Like Marc said, there is a limit to which correlations can be considered accurate. There is a
transitional stage between planing and displacement where you have parts of the hull doing one
thing while other parts are doing something else. There is almost no way that you could
adequately predict the behavior of a hull in this range. That's why tank testing and prototypes are
developed.

I can tell you from personal experience that a spi is not going to produce the fastest speeds on a
cat. The sail is too full to be efficient enough. A beam reach however is a different story. With
the much flatter jib and main combo, eff is much higher. Not to mention you have vector addition
of boat speed plus wind speed very much in your favor.

I'm sure if you were onboard one of the W1000 boats on the last two days, you experienced the
Inter 20 "wheelie". I watched the GPS as we accelerated to 31.x mph (27kts)SEVERAL times.
Usually the problem with sustaining that speed became the wall of water that you had to drive
your boat through. Amazing how fast you can come to a stop...


Will R