Fuente info BYM news
Nigel Irens is one of the world's most renowned multihull designers, having been responsible for the design of several record breaking trimarans such as, Ellen MacArthur's B&Q-Castorama, Thomas Colville's Sodeb'O and Francis Joyon's solo Round the World record holder IDEC. More recently, Nigel was a consultant to the Alinghi design team.
He has been talking to BYM News editor, Marian Martin, about some features of the Deed of Gift protagonists, starting with the catamaran v trimaran differences.
Nigel Irens:
Essentially both boats take the loads on a central structure. On the Oracle boat that structure is a hull that floats in the water when the vessel is at rest; Alinghi has chosen not to put the envelope of a hull around that structure, so clearly it mustn’t be allowed to touch the water, because that wouldn’t do a lot for the speed, because of the drag from the tips of the struts that come down. So that’s why the longitudinal vessel structure has to be held quite high in the air and the mast step, which is on it, is quite a bit higher than on the Oracle boat.
So how does this change things?
There’s a fundamental difference, at this point between trimaran and catamaran configuration. Because Alinghi’s central structure is above the surface of the water, when the boat starts sailing it doesn’t have to heel very much in order for the windward hull to come out of the water, only a few degrees. Obviously, both boats are going to be sailed on one hull, most of the time, and as the Oracle centre hull is floating you have to heel that boat a lot further to get that hull out of the water. That is a point you can consider to be in favour of the choice made by Alinghi, because when the Oracle boat is on one hull, the windward hull is really quite high in the air and the higher it gets the faster moving air passes over it, so there really is quite a bit of aerodynamic drag there, which won’t be the case with Alinghi. So that’s one plus for Alinghi; on the other hand Oracle, has built a hull that has quite a lot of rocker on it, which is consistent with the needs of the structure because you want the beam to be fat in the middle and thin at the ends, and that is actually quite a good shape for tacking. As the boat comes through the tack, or gybe and the power comes off the main hull lands back in the water and, because it’s a rockered shape like that the main hull is quite good at turning. So, I anticipate that the Oracle boat would be quicker through a tack. Obviously, that’s a strategic position; the legs of the race are long and, on paper there’s not a lot of tacking to be done. On the other hand, if the two boats are very similar in speed, which I think is quite possible, then they could get into a tacking duel. If one boat thought they were faster at tacking than the other they would probably look for a tacking duel in order to exploit that advantage. On the other hand, there is a motor to power the Alinghi deck, so that may make up for a boat that is perhaps not as easy to tack as Oracle.
One aspect I find very interesting is that we are absolutely not privy to what the Oracle boat weighs and, if we find the boats are quite similar in weight, then I believe we will find they are quite similar in speed and that, contrary to first speculation some time ago, there might be much more of a race here than we thought. I was imagining that one boat would be faster than the other and that would be the end of it and rather boring from a racing point of view. Now, unless the Oracle boat has come out way overweight, which we don’t know, then it could be a lot closer than was first anticipated.
Is that based on seeing the new version of the BOR boat?
Nigel Irens: Well, we don’t actually know anything about the performance of the old version or the new one. There’s been a lot of speculation, but the fact is that if you analysed the probable performance of both boats you would be likely to conclude that they would be similar. My personal feeling is that the difference between a trimaran and a catamaran is unlikely to be a determinant factor.
Hacer click acá para seguir leyendo este interesante reportaje
