What lessons from 2013 will help the six America’s Cup teams be ready when racing starts on Bermuda’s Great Sound on 26 May 2017? Some lessons have been imposed on the teams since they are implicit in the one-design aspects of the America’s Cup Class Rule. Other lessons will be applied by the designers and still others by the sailors. We’ll cover how the boats will be sailed next month. This month we’ll look at design, but first, let’s start with the highest priority.

The most important lessons concern safety.  Body armor, spare air bottles, knives, strobe lights and electronic locator systems are combined with rigorous safety training and protocols to reduce risk to the sailors. With cockpits required, the sailors are better protected in case of a capsize or a sudden deceleration. In 2013, when Emirates Team New Zealand buried their bows in Race 1 of the Louis Vuitton Cup Finals, Rob Waddell and Chris Ward were washed overboard. We’ve recently seen video footage of Ben Ainsley somersaulting through the air and crashing into the forward crossbeam while training on a foiling AC45. Franck Cammas almost lost his right foot when he went overboard and hit the rudder wing of a GC32. In comparison, when Oracle Team USA capsized their AC72 in October 2012, being in cockpits gave the crew protection. And when they capsized their test boat in Bermuda in early March of this year, wing trimmer Tom Johnson, on the high side, was able to hang on in his cockpit.

The teams have also learned how to right their boat after a capsize. When Oracle capsized their AC72, it looked like their plan for righting the boat was “don’t capsize.” They lost three months of testing while the heavily damaged boat was repaired and a new wing built. Now, instead of trying to pull a capsized boat up sideways, they point it into the wind and tow it forward with the wing trimmed down towards the hull in the water. Like an airplane with flaps down at takeoff, and the wing then flies the boat upright. The test boat in Bermuda was on its feet five minutes after it went over, and damage was probably limited to the electronics in the hull in the water.

We saw three very different approaches to ergonomics on the AC72’s from Oracle, ETNZ and Artemis Racing. Even if the rule did not dictate cockpit layout, it’s unlikely we would again see the inefficient grinder ergonomics that ETNZ had on their AC72. With their grinders sitting down or standing on the trampoline instead of on a solid surface they lost a lot of power that should have been transmitted to the handles. And, with the boats traveling upwind much faster than originally expected for the 2013 event, the importance of reducing windage is evident.

It seems that everyone is still on a steep learning curve about daggerboards, especially given the wide range of conditions to be expected in Bermuda. The Protocol now takes over two pages just to describe the limits on the number of daggerboards that can be built and how they can be modified. The short version is that the teams may only sail with four boards for their race yacht. Board design for the the AC72’s began with straight L-shaped and S-shaped daggerboards. Foil design has evolved to variations of a curved “vertical” section and a dihedral (upward sloping) wing. The dihedral angle combined with adjustable cant provides self-stabilising ride height, although resistance to leeway decreases as the boat rises and less of the “vertical” section is in the water. As they refined their AC72 daggerboard shapes, the teams traded off drag and stability. Oracle’s AC72 daggerboards had a noticeably bigger radius than ETNZ’s boards at the junction of the “vertical” section and the wing. Both teams were probably hampered by cavitation when speeds approached 40 knots. Daggerboard design is no doubt chewing up lots of simulation processor cycles and getting more sophisticated. What might the teams be modeling and testing? How about daggerboards with the maximum chord allowed by the rule on the vertical section to resist leeway, but with a much finer wing to reduce drag? Or how about fences on the wing to improve lift, especially in transition conditions? And might they be testing variable geometry? The class rule prohibits adjusting the daggerboard shape while racing, but what if the shape changes by itself, by deflecting under load?

Those other foils – the rudders – are also getting attention. Mid way through the match in 2013, Paul Bieker came up with a solution for reducing cavitation and drag. The fillets and bulbs he devised are now used on the AC45F. Maybe in this cycle we’ll see anhedral rudder wings or other interesting geometries to improve maneuverability. In 2017 the teams can change the rudder wing angle of attack while racing, by raking the rudder stock. No doubt the teams with development boats are already experimenting the the frequency and magnitude of rudder rake adjustments, and noting how much power is required from the grinders.

The systems that provide power to control the wing, daggerboards, rudder rake and jib trim will be crucial. In 2013 Oracle learned the advantages of frequently trimming the wing. They would connect three predestals to drive the wing winch mechanically for their “beast mode,” leaving only one pedestal to provide hydraulic pressure for board rake. With only two pedestals per hull in the 2017 boats, it’s likely that the teams are developing systems that will keep the forward pedestal pumping hydraulic oil and the aft pedestal switchable between the hydraulic system and a mechanical linkage to the wing winch. The hydraulic accumulators for board extension/retraction and rake provide enough energy for one tack or gybe. As long as the two men on the forward pedestal can repressurize the accumulators between maneuvers, the aft pedestal is available for the wing winch. Ruder rake adjustment and jib trim should take relatively little energy and adjustment are likely to be infrequent.

Next month we’ll explore how the sailors are learning to race these boats.