The Canadian navy once had a hydrofoil ship which would do better than 60 knots, as did the Norwiegans. The U.S. navy had armed and operational hydrofoil patrol vessels rated at 48 knots, just under the 50 knot limit you mentioned. There must exist a body(s) of engineering data on how to deal with cavitation issues. It can't all be classified. Can it? Did the designers of the current AC boats just decide not to deal with the cavitation issue, and deliberately choose to depend on rules limits for safety?
Steve Thomas C&C27 MKIII -----Original Message----- From: CnC-List [mailto:[email protected]]On Behalf Of Bill Coleman Sent: Tuesday, September 24, 2013 5:16 PM To: [email protected] Subject: Re: Stus-List America's Cup. I think it may be the best ever. I never could understand my friends jumping off the couch during football games and yelling and jumping - Now I understand a little better. Clipped this interesting tidbit from Lirakis's Blog - <<FROM SAILING ANARCHY: I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong. The boats ended up being faster than they predicted, i.e. the designs were too good. :-) This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems. Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range. The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge. If they want higher wind speed limits they have to lose the foiling to remove the "50 knot barrier" or they can lose the wing to reduce the top speed of the boats to under 3x wind speed. If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it. It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success. Stop bitching about the boats being too fragile to sail in 30+ Start celebrating that they are too fast to sail in over 25. I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.>> When the races are over, assuming these boats are toast anyway, they should see what they would take (and do) in 25Kts + With water ambulances on hand, of course. Bill Coleman C&C 39 From: CnC-List [mailto:[email protected]] On Behalf Of Ken Heaton Sent: Tuesday, September 24, 2013 4:37 PM To: cnc-list Subject: Re: Stus-List America's Cup. I actually think this is the best America's cup in years. I'm following this one every day and I haven't done that fir years, probably since the early 1980's. There are others who seem to agree with me. Have a look at this article in the Huffington Post: http://www.huffingtonpost.com/christopher-caen/a-cup-of-caen-yelling-at-_b_3975975.html Ken H. On 24 September 2013 15:51, Edd Schillay <[email protected]> wrote: Bev, The Cup racing has gone downhill to be sure -- both in the teams and the boats, but it is fun to watch any boat go 40 knots. I do believe, however, the America's Cup is not named after our country, but the boat "America". All the best, Edd Edd M. Schillay Starship Enterprise C&C 37+ | Sail No: NCC-1701-B City Island, NY Starship Enterprise's Captain's Log Website On Sep 24, 2013, at 2:48 PM, Bev Parslow <[email protected]> wrote: I am confused. We have a boat sponsored from a country that last time I used an atlas was in the Middle East. All participants being interviewed seem to have an accent from the Southern Hemisphere. Rumour has it that in fact we have only one American on board. If they win, it should be called the American's Cup. This really is quite a farce. Why not a boat, built, designed and made in that country, filled from citizens from there with sponsorship from the state. _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
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