On Mon, 29 Jun 2009 11:19:01 -0700 (PDT), Frogwatch
wrote:

From what I can determine, once a boat is on plane, it is primarily
the weight that determines fuel efficiency so a lighter weight boat
should give much better fuel economy.
BUT, as I have found with my Tolman which is very light for her size,
a lightweight boat is easily pushed around by a wave due to less
momentum. So, although you might consider a boat made from new
lightweight composites, would it be as seaworthy as a heavier one?
This is actually a practical consideration for me if I build a Tolman
Jumbo with slightly gretaer deadrise than the design. More deadrise
will make her pound less but will the lightweight make her less
seaworthy than similar heavier boats?

I'm not an engineer, but I'll guess a bit.
Yeah, weigh affects stability, and there's no way around it.
But, hull design can help as far as wave action.
The cat-type hulls on that Intruder seem to cut water and hold
direction to some extent. Didn't seem to pound badly, but I think you
have to be there doing a kidney-check to really tell.
Seems to me the major problem with a lighter hull will be the
"cork-like" aspect of bobbing up and down.
Anyway, I was thinking inshore boats more than ocean-going.
Fishing and other recreation boats.
The Intruder videos said they were in 8' seas.
Don't know if that was true.
But again, I'm not looking for a heavy weather boat.
I'll bet 90% of recreational boating miles is in good weather,
and 99.9% is in decent weather.
Can't make a perfect boat.
I was thinking along the lines of styrofoam-like weight.
Hardened on the outside with something light, and maybe
internally stiffened with something light.
Could even be made cheaply enough to throw away the hull
after not too many years.
Prettifying it and gussying it up will happen pretty quick for some,
but the Carolina Skiff has found a market for bare-bones, and an even
lighter boat will do it one step further.

--Vic

--Vic