60ft tris start their engines

The Daily Sail spoke to designers Nigel Irens and Vincent Lauriot Prevost about mast breakages and structural failures

Action in the 60ft trimaran fleet is hotting up with the ORMA 9 Telecom Grand Prix looming at Fecamps in northern France at the end of this week (12-15 September). This is the final event of the season prior to the start of the all-important Route du Rhum singlehanded transatlantic race in November.

Sailing at Fecamps usually provides the 60ft trimarans with some lively conditions and for competitors it is a favourite on the annual circuit because of the wind and the interesting effect the high cliffs along the coastline has on it.

Race pundits (that would be us) will see the Fecamps Grand Prix as a good indication of who is up to speed and who is not really ready for November's transat, particularly after a season dogged by a large number of major structural failures.

Snapping like twigs

Following the dismastings of Belgacom and more recently Alain Gautier's new Foncia II, Espace Composites, the builder of these two carbon fibre wingmasts, have identified a construction flaw in their latest generation spars that can cause them to fail when sailing under one or two reefs and the staysail. Espace have specified a fix that must be made to the masts to prevent this recurring hopefully. This requires uni-directional carbon fibres to be bonded into the inside of the tube to give the mast more 'hoop strength' and cut down the ability of the spar to deform under compressive load. One can only begin to imagine what an awkward job this must be to carry out inside the narrow confines halfway up the mast.

However designer Vincent Lauriot Prevost is not convinced that there is necessarily a structural problem with the trimaran's carbon fibre wingmasts. "It is difficult to answer about the mast problems because nothing is really clear," he told madfor sailing. "There have been four mast problems: Biscuits la Trinitaine, Foncia, Geant and Belgacom. It's difficult to find the same reason for the four masts coming down, although this is only according to what I know, because I am not the mast designer."

For example the mast on Alain Gautier's new Foncia broke midway between the inner stay and the foot of the mast. "We honestly don't know if it is because of the build process or the concept or the handling of the mast," says Lauriot Prevost. "There are some presumptions, but by the fact that they are only presumptions, I don't think it is in the interests of anyone to come up with too rapid conclusions about this."

The mast on Michel Desjoyeaux's Geant broke in much the same place, but even this says little. "The masts are not built using the same process, the rigging is not the same and the distribution of the sail effort is not the same, because it wasn't the same sail configuration," argues Lauriot Prevost.

One of the few common factors between the dismastings is the use of high modulus carbon. Foncia and Belgacom's masts were built in M55J carbon fibre, while Geant's was built in Pitch. "That is the common thing, although it may not be the reason they broke," admits Lauriot Prevost, adding that equally there are some boats like Banque Populaire who have been sailing with a mast made from Pitch for two years without problems. " Bayer, Tacchini and Banque Populaire are using the same mast with the same building process. The difference is that we don't have the same lower shroud attachments. The lower attachments are not on the float, they are on the beam on Geant," he continues.

Because there is now just two months to go before the start of the Route du Rhum, the teams in the process of getting new rigs are taking a step back and turning to more conservative options - masts made from lower modulus carbon fibre and built in one piece instead of two - the Espace masts are built in two halves with additional upper and lower sections (a complete 60ft trimaran mast won't fit into their autoclave).

Another aspect is in how the masts are used now they can not only be canted side to side but also fore and aft. "That is another point we have to work out," says Lauriot Prevost of the problems this may be throwing up... "Whether it is critical to have always equal tension of the inner shroud when the mast is canted laterally, because when you cant the mast you have different tension between the capshroud and the inner shroud..."


Continued on page 2...