The longest racing trimaran in the world

We speak to designer Vincent Lauriot Prevost about Pascal Bidegorry's new 40 METRE Banque Populaire trimaran.

No sooner has Franck Cammas' new 105ft Groupama III touched the water than yet another French 60ft trimaran sponsor has announced the creation of yet another new G-Class maxi-multihull. This time it is Banque Populaire skipper Pascal Bidegorry who, this summer staged a designer's dust up between Gilles Ollier, Nigel Irens and Van Peteghem Lauriot Prévost for a "fully crewed multihull, with a good all-round performance, suited to a mixed program, reliable, evolutionary and safe for the crew." In the end Bidegorry and his team chose a 40 metre long (that is 131.2ft in old money) maxi-trimaran proposal from the van Peteghem/Prevost design house. When launched the new Banque Populaire V trimaran will be the longest racing trimaran in the world.

While the new Banque Populaire Vis some 26ft longer than the already sizeable Groupama III, designer Vincent Lauriot Prevost is at pains to point out it is not proportionally 'bigger' boat, it is more accurately a 'longer' boat - this was the basic concept specified by Pascal Bidegorry. Yes, it's length is greater and as a result it will be around six tonnes heavier - 23 tonnes compared to Groupama III's 18 - but the power to weight ratio remains roughly the same with a similar beam and an enlarged sail plan (her mast height is 45m is compared to Groupama III's 40m) to handle the added displacement. In essence Groupama III is an enlarged ORMA 60 with the rig further aft, while the Banque Populaire is more a typical G-class boat. When these two massive race boats go head to head in 2008 it will produce an interesting race: for a given sail acreage is a longer heavier multihull faster than a smaller but lighter one?





The answer according to designer Vincent Lauriot Prevost is that they are likely to turn out to be horses for courses. "It will depend upon the conditions!" he says. " Groupama III is a light boat with a huge sail area and will be very efficient in light to medium conditions and after [ie in stronger winds and bigger seas] Groupama III will be more difficult to handle to make a good average high speed. When you are light you don’t have the same kind of inertia in the waves to go fast and when you decrease your speed you get slower more drastically than when you are bit longer and heavier. When you are a bit heavier your speed is helped by the inertia. It won’t be as nervous." By nervous he means a boat which shows greater acceleration and deceleration.

Despite the boat being designed for fully crewed record breaking, the philosophy is very similar to that which Nigel Irens and Benoit Cabaret employed with Ellen MacArthur's B&Q Castorama trimaran and subsequently to their latest 100 or so foot solo record trimarans IDEC and Sodebo for Francis Joyon and Thomas Coville respectively. The preliminary drawing (and the ones published here are very preliminary we are told), show the mast foot is around 2m aft of mid-ships down the length of the hull, resulting in huge reserve buoyancy in the elongated bows of her three hulls. However unlike Irens' boats Lauriot Prevost says they have prefered to gain reserve buoyancy from the length of the hulls rather than by length and extra freeboard. The sail plan comparison above indicates the freeboard of Groupama III and Banque Populaire V to be similar despite the length difference. However like the Irens boats (and unlike Groupama III), the centre hull of Banque Populaire V is longer than the floats. This is a function of length says Laurent Prevost - having the floats much longer would create structural problems for the boat.

At present Lauriot Prevost says they have four more months of R&D and design work to go before the build of Bidegorry's new boat starts at the end of January 2007. On the design development for the first time they have brought in two specialist engineers in Herve Devaux and SP Technologies/Gurit who will work together on the project. They also expect to carry out some wind tunnel testing to optimise the rig configuration. "We have never done that before," says Lauriot Prevost. "We mainly have worked on tank tests to work out the drag estimate on the hulls. So this time we would like to put the accent on the efficiency of the sail plan. We will have some CFD done to confirm the hull drag, just to have some good values to put into the VPP" While the design is likely to change and develop over the next months, the designer believes that the fundamental dimensions of the boat will remain more or less the same.



Banque Populaire V up against Paris' Arc de Triomphe

It will also be interesting to see how the boat compares with other existing G-class maxi-multihulls, in particular Bruno Peyron's all-conquering Ollier-designed Orange II maxi-catamaran at a mere 120ft LOA. The sail plan on the two boats looks to be reasonably similar in size - both have 25m rigs, yet Orange II weighs in the region of 32 tonnes compared to the new Banque Populaire's 23.

One reason why the rig on the new trimaran is no bigger than Orange II's is simply because while there are no written rule constraints for these G Class maxi-multihulls - anything goes design-wise - the only limiting factor is how big a sail plan a crew can handle with reasonable efficency, given that under WSSRC record breaking rules for such boats, powered winches are prohibited.

Lauriot Prevost adds his view: "We have two limiting factors with the boat, which are the sail area to displacement ratio, where we want to have a limited sail area to stay within the sail maker’s knowledge and range of loads which are existing now and the other limiting factor are the foils because we want to have a boat with foils for sure and we think that the foil surface should be proportional to the weight of the boat for the same range of use. So up to a certain weight we won’t be able to have efficient foils and we would have to reduce sail area."

Another difference between Groupama III and Banque Populaire is that while both boats have ORMA 60-style curved retractible lifting foils in the floats the former has (at present at least) no canting rig. While he suspects Groupama III will probably fit one in due course, Lauriot Prevost says that canting the rig will be introduced from the outset with the new boat. He also added that they haven't looked into the possibility of fitting two sets of lifting foils in each float, despite the length of the new boat, rather than just the usual one, in order to keep it simple to operate..

Once the design is finalised at the end of January build work will start. On this occasion Gilles Ollier's chantier Multiplast will not be building the boat - to date they have built almost all the G-Class maxi-multihulls. Instead the boat is being put together by CDK Composites in Port la Foret, although most of the bigger structures, for example the main hull and floats, will be built by sub-contractors such as JMW Indusries in Cherbourg. CDK will concentrate on the more awkward parts like the two crossbeams and mainsheet track beam, the daggerboard case and the case for the foils.

The duration of the build is expected to take 18 months and then once sea trials and on the water development have taken place, Bidegorry and his crew will set off attempting to break all the significant records from the Jules Verne Trophy for non-stop around the world, to the west to east transatlantic record from New York to the Lizard, the Route of Discovery, etc .

In the meantime Pascal Bidgorry and his team will continue to campaign their Banque Populaire IV ORMA 60. Next up is the Route du Rhum at the end of next month.