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The making of Geronimo, a three-hulled giant

VANNES, France -- The construction of the 20-tonne Geronimo follows debate among designers over whether a two-hulled catamaran or a three-hulled trimaran would be fastest around the world.

The result is the largest trimaran ever built -- 34 metres (l10feet) long and 22 metres (72 feet) wide.

Its goal is to enable Frenchman Olivier de Kersauson to break long distance ocean racing records in a four-year mission starting early 2002.

Geronimo has a rotating wing mast 43 metres (141feet) high and a carbon fibre hull with a Nomex core. It has an upwind sail area of 500 square metres and 900 square metres for the downwind sail.

French yard Multiplast, based in Vannes, took one year and 100,000 man-hours to build it.

Its construction followed considerable discussion in the lead up to The Race, the non-stop sprint around the world run by current Jules Verne Trophy holder Bruno Peyron. Two or three hulls?

Certainly the latest generation of Open 60 trimarans are the most refined offshore racing machines ever built with multiple foils, rudders and canting rotating wingmasts.

The arguments are that a trimaran is a better all-round performer in a variety of upwind and downwind and light and heavy wind conditions.

It is also considered safer -- less prone to capsize and with a central cockpit for the crew rather than the twin cockpits in each hull that can leave the crew exposed to the force of the water as they move around the wide trampolines when sailing at speed.

The mast is stepped on the main hull, rather than a cross beam between two hulls as in the catamaran configuration, so the compressive forces are easy to engineer into the structure.

There were several ambitious monster trimaran projects planned for The Race but they could not find funding and so all the entries for the race were catamarans, which are less expensive and easier to build for the same length.

There was never any doubt that Kersauson would chose three hull for his new record-breaking giant.

He has logged more miles in a trimaran than any other sailor since his early days with Eric Tabarly on Pen Duick IV in 1967 and has always considered the trimaran to be the fastest option for the Jules Verne.

He set a solo round-the-world record as well as the current Jules Verne Trophy in a trimaran designed by Marc van Peteghem and Vincent Lauriot Prevost.

Originally launched as Poulain in 1987, the 24 metre (75 feet) boat was modified and extended to become Charal, Lyonnaise des Eaux, and finally Sport Elec.

Despite a flamboyant career as a witty talk show TV and radio personality, Kersauson is considered conservative when it comes to sailing so it is not surprising that experts consider the design of his new trimaran simple.

Rather than go for the latest developments, Geronimo has just one foil and just one rudder on the main hull and a rotating, but non-canting mast.

Kersauson believes that the sheer size and power of Geronimo, with lightweight construction in carbon fibre, will give him the necessary speed to break his own record.

The proportions of Geronimo are also more conservative compared with the Open 60 feet trimarans that are practically square with the beam or width almost equal to the length.

Such a wide beam is difficult to engineer and more likely to lead to structural failure. Geronimo has a beam of only 21metres (68 feet) so the boat is less powerful and should be structurally sounder.

The Multiplast yard built three similar length catamarans, designed by Gilles Ollier, for The Race. Confirming the extra work involved in building three hulls, the trimaran is estimated to have taken 27,000 more hours to build than the catamarans.



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