60ft trimaran technology - pt1

Sergio Tacchini's Damian Foxall and Antoine Mermod on curved lifting foils, lifting rudders and daggerboards with trim tabs
Following on from yesterday's interview with Damian Foxall about how to sail a 60ft trimaran, today Foxall and French naval engineer Antoine Mermod, who looks after the technical side of Sergio Tacchini, explains some of the gear development and choices on their 60ft trimaran and within the fleet. For an extreme development class all the 60ft trimarans have a very similar look, the result of the class maturing and the teams finding out what is fast. The boats are all 60ft (18.28m) long and all have rotating wingmasts standing at the maximum allowed height of 28.5m off the deck. Beam One of the principle dimensions left open is beam. The trimarans are mostly around as wide as they are long - the narrowest in the Transat Jacques Vabre was Banque Covefi (originally Alain Gautier's Foncia), with a beam of 17.4m while the widest is Thomas Coville's Sodebo at 18.6m. The trade off is between added power available through wide beam versus the lighter weight and marginally better manoeuvability of the narrower beam boats. For the record TJV winner Groupama, a similar generation boat to Banque Covefi, has a beam of 17.7m. Beneath the water - foils One of the most signifcant areas of recent development in the 60ft trimaran class has been that of the retractible foils mounted in the float. Originally conceived by Marc Lombard and fitted on the 2000 generation Banque Populaire, these curved foils, mounted in each float just aft of the forward beam, are considerably more versatile than the older variety that are straight and pierce the float at an angle. For example their curved shape allow them to be used to provide lateral resistance upwind. "The curved foil gives more progressive," says Mermod. "At the beginning it is more lateral lift and later it is more vertical