How do those new Double Mainsail's on the AC72's work?
- Thread starter rpwillia
- Start date
I was just commenting on the cost of those sails compared to my low budget cruising sails. One of those sails is probably worth more than my boat.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,141
You got that right. Certainly my boat. But if you are racing to win the America's Cup for the pride and glory of your Patron. Then the using of his money is no hinderance to the result desired.
Probably all the above. I think the AC75s have a driver, a mainsail trimmer, jib trimmer, tactician and several guys to crank the hydraulics up. I would imagine any one of those trimmers has forgotten more about trim than I will every know.
I have been wondering how they control the camber. You can see lots of depth in the sail when they are trying to get up on the foils and then they really flatten them out at speed. Since some of them don't have a boom for outhaul purposes I wonder how they are doing this?
There is an internal framework between the 2 layers of the mainsail. Unlike the mainsails we all use, that have one piece of fabric, the AC 70 mainsails have 2 pieces with the framework between them. This allows the trimmers to trim both sides of the mainsail.
Closely guarded secret by the various race teams on “how” they do it no doubt. Quite a little mess of spaghetti coming out of the rear of the sail(s) - the “magic” is behind the curtain
Just a wild guess but if you had line attached to both ends of a batten you could adjust the amount of “bend” by changing the tension.
Just a wild guess but if you had line attached to both ends of a batten you could adjust the amount of “bend” by changing the tension.
I saw a quick description somewhere on line. The rules allow the dual mainsails and each team seems to have its own solution. All in all, it is a clever idea that none of us will ever be able to afford.Closely guarded secret by the various race teams on “how” they do it no doubt. Quite a little mess of spaghetti coming out of the rear of the sail(s) - the “magic” is behind the curtain
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Just a wild guess but if you had line attached to both ends of a batten you could adjust the amount of “bend” by changing the tension.
The theory is by altering the leeward side as well as what windward side of the sail there is increased efficiency of the foil. Keeping the leeward side flat with a full windward side removes some turbulence on the leeward side. Much like an airplane wing, flat on the bottom, curved on top.
(no doubt that description will generate some DOM thoughts.
)
Not sure about the affordability thing - kinda spendy nowI saw a quick description somewhere on line. The rules allow the dual mainsails and each team seems to have its own solution. All in all, it is a clever idea that none of us will ever be able to afford.
The theory is by altering the leeward side as well as what windward side of the sail there is increased efficiency of the foil. Keeping the leeward side flat with a full windward side removes some turbulence on the leeward side. Much like an airplane wing, flat on the bottom, curved on top.
(no doubt that description will generate some DOM thoughts.
but eventual trickle down would change that to some degree. The need to do it at all I think will depend on if there is a wide adoption of foiling hulls. Without the high speed involved I don’t see the value. The only thing I have experienced that is even remotely equivalent is high speed windsurfing and ice sailing. Big adjustments at 10 knots - little tweaks at 30 knots - no idea what happens at 50 knots
The video coverage of the sailing so far hasn’t allowed me to see how much shape “difference” there is between the inner and outer layers. The “inside” certainly isn’t flat
I haven't been able to follow this thread closely and maybe don't have that much to contribute. But I am interested in the difference between a sail - which is not shaped like a wing - and a sail that is shaped like a wing. A lot of questions arise: Is the wing shape more efficient? How much does the speed of the wing thru the atmosphere affect efficiency? What about drag? I've read that the most efficient shape for a wing is the Spitfire airplane wing. Most lift for the least drag. But speed still matters - I think.
@DArcy posted a link near the beginning of the thread that might answer some of your questions but I think the main reason they have gone to the double skin sail is that it is “hoistable” but can approach or perhaps exceed the efficiency of the hard wing “sails” of the earlier classes.
It also raises all kinds of renewed interest
It also raises all kinds of renewed interest
There has been a push in the past few years in the elite racing world to lower costs in order to keep and attract sponsors. Using a crane to remove the mast and wing sail every day gets expensive quick.@DArcy posted a link near the beginning of the thread that might answer some of your questions but I think the main reason they have gone to the double skin sail is that it is “hoistable” but can approach or perhaps exceed the efficiency of the hard wing “sails” of the earlier classes.
It also raises all kinds of renewed interest