Above: April 1937 and T.O.M Sopwith’s second J Class Endeavour II slides down the ways at Camper and Nicholson’s Gosport yard. Endeavour I and II will shortly cross the Atlantic under cut-down rigs for some pioneering two-boat tuning ahead of the 1937 Match. But Sopwith’s best shot at the Cup was already behind him when the faster Endeavour I failed to beat US Defender Rainbow in 1934. Right: controversial at the time… Australian Challenger Gretel II attempts to shut out Intrepid at the start of race 2 in the 1970 Match. Gretel II went on to take the winner’s gun but was later disqualified for luffing above close-hauled after the start gun had been fired. Alan Payne’s Gretel II was a faster yacht but made mistakes… the memory of which set Aussie teeth on edge during the 1983 contest
course, the victory of Australia II against Liberty in 1983. The contest as close on the water as it was acrimonious off it. As most readers will know the contest
was between what we will call a conven- tional 12 Metre of the time and a very different animal designed by Ben Lexcen. For this contest Ben designed two boats, Challenge 12, the conventional 12 Metre, and Australia II, the avant garde, radical solution that, by its very nature, trod a different path from the conventional Metre boat route. Both boats were built and, as I under-
stand it, the conventional boat was consid- ered, by many, to be the faster of the two, and it was only at Bond’s insistence that Australia II was chosen. He apparently reasoned that, because it was so different it would scare the bejusus out of the Ameri- cans and thus give the Australians at least a psychological advantage. Actually, I believe he was right and that ultimately the Americans were primarily psyched out of the competition rather than being beaten by the faster boat. During the 1986 12 Metre Worlds,
which preceded the America’s Cup of 1987, the late Graham Walker’s syndicate chartered Challenge 12 to gain experience of sailing 12 Metres competitively in a hot fleet and also to get some measure of where the competition were. I was lucky enough, as part of the design
team, to be there and witnessed the event. The boat was skippered by Chris Law and, because there were only a handful of us in Fremantle, we had a mixed crew of British and French sailors. From memory we finished last or nearly so. After the end of the event the Aus-
tralians, who had until recently been sail- ing Challenge 12, asked why we had done so badly and claimed that the boat was quicker than the winner of the event, Australia II. So what had we done? Well, we had a
54 SEAHORSE
crew who we had literally picked up off the dock and it had been some time since Chris had sailed a 12 Metre – but this remark tied in closely with our observa- tions during our recent tank testing. There were two design groups within our
syndicate. One was headed by Ian Howlett and used the facilities at the Wolfson unit in Southampton together with the tank at Haslar in Portsmouth. The second group included myself, the aerodynamicist Herbert Pearcey and, on structures, Stephen Wallis of Laurent Giles and Partners. For any research programme aimed at
improving the performance of a particular vehicle, be it a boat, a car or for that matter just about any competitive vehicle, you need a trial horse, a benchmark against which any improvements, or otherwise, can be measured. The best benchmark in the world is the previous winner of the particular com- petition that you are engaged in trying to win, so that it was fairly imperative that we had a model of the then last winner of the America’s Cup, Australia II. Because Ian had been involved first hand
in the 1983 America’s Cup competition and thus had first-hand knowledge of the boat, as well as the fact that Ian is pretty good at that sort of thing, he was commissioned to produce a set of lines that would best approximate the shape of Australia II herself. It is surprising just how close you can get
to any given shape given a set of good photo - graphs when taken from the right angles and with something in the background to help with the scaling; together of course with a rating certificate! From the rating certificate you know many of the key measurements and those measurements almost dictate the shape that will pass through them and also satisfy other parts of the rule, in this case the 12 Metre Rule, to which the boat was designed. I think that Ian’s effort got the boat pretty much spot on. I certainly was confident the shape was close enough to use
as a benchmark to test our own models. There will always be some slight differ-
ences but, despite what some designers might claim, in the real world most of those differences will hardly affect perfor- mance, and what differences there might be would probably be too small to measure accurately and would certainly be within the accuracy of scaling to full size. Anyway, we built large models of Ian’s rendition of Australia II at both one-tenth and one-third scale as our principal tank test trial horse models. When we started tenth-scale testing the
first thing that stood out was that the Aus- tralia II model was draggy, both down- wind and upright and upwind when yawed and heeled. However, when the results were fed through our early VPP the results were much better. The poor hydrodynamic performance was offset, to some extent, by the greater righting moment delivered by the lower VCG of the inverse taper ‘upside down’ keel with its lower concentration of lead. However, it was still not as good as a conventional delta-shaped keel as sported by most other 12 Metres at the time. I believe that other syndicates found
much the same thing but proceeded with the Australia II concept anyway because it did produce a boat that would accelerate out of a tack more quickly than a boat with a conventional keel and this trait became even better the longer, in span, the winglets were made. This should be quite obvious because increasing the span of the winglets increases the overall span of the whole boat and it is span that is the main determinant of lift-induced drag and it is induced drag that is the prime drag when a sailing boat is moving slowly with much side force, as when coming out of a tack. Additionally, Australia II, because she
was shorter than a conventional Twelve, could also be lighter and this also helped her accelerate more rapidly out of a tack or in a small increase in pressure – as had
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