WASUB 3 design report

DELFT UNIVERSITY OF TECHNOLOGY

May 3, 2013

Preface

This report is drawn up for the completion of the third edition of the WASUB project.A project in which a human powered submarine was designed and built with thepurpose to compete in the 12th edition of the International Submarine Races.

The WASUB team would like to thank all participating parties who helpedbring this project to a success. More especially we would like to thank Prof.Dr.Ir.M.L. Kaminski, Dr.Ir. J. Kooijman, Ir. T.J. van Beek, Ir. C. Pouw, Ir. J. Holtrop, H.Ramautar and Dr.Ir. W. Thijs for all their help and advice throughout the project. Wewould also like to thank all of our sponsors without which none of this would havebeen possible.

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AbstractThis report concerns the design of the WASUB 3 submarine. The submarine is de-signed to participate in June of 2013 in the International Submarine Races in theUnited States of America. The WASUB 3 will participate in the one person, onepropeller category.

For the design of the hull, the decision was made to base the shape on twoseparate wing profiles to take into account the different restrictions for the shape inthe xz plane and the xy plane.

The steering of the submarine will be done with the help of a simple but robuststeering joystick. This joystick will control four fins that have enough surface areato steer the submarine sufficiently, but also have minimal resistance in their neutralpositions.

The propulsion of the submarine will be realised with a self designed contra-rotating propeller. A regular pedalling movement was chosen to generate the powerto turn the propeller.

Contents

1 Introduction 31.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 WASUB 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Report build-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 List of requirements 5

3 Hull Design 83.1 Basis equations related to the hull . . . . . . . . . . . . . . . . . . 83.2 Pilot Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2.1 Concept 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.2 Concept 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.2.3 Concept 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.2.4 Pilot position concept selection . . . . . . . . . . . . . . . 9

3.3 Hull components . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.4 Critical Deflection Model . . . . . . . . . . . . . . . . . . . . . . . 10

3.4.1 Hull Shapes . . . . . . . . . . . . . . . . . . . . . . . . . . 113.4.2 Airfoil shape in XZ and YZ plane . . . . . . . . . . . . . . 11

3.5 Emergency exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.6 Materials and Production . . . . . . . . . . . . . . . . . . . . . . . 15

3.6.1 Fibres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.6.2 Resin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.6.3 production process . . . . . . . . . . . . . . . . . . . . . . 16

4 Stability & steering 174.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.2 Analysis of the stability . . . . . . . . . . . . . . . . . . . . . . . . 174.3 Fins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.4 Steering mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.4.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 204.4.2 Way of steering . . . . . . . . . . . . . . . . . . . . . . . . 214.4.3 Pulley system . . . . . . . . . . . . . . . . . . . . . . . . . 224.4.4 Steering rod . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5 Propulsion 245.1 Propeller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.1.1 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.1.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.2 Gear mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

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5.2.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 305.2.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 325.2.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6 Overview 38

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1. Introduction1.1 History

The WASUB team was set up by Francois Geuskens in 2004 after a design-synthesis-exercise at the Faculty of Aerospace Engineering at the Delft University of Technol-ogy. After a year of designing and building the submarine, they were able to competein the 8th ISR where they were the fastest one person propeller driven submarine.After the first WASUB year a new team of TU Delft students continued the projectto compete in the Human Powered Submarine Contest in San Diego, California, thefollowing year. Unfortunately the automatic pilot had problems with compensatingthe roll of the WASUB 2. Due to that problem the submarine crashed and they couldnot finish the contest.In September of 2011 Salomon Brummel and Gijs Bloemen heard about the WA-SUB 1 and WASUB 2 and decided to restart the project. After a year of setting-upthe project again and searching a good team, in September 2012 the WASUB 3 teamstarted officially with the design of the new submarine.

1.2 WASUB 3

The WASUB 3 team is a multidisciplinary team of the TU Delft. The team consistsof 5 maritime technology, 2 mechanical engineering, 2 aerospace engineering and 1civil engineering students. Next to the full-time TU Delft part of the team, the teamis also supported by 4 students of the Netherlands Defense Academy (NLDA), whichhelps the TU Delft team on a part-time basis.The goal of the WASUB 3 team is to break the world record for a one person propellerdriven submarine. The WASUB 3 team wants to reach that goal at the 12th ISR andas a second goal they want to win the ISR. The team decided to design an entirelynew submarine. A new hull, drivetrain, propeller, steering mechanism and safetysystem together with the teams management has led to the next division of the team(Figure 1.1). The blue blocks are students from the TU Delft and the orange safetypart are the students of the NLDA.

The different groups have the responsibilities as shown in the next table 1.1.

Function ResponsibilitiesTeam Manager Final responsibilityTechnical Manager Planning and pilot selectionFinancial Manager Sponsoring and control of the foundation’s financeChief Engineer Responsible for the total design and the integration of the parts designed

by the different subgroupsHull Responsible for the design of the new hullStability Responsible for the stability model and steering (manual and automatic)Propulsion Responsible for the design of the new drivetrain and the new propellerSafety Responsible for the design of the safety systems in the submarine

Table 1.1: Function responsibilities

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Figure 1.1: An illustration of the team build up

1.3 Report build-up

Chapter 2 gives the list of requirements upon which all of the engineers’ choices werebased during the design process. Chapter 3 takes the reader through the process ofthe design of the hull of the WASUB 3. Next, chapter 4 deliberates on the stabilityand steering. The propulsion of the submarine is discussed in chapter 5. Finally inchapter 6 an overview of the entire design is given.

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2. List of requirementsTo ensure that all engineers know at all times what the team is willing to achieve, alist of requirements was set up. This acted as a reference upon which engineers couldbase design choices. These requirements are listed below.

# W/D RequirementGeneral

1 D Must be able to reach a velocity of 7.2 knots over 10 meters with a runup of 75 meters.

2 W Submarine must be stable to assure that a minimal distance is covereduntil the end of the world record.

3 D Pilot must be able to override the autopilot the submarine at all times.4 D Satisfies ISR requirements [1].4.1 D Air tank pressure gauge must be at all times visible for the pilot.4.2 W The submarine be painted with high visibility coloration.4.3 D Must be liquid filled.4.4 D Handle or release mechanism.4.4.1 W Handle or release mechanism marked by 4 square orange patch bearing

the word rescue.4.4.2 D Handle or release mechanism easily accessible from both inside and

outside the submarine.4.5 D Any restraining method (harness, toe clips) must have the release mech-

anism clearly marked.4.6 D Crews face and head areas must be visible to the support and safety

divers at all times.4.7 D Each submarine will carry a white flashing strobe light that is visible for

360 in the horizontal plane.4.8 D All submarines shall carry a high visibility buoy that will release from

the hull and float to the surface when an emergency occurs.4.9 D Maximum width of 2.13 meters; re-attachable parts exceeding this width

are permitted.4.10 D The hull must cover the pilot entirely.4.11 D The pilot must be visible to the safety divers at all times.4.12 D Beyond the use of waxes on the submarines hulls and fins, the use of

drag-reduction material is prohibited. The submarine shall not releaseany type of fluid into the basins waters.

4.13 D Pilot can escape the hull easily within 10 seconds.4.14 D Everybody that goes in to the water must have a diver certificate.4.15 D Must operate entirely beneath the surface of the water.4.16 D Must have a propeller.

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4.17 D The primary air supply shall be carried onboard the submarine, and havethe calculated capacity to contain the air supply for a minimum of onespeed run, plus 150% in reserve capacity for each crew member.

4.18 D Submarine crews are required to monitor their own air supply, and shallnot allow their air supply to fall below 500 P.S.I.

5 D Producible within the given time period with the given materials andresources.

6 W Submarine does not break down during the races.

Stability7 D Submarine must be neutrally buoyant.8.1 W Hull has space for eventual extra weight to be added.8.2 D There has to be space for buoyant materials.8.3 W The buoyant material is incorporated in the hull.9 W The hull must have a big moment of inertia this is for stability of the

sub.10 D COG must be located in the centre of the sub, in longitudinal and trans-

verse direction.11 D COB must be located above COG.12 W Distance between COB and COG as big as possible.13 W Gz-phi curve goes straight up.14 D Must be steerable in all directions.15 D The air discharged is so that the buoyancy is not affected.16 W The excitation of the pilot does not affect the sub.17 D The torque of the propeller can be eliminated.18 W The propeller does not provide additional torque on the sub.19 W Stability mechanism does not create additional drag.20 W Autopilot, the pilot does not need to steer.21 D There has to be a mechanical steering system (if autopilot than this is a

back-up).22 D Always steerable.23 W Submarine is stable for the length of the entire race.24 D Pilot has to pay as little as possible attention to the steering system.

Hull25 W The drag coefficient must be minimal at every angle of attack.26 W As long as possible laminar flow in the design.27 D All parts which are necessary for the submarine must fit in the hull.28 D Must be drainable.29 D Must be producible.30 W As small as possible wetted surface in the design.31 W Least amount of pressure difference over the hull.32 W Frontal cross section must be minimal.33 W The turning point on the body must as far away as possible from the

nose.34 W Optimal relationship with the propulsion system.35 D The face and head of the pilot must be visible for the support- and safety

divers at all times [1].36 D Sub must be able to carry full load of water [1].

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37 W The resistance of the hatches should be minimal.38 W The hull must enclose the pilot in its whole [1].39 D The hull should not have any rough edges or protuberances that create

any drag.40 D The stickers on the hull should be places before the clear coat is applied.41 W The volume of the WASUB has to be minimal.42 W The Coefficient of resistance should be minimal for every angle.43 D The hull must not create lift.44 D The maximum thickness should be in the area of 40% and 50%

Propulsion45 D Make a correct ratio between the revolutions of the motion that generate

the power and the propeller.46 D Can be well attached to the hull, very little vibrations.47 W Propeller shaft delivers constant rotation.48 W Make a system that does not require much space.49 D Propeller is most efficient at a velocity of 7.2 knots.50.1 W Optimal ratio between torque and revolutions.50.2 W Design the hub diameter as small as possible.51 D Most efficient at 800W (power a person can deliver).52 Material of the propeller.52.1 D Design with a strong material so the propeller blades can be as thin as

possible.52.2 D Use a non-corroding material.53 D Propeller must fit on the gear mechanism.54 D Generate power with a motion that creates the most forward thrust rela-

tive to the drag needed due the frontal area that matches the movement.55 D The total system from generating power to the propeller shaft shall not

fail under the forces working on the system.56 D The connection between hull and gear mechanism/propulsion system

must be attainable, in such a way that it is serviceable during the ISRand testing.

57 W The gear mechanism losses as low as possible (the losses depend onwhat kind of propeller will be used).

58 D The system which generates power shall be movable in both x- and z-direction. Because of that, a perfect tuning on a pilot is possible.

59 D Create a transmissionratio which makes sure that the propeller neverexceeds the amound of rations per minut it is designed for. This becauseof the drop in thrust.

60 W Drive the propeller with a uniform motion. This ensures that the pro-peller has the same rotational speed throughout one rotation.

61 D The gears shall turn in air, instead of in water. To achieve that, thegears need housing. Because the gears do not turn in water, they do notencounter all the resitance from the water.

62 D The propulsion system must be symmetrical in the xz-plane in the hull.This gives the smallest frontal area and therefore resistance.

Pilot63 D Committed pilots (trains a minimum of 4 times a week).63 D Well trained pilots (min output 800 Watt).64 W Enough space to pedal in an optimal way.65 W Pilots upper body is well fixed in place.66 D Pilot must have a PADI diving certificate.

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3. Hull DesignIn this section the hull will be designed and the positions of all the components withinthe body will be determined. First pilot and components will be found and a modelwill be created to find the critical displacements of the pilot while cycling. With thehelp of airfoil selection the outer shape will be determined and the components foundwill be positioned into the hull.

3.1 Basis equations related to the hull

The importance of the hull can be seen in the next basic equations. The hull willcreate a total drag which consists of three types of drag seen in equation 3.1. Frictiondrag, pressure drg and wave drag. The main goal of the hull is to create a minimaltotal drag.

Dtotal = D f riction +Dpressure +Dwave (3.1)

If the equations are worked out one will get equation 3.2.

Dtotal =C f12

ρv2Swet +CD12

ρv2Scross +Cw12

ρv2Swet (3.2)

The friction drag consists of a friction coefficient and the wet surface of thehull. The friction coefficient is dependent on Reynolds number which depends onlength, thus minimum length is required. The wet surface can be reduced by usingminimum length and minimum cross section. The pressure drag consists of the dragcoefficient which is dependent on shape, cross section and the transition point be-tween laminar to turbulent flow. Because the relatively low speeds and depth of thesubmarine the wave drag is assumed to be negligible. The density is assumed to be aconstant because the race is in a straight line without height differences.

3.2 Pilot Position

The main constraint of the outer dimensions of the hull is the pilot. His size, shapeand position in the submarine will be of major importance. First the size of this pilothas to be determined. Pilot selection was done and two pilots were found. The tallestwas 185 [cm] in length so he will be the main length constraint.

Now the position of the pilot has to be determined. Three concepts were eval-uated and can be seen in figure 3.1.

3.2.1 Concept 1

In concept one the pilot is positioned head first and in a laid back position on thebottom of the submarine. The advantage of this is that it is a conventional cyclingposition. One can be trained on a conventional recumbent bicycle and no specialtraining facility has to be created. In this position the drive train is closest to the hubwhere the propeller is, what results in a shorter shaft and thus more efficient powertransmission. The main disadvantage is the view of the pilot this results in less com-fort of the pilot because he will not be able to see the submarines behaviour.

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Figure 3.1: Pilot position concepts

3.2.2 Concept 2

In concept 2 the pilot is positioned head first and supports his back against the top ofthe submarine. The advantage is as in concept 1 the shorter shaft between the drivetrain and the propeller. Thus, a more efficient transmission. The pilot has a clear viewand he will be more comfortable because he will be able to see the submarines be-haviour. The only disadvantage of this configuration is the unconventional position.This means that the pilot has to do a special training in a special training rig or in thesubmarine.

3.2.3 Concept 3

In concept 3 is the pilot positioned feet first and in laid back position on the bottom ofthe submarine. The advantage is a conventional cycling position as in concept 1. Theview is limited and that will result in less comfort for the pilot. For this position along shaft is needed from the drive train to the propeller, this results in less efficiencycompared to the other concepts and it is difficult to manufacture.

3.2.4 Pilot position concept selection

In Table 3.1 a comparison of the three concepts is made. Concept 2 is the best concepteven though it is an unconventional position.

Table 3.1: Pilot Position Concept Comparison

Concept 1 Concept 2 Concept 3Conventional Position + - +View - - + -Efficiency + + -Pilot Comfort - + -TOTAL - ++ - -

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3.3 Hull components

In order to design the hull there must be an indication of the components which willbe installed into the submarine. In Table 3.2 the components of the WASUB 3 aresummarized.

Table 3.2: Componenten in de romp WASUB

# Romp Components1 Pilot2 Scuba Tank3 Scuba Gear4 Pilot Supports(Safety belts, Shoulder supports)5 Drive train mechanism6 Control System(fins/actuators)7 Autopilot8 Manual pilot9 Lead, Foam en Thickness

10 Inserts in hull11 ISR (Emergency exit/strobelights/Emergency buoy)12 Canopy13 Service entrance

3.4 Critical Deflection Model

A model has to be created in order to know the deflection of the pilot while cycling.This deflections are the critical deflections and the boundaries for the hull shape.With the help of solidworks [2] and DINED [3] a model of the pilot is created as seenin figure 3.2.

Figure 3.2: Model of pilot in Solidworks.

This pilot model is put in cycling position as found in concept 2 of figure 3.1.Ovals are drawn around the body of the cyclist and the model is closed with splinesas seen in figure 3.3. This is the side view of the model and the cyclist will fit intothe hull if the splines and ovals of the model fit within the boundaries.

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Figure 3.3: Model of pilot in Solidworks side view.

3.4.1 Hull Shapes

Hull shapes have to be found. According to the equations and requirements the dragof the hull has to be minimum. In order to create minimum drag the cross sectionand volume have to be minimal. In figure 3.4 drag coefficients of different shapesare compared at different Reynolds numbers. A horizontal flat plate would be theminimum drag, however no components can be inserted into the hull. Therefore anairfoil shape would be optimal and these will thus be compared into the model.

Figure 3.4: Drag coefficient of 2D shapes against Reynold’s number [4].

3.4.2 Airfoil shape in XZ and YZ plane

In order to have minimal volume, minimal cross section and laminar flow as long aspossible, it was chosen to take two airfoils for the hull shape. One on the xy-plane,and one on the xz-plan (where the xy-plane is the shape as the hull is seen from above,and the xz-plane is the shape as the hull is seen from the side). Ovals between theseairfoils will enclose the hull. In figure 3.3 it is visible that the maximum thicknessin the XZ plane is at the knees at 40-50% from the leading edge. To get some con-cepts for the airfoil, first only symmetrical airfoils with a maximum thickness around40% or 50% have been looked for. This gave the concepts as summarized in table3.3.

Although the same concepts are chosen for the xy-plane and the xz-plane, thevolume of the airfoils for both planes are totally different. Due to the pilot lying in theWASUB, the maximum point in the airfoil on the xy-plane is the shoulderwidth ofthe pilot. The maximum point in the airfoil on the xz-plane, is the maximum distance

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xy-surface xz-surfaceParsec ParsecLWK 80 LWK 80RAE 104 RAE 104NACA 67 NACA 67AH 85 l AH 85 l

Table 3.3: Airfoil concepts for the hull shape

between the hip and the knee when the pilot is pedalling.These five concepts are compared on liftcoefficient, dragcoefficient, moment-

coefficient, maximum thickness position, pressure distribution and surface. To getthe right data the program XFLR5 [5] was used. In table 3.4 the decision matrix forthe concepts on the xy-plane are summarized.

airfoil AH 85 l LWK 80 NACA 67 Parsec RAE 104Maximum thickness 0 0 + + -Cd 0 - + - - -Total surface area 0 0 - 0 0Surface area middle 0 + - - + +Surface area end 0 + - - - +Cl 0 + ++ + ++Cm 0 - - - - - -Cp 0 + ++ - - -Total 0 ++ - - - - -

Table 3.4: Decision matrix for the 2D concepts on the xy-plane

The decision matrix for the concepts in the xz-plane are summarized in table3.5.

Airfoil AH 85 l LWK 80 NACA 67 Parsec RAE 104Maximum thickness 0 0 + + -Cd 0 - + - - -Total surface area 0 - 0 0 0Surface area beginning 0 + + - -Surface area middle 0 - + + -Surface area end 0 0 - 0 -Cl 0 + ++ + ++Cm 0 - – - - -Cp 0 + ++ - - -totaal 0 - ++++ - - - - - - - - -

Table 3.5: Decision matrix for the 2D concepts on the xz-plane

As can be seen in table 3.5, the NACA 67 concept is a lot better than theother concepts. Therefore, this concept is chosen as the only concept for the xz-plane.

To find the length of the airfoil, the solidwork model is used and a lengthof 3.00 meters was chosen as the initial length. By means of an iterative process

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the airfoil concepts found in table 3.3 and lengths are compared and drawn into thesolidworks model to check whether the pilot fits in that hull shape or not. In figure 3.5the xz plane is shown and one can see that the pilot fits inside this hull length.

Figure 3.5: NACA67 series with a 3.00 m length into model.

For the XY plane a narrower airfoil can be used because the shoulders arenarrower than the critical deflection of the knees when cycling. The Parsec airfoil isused first because this airfoil is the narrowest of all the concepts seen in table 3.3. theparsec in the model can be seen in figure 3.6, however the length is over designedbecause in the leading and trailing edge is unnecessary space. By doing the iterativeprocess a minimum length of 2.78 meters was found to fit the pilot. The result ofthis iterative process is seen in figure 3.7 both in the NACA for the xz plane and inthe parsec for the xy plane the pilot fits. However the parsec is not the best solutionaccording to the decision matrix in table 3.4. The LWK 80 airfoil was found to bethe second narrowest airfoil and put into the model as seen in figure 3.8.

Figure 3.6: PARSEC of 3.00 m in model top view (xy plane).

Figure 3.7: PARSEC in xy plane and NACA in xz plane of 2.78 m in model.

Figure 3.8: LWK 2.78 m in model top view (xy vlak).

The other investigated concepts are summarized in table 3.6.These concepts were compared on drag, volume and pressure, making use of

the program Delkelv. This gives the decision matrix in table 3.7 and it can be seen thatthe LWK80 and NACA67 combination is best and the pilot fits in this combination.Therefore this is the combination used for the hull of the WASUB 3.

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xy-plane xz-planeLWK 80 NACA 67RAE 104 NACA 67AH 85 l NACA 67Parsec NACA 67

Table 3.6: 3D concepts

Choice/shape LWK 80 -NACA 67

RAE 104 -NACA 67

AH 85 l -NACA 67

Parsec -NACA 67

Volume 0 - - - +Resistance 0 0 + - -Pressure distribution 0 - - - - -total 0 - - - - - - - -

Table 3.7: Decision matrix 3D concepts

3.5 Emergency exit

To be able to do an emergency egress the pilot should at least have one emergencyexit. The positioning of this exit has influence on the flow and escape time. In orderto find the best solution three concepts are compared. The concepts can be seen infigure 3.9. In concept 1 the hull can split in two separate parts. In concept 2 thecanopy can be opened and in concept 3 a hatch is located on top of the submarinehull. These concepts are compared by there influence on flow at zero angle of attackand nonzero angle, influence on strength, how easy it is to open them, ability to keepthe exit in closed position and the manufacturability.

Figure 3.9: Concepts of positioning emergency exit.

Concept 1 is best at zero angle of attack because the seam is parallel to theflow, however at an angle of attack the seam is long compared to the other conceptsand more drag will be created. The hull without cuts is a torsion box and makingcuts in this box results in less strength. The cuts in concept one will result in the hullno longer being a torsion box and thus concept 2 and 3 are more suitable. Concept2 is harder to open than the other two because the water pressure is pushing againstthe canopy. Although the problem results in a better ability to keep the exit in place.Concept 1 is is better manufacturable because the hull is made out of two separate

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Table 3.8: Comparison emergency exit

Concept 1 Concept 2 Concept 3Influence on flow at α = 0 0 - - -Influence on flow at α 6= 0 0 + ++Influence on strength 0 ++ +Easy to open 0 - +Ability to keep it closed 0 + +Manufacturability 0 - - -Totaal 0 - +++

parts, in concept 2 and 3 more work needs to be done. Overall concept 3 is best andwill be used for the WASUB 3.

3.6 Materials and Production

According to the ISR [1] best use of composites is rewarded, therefore composites areused. Apart from the fact that it is a requirement, composites have more advantagesseen in table 3.9

Table 3.9: Advantages Composits [6].

AdvantagesHigh specific strength. So high strength at low weightHigh formability and relatively manufacturableIntegration is possible. Insert can be easily added to the hull.Corrosion free. Does not absorb moisture.less maintenance needed, long lifetime.

3.6.1 Fibres

There are two types of fibres most used, fibreglass and carbon fibre. Carbon fibre ismostly used for lightweight structures while fibreglass is more flexible. The biggestdifference are the costs. The WASUB is not built to be the lightest and a small amountof flexibility is not required. To reduce the production costs fibreglass was chosen forin the WASUB 3.

3.6.2 Resin

Three different types of resins can be used for fibreglass. Epoxy, polyester andvinylester. Polyester is the cheapest but vinylester has a lower resin viscosity soit is easier to work with and it has an increased corrosion resistance and ability towithstand water absorption. Epoxy is a lot more expensive and unnecessarily strong.Therefore vinylester is used as a resin for the WASUB 3.

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3.6.3 production process

The hull will be produced using vacuum infusion. For this infusion a mould has to becreated. Because the hull of the submarine is symmetric around the X plane only amould for one half is needed. Both parts will be glued together afterwards. In figure3.10 the inverse of the mould can be seen. The location of the hatches and canopy ismilled into the mould to make positioning easier.

Figure 3.10: The inverse of the mould

The process of vacuum infusion is seen in figure 3.11. The dry fibres arestacked in the mould, so without resin between these fibres foam are stacked to createenough upward force to create neutral buoyancy. A vacuum bag is put over the fibresand vacuum is created. The resin is added and flows trough the fibres and foam. Ifcompleted a strong structure is created. This process is done three times. First forthe hatches, second one half of the hull and last the other half. Both sides are gluedtogether to one piece and this created the hull of the submarine.

Figure 3.11: Vacuum infusion

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4. Stability & steering4.1 Requirements

The main requirements for the stability and steering are that the submarine can ac-celerate freely and that the submarine is levelled horizontally during the entire race.More specified requirements can be found in the chapter List of Requirements. Thedesign choices that are made so that the submarine meets the requirements are dividedin several subsection listed below. First there is an analysis of the stability problem.And after that the systems that solve the stability problem are discussed. First theactuating systems and later the stabilization mechanism are explained.

4.2 Analysis of the stability

To understand the stability problem we made a hydrodynamic computer model of thebehaviour of the submarine. The model is divided in three large parts. The first partmakes a link between an earth reference system and a body reference system (figure4.1). This part can translate body reference accelerations to earth speeds. Equation4.1 shows the used formulas.

Figure 4.1: Degrees of Freedomxyz

=

cψcθ −sψcφ + cψcθsφ sψsφ + cψsθcφ

sψcθ cψcφ + sψsθsφ −cψsφ + sψsθcφ

−sθ cθsφ cθcφ

uvw

φ

θ

ψ

=

1 sin(φ) tan(θ) cos(φ) tan(θ)0 cos(φ) −sin(φ)0 sin(φ)

cos(θcos(φ

cos(theta)

p

qr

(4.1)

The second parts are the equations of motion 4.2. X,Y,Z are the acting forcesand K,M,N are the acting moments on the submarine.

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(a) Pitch angle over time (b) Speed in two directions

Figure 4.2

m 0 0 0 m×Zg 00 m 0 −m×Zg 0 00 0 m 0 0 00 −m×Zg 0 Izz 0 0

m×Zg 0 0 0 Iyy 00 0 0 0 0 Izz

uvwpqr

=

∑X∑Y∑Z∑K∑M∑N

(4.2)

The third parts are all the external forces and moments working on the subma-rine. These are fin forces, drag in all directions, hydrostatic forces, added mass andthe propulsion. When all the forces are implemented in the model we can analyse thebehaviour of the submarine. 4.2a gives the course of the pitch angle in time and 4.2bshows the speed in two directions.

The conclusion made after seeing these plots is that the biggest stability prob-lem of the submarine is the diving movement when the submarine is accelerating.The diving movement is a result of an imbalance between the drag and the propul-sion power and the positioning of those forces to the center of gravity. 4.3 shows thatwhen Xprop is bigger than Xdrag (when the submarine is accelerating this occurs)there will be a resulting moment around the COG.

Figure 4.3: Free Body Diagram

4.3 Fins

The requirement for designing the fins was that they could create enough lift tocounter the moment that is actuated by the imbalance between drag and propulsion.

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The lift must be created with a maximum fin angle of 20◦ because for fin angles of20◦ and more the fins create more drag than lift and that will affect the forward speed.All fins will have the same shape.

Shape When not steering, minimal drag is desirable from the fins. For this, thesame profile was chosen as for the xz plane of the hull, namely the NACA 67 for thebottom view; this profile can be seen in figure 4.4. The shape as is seen in figure 4.5was chosen because of the following equation 4.3 which represents the drag coeffi-cient of a 3D airfoil. The oswaldfactor e is 1 for an elliptical shape and less than onefor non elliptical. In order to have minimum drag an elliptical shape is used.

CD =Cd0 +Cl2

πAe(4.3)

Figure 4.4: Render of the under side of a fin

Figure 4.5: Render of the side view of a fin

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Surface area From the model discussed in the earlier section of this chapter a valueof 70cm2 was found as necessary for the surface area of the fins. Because of theuncertainty regarding the validity of the model, a safety margin of 2.5 was applied onthe result, giving a value of 175cm2 for the surface area of the fin. A side view of thefin can be seen in figure 4.5.

During the testing phase it will be discovered whether the model is indeedvalid. Depending on the outcome, the decision may be made to make the fins smaller.

Attachment to hull To connect the fins to hull extra pieces were made which allowfor a smooth transition between the hull and the fins (figure 4.6). Because the hull

Figure 4.6: Render of the attachment part of the fins

is not rotationally symmetric, separate connection parts were made for the verticalfins and for the horizontal fins. These were made to follow the shape of the hullperfectly.

Production The technique of 3D rapid prototyping was used to produce the finsand the attachment parts. This is a cheap and simple method. Next they were sandeddown a first time as when they come out of the 3D printer they have unwanted excessmaterial. A layer of epoxy was then applied, they were then sanded down again andto finish a layer of filler was applied.

4.4 Steering mechanism

In this section a design for the manual control system of WASUB 3 will be made.This control system will be used to rotate the four fins (in plus configuration) whichare located at 2.35 meters from the nose of the submarine.

4.4.1 Requirements

There are four requirements for the manual steering mechanism of the WASUB 3.1. (Demand) The control system has to be designed in a way (dimensioning, shape,

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choice of fasteners) that it can be produced easily by inexperienced turners andmillers of the WASUB 3 team.2. (Demand) The fasteners in the design must be available in the WASUB 3 stock(M4, M6, M8 bolts, nuts, torx etc.)3. (Demand) - Controlling the submarine must be intuitive so the pilot can mainlyfocus on supplying power.4. (Wish) The control system can be operated using only one hand. This way thepilot can use the other hand to push himself on the pedals.

4.4.2 Way of steering

According to the list of requirements controlling the submarine must be intuitive. Itis however, only possible to control two rotations at the time due to the fact that apair of fins can only co-rotate or counter-rotate. This leads to the following ways ofsteering: Roll & yaw, roll & pitch and pitch & yaw.

In the end the decision has been made to steer the submarine by controlling thepitch and roll angles. The corresponding steering manoeuvre can been seen in figure4.7.

Figure 4.7: The process of steering the submarine: 1. The sub rolls in a certaindirection. 2. The submarine moves to new position. 3. The submarine rolls back.

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4.4.3 Pulley system

The manual control system consists of four pairs of pulleys (figure 4.8). Of eachpair, one pulley is connected to a steering rod. The other pulley is connected to theshaft of a fin. A Dyneema wire connects both pulleys. Dyneema is chosen for itshigh tensile strength. The wires are prestressed by springs to prevent the wire fromslacking.

Figure 4.8: Pulley

4.4.4 Steering rod

The steering rod is mainly designed with ease of production in mind. Thus the ma-terial is aluminium and the shapes of the parts are either rectangular or cylindrical.The steering rod consist of two pulleys. The pulley with the handle is used to dive,the pulley without the handle is used to roll.

Figure 4.9 shows a render of the final design.

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Figure 4.9: The final design

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5. PropulsionThis chapter is a detailed description of how the entire propulsion system was de-signed from the pedals to the propeller.

5.1 Propeller

The design of the propeller is elaborated in this section. It begins with the require-ments for the design of the propeller. After that several concepts for the propellerdesign will be explained. And this section will be concluded with the actual designof the propeller of the WASUB.

5.1.1 Concepts

First the concepts will be explained and after that one concept will be chosen forthe design of the propeller. The following concepts are considered during the designof the propeller. Other concepts like a ducted propeller are considered also but itbecame obvious that these concepts are not suitable for the design of the propeller ofthe WASUB so they are not elaborated here.• Fixed pitch propeller (FPP)• Controllable pitch propeller (CPP)• Counter rotating propeller (CRP)

Fixed pitch propeller This is the conventional propeller. It is a single propellerwith fixed pitch blades so the angle of the blades is not adjustable. This propeller isdesigned for a certain speed and rpm at which this propeller is most efficient. So ifthe speed increases the rpm has to increase to maintain the same efficiency.

Figure 5.1: Fixed pitch propeller

Controllable pitch propeller A CRP is also a single propeller, but with this pro-peller it is possible to adjust the angle of the blades. The advantage of this propelleris that the pilot can produce the same rpm during the entire race.

Counter rotating propeller A counter rotating propeller is not a single propeller,but rather two propellers placed behind each other. The two propellers rotate in oppo-site directions which results in several advantages which will be explained later.

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Figure 5.2: Controllable pitch propeller

Figure 5.3: Counter rotating propeller

Trade-off concepts

The three concepts will be compared with each other to determine the best conceptfor the WASUB.

The advantage of a CPP is that the pilot has to produce the same rpm duringthe entire race. The disadvantage which comes with it is that the propeller is mostefficient at a certain pitch. If the pitch is changed also the efficiency changes. Thisresults in more power loss. The hub of the propeller also has to be a bit bigger tohold the mechanism to change the pitch of the blades. This also results in lowerefficiency. On the basis of these arguments this concepts is not used for the design ofthe propeller.

This results in a choice between the FPP and the CRP. To decide which conceptis better a database of testing results of propellers is used. With a programme thatpredicts the behaviour of a propeller based on this database a comparison is madebetween a CRP and a FPP.

The results of this programme are given in figure 5.4. In this figure VSS standsfor FPP and CRS stands for CRP. In this figure the diameter of the propeller is placedon the x axis and the thrust of the propeller is placed on the y axis. All the propellersare calculated with a power of 800 Watts. It appears that the counter rotating propellerproduces more thrust than a fixed pitch propeller. Another advantage of a counterrotating propeller is that the propeller does not create a rotational moment on thehull. With a fixed pitch propeller the propeller forces a rotating of the hull which hasto be compensated. All in all it appears that a counter rotating propeller is better thana fixed pitch propeller. So for the design of the propeller of the WASUB the counterrotating propeller concept will be used.

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Figure 5.4: Fixed pitch propeller versus counter rotating propeller

5.1.2 Design

The design of the counter rotating propeller will be elaborated here. First all theparameters of the propeller will be determined and after that the propeller will bedesigned using the lifting surface theory.

Wake factor The wake factor determines the flow around the hull and the effect ofthe flow on the propeller. It is a given factor for a certain hull. With a higher wakefactor the velocity of the water in front of the propeller is lower which means that thepropeller can deliver more thrust. The thrust is determined by the pressure differencebetween the front and the back of the propeller.With a program called PARNASSOS the flow around the hull is observed and thewake factor of the hull is given in figure 5.5. The wake factor variates with thediameter because the flow velocity is different at each diameter. A higher wake factorresults in a smaller propeller.

Thrust deduction factor The thrust deduction factor is a factor that is used to takethe effect of the propeller on the hull into account. The rotating propeller resultsin a lower pressure in front of the propeller. This lower pressure sucks the hull inthe wrong direction. To take this phenomenon into account the thrust is reducedaccording to formula 5.1.

T = T (1− t) (5.1)

T is de thrust and t is the thrust deduction factor. According to the calculationsmade with PARNASSOS the thrust deduction factor is as stated in formula 5.2. Inthis formula t is the thrust deduction factor and w is the wake factor.

t = 0.41 ·w (5.2)

According to the formulas a lower thrust deduction factor results in morethrust. This means that a higher wake factor results in more thrust and a lower thrust

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Figure 5.5: The wake fraction

deduction factor results in more thrust. Because they are related to each other a bal-ance has to be found here between the two factors.

Diameter and rpm The diameter and rpm of the propeller have to be determinedtogether because they are related to each other. The relation is stated in formula5.3.

P = Q ·ω (5.3)

In this formula P is the power, Q is the torque and ω is the angular velocity.The power of the pilot is 800 Watts. The diameter of the propeller determines thetorque and the rpm of the propeller determines the angular velocity.With this given and with the programme based on the testing results several propellersare calculated and plotted in figure 5.6.

In this figure the optimal rpm is 350. The diameter related to this rpm is 0.40m. The thrust of this propeller is 211.7 N.

Topspeed The goal is to break the world speed record so the top speed of the WA-SUB has to be just above the current world record. This is why the top speed used todesign the propeller is 7.2 knots.

Number of blades The number of blades for the propeller will be two. Severaltheories including the actuator disk theory state that two blades is the most efficientso the propeller will have two blades.

Hub diameter To determine the hub diameter figure 5.7 is used. This figure showsthat if the hub diameter will be under 0.25 times the diameter of the propeller theefficiency loss will be minimal. So the hub diameter must be less than 0.25 times thediameter of the propeller.

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Figure 5.6: Thrust against revs

Figure 5.7: Hub diameter

Material The material used to produce the propeller is aluminium. It is lightweight, it is stiff and it is non corrosive. The aluminium has a density of 2700 kg/m2

and a permissible material stress of 70 MPa.

Pitch ratio The pitch ratio is the ratio between the pitch and the diameter of thepropeller. This will be varied until the optimal ratio is found. The optimal ratio isdetermined by the load on the blade. The load has to be constant of the radius of theblade. This is stated in a formula in formula 5.4.

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η(r) =tan(β )tan(βi)

(5.4)

In this formula η(r) has to be constant over the radius of the blade.

The result

To design the propeller a programme is used that is based on the lifting surface theory.The lifting surface theory calculates the flow around the blades and determines on thebasis of the flow how the propeller will behave. The parameters given above are usedin this programme and with the programme the ideal propeller is designed. Theresults, the design of the propeller are given in table 5.1. A visual impression of thepropeller is given in figure 5.8. A visual design of the hub, designed separately, isgiven in figure 5.9.

Table 5.1: The propeller

Front propeller Back propeller

Diameter (m) 0.39 0.40

Rpm (1/min) 350 350

Number of blades 2 2

Blade area ratio 0.141 0.150

Hubdiameter (m) 0.10 0.08

Density (kg/m2) 2700 2700

Mass of the blades (kg) 0.216 0.249

Virtual pitch ratio 1.7498 1.6345

Pitch (m)(0.7r) 0.564 0.565

Thrust (N) 108.7 112.9

Torque (Nm) 10.6 11.2

Efficiency 0.85 0.83

Wake factor 0.270 0.276

Thrust deduction factor 0.111 0.113

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Figure 5.8: The propeller

5.2 Gear mechanism

5.2.1 Requirements

This subsection will discuss the requirements of the drivetrain of the new WASUB3. The gear mechanism and additional system is the heart of the submarine. The

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Figure 5.9: Cross section of the hub.

drivetrain contains three parts. At first, the pilot has to generate power, which will betransferred and used to activate a propeller. Figure 5.10 shows this.

From figure 5.10 multiple concepts can be developed. The motion which willgenerate power can also be varied. This will be discussed in 5.2.2.

Requirements have to be made, to test if a designed concept can be used. Thelist of requirements has two parts. It has demands and wishes. Demands have to beincluded in a concept. Some of the requirements are more or less straight forward,but it is still useful to write them down. Most of these requirements follow fromlooking at the systems that are connected to the drivetrain. All of the requirementscan be found in chapter 2.

These requirements will lead to different concepts. This is shown in the nextsubsection, subsection 5.2.2.

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Figure 5.10: Complete gear mechanism

5.2.2 Concepts

The first part of creating concepts is to determine which motion will give the mostpower possible in comparison with the frontal area. The motion that is known forgiving much power at a very small area is a cycling motion. A rowing motion alsogives much power, but a simple calculation was made which showed that the rowingmotion required too much surface area to produce the extra power in comparison withthe cycling motion. The decision was therefore made to use a cycling motion.

Three concepts were produced. They all have their pro’s and con’s, which leadto a trade-off. This trade-off, in combination with the requirements, will tell which isthe best concept.

Basic cycling system

The first concept is the most regular way to drive a human powered vehicle. Thissystem is part of every standard bicycle. It is a very simple system which makes iteasy to implement in the WASUB 3. The pilot of the submarine is face down, withhis face to the front. This ensures that the motion is generated in the back of thesubmarine. A regular chain is thereby not needed. A chain only moves a rotationfrom one place to another. Because of the simplicity of the system, it can be veryreliable and contains a very small amount of parts.

Non circular cycling system

The second system looks like a normal cycling system. Although the shape of thechain rings is different. The shape is non-circular, a bit like an oval. A picture isshown in figure 5.11.

The biggest advantage of a non-circular system is the reduction of the ’dead’point. The resistance of the ring changes on the outer side of the ring in order tomake the phase of work as long as possible. Because of the shape of the ring, a chainis needed. This system will therefore also need a derailleur to create tension on thechain. The chain and derailleur both have losses. The system will also need morelength because of the chain that is involved. The losses of chain and derailleur cause2% loss over the regular system.

Elliptical system

The elliptical system is a design that has been introduced in early 1990. The cranksare divided into two separate cranks. Therefore the motion described by the feet isnot circular, but oval. This makes the space needed for a rotation smaller than for theother two concepts. The expatriation of the legs stays the same. This is the limiting

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Figure 5.11: Non circulair cyclingsystem

distance for the frontal area. Therefore this system will not give an advantage overthe other systems.

Conclusion cycling systems

All the concepts are known. This leads to the following trade-off table.

Table 5.2: Trade-off table powersystems

Normal Elliptical Non-circulair

Simplicity 0 - - -

Reliability 0 - - -

Power 0 - 0

Expatriation knees 0 - 0

Volume 0 + -

Efficiency 0 - -

Table 5.2 shows that the normal system is the best system. This system has themost points out of the three concepts.

Drive propeller

Because the type of propeller is a contra rotating propeller, one rotation shall betransformed in two contra-rotating rotations. Three concepts will be produced forthis system.

Concept 1: Two bevel gears

This is the system which creates two contra rotating rotations with the least possibletransmissions. Therefore, it is the system with the highest efficiency. This system isshown in figure 5.12

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Figure 5.12: System with two bevel gears

If both the two transmissions are on the dotted line, the transmission ratio isthe same. This system does not give very much room for optimization on a pilot. Itis not adjustable in the z direction. Adjustability in the x direction is possible whenthe axes are telescopic.

Concept 2: One straight and two bevel gears

This system has both one straight and two bevel gears. This system is shown in figure5.13. This system gives more space for a perfect adjustment to the pilot. The negativepoint of this system is that it requires a lot of space between the cranks which resultsin a higher frontal area. This system has a few percent less efficiency because astraight transmission gives an extra 1 percent loss, while a bevel gear has a 2 percentloss.

Figure 5.13: System with one straight and two bevel gears

Concept 3: Three bevel gears

This is the most complex system of the three. It has the most 90 degrees transmis-sions. Therefore it has the worst efficiency. Nevertheless this system gives verymuch room for perfect adjustment for the pilot. Between point 1 and point 2 a car-dan coupling can be used. The cardan coupling can adapt to changes in height andlength.

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Figure 5.14: System with three 90 degree transmissions

Conclusion gear transmission

The three concepts lead to the following trade-off table.

Table 5.3: Trade-off table transmissionsystems

Concept 1 Concept 2 Concept 3

Adjustability 0 0 + +

Efficiency 0 - - -

Volume 0 - -

Symmetry 0 - 0

Because adjustability for the pilot is the most important, concept 3 will be thefinal concept although this has the worst efficiency. Adjustability is preferable overefficiency.

5.2.3 Design

The basic cycling system combined with the three bevel gears will be the final design.The gears that are used are high efficient spiral bevel gears to create the counter-rotating part and basic bevel gears to create the transmission ratio. The box withthe transmission ratio and cranks will have its own watertight seals. Then a cardancoupling will lead to the counter rotating part. The counter rotating part is in a secondwatertight box. The sealing will take place by oil seals between rotating and notrotating parts. A gasket will seal two static parts. The material is a combination ofaluminum and stainless steel. The framework is all aluminum and the turning partsare all stainless steel. All aluminum parts are anodized to get a strong layer of oxide.A render of the system is shown in figure 5.15.

And from the other side, without some of the housing.A more detailed render is shown in figure 5.17A last render of the counter rotating part of the drivetrain is shown in figure

5.18.

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Figure 5.15: Render of total system

Figure 5.16: Render of total system

Figure 5.17: A more detailed render

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Figure 5.18: A detailed render of the counterrotating part

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6. OverviewHere is a render of the final outcome of the submarine figure 6.1. If all of the partswork well it is expected that the sub will reach a velocity of at least 7.2 knots,hereby breaking the current world speed record for one person, propeller poweredsubmarines.

Figure 6.1: Render of sub

The hull shape is based on the wing profiles NACA 67 in the xz plane andLWK 80 in the xy plane. The volume has been made as small as possible such thatthe pilot and all the other components just fit in the hull.

The fins were made with a NACA 67 profile, the side profile is elliptical andhas a surface area of 175cm2.

For the propulsion of the submarine the decision was made to design a contra-rotating propeller. A regular pedalling movement was chosen to generate the powerto turn the contra-rotating propeller.

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References

[1] International Submarine Races (ISR) and Judging and Directors Committee andFoundation for Underwater Research and Education, “International SubmarineRaces Contestants Manual,” Jun. 2012.

[2] Dassault Systems, “Solidworks,” Jan 2013,http://www.3ds.com/products/solidworks/overview/.

[3] Department of Applied Ergonomics and Design Section, “Dined,” Dec 2012,http://dined.io.tudelft.nl/ergonomics/.

[4] B. R. Munson, D. F. Young, T. H. Okiishi, and W. W. Huebsch, Fundamentals ofFluid Mechanics. John Wiley & Sons, Inc., 2010.

[5] A. Deperrois, “Xflr5,” 2003.[6] E. J. Barberol, Introduction to composite materials design. CRC Press, 2010.

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