Technology


Ultimate plaything


At first no-one believed the AC75 concept could ever possibly work. Barely three years later and the smaller AC40 offspring of those as-it-turned-out spectacularly successful AC75s are available to all (well sort of...)


When the original concept for the new America’s Cup class was announced after Emirates Team New Zealand won in Bermuda, few could believe what they were looking at. A 75ft monohull with no keel, flying on a hydrofoil to leeward and a single T-foil rudder was difficult to imagine. But as we now know, the concept not only works; it is developing fast. North Sails’ designer Burns Fallow has been with Team New Zealand since 1993 where he and his team have both witnessed and been responsible for some of the biggest changes in the sail package. Understandably, for sailors and


spectators much of the focus has been on the foils, yet the last Cup revealed that the sailplan was also an area where huge progress was being made. And while development for the next generation of AC75 continues, the AC40 is taking some of the advanced technology beyond the rarefied Cup world and into the wider grand prix sailing arena. Aside from his extensive work with


North Sails that has spanned 35 years, Fallow has been at the heart of some of the biggest changes in the aero side of Cup boat design.


62 SEAHORSE


From his work as the initial design coordinator for the solid wing in the 2013 Cup in San Francisco through various iterations of the wing and then back to soft sails for Auckland in 2021, the step changes across Cup cycles have been large. For many watching from outside, it has been difficult to follow the rationale and potential benefits that have led Cup design from wings back to conventional looking sailplans. ‘The most obvious difference


between the wings of previous Cups and the current twin-skinned mainsails is that one is solid and the other essentially a soft sail, albeit two sails working together,’ he says. ‘But one of the most fundamental points when it comes to handling is that the solid wings needed an army of people to put them in and take them out each day, whereas the twin-skinned soft sails can be lowered easily by the crew. And that’s pretty significant when it comes to taking new technology forward and making it applicable to the wider racing world. ‘Under sail, the wing on the AC50s


had the advantage that you could control twist and camber at a range


Above: unlike the last Cup cycle, control systems at the top of the mainsail are not allowed in AC37 so the current AC mainsails operate more like a regular sail on a halyard lock. Cunningham, sheet and traveller are the primary controls


of heights up the rig using the control systems that were inside the wing. This allowed trimmers to go from positive to negative cambers. In the last Cup the rules allowed only two areas of control, at the bottom and at the top. ‘And now for AC37, control at the


top is not allowed, instead it’s just the bottom that can be controlled. So the current AC mainsails now operate more like a conventional sail on a halyard lock where the cunningham, sheet and traveller are the primary controls.’ Broadly speaking this means


that mainsail trim has returned to conventional techniques. Sheet on and the upper leech stands up, ease the sheet off and the opposite happens. But the AC75 and AC40s also have rotating masts which provides another area for control. ‘Being able to rotate the mast


does help in being able to change gear and this is especially important when it comes to the range of power that is required to get on the foils and then change the sail profile when you’re up and running at high apparent wind speeds.’ But while the basic functions may have been


ADAM MUSTILL/AMERICA’S CUP


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