Opposite: spot Charalʼs red shark… nasty thing to get in the way of. The push to reduce freeboard aft is leading to smaller cockpits along with more aggressive prevention of water ingress from the side and above with a mix of carefully positioned lips and screens to divert the water. The large sliding canopies of previous-generation Imoca designs are long gone in favour of the much lighter rigid solution. To save weight wherever practical reinforced Mylar film has been used in place of polycarbonate in Beyouʼs viewing panels
consequence of which can only be a much increased emphasis on foil and casing relia- bility… but more on that later. ‘To be clear, if something goes wrong, this new genera- tion of boat will be dramatically compro- mised if they ever have to sail relying on displacement mode only,’ warns Daniele. The impact of this new philosophy on hull behaviour and therefore shape is significant. As Quentin notes, the studies carried out for the 2016 generation assumed a displacement range of 7 to 8 tonnes, as designers took into account the lift provided by the keel alone. ‘The pres- ence of foils did not, at this stage, really influence the hull design,’ he confirms. ‘But that has completely changed for the current generation,’ adds Daniele. ‘Foils are now bigger, and the very first question we asked ourselves was “how is the boat’s general balance going to be affected”? We made a conscious effort to put aside our natural instincts, and to start from a new perspective altogether. This puts you in a different frame of mind from the outset.’ As has been observed in a variety of disciplines, trying to stretch an existing concept too far can ultimately result in self-censorship, since any really big change might be interpreted as an abnormal distortion of the basic building block. ‘By
contrast, starting from a relatively blank sheet of paper we felt comfortable asking ourselves fundamental questions,’ says Daniele, ‘and we quickly realised that pre- vious hull shapes we’d been producing would not be optimised or optimisable for what we foresaw the boat being capable of. So this time we started with an intu- itive, free-ranging imaginative process that we only later strived to back up with data.’ Given the new context, it’s tempting to look at the hull as a structure whose pri- mary function is reduced to supporting the foils. Much like a Moth! Displacement mode phases should be marginal and lim- ited as opposed to being the norm, which begs a whole different set of questions. ‘Yes, to a certain extent,’ says Daniele, ‘but the hull can’t be considered as a simple “foils receiver”, since we don’t have T-shaped rudders, so we’re not looking at a pure flight mode. When the skipper decides to take it a little easy the hull plays an important role, plus in the absence of lift- generating rudder foils the hull is nearly always driving the foils’ angle of attack. ‘To put things simply, we thought we would reduce the hull’s power to make gains in terms of drag, then the foils would kick in early and give us speed at this lower drag figure. Power versus drag is the usual
designer’s dilemma when it comes to offshore boats!
‘It’s clear, for example, with Class40s optimised for beam-reaching: the hull is the only parameter with which you can play to get power – then the trick is to gen- erate enough to compensate for the extra drag. But we got out of this constraint, knowing that we could afford to dial down the hull’s power. The key of course is to know how far to go in this reduction process, as well as to rethink the design methods for this new context.’ Quentin Lucet: ‘What’s important to stress at this stage is that no longer can we isolate various design elements to study them separately and then reassemble everything later; we can’t simply draw a hull, consider it done then move on to the foils and from there play with the keel tilt and cant etc… Today we look at the hydro constraints and must model the whole package all in one go. The whole performance package is now completely homogenous, if you like; it cannot be broken down into components.’ A systemic approach to design, then? ‘Precisely. The level of interaction is such that taking a “parts then sum” method won’t cut it. It’s extremely interesting because in terms of CFD hydro simulation work, we’re now examining attitudes of
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