LETTER OF THE MONTH

COUNTING CATS

Dear Phil,

I’m responding to the article by Kim Klaka about catamaran performance (June issue).

To be frank, I’m a bit confused in terms of exactly what it was telling us and also that I thought there were some key elements that are fundamental to good cat design missing.

For example, why is Kim talking about low aspect ratio theory when good daggerboard cats use high ratio boards. I know my builder spent a day getting the profiles for my daggerboards accurate to the half millimetre.

Also, there is no mention of prismatic coefficient when determining performance of a cat, as well as no reference to hull length/beam ratio. I thought these were critical to cat performance, especially when compared to sail area.

Also, why is Kim talking about hull speed formula. We’ve known for years that cats break that rule with abandon!

Finally, why is Kim talking about downwind speeds in cats? We know that cats generally do terribly downwind and, for the more performance oriented, are much better tacking downwind making the most of apparent wind.

So, in general I’m confused; the measures he was using seemed to make little sense to me, not sure what units were being used and also, what does it really tell us about the performance of different cats?

I’m very keen for this sort of comparison to be done, especially as I suspect there is a trend towards more performance sailing catamarans that sail efficiently to windward as well as they sail off the wind, usually with daggerboards. I see that Seawind now have two daggerboard cats that sail well.

Australia has some of the best catamaran designers in the