Hi Wouter…I think there is a flaw in your analogy…Bill has already stated

“PS. I put a SC20 together once that was 20ft wide and it sailed fine. To windward it was a rocket. Reaching don't trapeze. Downwind same as a normal SC20, watch the bows.”

Therefore, based on his testing, (even when taking it to the extreme of beam=Loa) I would come to the conclusion, that when factoring in all points of sail , the wider boat may not have a increase in usable speed down wind…but it will not be at an disadvantage either. While on the upwind and reaching legs it would have a clear advantage.

If you can advance performance on many points of sail, and keep performance of your slowest point of sail equal…I believe that is increasing the performance of the boat overall.

Maybe this would be a better analogy:

When Son goes to Dad for date Money…Dad gives him $20.00

Then Son goes to Mom for date Money…Mom gives him $20.00

Son tells Dad he has a date with the most beautiful girl in school and asks for more money….Dad says “that’s my boy”…gives him an extra $20.00 (beam increased)

Son tells Mom he has a date with the most beautiful girl in school asks for more money…Mom says I gave you enough already...no more money……$0.00 (length stays the same)

So originally the Son had $40.00 (original performance with original beam) but after approaching his parents again he picks up an extra $20.00 from Dad (increase in beam) he now has $60.00 to spend instead of $40.00.

$60.00 is greater than $40.00 no mater how you spend it…

Bob