Americas Cup

Technical discussion of ARC products
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Bill Roberts
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Americas Cup

Post by Bill Roberts »

Americas Cup, have they lost their way?
I have not seen the "Deed of Gift" for the race but as I understand the Deed, it addresses
a sailboat race between craft of design outlined by criteria that specifies max limits for the boat like boat length, boat width, boat weight, sail area/wing area, etc, etc, etc.
Boats/yachts are water craft vehicles that move through the water in the displacement mode or skim over the surface of the water in the planing mode. For a vehicle to be a "boat" it must operate as a boat at design point. The hulls of the so called "boats" in the last Americas Cup did not move through the water in the displacement mode or skim over the surface of the water in the planing mode at design point. These Americas Cup race boats at design point were/are carried above the water on foils, wings, at design point. By defination these craft are flying and are correctly called aircraft, like airplanes, like gliders. The hulls are not in the water, touching the water, in either the displacement mode or the planing mode. These craft are truely a special kind of airplane. The Americas Cup "Deed of Gift" does not address a contest between airplanes. It addresses a contest between boats, sailboats which meet specific design criteria.
What do you think? (This is a technical question, not a personal preference.)
Bill
Kevin Keller
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Re: Americas Cup

Post by Kevin Keller »

Well.... technically the foils displace some water also. Albeit a relative small amount.
Bill Roberts
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Re: Americas Cup

Post by Bill Roberts »

AC catamaraans have gone through a metamorphosis. At design point they no longer move through the water in the displacement mode. Today they/some fly over the water and have become airplanes.
A catapillar goes throgh a metamorphorsis and becomes a butterfly. It changes its means of locomotion from crawling on its belly to flying on its wings. It makes no snese and is incorrect to call a catapillar a butterfly or to call a butterfly a catapillar. A catamaran flying on foils is literally flying and is a special kind of aircraft. A catamaran moving through the water on hulls operating in the displacement mode is not flying and is not correctly called an airplane and is correctly called a boat or yacht
When it comes to watercraft, if it flies over the water on foils, it is an airplane. If it is supported by its hulls and moves through the water in the displacement mode, it is a boat or yacht.
Kevin Keller
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Re: Americas Cup

Post by Kevin Keller »

I think it is kind of a rhetorical question. Without the water it cannot move the way you want it to move. It's really not flying above the water, it is flying in the water. You take away the water and it doesn't work.

Personally I don't have an issue with it. It's more exciting than watching some big displacement hulls slowly moving around the course. But that's my opinion.
Bill Roberts
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Re: Americas Cup

Post by Bill Roberts »

The main body, the platform, is flying above the water. The wings are flying in the water. The same equations that calculate lift and drag in the air also work in water. The big difference is that salt water density is 64 pounds per cubic foot and standard air is 0.07654pounds per cubic foot. Water is 836 times more dense than air,therefore the wing area rerquired to fly a given weight in water is much smaller than in air.

As far as interesting to watch, I think 80ft cats with sails going 30 to 35 knots in the displacement mode would also be very interesting to watch. The benefit here is that there would probably be "trickle down" technology to you and I as beach cat sailors. The sailing and sailboat industry would benefit.
We, you and I will probably never have a foiling catamaran with wing. Such a boat/airplane/contraption would be built of all carbon. We just spent 50K$ on a 20ft cat. Now put foils and controls on it. Add 10k$. Now have a custom enclosed trailer built with well padded racks for wing and hulls etc. Add 20k$. The trailer also has a dressing room in the front end and generator for lights. Now to tow this trailer, you may need to buy a larger car or small truck. As you can see, one could easily spend close to 100k$ to have a well equipped foiling catamaran set up. Now on top of this you have to live you have to live on San Francisco Bay or somewhere where the wind blows 15 to 20 knots on a regular basis and has calmish water for that wind level.
Data Point: There has been a foiling catamaran on the starting line of the Miami to Key Largo Race for at least 10 out of the past 15 years. The foiling catamarans were either the Hobie Tri Foiler or the Rave. Both of these cats foil very nicely and go very fast relative to beach cats. Here in south Florida we have alot of 15 to 20 knot winds. The record in the Miami to Key Largo Race is 104 minutes for the 42 mile run. A foiling catamaran has never finished within an hour of the first boat to finish. WHY???
The foiling catamarans could not fly for the majority of the race. The wind was either the wrong direction or not strong enough. This situation/this question is going to face a foiling cat owner every time he/she thinks about going sailing. I don't see a foiling cat being a big seller.
I also failed to mention the other major cost item, 20k$ for an all carbon fully articulating wing for propulsion.
One other point. I have seen wing powered catamarans at races. They require a large number of crew members to put the boat together and install the wing. Then the boat is carried into the water by at least four people. They walk into the water up to their shoulders and then push the boat forward out into deeper water. Each wing boat arrives with two car loads of crew people who are well trained on the boat they support. They, the crew persons, are willing to sacrifice their day off from work to enable the wing powered boat with two persons to go sailing. It is a big deal in time and money to own and sail a wing powered catamaran or a wing-foil catamaran. It requires Racing Teams.
J Drew
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Re: Americas Cup

Post by J Drew »

With every sport there is always someone who has to build a better mouse trap. Whether it works or not is a different question. If somebody wants to spend that much on such a mouse trap, then more power to them.
I like my SuperCat the way it is. Sailing it by myself usually poses a challenge to my limits and that's the thrill I'm after. It's a great deal of work to set up and take down. If I grab my surfboard and go to the beach it's quick and easy. While it is a lot of fun the thrill is totally different and nothing replaces sailing..

As for the Americas Cup; it's still a boat, it floats and plows through the water a significant amount of the time. While I understand the point Bill is making, I think it's a new evolution that "big money" wants to play with. Hasn't the Americas Cup always been that way? I agree that 80 footers with normal sails would be just as interesting, technology has taken it to the next level and I am enthused by it.
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