America’s Cup: the boat AC50Over the last decade, the speed of yacht racing has increased by a factor of five and the age of the competitors has dropped by 10 years. When the 35th edition of the America’s Cup takes place in Bermuda in June, it will mark the beginning of an entirely new sport. Part 2: The new boat in 2017
Following the first America’s Cup in 1851 – and for the majority of the event’s history – gains in speed were incremental. But thanks to the arrival of hydrofoils in 2013, boats now literally fly above the surface. Foils are aerodynamic wings that lift the boat’s hull out of the water at a certain wind speed – as low as six knots (11kph) in the AC50. There’s much less drag because only small pieces of foil, as opposed to an entire hull, are in contact with the water, which is why the boats got exponentially faster overnight. In practice, the AC50s have topped 50 knots (92kph).
“It’s like Formula One on the water,” says Oracle Team USA skipper Jimmy Spithill. The comparison isn’t far off. Like F1 cars, the AC50s are purpose-built, state-of-the-art machines, designed using supercomputers to calculate fluid dynamics, and built from materials like carbon fibre and titanium.
THAT’S NO SAIL
The primary sail on the AC50 is actually a rigid wing, not a sail. But instead of providing upward lift, as it would on a plane, this wing pushes the boat forward in the water. Airbus helped design the wing, which has a carbon-fibre skeleton and is wrapped in a plastic film known as Clysar.
WIND OF CHANGE
Foiling boats are so fast and efficient they generate their own wind, known as “apparent wind”. As a result, it’s not unusual to see the boats reaching speeds as high as 25 knots (46kph) in meagre six-knot (11kph) winds.
The computer power available to Oracle Team USA is 100 times what it was just three years ago. About 100 tiny sensors on the boat capture more than 600 channels of data that’s transmitted in real time to an office, where engineers can study those results and make changes on a daily basis.
Conditions on the boat are violent. The wind in a sailor’s face can exceed 113kph, so the controls must be as simple as possible. Oracle Team USA skipper Jimmy Spithill has a steering wheel, developed in part with BMW, which has both push buttons – to raise and lower foils – and sections of grip that twist to adjust the angle of the foils.
Each team is allowed to design two sets of ‘daggerboard’ hydrofoils, one of which will most likely be for light winds, the other for heavy. Think of them in the same way as race tyres, which can be switched out depending on track conditions.
Oracle Team USA’s hydraulic systems were co-developed with Airbus and the aerospace company Parker Hannifin, both of which have assigned engineers to the team in Bermuda for the past two years. Airbus worked mostly on the control systems, while Parker built the hardware.