How to make the opposition fold

By ROBIN BAILEY

Auckland Gray Treadwell made a splash in the British boating press last month when his design was awarded first prize in the Royal Institution of Naval Architects Concept Boat 2002 competition.

He also picked up a cheque for £5000 ($12,000) at the London Boat Show at Earls Court. His winning design is Jasmin, a 9.3 m (31ft) multi-hull that he calls a bimaran. It folds its 5.8 m beam to fit on to a trailer.

One of the criteria for the 2002 Concept competition was for a transportable craft, and the second prize went to a rowing catamaran. The yacht has an unstayed mast on the hull instead of the centreline like conventional catamarans.

Here's where the design raises eyebrows, although the inventor is adamant it's really all quite simple and structurally sound. The hulls pitch independently of each other, within limits, which allows them to walk over the waves for smoother, drier sailing. Treadwell claims the result is a lighter, stronger boat.

The RINA judging panel was impressed with the engineering aspects of Jasmin and the Epsom inventor believes the model he had on display in the Concept 2002 court helped to swing the decision his way.

Treadwell, whose day job for the past 20 years has been in the computer industry, began his love affair with multi-hulls in the '80s, hooning around the Gulf with a mate in an old Tornado to let off steam. Then he fell under the spell of catamaran guru Malcolm Tenant and moved into a 28 ft Great Barrier Express followed by a 43ft Bladerunner.

"After these two yachts I decided I needed something different ... easier to sail," says Treadwell. "I felt there was potential in the balestron balanced rig that has been used on model yachts for more than 100 years. Having the rig in a hull rather than the middle of the yacht reduces the loads on the beam and gets the boom away from passengers.

"However, it was a bit of a mission to find someone who wanted to design an asymmetrical yacht. Eventually I persuaded Rob Denney (now in Perth) to take a break from proas and we traded ideas till we had a design for a 40-footer. Craig Stirling built her on the North Shore, opposite to where Cooksons were building Playstation at the time. The difference in the two yachts was staggering, about the same as the comparison between Jasmin 31 and the superyacht version, Jasmin 120, which I believe is where the eventual future of the design lies."

The yacht he calls W was launched in 1998 and since then has been a floating test bed as Treadwell explored her potential, much to the amusement of those sailors more at home with the conventional.

Treadwell again: "The engineering looks radical, but high modulus carbon structures and kevlar ropes mean we have to adjust our vision to what looks right. Sometimes things look undersized when actually they are way over strength. And vice versa. There is no substitute for detailed engineering analysis. "

Reading about the Concept 2002 contest in a British boating magazine got him thinking of developing a way to fold his existing bimaran. "After months playing off and on with Meccano models until I was happy I had optimised the design, I filed a patent for the structure and folding mechanism which has passed the international examination phase."

Then came the competition ... and the win. The inventor says the judges questioned him on a lot of points. "Putting the mast in a hull means you don't need a stiff structure between the hulls to get good sail shapes. You need only one beam, which can pivot, and this removes torsion loads and minimises fatigue. Also the stays between the hulls can have some stretch, again reducing peak loads, and you get a simpler folding mechanism.

"Conventional wisdom is the hulls must be exactly parallel. So we ran some actual comparison measurements. These proved you go faster as the hulls walk over the waves rather than pushing through."

Treadwell's team has now drawn the Jasmin 120. At 36m it will fit into a Viaduct monohull berth after folding its 21m (70ft) beam to 9m (30ft).

He believes it will be able to cruise and anchor in places other superyachts can never go because of the shallow draught. It will also have the speed advantages of a multi-hull, plus the luxury accommodation of a monohull.

Perhaps we will see Jasmin 120 in the next Millennium Cup in 2006.

Bimaran