Bill,

You may want to look at your numbers again.

I see you are use the third order power in your following statement

"An RC30 hull weighs 175 pounds rigged and painted; scale that down to 20ft and you get 52 pounds; scale it on down to 18ft and you get 38 pounds"

When you do this than your 18 ft boat will only have 20 % of the displacement of your RC30. Now when we take 75 kg's for the 18 footer (a-cat) then your RC-30 has a mimimum displacement of 375 kg's = 827 lbs.

After subtracting 2 fully fitted hulls of 175 lbs that leaves 477 lbs for just the beams, mast sails and trampoline. A bit much don't you think ?

You can't apply your 3 order shrinking formula here as the primatic ratio of your RC 30 hull is not the same as that of the imaginairy 18 footer. You example sounds good by has no meaning in the real world as cat design formula's aren't so easy.

Wouter