One look at any image of an America’s Cup boat at full throttle and it doesn’t take much to work out that one of the most highly loaded components is the hydrofoil boosting the boat out of the water.
If winning the America’s Cup is all about maintaining stable flight, then the engineering of the foils is the stuff of which critical paths are made. George Sykes of PA Consulting is Project Manager for the Land Rover Ben Ainslie Racing’s (BAR) Technical Innovation Group (TIG), a vehicle to bring the very best in British design, technology and innovation to bear on the project to win the America’s Cup. “When we were looking for technical expertise in the structural engineering of the carbon fibre dagger-boards that support the boat in flight, it’s hard to think of a better place to go than our partner BAE Systems,” he says. BAE Systems was happy to help, and word went out to its military aircraft team in northwest England.
Enter Tom Hume: an aerospace engineer who has worked on the composite engineering of both the Typhoon and the F35 Lightning II aerial fighters. Hume initially worked on the Typhoon before spending 10 years on the design of the F35’s fuselage. It goes without saying that the man you entrust with composite design on a trillion dollar fighter project probably knows a bit about carbon fibre. Which was good, because his skills were about to be fully utilised.
The design of the America’s Cup class hydrofoils is one of the team’s most closely guarded secrets, but the general principles are well known. Essentially, there are two conflicting goals. The first is to make the hydrofoil the most efficient shape, and in general, that means it needs to be thin. The second is to make it strong enough to cope with as many situations as possible – like being used as a hand brake at 30 knots. And this means that it needs to be fat, to pack in as much carbon fibre as possible. Working out this conflict for Land Rover BAR is the task of British structural engineer Mark McCafferty and Italian hydrodynamics specialist Mario Caponnetto. “It’s a loop between what’s possible structurally and what’s desirable hydro-dynamically,” explains Mario. “We have to find a compromise between weight, strength and low drag.”
“Once we’ve agreed the shape, I’ll define the structure and the materials that we want,” continues Mark. “Other people in the team will create a 3D CAD model from that, and then Tom takes that and creates the layup specification and the drawings that the manufacturer will use to build the piece.”
These are immensely complex structures, requiring enormous strength and very high precision of shape – nothing should be left to chance. “I take a solid representation of the part, the foil, and turn that into a carbon fibre lay-up plan,” explains Tom. “The builders have been very happy with what they have received. The boards are very complex, and to make it a simple task to lay up hundreds of layers of carbon fibre and fit them together in the mould is quite an achievement. “The people building the board are able to just cut the plies out to the shape that we give them, and put it on the tool and they fit. Normally they would have to spent a couple of days working out what shape each one needs to be manually... now it’s all done for them. It saves a lot of time in manufacture especially on something as complex as these boards.”
It’s often said that the most precious commodity in the America’s Cup is time; the first race in the qualifying series starts in Bermuda this May on schedule, whether the teams are ready or not. So anything that saves time is a fantastically valuable resource, particularly on such a vital component as the hydrofoils. “Boards are probably the most significant performance differentiator on our boat – critical for boat speed, boat handling, and flight stability. The support we’ve got from Tom and BAE Systems will significantly reduce our manufacturing time and increase the quality of our boards, and in doing so will make a significant impact on our campaign,” concludes Richard Hopkirk, Engineering Manager at Land Rover BAR.
This story is credited to Mark Chisnell, Land Rover BAR.