extreme manoeuvra-

bility, good dynamic positioning

ability and very short stopping dis-

tances are required. During mine

hunting, the ship must not emit any

signals to which the sensitive sen-

sors of the mines could respond.

This is a matter of minimizing the

underwater noise caused by the

propeller combined with air- and

structure-borne noise levels from all

sources of noise in the ship, which

can be radiated into the water via

Figure 36: MCMV of the US Navy Ospreyclass under shock test.

Mine Countermeasure Vessels (MCMV) with VSP

212222

the ship's structure. The low operat-

ing speed of the VSP (see Section

3) is a significant contributor to the

acoustically favorable behavior of

the Voith Schneider Propeller be-

cause its sound pressure is propor-

tional to the product ~n3*D4 [25].

The magnetic signature of each

individual component of the ship is

subject to strict controls. The Voith

Schneider Propellers for MCMVs

are manufactured with up to 90%

non-magnetic steels and the mag-

netic components that are required

to enable it to operate are degaused

or magnetically neutralized. During

mine hunting, there is always the

possibility that a mine will detonate

close to the ship. The Voith Schnei-

der Propeller has to withstand such

extreme shock loads, without oper-

ational restrictions 0or major dam-

age (Figure 36).

Over 70 modern MCMVs fitted with

Voith Schneider Propellers are in

use by leading navies worldwide.

7. Voith Cycloidal Rudder

(VCR)

The Voith Cycloidal Rudder (VCR)

is a new type of multi-functional

means to manoeuvre. It represents

an adaptation of the technology

behind the Voith Schneider Pro-

peller to other areas of application.

The VCR is used in combination

with conventional screw propellers

(Figure 37a, b). The basic idea of

the VCR is to modify a VSP with

just two blades in such a way that

it can be used for a dual purpose.

There is a passive mode, in which

the VCR acts like a conventional

rudder, and an active mode, in

which the VCR acts like the tried-

and-tested VSP ([26], [27], [28]).

The two modes are summarized as

follows:

Passive mode

Figure 38 shows the VCR in pas-

sive mode behind a screw pro-

peller. The blades are stationary

and only the rotor casing has been

turned, through about 30°.

Active mode

In the active mode, the VCR acts

just like a VSP. The direction of

thrust is infinitely variable over 360°.

The active mode is used when the

ship is moving at low speed. In this

case, the effects of a passive rud-

der are very slight owing to the

quadratic dependence of the rudder

forces on the inflow speed. At low

speeds, the VCR gives high ma-

noeuvring forces, thus simplifying

the ship's handling and enhancing

its safety.

Voith Cycloidal Rudder (VCR)

Figure 37a: VCR schematic diagram Figure 37b: VCR 3D-CAD drawing

What advantages are there in

using the VCR:

� The ship's rudder can be made

smaller. Ships' rudders are often

over-dimensioned for high speeds

because the required rudder

forces at low speed dictate their

area. With its two modes, the VCR

provides the choice of a smaller

rudder area entailing less drag.

At low speeds, the active mode

ensures manoeuvrability.

� As a result, the ship is highly

manoeuvrable. The VCR allows

all important ship's manoeuvres,

such as forward and reverse

motion, turning on the spot and,

when two VCRs are fitted or in

combination with a bow thruster,

pure traversing manoeuvres as

well.

� In terms of propulsion, the VCR

is a redundant system. If the

main propulsion system fails,

the VCR enables the ship to be

moved safely on its own, pro-

vided that the power supplied to

the VCR is independent of the

main propulsion system.

� Roll motion can also can be

reduced with the VCR. Like a

rudder roll stabilization system

[29], the VCR can damp the

rolling motion of a ship. This is

possible because thrust forces

can be transferred very quickly

from port to starboard in the

VCR's active mode, it is also

possible to reduce the rolling

motion while the ship is

stationary.

The VCR is currently at an ad-

vanced stage of development.

Numerical simulations, model and

full-scale tests have been carried

out. For the full-scale tests, Voith

Turbo Marine has worked together

with the marine educational estab-

lishment (Seefahrtschule) in Leer.

Seefahrtschule Leer operates the

“MS Aurora” as a training ship.

This is a former buoy layer, which

is fitted with two VSPs size 14. For

test purposes, a VSP was con-

verted to use as a VCR, as shown

in Figure 39.

The VCR can be used with advan-

tage on a very wide range of ships,

e.g. ferries, passenger ships, navy

vessels, container ships, offshore

supply vessels and research ves-

sels. The VCR's ability to act as a

redundant propulsion system is

also a way of increasing the safety

of ships carrying hazardous loads.

Figure 39: Voith Schneider Propeller (size 14) converted to a VCRon the training ship “MS Aurora” operated by Seefahrtschule Leer

Figure 38: Passive mode of the VCR

232244

Bibliography

[1] Jürgens, Birgit; Fork, W:

Faszination Voith-Schneider-

Propeller, Geschichte und Technik

[The Fascination of Voith-Schneider

Propellers, History and Engineer-

ing]. Hamburg 2002

[2] Kirsten, F.K.: The Cycloidal

Propeller in Marine Application.

University of Washington, Report

322, 1950

[3] Kracht, A.: Gegenläufige Propeller

[Contra-rotating Propellers], in:

Handbuch der Werften [Shipyard

Handbook], Volume XXV,

Hamburg 2000

[4] Coton, F.N.; Galbraith, A. McD.:

An Experimental Study of Dy-

namic Stall on a Finite Wing.

The Aeronautical Journal, May

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[15] Sturmhöfel, U.; Bartels, J.: Basic

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[16] Oil Pollution Act (OPA 90), Rules on

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[19] Det Norske Veritas, Rules for Ships.

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nathan, S.: New Insights into Voith

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[23] Bartels,J.-E.: Voith-SCHNEIDER

Propulsion Systems for Double-

Ended Ferries. Log´s Ferries `93

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[24] Swaan, W.A.; Hoogerheide, T.:

Propulsion and Manoeuvring of a

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[26] Jürgens, D.: Cycloidal Rudders and

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School "Manoeuvring and Manoeu-

vring Devices", Rome 2001

[27] Jürgens, D.; Moltrecht, T: Cycloidal

Rudder and Screw Propeller for a

very Manoeuvrable Combatant,

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2001, Future Surface Warships,

20 & 21 June, London, 2001

[28] Jürgens, D; Moltrecht, T: Combining

Cycloidal Rudder and Conventional

Fixed Pitch Propeller for Fast Very

Manoeuvrable Double-Ended

Ferries. 1st International Conference

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Molde 2001

252266

122

Voith Turbo Marine GmbH & Co. KG

Alexanderstr. 18

89522 Heidenheim, Germany

Tel. +49 7321 37-6595

Fax +49 7321 37-7105

vspmarine@voith.com

www.voithturbo.com/marine

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