Update
DEUS EX MACHINA – Jack Griffin When she moved from lecturing at Cambridge to working at McLaren 20 years ago Caroline Hargrove was one of the rare women engi- neers in F1. Simulators were even rarer – no team had one. The simulator Hargrove’s team worked on was limited by the graphics, displays and processing power of the late 20th century. Adrian Newey dismissed it as useless. The drivers mocked the graphics. Hargrove and her team plowed on. Processors and graphics chips got faster and more powerful. Displays became higher and higher definition. Along the way F1 limited track time. By the time Newey arrived at Red Bull he declared that a simulator was one of two key items the team needed. (The other was a gearbox dynamometer.) Luna Rossa imposed monohulls on Emirates Team New Zealand
for the 36th America’s Cup. Fans of speed and exciting technology groaned. When the Protocol was presented in late September ETNZ promised an exciting new boat. Many, including your scribe, doubted. Like Euripides, searching for a dramatic, surprise ending to one of his plays, Dan Bernasconi and the ETNZ design team turned to their ‘machina’, the simulator, to conceive the AC75 and stun the sailing world. In the weeks since they released their concept video intriguing details are starting to emerge. Having ‘sailed’ the AC75 extensively in their simulator, ETNZ tell
us it should foil in 9kt of breeze. Rather than raking the foils to control angle of attack, like the AC72 and AC50, the AC75 foil wings will have flaps to vary the lift. In ‘normal’ mode the leeward foil wing gives lift and is the fulcrum. Righting moment is from 1-1.5 tonnes of ballast in the windward foil wing, and the weight of hull, rig and crew. The single rudder will probably have rake control and/or may have elevators on its horizontal stabiliser to provide pitch control.
12 SEAHORSE
In ‘stable mode’, with both boards in the water, ETNZ predict
that the AC75 can stay up on the foils through pre-start circling – two foils can provide double the lift with only a slight drag penalty from the additional wetted surface. After the start a team might sail with both foils down in rough conditions or in windspeeds in the displacement-to-foiling crossover range. The rule will prohibit crews from using downforce from the windward foil to provide righting moment (which all teams did in Bermuda using the AC50 rudder foil). In the upper wind range this could put excessive loads on the rig and the hull. The hope is to keep the total righting moment fairly constant over the wind range. In a recent interview Bernasconi said he hoped to get the upper wind limit close to 25kt. Rig concepts were still under discussion in December. A
completely rigid wingsail has been ruled out in favour of ‘something hoistable’. Potential solutions include a wing mast with a soft sail, possibly inflatable or with two layers forward. The main might have a reef, but a smaller sail with the same hoist and a smaller chord are the more likely solution for muscular conditions. The crew, likely to be 12, will have plenty to do. The crew weight
limit will be higher per man, signalling the return of big grinders. Grant Dalton has said there will be no cyclors and that ‘we will never introduce a combustion engine’. There will, however, be battery power to drive the hydraulics needed to lift a tonne or more at the end of a 5m-long foil arm. The crew will need to trim and tack the jib – the self-tacking jibs from the AC72 and AC50 are gone. In light wind the Code 0 will need to be hoisted and dropped. During gybes the grinders will provide power to furl and unfurl it. Of course, we may not see much of the Code 0 in the high-speed, narrow-angle, apparent-wind sailing that the AC75 promises. Safety stipulations may include requiring crew to be tethered
CARLO BORLENGHI/SSL
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