A Design Study of an AC72 Catamaran

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2 A Design Study of an AC72 Catamaran Presenter: Peter Schwarzel RPEQ 1851: The Yacht America wins the 100 Cup by sailing around the Isle of Wight and beating all comers. The event is now called Cowes Week. Please remember that the AC is a war and disputes where still being settled by duels. 2

3 My AC72 Project VILLA This presentation is based on an article written for the Professional Boatbuilder Magazine to be seen in issue #133 3

4 What we shall discuss Briefly the AC72 Class Rules The Wing Aerodynamics The Hull Hydrodynamics The Platform Structures Structural Optimisation VILLA Design Review Design Cycle 1 - Weight Study 4

5 Presentation Objective To entertain you lot with an interesting story about yacht design To clock up some time towards my Professional Development Programme And its better then spending time watching Masterchef or The Block To find out what the audience would like me to speak on next time USA17 current holder of the Cup Replica of America with V5 IACC yacht 5

6 Any general Q s about the Cup? Or technical sailing questions? Larry Ellison, 5 th wealthiest person in the world, current holder of the AC The Auld Mug 6

7 The 34 th Challenge (in 160 years) The AC45 Class Has been created as a bridge to the new AC72 Class & to get the AC back into the media stream and get some momentum going. The AC is now a Brand and has to deliver sponsor & media value. 7

8 The AC72 Class Will be big and fast! None exist yet but they are in computer RAM (virtual drawing boards) and on their way. First launchings are expected July

9 The Shared Design Program 100,000 to 200,000hrs have already been spent on the design of the generic AC72 s, can by package for $1.2M USD Estimated cost for one AC72 is $10M USD The build will take 100,000hrs? 6 months for a big boat builder in France, 9 months for others, over a year here. Its clear I can t go into the details in one hour so I ll concentrate on the Wing as it s the New item and big difference. 9

10 The Big difference - Wing Sails Soft Sails - General development path: Polynesian rigs, Square riggers Bermudian rig Unarigs Wing mast and soft sail combination Wing Sail or Rigid Wing very developed in C-Class Catamarans Big Wings are easier to control than big soft sails, USA17 (68m, 747 wingspan 68m) Mainsheet load Soft 35T, Wing 3T Manual handling is the limit to sail size 10

11 Designing Sail Boats - The so called Design Spiral Digest the Rules, pay very close attention to the rules. Pete Melvin tried to keep it simple! Box Rule Design the hull, daggerboards and rudders Review the rig, establish aero loads and translate these to platform loads Design the Cross Structure or Platform Integrate the hulls, wing and platform Review the results Take a deep breath and find out where we are! Go around the next Design Spiral, again 11

12 AC72 Rules 36 pages of stuff see AmericasCup.com 22m long, 14m wide, 260m2 Wing 38m high Tack 4m in front of bow There are minimum and maximum weights, ~8500kg sailing displacement WSL70, AC45 example 12

13 Modelling Techniques Hull 22m long, Beam 14m NURBS, Parametric, wireframe, specialist, manual lofting Ratios Cp40, Cp45, Cf, Cb, Amax, L/B, wetted area, sectional area curve, hollow Reverse bow: Fashion or Function? 13

14 Small Parts Daggerboards & Rudders What speed to design to? Gybing Daggerboard 14

15 Materials Mainly Carbon Fibre Boron & Beryllium not allowed Materials controlled by Maximum Modulus for each major component 15

16 Wing General Stuff Planform vs the rules - Induced Drag (creating a wake) Aspect Ratio Profile Drag (boundary layer effects) - twist Wing Controls Quadrant Twist LE & TE wind shear + planform (soft sail explanation) Cι - lift Cd drag click 16

17 The Platform Structural Philosophy Tensile Structure 1, 2, 3 eg Beach Cats and Alingi 5 Spaceframe Structure (3d) 1 Truss (2d) Monocoque 1, 2 Structural Optimisation -Topological shape & subtractive processes may miss a good answer, use stochastic approach -Evolutionary (iterative, mutative) -Stochastic (broader investigation) 17

18 Rigging Design & Loadcases Upwind & Downwind (there are many others) First Principle - Aeroelastic Newtonian Approach - Hm=Rm Sag Materials Steel, PBO, Vectran, Polyethylene (Dynex), Carbon Fibre 18

19 Integration The General Arrangement whiteboard 19

20 Design Review Q: What did I learn? A: How Wings work & read the rules often What is possible? (IF TIME) Resulting Weight Study Crew Platform Sails max Wing min Hulls Rudders Daggerboards Displacement 1012kg 3700kg (need to estimate hardware weight) 250kg 1325kg 1400kg 300kg 500kg 8487kg 20

21 What we have discussed AC72 Rules very briefly The Wing Aerodynamics The Hull Hydrodynamics The Platform Structures Optimisation Design Review 21

22 At last, the Finish Thank you all for listening What would people like to see/hear next time? Last Questions? V-11A hull = VILLA The End 22