Engineers Race to Create the Winning Boat for America's Cup 34 - Sail Magazine

Engineers Race to Create the Winning Boat for America's Cup 34

Somewhere out there, America’s Cup 2013 is being won right now. During the recess before AC45 World Series racing resumes in April in Naples, Italy, design and engineering teams are racing to complete the first generation of AC72 catamarans eligible to race in America’s Cup 34.
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Somewhere out there, America’s Cup 2013 is being won right now. During the recess before AC45 World Series racing resumes in April in Naples, Italy, design and engineering teams are racing to complete the first generation of AC72 catamarans, boats that will begin launching in July of this year and will be eligible to race in America’s Cup 34. These boats will be 30 percent more powerful than the AC45s that raced three circuit events in 2011, but less stable, raising the possibility that a winning design could lose the Cup through the fortunes of war. It’s happened before.

“If you’re making 25 knots upwind and 40 knots downwind, tacking on someone and gassing them just isn’t happening,” says Paul Cayard, CEO of Artemis Racing, the Challenger of Record. “In seriously overpowered boats, the match will be about who can get the boat around the course and figure out how to avoid that extra gybe that costs you maybe 20 seconds.”

With a box rule that tightly limits the maximum dimensions of the wing and the maximum depth of the foils—and leaves the rest to the imagination of the engineers—the AC72s are ripe for innovation. Very, very likely, all will have three-element wings, rather than the simpler two-element wings on the one-design AC45s. But here’s a change from years past: a wing in test mode is up there for all to see. It can’t be hidden like a keel. The same is true of daggerboards, the other developmental hotbed. The boards on an AC45 are straight. They limit leeway. The AC72s will likely have curved daggerboards, with a straight (or straight-enough) section immersed below the leeward hull on the upwind legs and a curved section immersed on downwind legs to lift the leeward bow and resist the pitching moment of the wing.

On ocean-going multihulls, a curved daggerboard might support as much as 80 percent of the boat’s displacement. Let’s layman-guess that as a starting point for designing an AC72. The balance between the lift of the board and support from the hull is critical, because skinny bows are faster than fat bows—until they dig in and flip the boat. According to Cayard, “The board game is as big as the wing game. Maybe bigger. The next America’s Cup could be won or lost with the boards.”

 No more secret weapons: you can't hide wings and daggerboards--like this one on the BMW Oracle tri that won AC33--the way you can a keel

No more secret weapons: you can't hide wings and daggerboards--like this one on the BMW Oracle tri that won AC33--the way you can a keel

Insiders estimate that an AC72 wing could consume 40,000 man-hours and take six months or more to build. That’s more than the “boat,” each of which is likely to cost in the range of $4-5 million. One of the chief architects of the design rule was Pete Melvin, now working for the Emirates Team New Zealand/Luna Rossa partnership. According to Melvin, rulemakers arrived at a length of 72 feet because of its similarity to an ORMA 60 trimaran. “We know that on those boats you can sheet loads with humans and sail around a course pretty aggressively.”

We know also that naval architects and engineers at the America’s Cup level are pretty creative. The proof is in the current Artemis wing design, where 38 embedded hydraulic cylinders are activated electronically via a controlled area network (CAN) bus, which saves the weight of running hydraulic piping to each cylinder, or double wires to each electrovalve. This means push-button control for the trimmers, but—since stored power is not permitted—there will be two very large, very fit men grinding (and grinding, and grinding…) a primary pump to maintain hydraulic pressure. What we’ll see from the other teams is anybody’s guess, but they can’t hide whatever it is that they’re up to forever. If you think back through the America’s Cup tradition of relentless innovation, this is, in many ways, the America’s Cup at its best.

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