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

YSTay:

You are a day late and a dollar short - look at Derek Kelsal's web site
for panel construction method - if he still lists it; he's into the
third iteration at this time.

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

In "New Plywood Boats" TF Jones gives details of building a Dobbler 16
that way. He sells plans for the Dobbler 16 on his website at
www.jonesboats.com. The boat is normally built of plywood.

"YSTay" ) writes:
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







--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned

I suggest some experimentation.

Make up test panels of the fiberglass layup you described and a panel of the
plywood of your choice. Compare them for weight, stiffness and cost. I suspect
that, for a given weight, the FRP will be much less stiff than the ply.

Let us know the results.

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

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.

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 ;


Sounds a bit like:

http://www.glen-l.com/supplies/cflex.html


Dale

Hello all,
Sure seems that there's never anything new under the sun! No worries that
this has been done before. I just thought I might put this out there and
create some discourse. Who knows where it may lead.
Anyway,
cheers,

Arnold

On Thu, 29 Jul 2004 21:54:32 +0800, "YSTay"
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

Speak for yourself. I would need _perfect_ dust control.

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





************************************************** ***
It's not the milk and honey we hate. It's having it
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