Update
TIME, TEAMS AND TECHNICAL DETAILS – Jack Griffin Sometimes March 2021 seems a long way in the future, and sometimes it seems like tomorrow. Emirates Team New Zealand did a good job of publishing the AC75 Class Rule to meet the 31 March deadline, but they left out a few important technical details – in particular the specifications for the Foil Cant System (FCS) and the specs and drawings for the mast. Meanwhile, the America’s Cup ‘Racing Rules of Sailing’ are not part of the class rule, but they are also critical to the design process since they will directly affect how the boats are sailed. These missing details give the design teams a few extra
challenges. Put yourself in their shoes. Will the RRS require the yachts to sail with both foils in the fully down position during the pre-start? That would have a big effect on your hull design. What rules are needed for racing this daring new class of boat? And what about those specs for the FCS? How about the speed that the foils can move? That information is part of the as-yet-unreleased FCS specs. This will affect the yaw moment when the windward foil is dropped for a manoeuvre. Will teams use that moment to help turn the boat through a tack or gybe? How fast can we move that foil down to the position where it will generate enough lift to fly? That’s another factor that will affect hull shape. The class rule prohibits generating downforce with the foils. This
is logical enough – using downforce to generate righting moment would put extremely high loads on the structure at speed. The rule delegates to the FCS itself the enforcement of this downforce ban: the FCS will move the foil downwards if it senses a net downward moment. But the FCS cannot actually sense downforce – only the moment about the cant axis. The gravitational component of that moment will vary with both the cant angle relative to the hull and the amount of heel to windward and leeward. It will also be different for each set of foil wings if they vary in weight.
10 SEAHORSE
So the FCS will need to be programmable to net out the
gravitational component of each set of foil wings over the range of cant and heel angles. Designers will need the specs for all this so they can provide the crew with information systems to let them know when the FCS takes over control of cant angle. If the Defender and Challenger of Record want to change any of
this, they can do so. The Protocol allows them to make any changes to the class rule until the end of June. After that, unanimous consent of all competitors is needed. The end of June also brings the end of the entry period, so that is when we will probably know who all the competitors are. In addition to Defender ETNZ and COR Luna Rossa, the New York Yacht Club and Royal Yacht Squadron Racing have well-funded challengers: American Magic and INEOS Team UK respectively. Another US syndicate and another Italian syndicate have been
in the news recently and may yet have a chance of raising enough money to challenge. But these two, if they materialise, will be short on both time and money. The Italians have talked about a budget of 64 million euros – about half of what INEOS Team UK has. INEOS Team UK have said they will have a test boat sailing this
summer, so we will see a proof of concept soon. The first full-sized AC75s will hit the water nine or 10 months later, in April 2019. Stating the obvious, this will be interesting.
A CUSTOMER WRITES – Don Street Having both chuckled and marvelled at the mix of humour and insight that Peter Harken shared in your recent interview I need to add a word on my own history with Peter and Olaf in those early days… In the mid-1980s Olaf contacted me about my heavy, high-mileage
yawl Iolaire. He said Harken’s headsail furlers for small boats were proving popular and reliable and selling well. Now Harken had designed and built a unit for larger boats, with headsails 50ft on
ALL PHOTOS ROBERT DEAVES
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