We are only a couple months away from the giant America’s Cup catamaran wings being launched. A team led by American Paul Cayard already has theirs on sea trials. Blue Planet Times explains there was a lot of effort put into design regulation.
The box rule governing the AC72 is one big sandbox, so the engineers get to play. Oracle Racing Team Coordinator Ian Burns explains: “I was involved in writing the rule for the AC72s, and when we addressed the wing, we started with a complicated rule, to limit what a designer could do. We added more and more pieces as we thought of more and more outcomes, and we came to a point where it was so complicated—and it was still going to be hard to control, because the more rules you write the more loopholes you create – that we reverted to a simple principle. Limit the area very accurately, and make it a game of efficiency.â€
Here’s the basic box rule for the AC72:
Hull Length: 22m (72.18 feet)
Maximum Beam: 14m (45.93 feet)
Wing Height: 40m (131.23 feet)
Maximum Draft: 4.4m (14.44 feet)
Displacement: 5900kg (13007 pounds)
Wing Area: 260 sqm (2798 square feet
Jib Area: 100 sqm (1076 square feet)
Gennaker Area: 400 sqm (4305 square feet)
Crew: 11@92kg/per (203 pounds)
Cayard’s description of the latest engineering challenges to make those numbers work is not your usual scuttlebutt.
“We have 38 hydraulic cylinders. We want to avoid running hydraulic piping to each of them, because that would be heavy, so we have electrovalves embedded in the wing to actuate the hydraulics. But if you had two wires, positive and negative, running to each electrovalve, your wing would look like a PG&E substation, and that’s heavy too, so we use a CAN-bus [controlled area network] with far fewer wires. Still, it’s incredibly complex.
“We wind up with lot of hydraulics,†Cayard says, “and the America’s Cup rules don’t allow stored power, so two of our eleven guys—we think, two—will be grinding a primary winch all the race long. Not to trim, but to maintain pressure in the hydraulic tank so that any time someone wants to open a hydraulic valve to trim the wing, there will be pressure to make that happen.â€
Ok, so there’s thousands of hours in design of these wings but there’s something deeply ironic about a 72 foot catamaran with a 130 foot wing that can sail faster than the wind but can’t generate enough power to manage hydraulics without two crew constantly grinding a winch. It seems like a legacy mindset. A big part of the old America’s Cup boats was to be staffed with powerful yet heavy crew who can muscle the boat around. These boats surely call for lighter more nimble crew. What if someone even figured out a way to efficiently use the wind to generate power…?
Perhaps Luca Devoti said it best. These boats are pure racing machines that have power to burn. They should have no shortage of energy at their disposal, or they may even have a reason for absorbing excess.
You have to change completely your way of thinking: the boat is sailing from the moment the wing comes out of the shed because the wing can fly away at any moment.
The trick, as explained in the following video, is to make the wing secure yet light; to keep it as uncomplicated as possible to reduce risk and reduce response time. Most of all, it sounds like the designers want to hurry-up and make up for 20 years of lost time by borrowing technology and efficiency study lessons from the A-Class and C-Class catamaran fleets:
