34th America's Cup: multihulls!

Quite agree. Just give it a rest.

 

shifted the post on Artemis Racing to the appropriate thread

 

Coroner's verdict in on Artemis tragedy, article by Bob Fisher on Sail-World:

http://www.sail-world.com/Australia...122373&SRCID=0&ntid=0&tickeruid=0&tickerCID=0

 

Still so damn sad....

 

34th Foiling AC

Excerpt from an article in Sail World about the differences between TNZ and Oracle:
full article here- http://www.sail-world.com/USA/Americas-Cup:-Oracle-and-Team-NZ-designers-reveal-AC72-secrets/122447
>Video below is most extraordinary if you're interested in the tech developed during 34!!

He went on to highlight the key differences between Oracle and Team NZ development campaigns being:

- Time on the water: Team NZ were launched and sailing before Oracle and stayed that way right through the campaign (Team NZ has 85 days on the water and performed 2000 tacks and 2000 gybes in this build up)

- Disasters: Oracle broke her foils on the first day, losing 5 weeks, and capsized on Day 8, losing 15 weeks

- Wings: Oracle had prior experience with the wingsail development from the 2010 America's Cup. ETNZ's main element wingsail twist was more complex than OTUSA's. However Oracle had tried the same setup and did not believe that it offered significant advantages.

- Foils: Oracle Team USA made a gain on ETNZ having slightly thinner boards with a thicker radius and more highly stressed.

- Daggerfoil Control system: Oracle used an electro-hydraulic system operable from either side of the boat. ETNZ used a mix of electro-hydraulics and manual systems.

Key differences which determined the Match:

- Wing tune: Oracle improved upwind drive through increased lower aft loading. (interestingly this significantly increased the wingsail trim sheet loads, and the subsequent hydraulic demands required the crew to grind hard to maintain power from the race start to the finish)

- Crew work: Oracle mastered foiling tacks, gybes and upwind foiling. (While ETNZ led the way in the first two elements, the NZers admitted they never mastered upwind foiling to the extent achieved by Oracle)

-Board control: Oracle had improved positive positioning of the board pitch through electro/hydraulic systems development

- Rudder/Elevator refinement: Oracle added small anti-cavitation mods to the intersection of the elevators and rudder
=======================================================
https://www.youtube.com/watch?v=XQoNYe2jFP8

 

34th Foiling AC----------Pedal to the Metal!

The Oracle boys nail it:
http://vimeo.com/75364288#at=0

 

This was a triumph of technology as well as focused Oracle teamwork. Obviously technology and financial resource was there, but the Team had to understand new technology, then perform new maneuvers as a team on the job under a tremendous pressure. Wow, this brings back many memories. My heart went out for Kiwis as much as I enjoyed white knuckle thrills as Team USA made slow comeback.

So where is the application of these technologies for non-racing sailors? Any trickle down technologies to motor sailers and sailing pelagic sportfishers?

 

34th Trickle down

Average sailors(whoever they are) may benefit from the foil tech if they sail or want to sail multihulls or crew on friends cat. The foils were used in the last Little Americas Cup on C Class cats and there are several new boats that are using or will use refinements of the TNZ foils: the Flying Phantom(18'), the GC32, the California 45, the SL 33, the Gunboat G4, the Exocet 19 trimaran and more almost every day. The foils developed for 34 are a breakthru in hydrofoil technology.

 

34th AC

Here is a picture of the Oracle board system:

click to see it move---

 

Dough, thanks for posting this video, a must for anyone having interest on AC high tech, 1:20 of totally engaging action!

Now a technical question for the hydro experts: what are the advantages of a "bigger radius at transition" on boards profile?

-

 

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All I know about that is what was in a paper by Greg Ketterman about his "J" foils compared to a T foil. He said the the radius between the vertical and horizontal portions of the foil was critical because it allowed the effective aspect ratio of the foil to be based on the whole immersed portion of the foil rather than based on each portion of the foil separately. I'd like to hear an explanation from Tom or Mark.

Pictures-Kettermans Hobie Trifoiler foil:

 

After watching "Battle of the Boats", the IPENZ vid, I'm (not the hydro expert) seeing it the other way round. Oracle seemed to have chosen the thinner board profile (my presumption being that that was placing a higher priority on reduced drag = more speed). This choice lead them to use a larger bend radius to keep the stresses in the board manageable.

 

I notice there is a bit of an addendum posted on Sail-World to the article previously posted by Doug. This shows the Oracle test bench for their foils.

http://www.sail-world.com/Australia...122563&SRCID=0&ntid=0&tickeruid=0&tickerCID=0

 

I would imagine there would be at least three things going on at once.
1. The J foil will provide lift while acting as a dagger board. The lifting horizontal part of foil probably acts as wing tip vortex preventer.
2. As one of the catamaran hull is lifted, J foil will be tilted (heeled). The radius will transition smoothly throughout the tilt angle while providing additional lift from vertical portion of the foil, much lifting from radiused portion of the foil, and lifting horizontal foil providing additional resistance to leeward slip.
3. As the opposite hull is lifted and J foil is tilted, the horizontal part of foil will deflect and create more radius which should provide slight auto righting moment between vertical portions and horizontal portions of the foil through their dynamically changing lift forces.

The T foil cannot do #2 and #3 above.
Just a guess based on lifting wing theory principles, IMHO.

 

34th AC and a bit on the new rule

Interesting video by Pete Melvin where he discusses the new rule and what went right between Oracle and TNZ in 34. Interesting animation showing how wing twist can develop righting moment. Mentioned the difference in radius between the daggerboard and "L" on the UptiP foils with Oracle having a greater radius and, therefore, less drag. I'm sad to see the 72's relegated to the dust bin of history though the 62's should be fun to watch. The prediction by Melvin is that the 62's will be the same speed downwind and slightly slower upwind than the 72's:
https://www.youtube.com/watch?v=YUqcCnFmYm4