I guess I wasn't very clear. Weight has the advantage in non-planing
(displacement) craft of having a lot of inertia. In the case of rowing a
light craft, the oars will accelerate the craft quickly, but because the
craft has low inertia, it will decelerate just as quickly. This is
especially apparent in a wind. The heavier craft, on the other hand
accelerates slower, but once up to speed, will hold the forward momentum,
while the oars retract for the next stroke. This extra inertia will also
keep the craft on the intended course much better than a light one. We can
use the same example on sail boats when tacking through the wind. The boat
with the most inertia will maintain steerage way for a much longer time,
giving the crew much more time to ready the rig for the next tack. Now, boat
motion, for the same reason, the felt motion will be much less with the
heavier craft. Speed, most people assume that a lighter craft is faster than
a heavier one. This can be the case, because of hull resistance. The more
wetted surface the more drag. The exception that I was illustrating was for
those craft that do not approach the speed where that factor has significant
influence.

Material, GRP is not stiff, in fact it is quite flexible. In order to create
stiffness, it has to be thicker and that adds weight. Strength and stiffness
is often acheived by bonding in other material, like wood. As craft size
becomes larger, this lack of rigidity will add so much more weight to
compensate for the lack of stiffness and strength that the use of other
material like steel will often create craft that is much lighter than GRP.
Steve

"Old Nick" wrote in message
...
On Sat, 17 Apr 2004 17:58:37 +0200, "Steve Lusardi"
vaguely proposed a theory
......and in reply I say!:
remove ns from my header address to reply via email

If I am rowing a boat in a breeze, _and the windage is the same_, I
would prefer to be rowing the lighter boat. I has less warter
friction.

BTW. Your post compares an _architect's_ statements about _living_ in
corks and icecubes, to illustrate the problems between an inflatable
vs an aluminium boat, to talk about the relative "weights" (densities)
of GRP vs wood, and your apparent aim is to say that GRP is heavier
than wood, if one really thinks about it.

Care to elucidate?

Jess,
If you are inferring that GRP is lighter than wood, it is the unusual
case
if it is. GRP and its derivitives have many advantages, but light weight
is
not one. The best example I could give is trying to row an aluminum skiff
or
an inflatable in a breese. An architech once said to me "Would you rather
live in a cork or in an ice cube?" Lightweight craft have their place in
racing and carrying. If you don't race and you don't intend to carry it
on
your back, weight is on the bottom of your list of important items.
Steve


************************************************** **
I went on a guided tour not long ago.The guide got
us lost. He was a non-compass mentor.........sorry
........no I'm not.