Left/below: the Trident prototype mounted on Fast Forward’s Formula 40 test mule. The fully rotating, masthead rigged wing concept has been explored before but with little notable success outside the world of model yacht racing – largely due to the investment of time, technology and money needed to resolve the fundamental issues of free rotation and supporting a long, slender rig only at its two extremities. Without free rotation and a pivot far enough forward such a rig – even with a very narrow chord – could never be left untended and so was unlikely ever to find widespread interest. Two of the best C-Class sailors in the world spent every night on Oracle’s big tri USA-17 during the 2010 America’s Cup in Valencia to make sure the world’s biggest solid rig kept pointing the right way


they did things the old-fashioned way. They had a good idea how much the wing beam should be allowed to bend under load. With a bucket of sand hung at the middle, they began bending the wing’s structural beam. After each loading more material was added to the beam, reducing deflections until their bend criterion was met. No computer, no FEA. Just street smarts. Once finished the system was trialled off Randy’s beachfront


home in Fort Walton Beach, Florida where few were likely to notice. In relatively short order it was clear the idea had potential. The prototype sailed 7.50


closer to the wind than the same catamaran


conventionally rigged, and passed all the initial feathering tests. The newly named Hybrid Wing had grown wheels. The next step meant a larger proof-of-concept prototype for which


Gonzalez’s own Morrelli-designed Formula 40 cat was the chosen vehicle. The Formula 40 hybrid wing has a wing-sailplan ratio closer to 45%. As on Scissor, the sail is fitted with a boltrope. Again the mainsheet is simple: a single line leading from a winch on one side to a block on the slider, up to a block on the sail, back down to another slider-mounted block and thence to the opposite side winch. However, this bigger wing was too technical for amateur boat-


builders – and weight was critical. Hall Spars were chosen for the job. Hall engineer Gunnar Salkind took Randy’s ideas and translated them into an autoclave-cured structure optimised for weight and strength to suit the highly loaded masthead staying system. Kenny Madeiro, Hall’s composites guru, oversaw the building of the wing elements and Jim Gagnon put all the bits together (the latter two were the key players building Hall’s America’s Cup masts for both of Alinghi’s successful pre-wing era Cup campaigns). Hanging around wings for even a short time, it becomes clear


that a wing’s tendency to feather is not as simple as it looks. One might think that if most of the wing area were aft of the pivot the wing would readily feather. But because a wing’s centre of pressure is well forward, even with a pivot point at or slightly ahead of the 20% chord point it will still rotate back and forth unpredictably. To help address this the pivot point at the base of the Hybrid Wing is set as far forward as it can be practicably installed. The wing construction itself consists of a leading-edge structural


box beam with featherweight ribs bonded onto it – the beam itself was autoclave-cured and female moulded using carbon-Nomex honey comb throughout. The female mould later served as a jig in which all the components were assembled. The leading-edge element is mated to a smaller I-beam of similar construction running back from wing tip to about mid-span. Below mid-span the I-beam jinks back forward to align with the mast step ‘trailer hitch’ pivot, keeping all compression loads within the structural element. The ribs were computer cut from a sheet of Nomex that had been


covered with thin carbon facings. Because the rib edges were exposed honeycomb the surface was unsuitable to directly apply the Clysar heat-shrink membrane film; to provide the right surface, a carbon-foam edge member was bonded to each rib face. Although Clysar covering is suitable for proof-of-concept testing, a tougher covering will be used if rigs are later produced for sale. Where the I-beam moves into the leading-edge element below


mid-span to line up with the wing pivot, the wing ribs serve to maintain the leading-edge shape. The next to last rib at the base of the wing is also angled down to create a triangle with the base rib, boltrope tunnel and box beam stabilising the rib system, similar to how rib systems in fabric-covered aircraft wings are stabilised. A student of C-Class and America’s Cup construction will recog-


nise structural details where the ribs meet the leading-edge box, an example of which are the gussets at the rib-box beam interface which serve to strengthen the connection as well as provide extra area for bonding on the heat-shrink covering. A solid carbon boltrope tunnel is bonded to the aft edges of the ribs. Because the stays are now all at the masthead, the structural


box beam is subjected to higher bending and compression loads than a wing with stays attached partway up. A very loose parallel is a masthead vs fractionally rigged spar, the latter having smaller section requirements. The structure required at the top of the wing leading-edge box


beam is more substantial as a result, looking a bit like the crane on a conventional masthead rig. The reason for the extra structure is to provide a mount for the rotating three-spoked stay attachment yolk, which is designed to take the stay loads as well as thew


SEAHORSE 49


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