Decompression
It started with the racing code zero but already the benefits are spreading rapidly out through the superyacht world (and elsewhere...)
Since Doyle Sails launched its ground-breaking cable-less Code Zero technology, the company has expanded the concept to embrace jibs, staysails and even mainsails, achieving significant load reductions in the process.
Structured Luff Technology is the new branding, which encompasses the full sailplan including cable-Less code zeros. ‘What we are talking about is sails where, rather than hanging them off a stay, we are taking the load around the natural load line of the sail,’ says Doyle CEO Mike Sanderson. ‘A whole raft of benefits come from that. ‘This applies to any jib, genoa staysail, spinnaker staysail, code zero or mainsail.’
Taken to the logical conclusion, structured luff headsails could remove the need for a forestay altogether but for practical reasons a forestay should probably be retained. However, because the sail is sharing a considerable proportion of the load, the forestay can be significantly reduced in size.
While the technology has
important load-reducing implications in all applications, Sanderson believes the biggest benefits will apply to superyachts, where forestay sag is a perennial performance killer. The physics of all this are complicated, so Sanderson draws the basic triangular shape of a headsail. To demonstrate that the
74 SEAHORSE
loadlines do not follow the outer edges of the triangle, he draws scallops curving inside the luff, leech and foot of the sail. The result looks like a series of lenses, which is the term Doyle uses.
The primary interest lies in the luff lens. ‘By following the loadline down the lens with a series of fibres, you are able to reduce the load on the forestay,’ Sanderson explains. ‘On a superyacht, if you wanted to limit forestay sag to 400mm, for example, with a conventional headsail you might need 10 tons of tension on the halyard and 30 tons on the forestay. With a Structured Luff headsail, you would restrict forestay sag to the same extent with approximately 13 tons of halyard tension, but potentially as little as eight tons on the forestay, so there is a total compression reduction of almost 50 per cent.’ Put another way, many
superyachts operate their jib locks well below their maximum safe
Above: before and after... these two pictures from the masthead of an 18ft skiff show the dramatic reduction in forestay sag that can be achieved with Doyle Sailsʼ Structured Luff
Technology. Scaling up to a superyacht rig, the sag reduction can be as much as two metres Above:
this stress direction map of an MC38 headsail
illustrates the loads along the lenses
working load. ‘So, another option in the retrofit world is that by taking just 30 per cent of extra load into the Structured Luff jib, suddenly two metres of forestay sag is down to as little as 500mm. That is a huge gain.’ Sail management also becomes easier, with crews relieved of trying to manhandle removable code zeros or staysails with large diameter cables. One superyacht owner, for example, only used his code zero for racing, leaving it in the container ashore while cruising because it was too big to go into the lazarette. With cables down to a third of their original size (or completely eliminated), the new technology code sails and staysails flake easily and stow in the lazarette, which in turn allows them to be in constant use while cruising, improving the enjoyment and efficiency of the boat. In some applications, Doyle’s designers have targeted forestay compression reductions by as much as 50 per cent. The immediate
ALEX VALLINGS
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