tp52 design report rumb runner

7/27/2019 TP52 Design Report Rumb Runner

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The Design and Model Testing ofRhumb Runneran Ultra Light Displacement Sailing Yacht to

Conform to the Transpac 52 Box Rule

Terminal Flow Design Group:

Christopher A Amory

David E. Elwood

Benjamin J. Van Dam

June 3, 2005


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TFDG worked extensively with theowner to design a deck layout that tookinto account his personal taste while alsocreating the most efficient deck layoutpossible to allow the boat to operate atfull potential at all times. The deck lay-out was designed to reduce the amountof time a crewmember would be waitingfor an open winch or waiting for othercrew members to get out of their way,which was accomplished by isolating thedifferent areas on the boat, namely usingonly the cabin-top winches for halyardsand other lines run from the mast, andplacing both primaries and secondaires inthe cockpit for use with the jib sheets,spinnaker sheets, and spinnaker braces.The primaries are run off a pedestallocated on centerline in the forward sec-tion of the cockpit, while the single main-sheet winch, also on centerline, is pow-ered by a second pedestal located in front

of the mainsheet winch. The secondariesare powered by top handles as these willbe used for the spinnaker braces andchanging headsails during distance racesand will therefore not require the highspeed benefits of a pedestal.

Dual helm stations were incorporated intothe design to allow the driver to alwaysbe on the high side; adjustable tableswere also positioned behind each helmstation to allow the driver to always bestanding on a horizontal surface to

reduce fatigue and increase the line ofsight forward.

Rhumb Runner also is one of the firstTP52s to use transverse jib cars insteadof longitudinal jib cars. Transverse jibcars are usually only seen on much larg-er maxis but TFDG and the ownerdecided that the ability to completelycontrol the shape of the jib is very impor-tant and therefore the transverse carsshould be used to help the boat reach itsmaximum speed potential.

The foredeck is very open to prevent linesfrom catching on anything and the spin-naker pole is held in chocks located onthe starboard side for easy port markroundings. The pole is located off center-line to allow the forward hatch to be eas-ily opened without having to move thepole which simplifies the job of the bow-man and reduces the amount of time thebowman must be forward of the mastwhich helps to keep weight as far aft aspossible.

Top to bottom: The clean fordeck and starboard spinnaker pole chocks simplify the bow-mans job, the view forward from the dual helm stations is clean and unobstructed, andthe helm platforms help keep the driver level and reduce fatigue.


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The interior ofRhumb Runner is fairlycommon for a grand prix racingmachine, with very little in the way ofamenities below decks; rather, theinterior is designed to keep as much ofthe boat as dry as possible while allow-ing the navigator as much comfort aspossible, and still meeting all interiorspace requirements from the TP52

rule.

The navigation station is located aft ofthe engine below the cockpit to reducethe motions that would be experiencedby the navigator while under sail. Thespace is designed for someone who is6' tall, but there is adequate headroom for someone even taller. Thenavigator can communicate with thehelmsman on deck through portholeslocated on each side of the cockpit.Rhumb Runnerhas been outfitted with

a complete Brooks and Gatehouseelectronics package including the

RaceVision 2 and RemoteVision sys-tems which allows the navigator to beon deck and have the exact sameinformation available on deck as isavailable at the navigation station.This helps to keep weight on the railand maximize the ability of the naviga-tor and helmsman to communicateefficiently and effectively. The elec-

tronics package also features straingauges on all shrouds as well as theforestay and backstay which will allowthe rig tension to be easily monitoredand adjusted for different wind condi-tions.

Rhumb Runnerhas a wet locker locat-ed forward of the companionway onboth port and starboard sides whichallows the wet area of the boat to bekept to a minimum. Once a crewmem-ber's wet gear has been removed,

there is a seat on the starboard sidewith easy access to a number of small

cubbies to hold dry clothing and othersmall pieces of crew gear. The galleyis located to port, with a small 4-burn-er propane stove and shelf space tohold food, with one of the shelves eas-ily convertible to an ice box to keepfresh food. The head is located for-ward of the main bulkhead, with acloth door to separate the main cabin

from the head.

Overall Rhumb Runnerhas been devel-oped to be a competitive grand prixrace boat that will perform well bothinshore in short course buoy races aswell as in offshore distance races. Thedeck layout has been developed tomaximize the performance of the boatand to allow as much control of thesails as possible to give the crew asmuch control over the boat as possiblewith the interior designed to maximize

crew comfort while still maintaining theperformance aspect of the boat.

LOA 52ft

LWL 51ft 3in

Beam (Max) 14ft 6in

Draught 10ft 6in

Disp (Lightship) 16,500lb

Ballast 7,550lb

Percent of Ballastin Keel

44%

Sail Area(100% foretriangle) 1694ft

2

Berths 8

Engine YanmarPower 54hp

Water 140gal

Fuel 25gal

Sail Area: Disp 72.6

Disp: LWL 54.8

Price $808,107

Specifications

Interior view showing the two wet lockers, cubbies for crew gear, galley and forward set ofbunks and the navigation station, with plenty of headroom for the navigator.


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Table of Contents:

1. Owners Requirements .............................................................................................. 142. Design Approach ........................................................................................................ 163. Hull Form Design and Model Testing...................................................................... 17

3.1 Summary................................................................................................................ 173.2 Hull Design ............................................................................................................ 183.3 Model Construction Process .................................................................................. 203.4 Test Matrix............................................................................................................. 233.5 Testing Set Up........................................................................................................ 243.6 Calibration Procedure ............................................................................................ 253.7 Testing Procedure .................................................................................................. 263.8 Dynamic Wetted Surface Analysis ........................................................................ 273.9 Comparison Testing Analysis ................................................................................ 273.10 Keel Construction ................................................................................................. 323.11 Appendage Testing ............................................................................................... 32

3.12 Appendage Test Analysis ..................................................................................... 334. Sail Plan Design.......................................................................................................... 394.1 Summary................................................................................................................ 394.2 Methodology.......................................................................................................... 394.3 Design and Calculations ........................................................................................ 40

5. Appendage Design...................................................................................................... 435.1 Summary................................................................................................................ 435.2 Methodology.......................................................................................................... 435.3 Design and Calculations ........................................................................................ 44

6. Velocity Prediction Program .................................................................................... 546.1 Summary................................................................................................................ 546.2 Methodology.......................................................................................................... 556.3 Design and Calculations ........................................................................................ 57

7. Structures.................................................................................................................... 587.1 Summary................................................................................................................ 587.2 Methodology.......................................................................................................... 587.3 Design and Calculations ........................................................................................ 59

8. General Arrangement................................................................................................ 668.1 Summary................................................................................................................ 668.2 Methodology.......................................................................................................... 668.3 Design .................................................................................................................... 66

9. Deck Layout................................................................................................................ 719.1 Summary................................................................................................................ 719.2 Methodology.......................................................................................................... 719.3 Design .................................................................................................................... 71

10. Machinery ................................................................................................................. 7710.1 Summary.............................................................................................................. 7710.2 Methodology ........................................................................................................ 7710.3 Design and Calculations ...................................................................................... 79

11. Electrical System ...................................................................................................... 82


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11.1 Summary.............................................................................................................. 8211.2 Methodology ........................................................................................................ 8211.3 Design and Calculations ...................................................................................... 82

12. Weights...................................................................................................................... 8512.1 Summary.............................................................................................................. 85

12.2 Methodology ........................................................................................................ 8512.3 Design and Calculations ...................................................................................... 8613. Stability Analysis...................................................................................................... 96

13.1 Summary.............................................................................................................. 9613.2 Methodology ........................................................................................................ 9613.3 Design and Calculations ...................................................................................... 97

14. Seakeeping .............................................................................................................. 10014.1 Summary............................................................................................................ 10014.2 Methodology ...................................................................................................... 10014.3 Design and Calculations .................................................................................... 101

15. Cost Analysis .......................................................................................................... 102

15.1 Summary............................................................................................................ 10215.2 Methodology ...................................................................................................... 10215.3 Calculations........................................................................................................ 103

16. Appendix................................................................................................................. 12416.1 Transpac 52 Box Rule........................................................................................ 124

17. References ............................................................................................................... 134


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List of Figures:

Figure 1: High speed model testing .................................................................................. 17Figure 2: Lines plan of the extreme downwind hull ......................................................... 19Figure 3: Lines plan of the all-around hull ....................................................................... 19

Figure 4: Picture of the first model during construction................................................... 22Figure 5: Yacht dynamometer in operation ...................................................................... 24Figure 6: Photographs of the roll, side force and yaw moment calibration procedures ... 25Figure 7: Model 1 Prohaska Plot ...................................................................................... 29Figure 8: Model 2 Prohaska Plot ...................................................................................... 29Figure 9: Full Scale Drag Coefficient vs. Froude Number for 00 Heel and 00 Yaw......... 30Figure 10: Full Scale Drag Coefficient vs. Froude Number for 10

0Heel and 0

0Yaw..... 31

Figure 11: Full Scale Drag Coefficient vs. Froude Number for 200 Heel and 00 Yaw..... 31Figure 12: Graph of Regressed Lift and Drag Data.......................................................... 33Figure 13: Lift Side force at 0

0Heel................................................................................. 35

Figure 14: Lift Side Force at 100 Heel .............................................................................. 35

Figure 15: Lift Side Force at 20

0

Heel .............................................................................. 36Figure 16: Lift Side Force vs. Drag Force at 00

Heel ....................................................... 36Figure 17: Lift Side Force vs. Drag Force at 10

0Heel ..................................................... 37

Figure 18: Lift Side Force vs. Drag Force at 200 Heel ..................................................... 37Figure 19: Visual output from Excel comparing the IMS limits to the final.................... 41sail dimensions.................................................................................................................. 41Figure 20: Loading Condition for Optimization of the Keel Strut and Keel Bolts........... 44Figure 21: Rhino Rendering Illustrating the Geometry of the (from left to right) Circular,Elliptical, Half Round, and Beaver Tail Cross Sections................................................... 45Figure 22: Graphical Output from Keel Strut Optimization Spreadsheet Showing the KeelStrut Box Girder................................................................................................................ 46Figure 23: Free Body Diagram and Force Diagram for Keel Support Structure.............. 47Figure 24: Graphical Output of Rudder Stock Optimization Spreadsheet ....................... 48Figure 25: Required Rudder Stock Thickness as a Function of Length ........................... 48Figure 26: Speed polar diagram for all wind speeds and headings for a spherical bulbform................................................................................................................................... 54Figure 27: Comparison between the model test data and the regression equations used inPCSAIL............................................................................................................................. 55Figure 28: Comparison between Delft Series and TP52 Model Test ............................... 56Figure 29: Speed polar diagrams for the spherical and elliptical bulb forms. .................. 57Figure 30: Interior rendering showing the wet lockers and dry cubbies........................... 66Figure 31: Rendering of the galley ................................................................................... 67Figure 32: Navigation station rendering showing head clearances .................................. 68Figure 33: Exterior view showing the open deck and pole storage. ................................. 71Figure 34: Transverse jib track detail ............................................................................... 72Figure 35: View forward from the port wheel .................................................................. 73Figure 36: Calm water resistance and storm resistance.................................................... 78Figure 37: Locations of the longitudinal centers of gravity for each condition................ 85Figure 38: Graph of the righting arm versus heel angle in the measurement condition... 96Figure 39: Cross curves of stability in the measurement condition.................................. 97


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Figure 40: Righting arm curves in the buoy and distance racing configurations ............. 98Figure 41: Graph showing the comparison between the righting arm curves in themeasurement and racing conditions.................................................................................. 99Figure 42: North Sails Mainsail price quote................................................................... 107Figure 43: North Sails Light 1 price quote ..................................................................... 108

Figure 44: North Sails Medium 1 price quote ................................................................ 109Figure 45: North Sails Heavy 1 price quote.................................................................... 110Figure 46: North Sails Number 4 price quote................................................................. 111Figure 47: North Sails Code 0A price quote................................................................... 112Figure 48: North Sails Code 1A price quote................................................................... 113Figure 49: North Sails Code 2A price quote................................................................... 114Figure 50: North Sails Code 3A price quote................................................................... 115Figure 51: North Sails Code 4A price quote................................................................... 116Figure 52: Brooks and Gatehouse electronics specifications and price estimate ........... 117


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List of Tables:

Table 1: TP52 Box Rule Restrictions ............................................................................... 14Table 2: TP52 2006 East Coast, Caribbean and West Coast Race Schedule ................... 15Table 3: Principle Dimension Comparison between Hull Forms ..................................... 18

Table 4: Test Matrix for Bare Hull Tests.......................................................................... 23Table 5: Test Matrix for Appendage Test......................................................................... 23Table 6: Sail Plan Dimensions.......................................................................................... 39Table 7: IMS Mainsail Limitations................................................................................... 39Table 8: Final Mainsail Dimensions ................................................................................. 40Table 9: Specifications of the Four Bulbs with Varying Cross Section ........................... 45Table 10: Results of Keel Strut Structural Calculations ................................................... 47Table 11: Results of Keel Bolt Structural Calculations.................................................... 47Table 12: Geometry of the Rudder Stock ......................................................................... 49Table 13: Loading of the Rudder Stock............................................................................ 49Table 14: Stresses on the Rudder Stock............................................................................ 49

Table 15: Comparison of Rudder and Keel Areas with Total Sail Area .......................... 49Table 16: Comparison of section modulus calculations ................................................... 60Table 17: ABS structural calculations .............................................................................. 61Table 18: Larsson and Eliassons structural calculations ................................................. 62Table 19: Resistance due to hull, mast and standing rigging............................................ 78Table 20: Resistance due to waves ................................................................................... 78Table 21: Total resistance for calm water and storm condition........................................ 78Table 22: Calculations for the calm and storm conditions for a Troost series propeller. . 79Table 23: Summary of weight section breakdown ........................................................... 87Table 24: Summary of the measurement conditions......................................................... 87Table 25: Summary of the flotation calculations.............................................................. 87Table 26: Detailed weight breakdown .............................................................................. 89Table 27: Hull weight calculation..................................................................................... 94Table 28: Deck weight calculation ................................................................................... 95Table 29: STIX category breakdown.............................................................................. 100Table 30: STIX calculations ........................................................................................... 101Table 31: Cost breakdown summary for the TP52......................................................... 102Table 32: Cost breakdown by section for the TP52........................................................ 103Table 33: Detailed cost breakdown................................................................................. 104


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List of Drawings:

Drawing 1: Hull Lines Plan .............................................................................................. 38Drawing 2: Sail Plan ........................................................................................................ 42Drawing 3: Keel Structure Detail ..................................................................................... 50

Drawing 4: Bulb Detail..................................................................................................... 51Drawing 5: Rudder Detail................................................................................................. 52Drawing 6: Balance Calculations...................................................................................... 53Drawing 7: Internal Structures.......................................................................................... 63Drawing 8: Midship Section ............................................................................................. 64Drawing 9: Midship Section Calculation.......................................................................... 65Drawing 10: General Arrangement................................................................................... 69Drawing 11: Tankage Arrangement.................................................................................. 70Drawing 12: Deck Layout................................................................................................. 76Drawing 13: Engine Detail ............................................................................................... 81Drawing 14: Electrical Diagram....................................................................................... 84


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List of Symbols:

AR Aspect ratio

Awp Area of the waterplane

B, b Beam

BAS Boom height above shear

BWL Waterlien beam

c Correction factor for curved plating

C Minimum compressive strength

CA Allowance coefficient

Cah Wind resistance coefficient of the hull

Cam Resistance coefficient of the mast

Car Wind resistance coefficient of the rigging

Cb Block coefficient

CD Drag coefficient

CDAS Full scale appendage drag

CDI Coefficient of interference drag

CDIM Coefficient of interference drag at model scale

CDS Full scale drag coefficient

CDvisc Viscous drag

Cf Coefficient of frictional resistance

CfCS Full scale frictional resistance coefficient of the canoe body

Cform Coefficient of form drag

CG Center of gravity

CL Lift coefficient

CLAS Coefficient of lift of the appendages at full scale

CLCM Coefficient of lift of the canoe body at model scale

CLS Full scale lift coefficient

Cp Prismatic coefficient

CR Coefficient of residual resistance

CRCM Residual resistance of the canoe body at model scale

Ct Coefficient of total drag of the model

CW Coefficient of wave drag

Cwp Waterplane coefficient

D Drag

Dp Diameter of propeller

E Minimum flexural strength from IMS regulations

Etc Average of the minimum tensile modulus and minimum compressive modulus

F Minimum flexural strength

Ff Freeboard in the forward sections

Fr Froude number

Fx Force in the x direction

Fy Force in the y direction

g Gravity

HB Headboard length

I Moment of inertia

IM Jib hoist

ISP Spinnaker hoist

Ix Moment of inertia in the x direction

Iy Moment of inertia in the y direction


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J Distance from mast to forestay on deck

k ABS coefficient

k1 ABS coefficient

l Length

L Lift

L1 Distance from the transom to the aft face of the mast

L2 Distance from the bow to the forward face of the mastLCB Longitudinal center of buoyancy

Lm Mast height

LOA Length overall

LP Perpendicular distance from clew to forestay

Lr Length of the rigging

LWL Waterline length

M Bending moment

Mbhull Bending moment in the hull due to mast compression

n Propeller rotation rate

P Mainsail hoist

p ABS design head

P Propeller pitch

PD Delivered power

Pmast Mast compression

Rah Resistance of the hull due to wind

Ram Resistance of the mast due to wind

Rar Resistance of the standing rigging due to wind

Re Reynold's number

Rf Frictional resistance

Rh Heeled resistance

Ri Induced resistance

RM30 Righting moment at 30 degrees

Rprop Propeller resistance

Rr Residual resistance

Rtot Total resistance

Rwaves Wave resistance

S Wetted surface area

s Panel spacing

SMi Section modulus of the inner skin

SMo Section modulus of the outer skin

T Minimum tensile strength

ta ABS required thickness for outer skin

tb ABS required thickness for inner skin

Tc Canoe body draft

tm Average of the mast thickness

tr Thickness of the rigging

Tr Propeller Thrust

V Velocity

Va Apparent wind speed

VA Velocity of advance of the propeller

VCG Vertical center of gravity

Ws Panel weight

u Thrust coefficient


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o Propeller efficiency

Kinematic viscosity

Density

a Density of air

beam Stress


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1. Owners Requirements

Recently yacht owners around the world have desired grand prix racing sailboats with theability to perform in both long distance offshore races and near shore short course racing.These owners want a boat that is safe, fast in a range of conditions, and fun to sail. Due to

the difficulties of handicapping racing sailboats, many owners are seeking yachtsdesigned to a set of rules that allows for level racing, meaning that the first boat to finishwins the race. These so-called box rules give designers restrictions on length, beam, draft,and sail area amongst other things while allowing for a high degree of technicalinnovation.

One of the fastest growing box rules for grand prix racers is the Transpac 52 (TP52) rule.The TP52 class was started in 2001 and aimed to create a fleet of all out carbon fibre raceboats that could be raced without handicap in both buoy races and bluewater offshoreraces. Boats designed to the TP52 rule are fast, sailing both upwind and downwind withboats reaching speeds well over 25 knots off the wind. Boats designed to the TP52 rule

have sailed and won regattas such as the Newport to Bermuda, Chicago to Mackinac, TheTranspac, Key West Race Week, Miami SORC, and the St. Francis Big Boat Series. Bythe end of 2005 there will be 27 TP52s on four continents and flagged in 13 countrieswith large fleets developing both in the US and the Mediterranean.

The maximum and minimum dimensions set by the rule are outlined in Table 1. The rulealso stipulates that the boats can be built entirely of carbon fibre with their structuraldesign being governed by American Bureau of Shipping (ABS) criteria for offshoreracing yachts. In addition the rule gives a narrow envelope for the total weight of theyacht between 16,500 to 17,000 pounds and requires that the vertical center of gravity ofthe yacht be no lower than 2.7 feet below the bottom of the design waterline. The sail

area and crew weight allowed are also strictly controlled by the rule. The complete TP52rule is included in the appendix.

Table 1: TP52 Box Rule Restrictions

Box Rule Restriction

LOA 52 ft.

Beam 14 ft 6in

Draft 10 ft 6in.

Displacement 16500-17000 lbs.

Within the confines of the box rule the designer is able to optimize the boat based on the

owners requirements. Typically a TP52 yacht competes in a variety of different types ofraces in a range of wind and sea states. As such a competitive owner desires a boat that isfast in light air upwind sailing conditions as well as downwind heavy weather conditions.Existing TP52s tend to do about 70% of their racing on inshore windward leewardcourses with the remainder of their races being offshore distance races in a range ofconditions from heavy weather downwind races, to reaches, and occasionally upwindraces. Table 2 gives the details of a typical TP52 season showing the distributions ofinshore and offshore races.


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Table 2: TP52 2006 East Coast, Caribbean and West Coast Race Schedule

TP52 East Coast and Caribbean Schedule

Jan 12-14 Fort Lauderdale to Key West Race Distance

Jan 16-20 Key West Race Week Buoy

March 8-13 TP52 2006 Global Championships Distance/Buoy

March 24-26 St Thomas Rolex Regatta Buoy

Apr 2-4 BVI Spring Regatta Buoy

Apr 30 - May 6 Antigua Race Week Buoy

May 26-28 Block Island Race Buoy

June 9-12 2006 TP52 North American Championships, Distance/Buoy

Jun 16-20 100th Anniversary Newport to Bermuda Race Distance

Jul 28-30 Around Long Island Distance

Aug 11-12 Monhegan Island Race, Portland Yacht Club Distance

Sep 1-3 Stamford Vineyard Race Distance

Oct 21-22 Annapolis Yacht Club Fall Regatta Buoy

Dec 2-3 Lauderdale Yacht Club TP52 Regatta Buoy

TP52 West Coast Schedule - Exact date TBD

February San Diego to Puerto Vallarta Race & MEXORC Distance

April Vallejo Race Distance

May 19-20 Stone Cup, St Francis Yacht Club Buoy

May 26th Spinnaker Cup- San Francisco St Francis Yacht Club Buoy

June Coastal Cup Race- San Francisco to Santa Barbara Distance

July Pacific Cup Race- San Francisco to Oahu Hawaii Distance

August Waikiki Offshore Championships Buoy

September Windjammer Race & Big Boat Series Buoy

October Cal Cup Regatta, Marina Del Rey California Buoy

November Hot Rum Series, San Diego California SDYC Buoy

December Hot Rum Series, San Diego California SDYC Buoy


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2. Design Approach

Based on the owners requirements, the design approach began with a series of modeltests to evaluate tradeoffs in the hull design and collect data for use in a velocityprediction program (VPP). After the model tests were completed, the detailed design of

the yachts appendages, sails, structures, arrangements and machinery was completed.The final product was a contract level design of a light displacement racing sailboat thatmeets the requirements set forth in the Transpac 52 box rule.

While many yacht designers have conducted model tests of light displacement yachts atplaning speeds there is no published data on their resistance characteristics. As a resultthe design team felt that model testing would be required to evaluate tradeoffs in the hulldesign and provide accurate data for use in a VPP. The model test program wascompleted in two phases with the first phase consisting of a comparison test between twodifferent hull shapes to compare their resistance characteristics. Based on the results ofthis comparison test, the final hull shape was selected and tested with a generic keel and

bulb. The data from the appendage testing could then be used as input for a velocityprediction program.

After the model tests were completed, the appendages and sails for the yacht wereoptimized. The design team chose to design two sets of appendages, one for the nearshore buoy races, and another for offshore distance races. The sails were optimized toconform to all the applicable rules for the boat. Concurrent to the design and optimizationof the appendages and sails, the transverse and longitudinal structure for the yacht wasdesigned and analyzed. The machinery for the yacht was also selected and placed in thehull. The structural arrangements and machinery position then drove the generalarrangements of the yacht. The general arrangement of the yacht was designed to

maximize crew efficiency while minimizing weight.

Once the general arrangement was completed the weight distribution of the yacht wascalculated. The longitudinal position of the keel was driven by trim considerations as wellas sail balance considerations. The stability of the boat was also analyzed based on thefinal weights and compared with the TP52 box rule requirements. While the weights andstability were being analyzed the deck layout was designed in order to make the boat aseasy to sail as possible. Finally the speed of the yacht was predicted using a velocityprediction program in order to accurately gauge the performance characteristics of theyacht.


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3. Hull Form Design and Model Testing

3.1 Summary

The design project began with an initial desire to create two hulls, one of which would be

an extreme downwind sled with a large flat planing surface while the second hull wouldbe more traditional, similar to many of the current Transpac 52 designs. The use of theUniversity of Michigan Hydrodynamics Laboratory Tow Tank allowed the two hulls tobe compared during a series of model tests. The models were initially tested withoutappendages in order to be able to accurately compare the differences between hulldesigns.

Compiled data analysis showed, as expected, the hull designed to perform as a downwindsled had poor performance upwind at slow speeds, while excelling off the wind at higherspeeds. The traditional hull had much better upwind speed and was minimally slower offthe wind than the downwind sled. Because more of the yachts time will be spent sailing

buoy races with equal upwind and downwind legs than typically downwind offshoredistance races, the more traditional hull was selected for the completion of the design.

A second set of tests was completed with the traditional hull with a standard strut andbulb to calculate the interference drag on the hull. In addition the effect of the hull on thelift generated by the foils was analyzed. Data from the appendage model tests could thenbe used as input into a velocity prediction program to derive speed polar diagrams for theyacht.

Figure 1: High speed model testing


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3.2 Hull Design

The Transpac 52 design team decided to perform a series of resistance tests as a basic

hull comparison so that the relative merits between two hulls could be determined. Inaddition, the data from model tests can later be used in the creation of a VelocityPrediction Program to predict the performance of the yacht over a given course. Testinga planing hull such as the Transpac 52 is necessary as there is little data publicly availableregarding the performance of a semi-planing hull.

The TP52 box rule specifies many of the primary dimensions of the yacht, but the shapeof the hull is left open to the designer. This allows a large range of designs to beconsidered for the potential design of the hulls. The design process for the first hullbegan by looking at current design trends in the field of ultra light displacement boats anddeciding that the first hull would be rather extreme and optimized for downwind

performance; the second design would be more along the lines of a contemporary ultralight displacement hull designed for upwind and overall performance.

The main differences between the two designs would be the location of maximum beam,the flatness of the aft section and the hardness of the knuckle along the chine. The bowsections of the two hulls were planned to be similar, but after observing undesirableseakeeping characteristics of the first hull, the second hull was modified to have moreflair which led to a finer entrance into the water. In addition, there is more of a definedridge along the keel on the second hull to aid in seakeeping performance. Table 3provides a comparison between some of the primary dimensions and coefficients of thetwo different hull forms.

Table 3: Principle Dimension Comparison between Hull FormsHull 1 Hull 2

LOA 52 ft 0 in 52 ft 0 in ft

LWL 51 ft 7.45 in 51 ft 2.88 in ft

BWL 11 ft 2.78 in 10 ft 7.03 in ft

S 402.8 371.11 ft2

Tc 1 ft 2.22 in 1 ft 4.16 in ft

Sectional Area 8.94 9.89 ft2

Awp 380.94 348.14 ft2

Cp 0.561 0.51

Cb 0.377 0.354

Cwp 0.657 0.642

The extreme downwind performance hull had its maximum beam located far aft, with avery flat aft section to accelerate the planing performance of the boat, which wouldincrease speed when reaching and going downwind in general. The hull also had adefined knuckle along the chine which allowed the increase of the size of the aft sectionsto increase the planing surface. This was beneficial if the hull was sailing upright, but


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would exhibit poor performance when heeled. Figure 2 shows the lines plan of the firsthull.

Figure 2: Lines plan of the extreme downwind hull

The second hull was designed as an all-around boat that could sail competitively bothupwind and downwind, with no major design characteristics being chosen to favor onepoint of sail over another. The aft sections were rounded out more and the maximumbeam was moved forward from the first hull position to allow for a more ellipticalwaterplane section and less of a tear drop shape that the first hull exhibited. This wouldchange the speed at which the boat would plane, but this tradeoff would result in betterupwind performance below hull speed. The knuckle along the chine of the second hullwas flattened out which allowed the boat to have more of a flat waterplane when heeledover which would help the upwind performance. The bow section was given a moredefined shape to allow the boat to cut through waves instead of banging over them. The

lines plan for the second hull can be seen below in Figure 3 as well as at the end of thissection in larger form.

Figure 3: Lines plan of the all-around hull


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The displacement for the TP52 rule is specified as a minimum of 16,500 lbs and amaximum of 17,000 lbs. We chose to design both boats for the minimum designdisplacement, with the ability to change to the maximum displacement by changing to aheavier keel. The choice to test at the lighter displacement was made so that the accuratehigh speed performance of the boat could be measured as this is the data that is not

available to the general public.

3.3 Model Construction Process

The models were built using the strip-cedar planking method, which was chosen for itsease of construction and good strength-to-weight ratio. This method involves layingcedar strips over a number of stations cut out of plywood with a layer of fiberglass oneither side for strength.

After the model scale size was determined, the skin thickness had to be determinedbefore the plans could be printed. A skin thickness of was chosen based on

experience from previous model construction. This thickness provides a relatively lightmodel while still retaining good stiffness and rigidity. Once the thickness of the skin wasdetermined, the lines plan was scaled and divided into ten stations which would be turnedinto 10 frames that would constitute the mold. There were also frames added at halfstations in the forward sections, from stations one to three. These frames were laid out inthe computer, their lines representing the outside surface of the hull.

The stations were all offset inboard to take into account the skin thickness. The stemprofile was also offset and printed. At that point the frames and stem profile were scaledto the correct model size and the skin offset , so they were ready for printing, whichwas done on a large plotter courtesy of Van Dam Wood Craft.

The printed frames were cut out and glued onto Medium Density Fibreboard (MDF).These were then cut and sanded to the offset line representing the inside of the cedar skin.The transom frame was built using 3/8 Okume plywood since it would be permanentstructure. In order to correctly lay out the frames, a strongback, or ladder frame, wasbuilt with station lines and a centerline drawn on it. A strongback is essentially arectangular box that is the length of the model and wide enough that the frames can besecurely fastened onto it. It was constructed out of MDF with a piece on the top thatgave it a perfectly flat and square surface to work from. In order to give the model addedstiffness, a keel and a set of sheers were added. These were constructed out of x mahogany, and pockets were routed out of the frames to accommodate them.

Once the strongback was constructed, the frames were then placed perpendicular to thestrongback and fastened down. The keelson and sheers were then secured to the framesusing small finish nails that could be easily removed later. This also helped to lock theframes in place and to keep them from moving. At this point the mold was essentiallybuilt. Tape was put on the MDF frames so that the glued planks would not stick to themas they were only temporary frames. The keelson and sheers were left as raw wood,since it was desired to have them as permanent structure.


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The planking was milled out of a 2x 4 Western Red Cedar Board. The cedar wasripped to width and then run through a thickness planer to make certain that gluing edgeswould be perfectly straight. It was then ripped to thickness. The planks were not runthrough the thickness planer for thickness because the hull needed to be faired after the

planks were laid, so there was no need to have a perfectly flat surface. The saw cut wasflat enough. The cedar planks finished at x .

The first planks location was crucial since it would drive the location of all of the otherplanks. If it was not placed correctly there would be large amounts of edge set, ortwisting in the planks which would result in broken planks. The first plank is typicallylocated along an imaginary chine, or the part of the boat that has the hardest bilge turn.This was approximately where the first plank for these models was located. Only oneside was done at a time. Once the first plank was located, it was nailed to the MDFframes using finish nails with 3mm pads under them. The pads were knocked off afterthe glue dried which exposed the head of the nail and allowed them to be more easily

removed. Once the first plank was fastened, glue could be mixed and put on the edges ofthe next few planks which were held in a small jig. The glue that was used for thisproject was West Systems epoxy with both Cabasil and Microballoons for strength andthickness. The next plank, with glue on one edge, was then pushed up against the firstand nailed on. This caused most of the glue to squeeze out, which also helped the buildertell if the joint was tight.

The entire hull was planked this way, plank by plank. After the first side was completedand it was allowed to cure, a saw cut was made down the centerline, which allowed thenext side to be fitted to it. When planking the other side, the ends of the planks needed tobe fitted before gluing, so they were laid out in a process called dry-fitting. Dry-fitting,in this application, was done using only four to five planks to avoid the potential forplank slippage upon glue application. If more than four or five planks were used theywould typically end up in slightly different places from where they were originallyplaced. The centerline fitting can be slightly rough, since any gap can be filled with glue.Once the second side was glued on, it was allowed to cure and then the hull was ready forfairing.

Before fairing could begin, all of the pads under the nails were removed, and the nailswere pulled out. The hull was then rough-sanded to remove any excess epoxy and anyplank imperfections. The rough-sanding was done using a portable disk sander with 80grit sandpaper. After the hull was rough-sanded, general fairing was achieved usingplanes. Battens were used on these models to be certain that the hull was fair. Once theplaning was done, the hull was hand-sanded using half sheet sanding pads to finish thefairing process. Once the hull was faired, it was slightly smaller than the lines planrequired: heavy planking was used and then material was removed. This slight sizedifference roughly takes into account the thickness of the fiberglass cloth that would beapplied to the outside along with paint thickness.


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Upon completion of hull faring, fiberglass was applied to add additional strength to thehull. Ten ounce glass cloth was used with West Systems Epoxy. The cloth was laid outonto the hull and the epoxy poured over the cloth and spread out using a squeegee. Theglue was worked into the cloth and wood using the squeegee, and then all of the excessglue was removed by applying extra force on the squeegee in order to squeeze the extra

glue out of the cloth, leaving only the minimum required glue. This kept excess gluefrom causing bubbles or wrinkles in the glass as well as reducing unnecessary weight.Once the first layer of epoxy cured, four more coats of epoxy were used to add enoughthickness to hide the weave of the cloth which resulted in a smooth outer surface. Thesecoats were applied using a process called hot-coating which means that the coats were puton before the previous coats had completely cured, and could still bond to another layerapplied on top. The process for deciding whether or not a surface is ready to be coatedagain is very simple but effective: if a finger dragged along the top of the glue does notstick, or leave a drag mark, but sticks when a nonmoving finger is placed on it, the glue isready. This state of cure is commonly called being green, and depending on the hardenerused, can be achieved in several hours.

Once the glue on the outside has cured completely, the mold and hull were removed fromthe strongback, and all the inside frames, which were taped so that the glue would notstick, were removed from the hull skin. The inside of the hull was then roughly sanded,and a layer of glass applied using the same techniques as the outside. This created a verystrong, stiff and most importantly, light hull shell. The first model can be seen in Figure4 below, after having the fiberglass applied to the hull.

Figure 4: Picture of the first model during construction

Next, the sheer lines and the transom were trimmed and the bottom was sanded with 100grit sandpaper to prepare for a coat of primer. A product set from U.S. Paint was used forthese models: Awl-Grip and its recommended primer, 545 Epoxy Primer. The 545 wassprayed first in three coats. After the primer had adequate time to cure, the Awl-grip wassprayed in three coats. For the first model, Flagship Yellow was used. The secondmodel was sprayed with Apple Red. In hindsight the yellow seemed to show up muchbetter in the videos and pictures and should have been used for the second model as well.


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Once the models were painted, they were wet sanded with 400 grit sandpaper to roughenthe surface to that of a full scale bottom. Waterlines and stations were drawn at knownintervals on the hull to make ballasting easier. A sand strip was placed at 5% of thewaterline length to induce turbulent flow like that of the full scale yacht. A metal plate

with bolts was also placed inside the boat in order to attach the dynamometer, positionedto simulate towing from the mast location.

3.4 Test Matrix

The TP52 Design Team chose to test at various conditions that would most likelyrepresent the conditions frequently seen on a race course while keeping in mind that thehull is designed as an ultra light displacement boat which has been designed to sail atrelatively low angles of heel. The speeds that were chosen to test ranged from 4 knots,which was the slowest chosen due to inaccuracies in the speed of the testing equipmentbelow that speed, and up to 25 knots for the fastest condition. This speed is easily

achievable, especially given information from crewmembers sailing on existing TP52s.The runs for the main part of the matrix were limited to speeds from 4 knots to hullspeed, which is approximately 10 knots. For the main part of the matrix, all possiblecombinations of 0, 2, 4 and 6 degrees of yaw were tested, as well as 0, 10, and 20 degreesof roll for speeds of 4 to 10 knots. High speed testing from 11 to 18 knots with 0 and 1.5degrees of yaw and 0 and 10 degrees of roll was also completed to enlarge the matrix inareas that were felt to be important to the off-wind condition. The rationale behind thesechoices was that the boat will be planing above hull speed and unlikely to be yawing verymuch; also the hull will not be planing while heeled so it would be unnecessary to test thehulls at unrealistic sailing conditions. Tables 4 and 5 contain the specific test matricesthat were used during each phase of the testing.

Table 4: Test Matrix for Bare Hull TestsHeel Angle

(deg)Speed(knots)

Yaw Angle(deg)

0 2, 4-25, 30 0

0 11-16 1.5

0 2, 4-10 2, 4, 6

10 2, 4-10 0, 2, 4, 6

10 11-16 0

20 2, 4-10 0, 2, 4, 6

Table 5: Test Matrix for Appendage Test

Heel Angle(deg)

Speed(knots)

Yaw Angle(deg)

0 5-12 0, 2, 4, 6

0 14, 16 0, 2, 4

0 18, 20 0

10 5-12 0, 2, 4, 6

10 14, 16 0, 2, 4

20 5-12 0, 2, 4, 6


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3.5 Testing Set Up

Once the first hull was designed, it was necessary to determine a scale factor to use in thecreation of the models. The limiting factor in the choice of size was the maximum speedachievable in the University of Michigan Marine Hydrodynamics Laboratory (UMMHL)

Tow Tank, which is approximately 18 feet per second. The desire was to test the hulls atspeeds of up to 30 knots which, combined with the maximum speed of the carriage,dictated a model scale of 1 to 8, which resulted in the models being 6.5 feet long. Theoptimal scale for model testing sailboats is 1 to 3, but this is not physically possible for a52 sailboat in the facilities available for use at the University of Michigan. Constructionof a 6.5 model is also much simpler than a larger version.

The yacht dynamometer was used in conjunction with the drag force dynamometer tomeasure drag force, roll moment, yaw moment, and the lift force of the model. Thetesting procedure began by taking apart the dynamometer and cleaning all of the bearingsand checking to make sure all range of motions were free to move and that all of the other

fittings were tightened as necessary. The dynamometer can be seen in operation inFigure 5.

Figure 5: Yacht dynamometer in operation


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3.6 Calibration Procedure

After determining that the dynamometer was working as desired, a series of calibrationtests were performed to make sure that the instrumentation was performing correctly.Linear responses were achieved for all of the range of motions. A calibration mechanism

that would allow for easy and accurate calibration of the dynamometer once it wasinstalled in the model and attached to the carriage was also developed. The calibrationprocedure was developed to take into account the flexing of the dynamometer.

The dynamometer required calibration in all 4 ranges of motions, and the carriage speedhas a fixed calibration value. The drag force was calculated using the weight panattached to the drag dynamometer, and was calibrated to a maximum of 10 pounds ofdrag. The lift side force was calibrated by mounting a series of blocks onto the carriageand then attaching a string to the pivot point of the dynamometer and then hangingweights to pull the dynamometer sideways in the same manner as that of the side forcegenerated by the model. The side force was calibrated for a maximum of 6 pounds of

force. The roll moment was calculated by placing weights on the shear of the model at aspecific point, and then the moment was calculated by measuring the distance from thecenterline to the point at which the weights were applied. The roll moment wascalibrated for a maximum of 5 foot-pounds. The yaw moment was calibrated by usingthe same system of blocks and weights that was used for the side force but the string wasattached to an eye screwed into the bow. The moment was calculated by measuring thedistance from the eye to the center of the shaft in the dynamometer about which themodel rotates. The yaw moment was calculated for a maximum moment of 6 foot-pounds. During the testing of the models, we would calibrate every morning beforetesting and then would also recalibrate multiple times during the day to make sure thatthe data that we were collecting would be consistent. Figure 6 shows some of thedifferent calibration procedures; from left to right the roll moment, side force, and yawmoment procedures.

Figure 6: Photographs of the roll, side force and yaw moment calibration procedures

During the appendage test, it became evident that the strain gauges on the dynamometerthat were used to measure the roll and yaw moments were not functioning correctly, and


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therefore we were unable to use the roll and yaw moment data for either the comparisontest or the appendage test. This is detrimental in that it prevents us from accuratelycalculating the center of lateral resistance for the hull. This is problematic, but can beestimated using various methods and does not overly hamper our design project.

3.7 Testing Procedure

The displacement for the model was calculated from the hydrostatics of the full scaleacht and then scaled down to the model size. The model and dynamometer were

s.of

as ballasted and attached to the carriage, it was necessary to center theodel so that it would run straight down the tank. This was accomplished by hanging a

rocedure involved zeroing all of the instrumentation for a period of 40econds before each run, which is the slosh time for the towing tank. Then a model speed

lect

so that the unsteady effects would beinimized, but this is dependent upon time, so at higher speeds there was a noticeable

a

sturb the tank very much so a time interval of0 minutes was chosen between runs. It has been shown that there are vortices in the

still photographs were taken for each run.wo video cameras were used to record the profile of the yacht as well as the transom

ts,

yweighed and then the remaining weight necessary was added in the form of lead blockThe blocks were positioned so that the yacht would float at a level trim. The blockslead were then glued in place using silicone to movement during the starting and stoppingof the carriage.

Once the model wm

plumb bob off of the drag dynamometer and visually aligning the bow with the plumbbob. Once the position was set, the heave staff was clamped into place so that it couldnot rotate.

The testing pswas programmed into the carriage and set for an automatic run. We attempted to col30 seconds of data for every run, which was possible at all of the slow speeds but not athigher speeds. For the highest speeds, we were only able to collect 10 seconds of data.The data was collected at a rate of 40 Hz. This value was chosen as it would give usenough data to analyze without showing aliasing.

The acceleration rates were adjusted for the carriagemsurge in the model once the carriage had achieved the test speed. This was taken intoaccount by watching the carriage speed fluctuate and once the fluctuations had reachedsmall enough value, data was recorded.

The model size was such that it did not di1tank that last for a much longer period of time, but we did not have the necessary tanktime to wait multiple hours between each run.

In addition to recording data, video footage andTflow. The profile view was used to estimate the dynamic wetted surface while thetransom view was used as a comparison between hull forms. During the appendage tesan underwater camera was set up to more accurately calculate the dynamic wettedsurface.


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3.8 Dynamic Wetted Surface Analysis

The wetted surface of the hull changes for each speed and as the force scaling is basedrmine the wetted surface for each speed at

ifferent heel angles. During the comparison test, a profile video was recorded for each

od

were taken for each run so

at the location of the intersection between the water and the bow could be accurately

ng

n order to finalize the hull design for the Transpac 52, two models were tested and theirhe first model was designed to be as wide and flat

s possible to facilitate planning in downwind and surfing conditions. The second hull

dto a Microsoft Excel spreadsheet. The data were then non-dimensionlized with

roude number being calculated using equation 1, Reynolds number being calculated

d

upon surface area, it was necessary to deted

run which was used to determine the approximate wetted surface. The waterline lengthwas determined by measuring the amount of the bow that was out of the water. Thetransom intersection was measured in the same fashion as the bow, and once the bow andstern intersections of the waterplane were known, a straight plane was generated throughthe hull and the surface of the resulting section was measured in Maxsurf. This methdoes not take into account the additional wetted surface of the wave profile, but it wasassumed that the peak and trough would roughly cancel out so that the wetted surfacemeasured using the above method would be fairly accurate.

The wetted surface for the appendage test was calculated from still frames from anunderwater video camera. In addition, still pictures of the bow

thmeasured. The wake from the hull made using the underwater camera for the bowlocation virtually impossible, but with the use of the still camera the location was foundvery accurately. The wetted surface was calculated at 0, 10 and 20 degrees of heel foreach speed and the wetted surface was assumed to be the same for each correspondiyaw angle.

3.9 Comparison Testing Analysis

Iresistance characteristics compared. Tawas designed with a much more elliptical water plane and a finer entrance to reduce formand wave drag in the displacement range of the boat. Both models were tested withoutappendages. Before testing it was hypothesized that the first hull would have betterresistance characteristics at high speed when the effects of dynamic lift on the hull wouldbe most pronounced. It was also hypothesized that the second hull form would havebetter resistance characteristics at slower speeds with its more traditional water planeshape.

After the data for drag vs. speed had been collected for both models it was compiled aninput inFusing equation 2, and CDM being calculated using equation 3. The wetted surface usedfor non-dimensionlizing the drag was the static wetted surface for each model for thegiven heel. The density used for non-dimensionlization was assumed to be constant anequal to 1.99 lb/ft^3.

lg

VFr=

*

(1)


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(2)

(3)

v

lV*Re =

SV

D

CD ***2/1 2=

Once the data had been non-dimensionalized the drag for each model was broken downsing both Froudes method and Hughes method. For Froudes method it was assumedat the drag could be broken down into frictional, Cf, and residuary, CR, drag. For the

d

is

CD = Cf + CW + Cform

uthHughes method approach the drag was further divided into form drag, wave makingdrag, and frictional drag. A form factor, R, was calculated using Prohaskas method inorder to determine the components of form drag, Cform, and wave making drag, CW,using Hughes method. For both methods the coefficient of frictional drag was calculateusing the ITTC mean line for turbulent flow. Turbulence was tripped on both modelsusing a sand strip. For both methods a correlation allowance, CA, of 0.00031 wasassumed. The drag breakdown for Froudes method and Reynolds method is describedin equations 4 and 5. The Prohaska plots for both models are included as Figures 7 and 8.The ITTC mean line equation used to compute the frictional resistance coefficient, Cf,included as equation 6.

CD = Cf + CR + CA

2)2(log(Re)075.0

=Cf

(4)

(5)

(6)


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0.0

0.5

1.0

1.5

2.0

2.5

0 2 4 6 8 10 12 14

Fr^4/Cf

Ct/Cft

Figure 7: Model 1 Prohaska Plot

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30 35 40

Fr^4/Cf

Ct/Cf

Figure 8: Model 2 Prohaska Plot


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Applying Froudes method and Hughes method to the data full scale drag coefficientsfor both models were calculated. These results were plotted for zero, ten, and twentydegrees of heel and the results were compared. Both Froudes and Hughes methodshowed similar trends in the data with Hughes method predicting less full scale drag inall conditions. Plots of full scale drag coefficient, CDS, versus Froude number in each of

the three heeled conditions are include as Figures 9 through 11.

Drag Coefficient vs. Froude Number

Heel=Yaw=0

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10

Froude Number

DragCoefficient Froude Model 1

Froude Model 2

Hughs Model 1Hughs Model 2

Poly. (Froude Model 1)

Poly. (Froude Model 2)

Poly. (Hughs Model 1)

Poly. (Hughs Model 2)

Figure 9: Full Scale Drag Coefficient vs. Froude Number for 00

Heel and 00

Yaw


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Drag Coefficient vs. Froude Number Heel=10,

Yaw=0

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70

Froude Number = v/sqrt(g*l)

DragCoefficient

Figure 10: Full Scale Drag Coefficient vs. Froude Number for 100 Heel and 00 Yaw

Drag Coefficient vs. Froude Number Heel=20,

Yaw=0

0.0030

0.0035

0.0040

0.0045

0.0050

0.0055

0.0060

0.0065

0.0070

0.20 0.25 0.30 0.35 0.40 0.45

Froude Number = v/sqrt(g*l)

DragCoefficient

Figure 11: Full Scale Drag Coefficient vs. Froude Number for 20

0Heel and 0

0Yaw


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Once the bare hull resistance characteristics for both hulls were graphed it was possible tocompare the relative performance of the two hull shapes. As expected the second hullform seemed to perform better in the displacement range with the more extreme planinghull outperforming the traditional shape at high speed. Another result of the analysis wasthe difference in relative performance at differing heel angles. One can observe that the

Froude number at which the two trend lines cross changes as the models heel increases.For zero degrees heel the two curves cross at Fr=0.35, at 10 degrees heel the crossingpoint moves to Fr=0.42, and at 20 degrees heel it moves back to Fr=0.38. This may beaccounted for by the degree of curvature of the two hulls at the bilge. The second hullform has a more gradual bilge turn which may give it a better water plane shape around10 degrees heel.

3.10 Keel Construction

After the data from the comparison test was analyzed and the second hull was chosenbased on its better upwind performance, a keel and bulb were added to the hull for a

second set of tests to measure the interaction forces between the hull and keel. The keeland bulb sections were determined using known sections that lift and drag could becalculated for analytically. A NACA 0015 section was chosen for the keel and a NACA66021 for the bulb with the chord length of the strut consistent with that of other TP52s ata scale of 1 to 8.

The keel was built out of 6064 T6 Aluminum. The section shape was scribed into oneend of a piece of flat-stock 2 x 5/8. The flat-stock was then placed on the mill andthe mill head was angled as passes were made down the length of the foil. This was doneto both sides and resulted in a very accurate foil shape. Sand strips were also placed onthe foil to ensure that turbulence was tripped.

The bulb was made out of oak, and was turned on the lathe. The section thickness wasdetermined at multiple points along the length of the bulb and was turned down to thatthickness at each point and then faired in between. The bulb was coated with epoxy andthen bonded to the foil.

The foil was attached to the hull using two #8 flat head machine screws that went througha secured plate and into the top of the keel. A fillet was faired around the keel-hull jointin order to replicate what would be done on a real boat.

3.11 Appendage Testing

From the results of the comparison model test the more conservative hull form wasselected based on its relative performance in the displacement range. A condensed matrixwas created for the model with bulb and strut and the testing was completed using thesame methods as used during the comparison model tests.

The lift and drag data from the appendage model tests was non-dimensionlized using thesame method described for the comparison model tests. A simplified stripping method


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similar to that used by Teeters was used to further break down the lift and drag of themodel. Equation 7 defines the total drag with equation 8 showing the breakdown of thecanoe body drag. Equation 9 shows the breakdown of the lift.

ceinterferanappendagescanoe DragDragDragDrag= (7)

(8)

(9)

residualfrictioncanoe DragDragDrag =

appendagescanoe LiftLiftLift=

The lift and drag of the canoe body was assumed to be equal to those obtained from thebare hull resistance testing performed during the comparison model test. Since the yawangles for the comparison model test were not exactly the same as those for theappendage model test, drag and lift were regressed from the comparison data as afunction of yaw for each speed and heel, and these linear equations were used for the

appendage model test analysis. The trend line function in Microsoft Excel was used toderive the regression equations. Figure 12 shows the method used to regress the lift anddrag data.

Bare Hull Lift and Drag vs. Yaw @ 4.7535 ft/s, 10

Heel

y = 0.0086x + 0.6756

y = 0.0081x + 0.0308

0

0.1

0.2

0.30.4

0.5

0.6

0.7

0.8

0 2 4 6 8

Yaw (degrees)

Force

(lbf) Drag

Lift

Linear (Drag)

Linear (Lift)

Figure 12: Graph of Regressed Lift and Drag Data

3.12 Appendage Test Analysis

In order to determine the interference drag generated at the interface between the strutand the canoe body elliptical loading was assumed. Equation 10 was then used tocalculate the drag coefficient of the strut. Equation 11 defines how to calculate the aspectratio of the strut. The lift coefficient of the strut was calculated using equation 12. Thedrag of the bulb was assumed to be equal to the skin friction of the bulb using a frictionaldrag coefficient calculated from the International Towing Tank Conference (ITTC) meanline. An attempt was made to further break down the lift of the model into the lift of the


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strut and the bulb combination and the effects of the appendage interaction with the hull.It was found that the theoretical methods available did not give precise enough results incomparison to the errors in the testing to perform such an analysis.

(10)

(11)

(12)

2

**7.0 AR

CLCD =

Area

SpanAR

2

=

SV

LCL

***2/1 2=

The final step in the analysis was to scale the lift and drag data back up to full scale inorder to use the results as an input into a velocity prediction program. The non-

dimensional interference drag, CDIM, was assumed to be constant between model andfull scale. The coefficients of appendage drag, CDA, are different at model and full scaledue to Reynolds scaling effects. A term was added to the full scale lift coefficient toaccount for changes in the design of the appendages from those that were tested.Analytical methods will be used to determine the change in lift coefficient from thebaseline appendages. The drag coefficient for the new appendages can be calculatedusing equation 10. Equations 13 through 16 give the details of the process used todetermine the full scale forces on the hull.

(13)

(14)

(15)

(16)

CACDASCDIMCRCMCfCSCDS=

)(***21 2 appendagescanoe

appendagescanoemodel

SSV

DragDragDragCDIM

+=

CLCLASCLCMCLS =

BASELINENEW CLCLCL =

Once the full scale forces acting on the hull were determined, the lift coefficient of theyacht was plotted at each of the three heel angles versus speed for constant yaw. Theseresults can be used to develop speed polar diagrams for the full scale yacht using the

velocity prediction program PCSAIL developed at the University of Michigan. The liftcoefficient of the yacht for various yaw angles in each of the three heel conditions wasplotted and is included below as Figures 13-15. The lift to drag ratio was also plotted andis shown below as Figures 16-18.


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CLyacht vs Vyacht 0 deg Heel

0.000E+00

2.000E-03

4.000E-03

6.000E-03

8.000E-03

1.000E-02

1.200E-02

0.00 5.00 10.00 15.00 20.00

Vyacht (knots)

CL(non-dim)

2.81 deg Yaw

4.74 deg Yaw

Figure 13: Lift Side force at 0

0Heel


5.000E-03

6.000E-03

7.000E-03

8.000E-03

9.000E-03

1.000E-02

1.100E-02

1.200E-02

1.300E-02

0.00 5.00 10.00 15.00 20.00

Vyacht (knots)

CL(non-dim)

2.81 deg Yaw

4.74 deg Yaw

Figure 14: Lift Side Force at 10

0Heel


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4.000E-03

5.000E-03

6.000E-03

7.000E-03

8.000E-03

9.000E-03

1.000E-02

1.100E-02

1.200E-02

1.300E-02

1.400E-02

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Vyacht (knots)

CL(non-dim)

2.81 deg Yaw

4.74 deg Yaw

Figure 15: Lift Side Force at 200 Heel

CL/CD O deg Heel

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.00 5.00 10.00 15.00 20.00

Vyacht (kts)

CL/CD(non-dim)

2.81 deg Yaw

4.74 deg Yaw

Figure 16: Lift Side Force vs. Drag Force at 00 Heel


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CL/CD 10 deg Heel

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.00 5.00 10.00 15.00 20.00

Vyacht (kts)

CL/CD(non-dim)

2.81 deg Yaw

4.74 deg Yaw

Figure 17: Lift Side Force vs. Drag Force at 10

0Heel

CL/CD 20 deg Heel

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Vyacht (kts)

CL/CD(non-dim)

2.81 deg Yaw

4.74 deg Yaw

Figure 18: Lift Side Force vs. Drag Force at 200 Heel

From Figures 13 through 18 it can be seen that the lift and drag coefficients of the yachtseem to gradually decrease with speed in the displacement range of the hull and thenincrease linearly once the boat enters a planing mode. While we expected the lift and dragcoefficients to be more constant in the displacement range these results seem to beconsistent with theory.


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4. Sail Plan Design

4.1 Summary

The primary dimensions of the sail plan for the TP52 are specified by the rule but allow

the designer some leeway in designing the mainsail through the choice of the boomlength, mast height and the length of the sail at specified heights above the boom, whilemaintaining an area of 985 ft2. The mainsail shape was chosen to create as much of anelliptical form as possible to maximize efficiency, while not allowing the roach of themainsail to become too large so that it would catch on the backstay during tacks andgybes. The maximum jib area is specified through the maximum specification of I, LPG,and J and the maximum spinnaker area is specified at 2665 ft2. The specifications of thebox rule as well as the final dimensions chosen are shown below in Table 6.

Table 6: Sail Plan DimensionsMaximum Minimum Final Design

IM 64.7 ft 64.7 ftJ 20.3 ft 20.3 ft

LP 20.9 ft 20.9 ft

ISP 73.5 ft 73.5 ft

P 67.0 ft 67.0 ft

HB 0.5 ft 0.5 ft

BAS 6.5 ft 7.0 ft 7.0 ft

4.2 Methodology

The jib and spinnakers will be designed by the sailmakers as they have extensiveexperience and access to wind tunnel tests to determine the optimum shape and size for agiven boat, whereas the principle dimensions of the mainsail will be provided by theyacht designer to the sailmaker. TP52 boats are required to obtain an IMS certificate aswell as to fit inside the box rule, and the IMS requirements provide additional limitationsshown below in Table 7.

Table 7: IMS Mainsail LimitationsLimit

MGT 0.22*E

MGU 0.38*E

MGM 0.65*E

MGL 0.90*E

MGT, MGU, MGM, and MGL are defined as the lengths of the girths of the mainsailtaken at points 7/8, 3/4, 1/2, and 1/4 of the leach from the clew respectively. This helpsto define the maximum roach in the sail for a given length of the boom E. The mainsailarea, MSA, was calculated from equation 17 which was specified in the TP52 rule.


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++

++

++

++

+=

2828

242424

HBMGTPMGTMGUP

MGUMGMPMGMMGLPMGLEPMSA

(17)

This equation was used in combination with the IMS measurement points to determinethe mainsail area which must equal 985 ft2.

The mast and standing rigging for this yacht would be designed by a spar manufacturer,which was chosen to be Hall Spars for the Rhumb Runner. The final sizes of the sail planwould be given to Hall Spars to create a mast as well as the standing rigging. Theminimum mast weight is specified in the TP52 rule, as well as the requirement that thestanding rigging must be stainless steel and circular in cross section.

4.3 Design and Calculations

The driving force in the calculation of the mainsail dimensions was the desire to create anelliptically shaped sail to maximize efficency, while preventing the roach of the sail fromoverlapping the backstay too much. This was accomplished by creating an Excelspreadsheet that would allow the visual comparison between the IMS maximumdimensions, the backstay of the boat, and the chosen distances at each of the points in theabove equation. This allowed the creation of a sail that is elliptically shaped, within thelimits of the IMS rule, and also does not have an excessive amount of overlap that willcause problems and the visual output from the Excel sheet can be seen below in Figure 19with the final dimensions of the mainsail shown below in Table 8.

Table 8: Final Mainsail DimensionsP 67.0 ft

E 25.25 ft

HB 0.5 ft

MGL 21.0 ft

MGM 15.75 ft

MGU 8.94 ft

MGT 5.2 ft


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TP52 Sail Plan

-10

0

10

20

30

40

50

60

70

-32 -22 -12 -2 8 18

Boom

Mast

Mast

Boom

Sail

Backstay

Jib

Deck

Max Main Sail

Figure 19: Visual output from Excel comparing the IMS limits to the final

sail dimensions


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5. Appendage Design

5.1 Summary

The design and optimization of the appendages was conducted using the results of

experiments, first principle calculations, and design guidance from experience. Thedesign of the bulb focused on minimizing the surface area and length of the bulb for therequired volume. Once the weight of the bulb had been established the structuraloptimization of the keel strut was completed with an emphasis on minimizing thicknessand weight. The keel foil was designed around the strut configuration and its area wascompared with the total sail area and the design guidance of Larsson and Elliassion. Therudder design focused on maximizing the lift generation capacity for a given drag whilehaving good stall characteristics. Finally the balance of the sails and lifting surfaces waschecked against design guidance in order to ensure balanced sailing in all conditions.

5.2 Methodology

In order to optimize the appendages, experimental results were combined with firstprinciple calculations to determine the best configuration for the keel, bulb, and rudder inboth the buoy racing and distance racing modes. The section shape for the foils wasselected using the experimental results from Abbot and Von Doenhoff withconsiderations being made for lift, drag, and stall characteristics. The profile of the bulbwas also based on section data from The Theory of Wing Sections. The cross sectionalshape of the bulb was then optimized to minimize surface area, cross sectional area,length, and vertical center of gravity for a given volume.

Structural considerations became the driving force in the design of both the rudder and

the keel. Two dimensional ideal beam theory was used to design the keel strut and therudder stock to allow for the thinnest possible foil sections. Equation 18 was used tocompute the bending stress in the strut and stock.

y

beamI

Mc= (18)

Design loads for the keel strut were calculated for a knock down condition with a heelangle of 90 degrees and the bulb completely out of the water. Figure 20 illustrates thedesign condition for the keel strut calculations. The design loads for the rudder werebased on the lift and drag forces at stall with a boat speed of 15 knots. Elliptical loading

was assumed to compute the lift and drag acting on the rudder in the design condition.Microsoft Excel spreadsheets utilizing the solver function were used in the optimizationprocess. Once the structures had been optimized with a suitable factor of safety, the sizeof the foil sections was compared to that recommended by Larsson and Eliasson in orderto ensure adequate side force production and maneuverability.


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Figure 20: Loading Condition for Optimization of the Keel Strut and Keel Bolts

The detailed design of the keel attachment to the hull was completed to assure adequatestrength in the connection system while maximizing the ease of keel installation andremoval. The keel bolts were sized using two dimensional beam theory in two loadingconditions: the knock down condition and the upright condition. The knock downcondition with the bulb out of the water was used to determine the shear stress and theupright condition was used to determine the stress due to the bulb weight.

To insure that the forces acting on the appendages were balanced with the sail forces, thecenter of effort of the sails and the center of lateral resistance were calculated using themethod from Larsson and Elliasson. The lateral separation, or lead, between the center ofeffort and the center of lateral resistance was then compared with the guidance of Larssonand Elliasson.

5.3 Design and Calculations

After analyzing the available airfoil shapes presented in the Theory of Wing Sections byAbbot and Von Doenhoff, a NACA 64 series thickness form was selected for the keel and

bulb sections. The 64 series foil shape provides an excellent lift to drag ratio and a stallangle of 13 degrees. In addition the 64 series airfoils have a drag bucket around zerodegrees angle of attack that can lead to significant reductions in drag in laminar operatingconditions. While this drag bucket does not occur when the foil is operating in turbulentconditions the potential for speed gains in calm water was considered desirable.

Once the section shape for the bulb had been selected bulbs with several possible crosssectional shapes were modeled in Rhino. The weight of the bulb was first determinedusing an estimate of the structural weight of the hull based on data for an existing TP52provided by Bakewell-White Yacht Design. The maximum bulb weight was thendetermined by subtracting the structural, machinery, and rig weight from the maximum

displacement stipulated by the TP52 rule. The density of the bulb was assumed to be 700lb/ft3 which is approximately 95% pure lead and 5% antimony, a ratio believed to berelatively standard in keel production. The first bulb was designed used a NACA 64-021in profile and a circular cross section. Three other cross sections were used with the 64-021 profile in an attempt to minimize the vertical center of gravity, surface area, andlength of the bulb. The center of gravity was minimized in order to gain the greatestrighting moment from a given bulb weight, the surface area was minimized in order tominimize the frictional drag of the bulb, and the length was minimized in an attempt to


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minimize the yaw added mass and increase the speed through tacks and gybes. Table 9details the specifications of the four bulbs designed while Figure 21 provides a Rhinorendering of the four bulb shapes.

Table 9: Specifications of the Four Bulbs with Varying Cross Section

Cross Section Surface Area Volume Length CG above BL Weightft

2ft

3ft ft lbs

Circle 31.01 10.714 8.522 0.915 7500

Ellipse 30.12 10.714 7.444 0.792 7500

Beaver Tail 39.43 10.714 9.464 0.386 7500

Half Round 38.25 10.714 10.113 0.44 7500

Figure 21: Rhino Rendering Illustrating the Geometry of the (from left to right) Circular,Elliptical, Half Round, and Beaver Tail Cross Sections.

After the final weight study had been completed it was determined that the minimumVCG requirement in the TP52 rule was a limiting factor in the bulb design. The rule

dictates that the vertical center of gravity of the hull cannot be more than 2.7 feet belowthe design waterline. This requirement forced weight to be moved out of the bulb to keepthe VCG within the limits of the box rule. Once it was determined that the rule wouldlimit the VCG, the half-round and beaver tail bulbs were eliminated from considerationsince their only performance advantage were their low centers of gravity. The ellipticalsection bulb will be fitted for the buoy racing condition since it has slightly less wettedsurface than the round section bulb and is significantly shorter. Less wetted surface willdecrease skin friction on the bulb at slow speeds and the shorter length will dec

tp52 design report rumb runner

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