34th America's Cup: multihulls!

funny that pic, if theyre sailing along with that much twist and the windward foil catches the sea surface, it will pull down quite markedly. Are they doing this for more RM?

 

34th AC on Foils!

--------------------
Well, I think we know that the rudder t-foil will support around 20% of the boats weight at initial takeoff with that load going down as the boat goes faster. So that gives a concrete figure of what the download force from a negative angle of attack could be. We also know that foilers designed to utilize negative lift work and are fast(Rave, Osprey, Hobie Trifoiler, Skat, Long Shot)-in other words the drag produced by the negative lift is offset by the increase of RM on those boats. They use dual altitude controlled main foils with the windward main foil pulling down. The rudder t-foils on these boats lift about 20% of the boat at initial takeoff and go to pulling down as the boat goes faster.
What this means is that the Oracle system could be getting around the rule that says the main foil can't pull down by allowing the twist to change the angle of attack of the windward rudder foil. They would have to adjust the windward main foil so that it was neutral if the windward hull was immersed while it was twisted.

 

Well that puts a whole new twist on things.

 

34th AC on Foils!

The Twister back on the Bay:
http://www.youtube.com/watch?feature=player_embedded&v=zr6nw77I6CQ

 

whats the deal with team USA, seems the whole damn crew are Australian!

 

May be its the Australian team in drag.

 

34th AC on Foils!

=====
We hire only the best.......

PS-just for the record: I think these mercenary AC crews are a crock. The Crew and the designers should be 100% from the country of the challenge or defense.

 

Doug,

Look at the near foil back at post 555.

It only sticks up above the hull a small amount and barely sticks down below the hull at all before it turns in for the "L" section.

Even with it fully lowered, it will have a very mall amount of vertical section. Any clue as to what is going on?

Skip the above, as I was looking at a later video, I saw that one foil is full length, the other is not.

 

Heck I would settle for skipper plus at least 50% of the rest of the crew.

 

==========
According to the scuttlebutt(I haven't double checked) Oracle is using just a portion of the foil that was damaged so they can get out and test sail.
When I first read your post I thought you said "rear" instead of near so I went and looked at the rudder foil after blowing up the picture and what I think I discovered blows my mind: the t-foil seems to have a positive angle of incidence when compared to an estimated line from the bow of the ama to the bottom of the transom! So if thats not an optical delusion then my theory that they might try to increase RM using negative lift from the rudder foil is dead. On most foilers the rudder foil is set at zero degrees relative to the line above(and/or the flight waterline when this ama is the LEE ama)-this one does not appear to be set up that way. And the rules prohibit the angle of incidence of the rudder foil from being adjustable. Take a look and see what you think:
UPDATE: on further study I'd say the foil is probably at zero like you would expect. There is a bit of light that hits the tip and makes it look positive?
UPDATE#2: Geez, here I go flip flopping: look at the second photo-blow it up max and notice the two lines. The line representing the t-foil is at a positive angle relative to the estimated line parallel to the flight waterline(flight waterline when this ama is the LEE ama). Surprising and not very accurate but interesting to me.....

click on picture, then click on expand, then click on picture again:

 

34th AC on Foils!

A couple of pix by Guilain Grenier from Oracles facebook page:

click-

 

I agree 100%, this is the only reason why, they will not attract a much larger world wide audience. People want to cheer on their own country, even if they dont understand, watch, or care about the sport......

 

The AC has and always will be about the "Sailor" with the biggest wallet. Its embedded in the Deed. Its not a sport like tennis or football. Its a duel. If you read the deed it reads exactly as a duel document would 150 years ago. Challenge the cup holder to a race/fight. The defender accepts, you pick the weapon of choice and then this has to be agreed to. You agree to an umpire, then you agree to a place. Bring the weapons have the fight take away the glory (or not). The boats can be from 45-110ft long thats about it. Let it continue!! The 34th AC has just caught up on 150 years of development started by Francis Herreschof. We can now accelerate into unknown territory! Peter

 

Note Tom Speer hasn't chimed in lately. Oracle's certainly aware the cameras are focused on the 72. I don't doubt the hydrofoil R&D is ongoing, and that when the America's Cup is actually sailed we'll see a well engineered foiling cat from Oracle.

In the current Professional Boatbuilder magazine Sam Bradfield is quoted saying hydrofoils need to flex some. He's apparently learned from experience that overly rigid foils are prone to failure.

I agree about nationality of designers, skippers, and crew, but it was a hard thing to police where Australia II and use of the Dutch hydro lab was concerned. Someone would have to come up with a rule that is both clear and somewhat elastic. I think this should apply to all sports - Green Bay Packers should be from the Upper Midwest, New England Patriots from New England, etc. - but I seem to be in the minority on that.

 

===============
You're right. However,he is a firm believer in a rigid platform-at least for a foiler using dual independent wand altitude control systems that develop vertical lift and all the RM for the boat. The AC boats don't use that system.....