[PCW] A question of weight

[Robert Deering]

Gary,

You're certainly correct regarding the physics, but I think you're
ignoring a couple considerations.

In your example you're increasing displacement by 65%.  That's
substantial.  Either your draft will be much deeper (with a
corresponding decrease in wing deck clearance, etc.) or you'll have to
significantly increase the beam of the hulls to compensate - think
Archimedes instead of Newton.  

Either way you solve it produces more problems.  Deeper draft will yield
a lot more skin friction (not a little) for a boat traveling 16 kts.
Wider hulls mean a much bigger bow wave that you have to overcome at 16
kts.

If you want a 7 kts boat, then adding displacement won't matter nearly
as much.  But when you get into the higher speeds the nonlinear
mathematics of the resistance factors start to work against you.  But
you can overcome them pretty easily with larger motors and more fuel.

Bob Deering
Juneau Alaska