Ellen MacArthur’s original Open 60 Kingfisher marked the opening shot in what would be a raising of the bar in the class, being the creation of an America’s Cup-style design group led by Owen, Rob Humphreys, structural engineer Giovanni Belgrano and Andy Claughton of the Wolfson Unit. Kingfisher won on its debut in the 2000 Transat before going on to finish as runner-up in the Vendée Globe
Fashionable logic
Twenty-one years’ history of high-speed sailing hull development and twin rudder designs… with Merfyn Owen of Owen Clarke Design
It is 21 years since Merfyn Owen and Allen Clarke began drawing monohulls, having branched out from where they started, designing and building racing mul- tihulls, pursuing a knowledge-based design process from the very beginning utilising probably the world’s first multihull VPP. The software, written by Owen himself in Fortran 77, took a year to develop, before design work on the yacht itself began with the end result being the then radical ‘as wide as long’ 11m trimaran, Fiery Cross. Not surprisingly, their first monohull was no ordinary raceboat either; inspired by John Martin’s Allied Bank, Maverick was a ULDB (ultra light-displacement boat), with a hull shape and waterline beam that necessitated the fitting of twin rudders. The yacht was designed primarily as a double-handed racer for events such as the AZAB and the RWYC Round Britain Race, but she also featured a lifting carbon keel allowing her to sail over the
river bar at Ravenglass and so race competitively against multihulls in the Karrimor Three Peaks Race.
At only 1,550kg, more than 3m wide on a length of just 9.1m and water ballasted, Maverick was capable of very high sustained speeds and 300-mile days sailed by only two crew. In the double-handed Round Britain Race in the year of her launch, her skipper Mark Turner arrived at the finish in Plymouth a very wet second… and if not for destroying the head of his mainsail in the first leg and thus limping late into Cork, he would more than likely have won that prestigious race on his first attempt.
‘Unlike recent times,’ designer Merfyn Owen explains, ‘where twin rudders are considered a fast solution in their own right, ourselves and a small group of mainly French designers were then devel- oping higher-Froude number, higher-speed hulls specifically to suit the displacements, righting moments, sail plans and target wind speeds we were dealing with. ‘Significantly, these hulls had far less rocker than IOR and other designs of the period and, as with our later Class 40s and Open 60s, designers needed a twin rudder solution because, among other less obvi- ous reasons, a centreline-mounted single rudder would have ventilated when heeled. Two rudders were fitted and were essential for good control, but it’s the development
of an appropriate hull form, suited to the mean speed and sailing conditions experi- enced by the yacht, that was and still is the overwhelming factor when designing what people refer to as “twin-rudder boats”. ‘One cannot simply append twin rud- ders to a conventional design and expect to get the performance gains and levels of control that a well-considered design will produce. You might be lucky, but equally we’ve seen plenty of evidence and con- sulted “after the fact” on yachts that don’t benefit and would have been better off sticking to a more conventional rudder arrangement. We’ve also, for that matter, seen the same kind of “fashion in hats” approach to the addition of chines into inappropriate hull forms,’ adds Owen. Thursday’s Child, the ULDB designed by Lars Bergström and one of the first boats created to the early Open 60 rule, was a good example of a hull form that merited the use of a single appendage. She was fitted with a single transom-hung canting rudder, one of many innovations on this groundbreaking design. Owen delivered her to the United States from Australia via Brazil for owner Alan Wyn- Thomas in 1994 after the boat’s retirement from the Vendée Globe. From there he then went on to project manage the yacht’s circumnavigation in the BOC race of that year for American Arnet Taylor. This was the beginning of Owen Clarke Design’s
SEAHORSE 33
THIERRY MARTINEZ
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