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                           RV4-List Digest Archive
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                     Total Messages Posted Tue 08/30/05: 1
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Today's Message Index:
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     1. 08:50 AM - Heating and Shaping Fiberglass  ()
 
 
 
________________________________  Message 1  _____________________________________


Time: 08:50:48 AM PST US
From: <flyingrv@cox.net>
Subject: RV4-List: Heating and Shaping Fiberglass

--> RV4-List message posted by: <flyingrv@cox.net>

Heating and Shaping Fiberglass

        OK Gang, heres the deal on heating and shaping fiberglass.  This is always
true with ester resins (more or less) and somewhat true with epoxy (most of
the time.)
        When resins harden they form a molecular, 3 dimensional fishnet looking
structure.  This fishnet is wrapped, wound, in, over and throughout the fiberglass
strands.
        The fiberglass strands are about the same as the window you are gazing
out of wondering why you are reading this.  Chemically there are differences,
but I dont have a clue just how that works.
        If you got way down in the strands you would find teeny tiny fibers that
look like a barb wire fence made by a guy that went insane putting the barbs
on. 
        When you heat this thing up, the molecular bonds weaken in the fishnet
and as you bend/reshape the part the fishnet tears apart and the fibers in the
glass break because they cannot slide past each other like they could when the
resin was a fluid.
        If you have been following along here, you can see that you just broke
the part.  You probably cant see it because its more or less on the molecular
level, but it is broken.
        Now the question is are you ever going to care.  If it is a no or low stress
area it probably isnt going to cause a problem.  If its a stressed or vibrated
area it will crack after you put that 1OK paint job on.
        Epoxy is a little different deal, sometimes and sort of.  It is more a
temperature cure where -ester resin is more related to time.  Most -ester laminates
will be cured in 24 to 72 hours.  The epoxy we use will be hard when it
has been to 150 to 175 degrees F.  What this says is, if you make a part and it
has been to, say 80 degrees you can heat it to 120 degrees and reform it some.
The resin will reharden but the glass strands my not like it much.
        Now experts and engineers dont argue with me!  Im old, crotchety, and dont
want to be confused by facts.  Nevertheless, do feel free to add your thinking
to the discussion.

Bob Snedaker
Fairings-Etc
bob@fairings-etc.com