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Flat and flying, as Fujin sets off down a breezy reach in St Maarten. It is the Polynesian flavour of the raised stems – which help lift the front beam well clear of the water – that first catches the eye with Paul Bieker’s big new cat, but the main design smarts are less obvious. Substantial hull rocker (right) helps ensure a sensible balance of all-round performance, with Veed lower hull sections and carefully sculpted chines to provide lift and also to efficiently disperse the speed-sapping spray that is inevitable at high speed
Old school fast
Oracle USA designer Paul Bieker’s ‘traditional’ new 53ft cat Fujin left her more contemporary modern rivals trailing breathlessly in its wake at this year’s St Maarten Regatta… Greg Slyngstad, a fellow Seattleite, first approached us about designing a performance cruising catamaran about a month after we finished our work for Oracle Team USA in the 34th America’s Cup. Greg had visited the Oracle base in San Francisco during the final week of the Match and I was excited to have a project to sink our teeth into as I tried to wind down from the experience. The design brief was for a catamaran in the 50ft size range that
would be designed primarily for the racing and cruising scene in the Caribbean. The boat needed to be comfortable and safe for cruising but fast and fun to sail with a racing crew. Having primarily been a monohull sailor, Greg was free from preconceptions of what the boat should be like. Since it was the first project of this type for us we were open to new ideas as well! My opinion is that this type of boat has three enemies: 1) weight
2) windage and 3) the boats are much more stable transversely than fore and aft so they are susceptible to bow-down trim when being driven hard. Weight increases the power necessary to fly a hull and a cata-
maran is slow until it can fly a hull. The only way to compensate for a heavy boat is to increase the rig height which makes the boat harder to sail and exacerbates trim issues. Windage is an issue because these boats have tall freeboards to help compensate for bow-down trim and most have stand-up accommodation across the entire wet deck, creating a large frontal area to overcome upwind. Our aim with Fujin was to reduce these issues as much as
possible within the constraints of the design brief. To combat weight we hired a friend from our America’s Cup work, Steven Robert of ST2 Design, to engineer the platform and rig structures. We did the detailed engineering and appendage structures in-house. We chose resin-infused carbon/epoxy skinned foam cored structures as a reasonable compromise between weight and cost
50 SEAHORSE
and we used pultruded carbon rods for the first time in the beam and appendage structures as a cost-effective way to get pre-preg carbon compressive strengths in a room temperature cure process. At a light ship weight of around 6.7 tons, I am confident that Fujin
is significantly lighter for its size than any other boats of this type. We kept the interior simple but comfortable, with a focus on well- executed simple structures and minimal non-structural linings. To combat windage and improve the fore and aft trim issues
we put a fair amount of volume into the lower bows, added chines for increased dynamic lift when hard pressed and reduced the freeboards. We kept the chine angle in profile fairly steep to help ensure
that it retains a positive angle relative to the waterline when trimmed bow down into a moderately big wave (it’s been my experience that you can trip over chines if they are too flat in profile). The upper stem is heavily cut back also for reasons of weight and windage. We had Len Imas run RANS analysis of three different hulls over
a range of speeds and longitudinal trimming moments in order to choose the best balance of dynamic lift and low drag. We also left vestigial tall stems on the bows to keep the forward
cross beam high enough above the water and reduce foredeck wetting in big ‘stuffs’ – an interesting detail I observed on some Polynesian craft when sailing there many years ago as a teenager. Most of these performance cruising cats are compromised by
the weight and windage of a full standing-room cabin between the hulls; on Fujin the windage and visual impact of the central house are reduced by lowering its sole a few steps down from the wet deck into a central V-bottomed pod. Being a rudder hydrofoil guy from way back, I felt obliged to fit
Fujinwith T-foil rudders. They have sailed the boat with and without them and it sails better with them even in light air (at least with a chop). The T-foils seem to help moderate pitching through a seaway in all wind strengths.
INGRID ABERY
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