Message-ID: <001801beb6da$b3895440$3ca0490c@ckrouse_ra.spk.hp.com>
Reply-To: "Curtis Krouse" <ckrouse@worldnet.att.net>
From: "Curtis Krouse" <ckrouse@worldnet.att.net>
To: <lancair.list@olsusa.com>
Subject: Re: methylene chloride
Date: Mon, 14 Jun 1999 19:56:42 -0700
Mime-Version: 1.0

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Since the recent discussions concerning MC, and since I am using MC in the
form of paint & epoxy remover (paint stripper), and hearing some of the
comments concerning this substance, I thought that I would try an experiment
or two.  I started by using a piece of the prepreg skin that I trimmed out
from the cockpit closeout ribs and some scrap bid cloth.  I cleaned half the
surface with the MC paint stripper and the other half with the MC paint
stipper and didn't wipe it off.  So, I had what was supposed to be half
clean and wiped and half just cleaned.  I then layed a 3 bid layer over the
surface and let it cure for a day.  The next day I pulled as hard as I
could, and the 3 bid strip peeled right off.  This was very disturbing to
say the least!!!

I then took the same piece of prepreg and cleaned and wiped it with the MC
paint stripper and then lightly sanded the surface with #80 grit sandpaper
(like the manual suggests) and then vacumned the dust off.  I then layed up
a 3 bid layer over the same area.  I should say that I left a 1 inch square
spot uncleaned so that I could get a start on the pulling of the layer off
the next day.  Today I went out and pulled the good pull and the 1 inch spot
gave way, but the rest of the cloth stuck there as a good bond should and
the layup ripped away leaving all the layer under the cleaned and sanded
area bonded to the prepreg.  This was very good!!!!  Especially since this
is the process that I have used on all my layups so far.

The lesson that I learned is that the cleaning agent is important......but
even more important is the sanding of the surface after cleaning.  This
roughing up of the surface must leave the surface in a state that allows the
epoxy to get a good hold and bond to it.  I don't think that I'm going to
worry about the MC paint stripper so much as long as I'm sure that I wipe it
off well enough and ALWAYS make sure that I prepare the surface by sanding
and vacumning after that.  I don't think that I need to stop building until
I find a source for pure MC anyway.

Regards
Curtis Krouse N753K

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