Nigel Irens speaks at NEMA Annual Dinner

On Saturday, February 6, NEMA held its Annual Dinner at Anthony’s Pier 4 in Boston. Nigel Irens was guest speaker. Renowned for his award-winning multihull designs, Iren’s trimarans and catamarans have won numerous world class multihull races.

Here is a summary of the event, contributed by NEMA member, Ted Warren. Nigel covered two main topics, the Open 60 class and "The Race".

Open60 class

The class has become standardized on the wide trimaran. Nigel made two points on this, one that the trimaran develops more power for a given length and that the trimaran is more forgiving when sailing on one hull as it's stability curve allows more righting moment at higher angles of heel.

He is using additional daggerboards in the amas, well forward. The problem with multiple headsails is the the center of effort is in multiple locations and he is using the leeward foil and the main hull foil in variable balance. He has also seen problems with rudder stall and balancing the rig with the two daggerboards eliminates this (unloads the rudder). The rudder on the main hull has gotten smaller, also, and is now the same size as the rudders on the amas.

Nigel made the point that stuffing the bows in a modern Open60 is not a catastrophic problem as the boat stops, and the apparant wind clocks aft and the sails stall. This was demonstrated on video tape. He also showed the stability of these tris when sailing at extreme angles of heel.

He talked a bit about safety issues and capsize. The modern wide monohull race boat is now quite stable upside down and this has become a problem for their fleets, with the more aggressive boats threatening not to race rather than adding ballast. Still, we haven't solved this problem with multihulls and he considers this more of a problem for races in desolate ocean areas. He talked some of the dynamics of capsize in the Open60s, as the windspeed increases, and the true wind heading rotates aft, the boat accellerates, increasing the apparant wind and before you know it you are sailing in 30+ kts of apparent wind and on your way over. He has designed his latest Open60 with enough bouyance and shape in the beams to keep the mainhull out of the water when inverted.

Nigel talked about some of the trade-offs in full ama sterns. The tendency has been to keep the bows full to generate diagonal stability. This works great off the wind, but to windward most of the force is athwartships and the sterns will squat. Fuller sterns have been used lately to prevent this, but too much and you pitchpole off of the wind.

He also comment on individual team boat development. The problem mentioned is that some teams are not very disciplined and try five changes at once, or the development team is different than the racing team.

Nigel gave some history as to the Open60 class. It happened as a fortuitous combination of tax laws in France and a large interest in ocean racing. He mentioned that one company had the choice of paying taxes to the government or financing the building of an Open60. It seems that less sponsorship money has been available over time.

The Race

Nigel talked about the interesting design issues, that the parameters are different than Open60's because there is no length restriction, and that the boats are so large that they develop large righting moments just based on weight. He made the point that we don't know yet what the best configuration is. He felt that modern ropes had eliminated some of the sail handling issues with these big rigs.

He was asked how many boats will enter. He stated that if you listen to the organizers then 16 boats will be there, but the other possibility is that only two boats will make it, Playstation and Peter Goss' boat, and that there hasn't been much progress on Peter's boat. He mentioned that sponsorship is the big problem and offered that it might take some cross market financing and crews based across two countries. The problem is that local companies, say in France, can't justify the local market exposure that they would get for the cost of a boat for "The Race".

A glowing report on the presentation by Spencer Merz is in the February Newsletter