Interesting. I'd be concerned about the sandwich properties though.

Bare with me as I think "outloud". I'm certaintly not the expert so I'll
try to keep my reasoning general.

In sanwich construction, the skins are supposed to work together to
offset tension and compression in the sandwich. By building the panels
flat and then bending them, you're placing the outer skin in tension
already. It seems like you'd lose some of the benefits.

Someone help me. Am I comparing apples and oranges?

--
Matt Langenfeld
JEM Watercraft
http://jemwatercraft.com

YSTay wrote:
Hello all,
I've been working alot with fibreglass lately and this idea popped into my
head:

Say you want to plank a hull with ply sheets, traditionally, you would cut
out the strakes and fit them onto stringers. Instead of using ply, I'm
thinking that I could use pre-made fibreglass sheets instead of ply. Here's
the kicker; Instead of just laying up large sheets of FRP, I suspect that
one could get better results from the following method ;

Spray gel coat onto large flat surface.
Lay up one (or however many) layers of glass. Lay the resin on really wet
such that its really juicy.
Then place a layer of core mat (spongy core material used to add stiffness)
onto juicy laminate.
Gently press into laminate such that the core mat takes some of the resin.
Let cure.
You should now have a large laminate with hard gel coat on one side and raw,
untouched core mat on the other. This will be very floppy, which is the
general idea.

Now cut the required shapes out of this laminate. This is easily done with
a sabre saw or even double action shears. Install onto stringers with gel
coat facing outwards. Then lay up lay up on the inside with FRP. You will
end up with a very stiff hull because of the sandwich construction.

I've done this on small flat sided boxes and had good success. Maybe some
one would like to take this on?

Pro's:
Good where quality ply is not available or too expensive.
Cheap!
None of that "woody" type issues.
Pre-faired hull surface.
Extreme hull stiffness

Con's:
Scantling issues.
Possibility of resin starved areas under the core mat.
Bonding of hull strakes to wooden stringers prior to interior glassing (Poly
resin and wood isn't that great, so I'm told although I have evidence that
it can be done).
And many others, I'm sure.
BTW, complaining that FRP is horrible itchy stuff is not valid! Good dust
control takes care of everything.
I look forward to all comments.

Cheers,
Arnold

On Fri, 30 Jul 2004 00:27:05 GMT, Matt Langenfeld
wrote:
In sanwich construction, the skins are supposed to work together to
offset tension and compression in the sandwich. By building the panels
flat and then bending them, you're placing the outer skin in tension
already. It seems like you'd lose some of the benefits.

Someone help me. Am I comparing apples and oranges?
==========================================

I think that the proposal was to build a "single skin" laminate, bend
it into place, and then add the inner skin as a last step. Could be
wrong, but that's how I interpreted it.