
USA-17 is the specially built sloop rigged racing sail trimaran (a catamaran with three hulls) launched by the BMW Oracle Racing team that won the 33rd America’s Cup. It’s 27m long square at the waterline and displaces 17 tons of water. The USA -17 was designed by VPLP Yacht Design and is constructed primarily out of carbon fibre composite. This makes her exceptionally light and fast for her size. When travelling downwind with a 5-10 knot winds in last year’s America’s Cup, the USA-17 was recorded rocketing along at an astonishing 19 knots.
The hulls are constructed from millimetre-thick carbon epoxy laminated around an ultra-light honeycomb core and then baked in a vacuum chamber within a massive oven for eight hours at 80C. This results in a hull that is exceptionally strong, stiff and, most importantly, light. And it’s got to be — tight turns can generate as much as 15 tons of torque on the hull.
It’s also designed to cut through waves. The USA-17 has a very narrow bow that’s much less buoyant than the rear of the ship. This forces the hull through, rather than over, the wave which results in a smoother ride and reduces the ship’s resistance through the water.
The USA-17 is propelled by its massive 68m tall, 3493kg main wing that’s attached to a 3.5-ton carbon fibre and Kevlar mast. It’s taller than the Statue of Liberty and larger than any plane wing in existence. This airfoil works just like a plane’s wing, except that it produces horizontal thrust rather than vertical.
The amount of curve in the wing determines how much lift it produces. The mast rotates to control the angle of the wing while nine, two-storey tall trailing wing flaps can be independently angled to adjust the wing’s overall curve. These trailing wings form a slotted flap when deflected, much like the flaps on an aeroplane’s wing which produces more thrust than earlier wingmast/sail combinations. In addition, these flaps can be adjusted to maximise the lift on the wing near the base of the mast and lessening higher up to produce lots of power without a lot of heeling force (which is what causes boats to flip).
In addition, her sails — the mainsail, headsail and gennaker — have a massive combined surface area of nearly 2044sqm.
All of this design means there’re lots of parts that can break. To monitor the stresses and loads placed upon the boat as the crew trains and races, 250 sensors located throughout the hull, mast and sails, beam real-time data to a PDA on the skipper’s wrist.
[New York Times, America's Cup, Wikipedia, Tom Speer]
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Ollie
Tuesday, October 11, 2011 at 7:16 AMInteresting… considering multi-hull vessels don’t travel downwind, they have to gibe.
mark
Sunday, March 11, 2012 at 5:37 PMAll decently performing sailboats gibe downwind for optimal downwind velocity made good and most performance sailboats can sail faster than the wind on certain points of sail. Also, all sails are airfoils like a plane, BMW Oracle’s is merely a hard fixed one instead of a fabric one…nothing new here, just BIG.
Stuii
Tuesday, October 11, 2011 at 8:21 AM15tons is weight not torque
Roland
Tuesday, October 11, 2011 at 8:49 AMYes she’s a beautiful sailing vessel, but people have been sailing faster than the wind for a while now… I do it most weekends on my sailboard…
mr_herkt
Tuesday, October 11, 2011 at 9:31 AMUSA-17 is the specially built sloop rigged racing sail trimaran (a catamaran with three hulls)
as far as I am aware, a trimaran is just a three huller yacht, the same as a catamaran is a two hulled yacht..
That like saying a car is a four wheeled motorbike
Boat
Tuesday, October 11, 2011 at 9:49 AMRe-iterating Rolands comment, its difficult to get your head around at first, but sailing faster than the wind is very common and pretty simple physics. Picture a surfer surfing across the face of a wave. They are traveling a lot faster than the wave itself. Similarly, sailors will sail across the wind resulting in greater boat speed. (Theres also some other things to consider such as apparent wind but lets not go there now)
Having said that, im not denying this is a quick boat. I just wanted to explain some of the physics :)
Ben
Tuesday, October 11, 2011 at 10:05 AMSailing faster then the wind isn’t the most impressive thing this boat does, most performance boats can.
The fact that it can acheive a velocity made good (VMG) of more then twice the windspeed is what is really impressive. In laymans terms it can sail into the wind (by tacking) twice as fast as the wind.
That means that on a upwind-downwind course, it can sail from the upwind mark to the downwind mark and back, before a balloon released at the upwind mark makes it to the downwind mark.
It’s a phenomenal piece of engineering.
Sean
Tuesday, October 11, 2011 at 10:38 AMNot quite. The wind speed was an average estimate while the boat’s speed was accurately recorded, the peak of 19 knots was probably acheived during a 10+ knot gust. However, even assuming more than twice the wind speed, the boat is going to cover more than twice the distance tacking and gybing on it’s way to each mark. About 1.4 times the distance on each leg if it is travelling at 45 degrees. So it will beat the balloon to the downwind mark, but the balloon will get there long before the boat has gotten back to the upwind mark.
Ben
Tuesday, October 11, 2011 at 11:34 AMHm, wiki thinks it did 1.8 times windspeed vmg upwind, and 2.5 times windspeed vmg downwind.
http://en.wikipedia.org/wiki/USA_17_(yacht)
also, 19kts was the vmg downwind, not the actual boat speed, which would have been closer to 30kts. As always with sailing, it depends on where you measure the wind as the wind gradient would be pretty significant over the height of that mast. This thing is phenomenally fast, can only imagine what it would do in ideal conditions.
There was a chart floating around that showed the true boat speed and vmg of USA17 sailing at various angles, but can’t find it at the moment, some of the stats on that thing are immense.
Sean
Tuesday, October 11, 2011 at 1:19 PMI stand corrected, I hadn’t appreciated that it was VMG. That’s much more impressive.
smileysmoke
Tuesday, October 11, 2011 at 10:55 AMit is cool..
fkn engineers come along and have a p1ssing contest.
luck
Tuesday, October 11, 2011 at 3:53 PMi enjoyed the sail geeks geeking out.
i recently acquired a trimaran myself, but it’s, er, not quite as impressive as USA-17.
TSH
Wednesday, October 12, 2011 at 11:07 AMI’m sure this is old news to regular sailors, engingeers and such but I never thought of using the airfoil effect to propel horizontally rather than provide lift/downforce. One of those things that I feel should have been obvious, but just never occurred to me!