On Aug 24, 5:17*pm, "Roger Long" wrote:
...
*The speed differences, for equal horsepower and displacement,
between power cats and monos are significant but much less dramatic. *At low
speeds, a cat may even require more.
...

I think you're being generous. At low speeds a cat will very likely
require more power to attain the same speed as a mono of the same
displacement. As Ted Hood was fond of pointing out, at very low
speeds fat and heavy may have less resistance than slim and light. Of
course, once a boat gets above a very modest speed to length ratio (Fn
if you must) a long skinny hull offers less drag than than a short fat
one. At some point a really skinny hull will have a tendency to roll
over and one solution to that is to split it in two. Another might be
to add outriggers. If we're talking fuel consumption at speeds that
we're willing to put up with the graph in this paper of fuel/speed for
three hull types is interesting:
http://www.hiswasymposium.com/pdf/20...el%20Irens.pdf .

-- Tom.