Technology
Leaving the world
behind Imitation really is the sincerest form of flattery for the generous folk behind Doyle’s brilliant Structured Luff technology. Greater forward thrust, kinder on your rig, forgiving to trim... what’s not to admire?
After eight years of developing and validating the performance benefits of its Structured Luff technology, Doyle Sails passed a significant milestone this year when the concept reached the market-acceptance tipping point to become mainstream. ‘Customers have seen and understood the benefits of Structured Luff technology and increasingly the pro sailors advising owners are pushing them in this direction,’ says Doyle Sails CEO Mike Sanderson.
Any number of business school studies have shown how innovations, be they screw-top wine bottles, online shopping, electric cars or sails, follow a rite of passage from resistance to acceptance, charting how markets let early adopters risk the leap to test their merits. Ultimate validation comes when rival brands shift from demonising the disruptive newcomer to launching their own versions. Sanderson has watched Structured Luff pass through all these stages, greeting the new imitations with a philosophical shrug. ‘We could either be offended or flattered’ he says. ‘We choose to be flattered. The industry is well aware of how this all began.’ It began in 2013 when Sanderson came up with “a crazy idea” for a Code Zero for the Maxi 72 Bella Mente. To get around the 75 per cent mid-girth measurement rule for asymmetric downwind sails,
68 SEAHORSE
sailmakers were looking for ways to create masthead Code Zeros that could be sheeted flat as the apparent wind moved forward. The standard solution was a genoa-type shape supported on an integral luff cable, with superfluous material attached along the leech to achieve the 75 per cent mid-girth target. As the trimmers cranked up the luff load and sheeted on hard, the excess leech material flapped away – disturbing windflow and losing efficiency.
Sanderson’s idea was to build vertical structure into the natural leading edge load lines of the sail itself and meet the mid-girth dimension by shifting superfluous material from the leech and placing it ahead of those load lines. Making that concept work relied on the “genius” of designer Richard Bouzaid, according to Sanderson. Bouzaid ran a structural study and came up with one-piece vertical panels that would take the load and allow the sail to set up without a cable. Because of the curved shape of the load bearing vertical panels, he described it as a lens. ‘The first trial was a 90 per cent success,’ Sanderson recalls. ‘The design was a bit compromised as we adapted an existing sail and the front floppy bit shook around too much, although it did want to fold back along the leeward side as
Above: pressure
distributions on the same section of Structured Luff and
conventional Code 0s. On the Structured Luff sail, the suction is aligned more closely with the drive force axis. For a similar force
magnitude generated at that section the Structured Luff sail has it pointing more forward, in turn deliv- ering extra drive force
planned. But the big shock was how the sail set up. There was basically no sag. This was a phenomenon we had stumbled across.’
On further development, the Doyle Sails team found that, freed of the constraints of a 30mm cable locking the luff in a bar-taut line from masthead to bowsprit, they could project the lens effect further forward enabling them to meet the mid-girth dimension without any superfluous material. And, in a rare win-win situation, the cable-less version flew straight on the centreline, even slightly positive, under four-ton tack loads, compared with the six tons required for a conventional sail.
The Doyle designers immediately recognised the ramifications of achieving more efficient sails with a significant reduction in loads were enormous. It could mean lighter rigs, lighter forestays, lighter runners, smaller runner winches, more righting moment – huge benefits for racers but also for superyachts, which could specify smaller engines and reduce fuel consumption. Doyle Sails quickly applied for “patent pending” protection of the concept. ‘To get that protection, the authorities first go through a rigorous due diligence process to ensure there is nothing else like it in the market,’ says Sanderson. ‘The fact that we received that protection is
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