To anyone wondering about how mega the carbon work – and modulus – must be to build rudders and foils this fine, relax, there’s a lot of expensive metalwork hidden under the paint where the loads are very high but the sections need to be very fine. There was a lot of metal in the boats in Bermuda too, but it wasn’t good for the image to mention it too often. Prada (inset) went afloat with two different wing arrangements, as did the magnificently named Britannia. The AC75s are not going to be staying dry around the course for a long time – the concept is very aggressive and technically very exciting but almost everything about these boats is like nothing that has been tried before. Plus structures that look solid from the outside are in reality fragile… Things will be breaking for a while
parameters – roll, pitch, rudder angle, rudder rake, ride height, apparent wind angles and, perhaps most complex, the extreme variation of righting moment as the foil arm is canted and the yacht transitions from displacement to foiling mode. ETNZ tested their Waka in 2011 and foiled their AC72 in 2012.
But the first foiling tack in an AC yacht did not come until Bermuda in 2017. Some of the AC75s have allegedly accomplished foiling tacks within days of launch. None have been caught on film… Stating the obvious, racing in Cagliari in April will be exciting.
A NEW LUNA ROSSA – Giuliano Luzzatto Luna Rossa AC75 is the ninth boat launched with this name, the result of 78,000 hours of work by around 100 people in 18 months, built at the Persico shipyard. It is the distillation of the ideas of 37 designers from 12 nationalities co-ordinated by Dr Martin Fisher, foiling pioneer and a fluid dynamics expert. The Luna Rossa design team ran about 600 candidate hulls
using CFD and probably even more wing configurations for the one- design arms. The Luna Rossa design team is truly international, but the sailing team, the most visible part of the challenge, is by choice almost entirely Italian, with only James Spithill not holding an Italian passport. In this regard, rumours about the simultaneous presence onboard of two helmsmen, one on each side, have not been confirmed or denied by the team. Returning to the boat, there was not as in the past a great deal
of emotion when the foils and underbody were revealed, since the current rule forbids any part of the boat to be hidden. Despite this,
in the days following the launch we sought confirmation of some of our assumptions from Martin Fisher. ‘It is not simply a new boat,’ he told us. ‘It is a new generation of boats for everyone. The rule is still very open, and it is only the first cycle. So there are enormous differences, which is useful even for spectators. I like it very much.’ The bow: apparently very classic, we expected something totally
original because rumour had it that the cause of the launch delay (2 October when it was initially scheduled for 25 August) had been to delay disclosing the design to the other teams. The great originality of Luna Rossais instead under the hull: a longitudinal protuberance, a kind of long keel or skeg, which has the task of reducing as quickly as possible the wetted surface in the post-displacement phases, thus facilitating the take-off onto the foils. So is Luna Rossa’s design philosophy similar to the Kiwis’?
‘There are two schools of thought,’ says Martin Fisher. ‘The boats are different but divided into two groups, Luna Rossa and ETNZ, and Ineos UK and American Magic. The rule does not allow you to have a scow, but the Americans have found ways to do something similar while respecting the rule. The English boat is very interesting – we are analysing it based on the information available to us, trying to understand their ideas. We respect our opponents very much, that’s why we look at everything that they do very closely.’ Like the other AC75s seen so far Luna Rossa features a long,
curved centre fairing that extends in an arc right up to the stern, with separate working decks either side. The function is primarily aerodynamic but the fairing makes a useful structural contribution. The new AC75s are definitely the most complex sailing boats
ever launched. SEAHORSE 13
CARLO BORLENGHI
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