Heat bending fiberglass

[JFLEISC]

I have been told that one can heat fiberglass to slightly rebend it to solve
some small warpage problems. If so can anyone tell me the approximate heat that
needs to be applied without doing damage? (I don't want to burn it)

Jim

[Charles K. Scott]

In article <19971215134...@ladder02.news.aol.com>
jfl...@aol.com (JFLEISC) writes:

When I attended a composite course at Alexander Aircraft, which was
taught by Stan Montgomery, he (Stan) mentioned a guy in Texas who was
capable of permanently correcting warped fiberglass parts, including
wings. He simply jigged them such that they were bent a little beyond
the correct direction and wrapped them in black plastic and left then
in the sun for a while. That Texas sun, or maybe it should be **
SUN**, makes for a very effective heating source.

Of course, the expertise lay in knowing how long to leave it out there
and how much to warp the wings or part in the jig to get it to the
proper twist or shape. Stan said the guy got paid to do this.

Corky Scott

[RobertR237]

In article <19971215134...@ladder02.news.aol.com>, jfl...@aol.com
(JFLEISC) writes:

>
I have been told that one can heat fiberglass to slightly rebend it to
>solve
some small warpage problems. If so can anyone tell me the approximate
>heat that
needs to be applied without doing damage? (I don't want to burn
>it)

Jim

Yes it is possible to obtain a certain amout of rebending to fiber glass by
heating it to slightly above the transition temperature. This temperature
varies depending on the epoxy used in constructing the part and will generally
be between 150 and 200 degrees. I used a heat gun and heated an area I needed
to bend slightly and just waited for it to soften and give under pressure. I
then clamped everything in place and allowed to cool. Also the temperature
necessary varies depending on weather the part has been post cured or not.

I sould suggest that you determine the exact composition of the part and then
refer to a chart showing the transition temps for the part. I can not recall
exactly where I ran across a table showing the transition temps but there is
one available. Check the Acraft Spruce and Speciality Catalog and I think you
will find the table there. The best bet may be to experiment on some scrap
material before attempting the actual part.

Bob Reed,
KIS Cruiser in progress...Oshkosh 2000 by Gosh!

[David Parrish]

In article <673f4q$s0c$4...@dartvax.dartmouth.edu>, Charles...@nospam.dartmouth.edu (Charles K. Scott) wrote:

>When I attended a composite course at Alexander Aircraft, which was
>taught by Stan Montgomery, he (Stan) mentioned a guy in Texas who was
>capable of permanently correcting warped fiberglass parts, including
>wings. He simply jigged them such that they were bent a little beyond
>the correct direction and wrapped them in black plastic and left then
>in the sun for a while. That Texas sun, or maybe it should be **
>SUN**, makes for a very effective heating source.

It will work as long as you heat the part to above the Tg temperature of the
epoxy. (The temperature were epoxy starts to soften.) For most epoxies we use,
that's around 150-200 degF. Remember. If the item has blue foam in it,
(Styrofoam) it starts to melt at about 220-230 degF. (Or there abouts.) You
need to keep a close watch on the temperatures. PVC foams will also melt, but
I believe at a higher temperature. I don't think urethanes really melt at all.

---
David Parrish

[ERacerVinn]

>a guy in Texas who was
>>capable of permanently correcting warped fiberglass parts, including
>>wings. He simply jigged them such that they were bent a little beyond
>>the correct direction and wrapped them in black plastic and left then
>>in the sun for a while.

Group,
From my experience, I think this will depend on the resin system used to build
the parts. I purchased some prefab scoops for my E-Racer from the Berkut
people (nice people). I tried to heat the parts to re-form them to match my
geometry, no dice. I finally used a heat gun, the parts got more flexible
with LOTS of heat, but no permanent deformation. Bummer.
Yours truly,
Bruce Vinnola