Coincidental but quite appropriate, Team New Zealand’s first full-scale twin-skin test rig was mounted on this tidy little F-22 trimaran just a few months after the death of the boat’s designer, New Zealand multihull pioneer Ian Farrier. These small tris are raced hard and there is plenty of performance data and anecdotal experience available to help the Cup defenders reach some quick judgments
intimately linked,’ continues Fallow. ‘You can manipulate mast rotation, traveller position and sail twist, and they will all be interrelated. Add the ability to control the top 4m and the bottom 1.2m and you have a lot of control over the available power.’ There is room for manoeuvre with sail
shapes. The mainsail has five girth stations ranging from 7-7.4m at the foot to 2.6- 3.6m at the head, with a formula further dictating the sail’s shape. Between the two ‘zones’ mainsails can be fitted with up to six full-length battens and up to six addi- tional battens of up to 1m (that must have one end terminating at the leech). With a luff length of around 26.5m
(87ft) and foot length of 7m (23ft) the sail plan is relatively modest, but ample con- sidering the AC75’s featherweight dis- placement of 7 tonnes – similar to a TP52. Thanks to this and its foils, the promised performance of the flying AC75 should be comparable to that of the AC50. Fallow explains: ‘We didn’t want the
new set-up to be any heavier than a con- ventional sail would be. By generating an extra 15 per cent or so of lift we could reduce the rig height and save weight.’ With the wings the internal frames took
the loads, the entire structure covered with a Clysar film. With the new mainsails the sail material will be structural. ‘If you were relying on the battens to deal with all of the loads and transferring those forward into the mast tube you’d need to reinforce the mast, which would be heavy. So the inten- tion is for the skins to be structural, just like a regular sail, although there will be a sharing of the loads between the two skins so each individual skin can be a little lighter than a single one by itself would be – so you haven’t got double the sail weight.’ As with the wing, the majority of sail
controls are likely to be hydraulic, although the rule specifies that rope must be used for the headsail sheeting. Other- wise, Fallow says, AC75 sail plans will look similar to an AC72’s, with mainsail,
38 SEAHORSE
jib and code zero flying from a bowsprit. ‘Bear in mind that because you can’t gener- ate as much lift from the mainsail as we could from the wing, there will be more total headsail area and the amount the headsails contribute will be more signifi- cant than during the last two Cup cycles.’ Boats will have jibs and code 0s of differ-
ent sizes and weights for different condi- tions but onboard are likely to be just three sails. Headsails will be fairly flat as they only have to operate through a small apparent wind angle range, as well as having mid-girth restrictions in the rule. If AC75 speeds are as advertised then it
seems probable that teams will go through similar development as they did with the AC72s, when gennakers became redundant in all but light conditions. ‘There will be times when you won’t sail downwind with the code 0,’ confirms Fallow. So if you’ve only got three sails onboard,
what are the 11 crew going to do? Fallow: ‘These boats have significant righting moment and big corner loads out of the sails… A lot of energy will be required to do all the sheeting, plus aside from all the nor- mal mainsail stuff you’re going to have mast rotation and head control systems that are variables. So there are plenty of controls.’ After two Cups where the focus has
been on wings, the 36th America’s Cup is back to being a ‘sails’ event. As Fallow quips about twin-skin mainsails: ‘Well, at least it makes up for the last two cycles when we haven’t sold any mainsails!’
SIGN OF THE TIMES – Martin Tasker Paragraph 27.1 of the AC75 Class Rule says: ‘There shall be 11 crew members, unless reduced by accident, who shall all be human beings.’ Dan Bernasconi is one of the key
authors of the rule and he chuckles at this rare moment of levity in the 62-page docu- ment. ‘We did wonder during the last Cup when we had some of our sailors following
a dot on a screen to control the foil,’ recalls the technical director for Emirates team New Zealand. ‘We thought, “You could build a robot to do this job and probably do it better than a sailor.” So androids are taking over and we thought we’d better make sure that someone didn’t turn up with a crew member that wasn’t human.’ Those 11 humans will never have been
so busy. The cyclors are gone but grinders are back with up to eight on the pedestals at any one time. And as with the cyclors they’ll be multitasking: ‘There will be more grinders but also more sailing roles, and that will be a combination of more tradi- tional sail handling – maybe being on the foredeck to get a code zero down or on a jib sheet to cast off and to load up the new winch in a tack – but for sure the buttons aren’t going to go away. There are still going to be a lot of hydraulics on the boat,’ says Bernasconi. So, as in the last two Cups, the grinders
will be hauling in sheets and producing oil pressure? ‘Probably, yeah. Again that’s left open to the teams. The jib sheet has to be on a winch, that’s a requirement because we didn’t want everything on the boat to be completely hydraulic with more grinders and fewer sailors being involved in the sailing of the boat. So jib sheets are required to be on a winch and everything else is optional. ‘We’ve discussed it a lot – pros and cons
of whether you put the mainsheet on a winch, or the traveller or the runners and all those are possibilities. But I think that will be part of the interesting process of the next three years – seeing where those things end up. It could well be that some teams tick one option and some pick the other. ‘Like soft sails instead of a wing and
more supplied parts, it’s all part of a rule thrashed out over four months by ETNZ and Luna Rossa, with which they’re striving to “ensure fair and exciting racing while leaving plenty of freedom for inno- vation to flourish”.
HAMISH HOOPER
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