Nothing new under the sun (maybe)? — Part 1

Due to the twin constraints of handicap systems and the precision required for the concept to be effective, we are little the wiser about the ultimate potential of the tandem-keel configuration. The issue surfaced again in Valencia this summer — are they fast, can they be fast, are they once again under full-scale investigation? In this new series aerodynamicist Dave Hollom looks at the evolution .... and at the science.

Ever since Australia II won the America's Cup in 1983, every competition for the trophy has had stories of experiments with some form of tandem keel or canard. Some were true, others were not.

Before we launched the 12-Metre Crusader 2 in Fremantle in 1986 the rumour mill had her with a tandem-type keel so our shore boss obliged, employing the simple process of painting in matt black those areas where no appendage was meant to be. A vertical oblong was painted on the fin, leaving the front and rear seemingly as two separate fins in a layout similar to that previously patented by Warwick Collins.

It was very effective. No sooner had we passed through the breakwater for the first time than half a dozen helicopters appeared above, as if by magic, and that night's TV news was full of pictures of our 'twin-keel' together with any number of pundits explaining its supposed advantages...

Nevertheless, many syndicates have since genuinely experimented with such a concept in the ACC era, including Stars & Stripes, GBR Challenge, the Nippon syndicate and of course New Zealand's original Farr-designed NZL 20. However, other than NZL 20, none of these experiments appeared to be particularly successful (either that or the sailors, for whatever reason, preferred the conventional boat); and because NZL 20 was a very different boat in broader concept, other features may have been responsible for her comparative success. Because the centre of lateral resistance (CLR) is further forward...

To read the remainder of this and many other articles, please purchase your copy of the November 2006 edition of Seahorse International Sailing available at selected newsstands or by calling: + 44 (0) 1590 671899 or by email at: info@seahorse.co.uk

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