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<DIV><FONT face=Arial size=2>Gray,</FONT></DIV>
<DIV><FONT face=Arial size=2>I am pleased to see your scientific answer.
It is very helpful and I would love to have the epoxy you could make up. I
thought about putting my existing mix full strenght but I know I could never get
all the excess out. Fortunately, having a weakened epoxy has no real
detrimental effects on glassing a wing. With the info you have given it
will lead me to delay primer for a while. I would think the solvent
evaporation rate would be inversely exponential, meaning most of the
evaporation/shrinkage would occur within a couple of months. Since it is a
model and not a bomb, there is room for lax tolerances. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks</FONT></DIV>
<DIV><FONT face=Arial size=2>Mike</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=gfowler@raytheon.com href="mailto:gfowler@raytheon.com">Gray E
Fowler</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, November 26, 2007 9:23
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] epoxy
question-I am back</DIV>
<DIV><BR></DIV><BR><FONT face=Arial size=2>1. "Thinning the epoxy saves
no weight by evaporation. There is virtually no evaporation and no
weight loss-a big time erroneous assumption on my part. So if you mix 2
ounces of epoxy and add 2 ounces of thinner and put it all on the airplane,
you have added 4 ounces to the airplane. "</FONT> <BR><BR><FONT
face=Arial size=2>After seeing the real question I expected a weight increase
of at least 9% (how much water in the mix). If you put 1oz (by weight) of
solvent in 1 oz of epoxy, and apply it as a coating , thin, you will
eventually end up with 1 oz of epoxy. Mike, your solvent got trapped, and now
it will have less adhesion, less tensile, Compression and flexure strength,
and will now shrink slowly as the alcohol exits the cured epoxy, over a year
or so (see Wayne's answer).</FONT> <BR><BR><FONT face=Arial size=2>None of the
solvent's listed will react with any epoxy blend. Exotherm is negligible when
applied as a thin coating, but significant in mass. The ability to have the
solvent evaporate out of the epoxy coating is directly related to the mixed
viscosity of the neat epoxy blend and the cure rate of the epoxy. Those of you
who ran experiments with 5 minute epoxy reported bad results because of high
viscosity and fast cure rate.The high viscosity (even Mike's blend is
apparently too high) will cause a skin effect where the solvent evaporates
from the surface first, creating a high viscosity skin, then the epoxy starts
to cure increasing viscosity even more, thus trapping the solvent. Using
fiberglass makes this even worse. MIKE- in one year from now your wings will
weigh less.</FONT> <BR><BR><FONT face=Arial size=2>So it sounds like the the
Pattern Dudes of the world need a solution. What AeroSlave can do is
provide a super low viscosity epoxy for sale. This will be 100% solids (which
means NO solvents). Chances are, as a mixed epoxy, the viscosity will be lower
than even blends with some solvent in them. This can be used to apply
fiberglass to wings or as a general laminating resin.</FONT> <BR><BR><FONT
face=Arial size=2>How much interest would there be for such a a product? It
would probably cost about $50/ quart, $25/ pint. It would absolutely require
an accurate scale (+/- 1 gram) to WEIGH the epoxy and hardener into the
appropriate mix ratio. AND I offer no warranty, simply because you guys are
the biggest bunch of experimenters in the world, and I cannot control, nor
anticipate how this could get screwed up.</FONT> <BR><BR><FONT face=Arial
size=2>1. Operator cannot operate a scale.</FONT> <BR><FONT face=Arial
size=2>2. Operator has a crappy scale.</FONT> <BR><FONT face=Arial size=2>3.
Operator added solvent anyway because thats how he has always done it...since
1976</FONT> <BR><FONT face=Arial size=2>4. Operators basement is 100%
realative humidity..condensation on the wing.</FONT> <BR><FONT face=Arial
size=2>5. Operator added "more" hardener to make it cure faster.</FONT>
<BR><FONT face=Arial size=2>6. Operator......(enter F/U here).</FONT>
<BR><BR><FONT face=Arial size=2>As you can see there is one common theme to
all of these possible problems, Operator, i.e. customer.</FONT> <BR><BR><FONT
face=Arial size=2>So if you are STILL interested please respond and Lance and
I will take it under advisement.</FONT> <BR><BR><FONT face=Arial
size=2> </FONT> <BR><FONT face=sans-serif size=2><BR><BR><BR>Gray
Fowler<BR>Senior Principal Chemical Engineer<BR>Radomes and Specialty
Apertures<BR>Technical Staff Composites Engineering<BR>Raytheon</FONT>
<BR><BR><BR>
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<TD width="40%"><FONT face=sans-serif size=1><B>"Dr. Mike Harrison"
<drmikedds@sbcglobal.net></B> </FONT><BR><FONT face=sans-serif
size=1>Sent by: nsrca-discussion-bounces@lists.nsrca.org</FONT>
<P><FONT face=sans-serif size=1>11/23/2007 01:57 PM</FONT>
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<DIV align=center><FONT face=sans-serif size=1>Please respond
to<BR>NSRCA Mailing List
<nsrca-discussion@lists.nsrca.org></FONT></DIV></TR></TBODY></TABLE><BR></P>
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<DIV align=right><FONT face=sans-serif size=1>To</FONT></DIV>
<TD><FONT face=sans-serif size=1>"NSRCA Mailing List"
<nsrca-discussion@lists.nsrca.org></FONT>
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<TD>
<DIV align=right><FONT face=sans-serif size=1>cc</FONT></DIV>
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<TD>
<DIV align=right><FONT face=sans-serif size=1>Subject</FONT></DIV>
<TD><FONT face=sans-serif size=1>[NSRCA-discussion] epoxy
question</FONT></TR></TBODY></TABLE><BR>
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<TD></TR></TBODY></TABLE><BR></TR></TBODY></TABLE><BR><BR><BR><FONT face=Arial
size=2>I have read with interest all the comments and some of you have
educated me on this issue. If I may, I will share what I have
learned.</FONT> <BR><FONT size=3> </FONT> <BR><FONT face=Arial size=2>1.
Thinning the epoxy saves no weight by evaporation. There is
virtually no evaporation and no weight loss-a big time erroneous assumption on
my part. So if you mix 2 ounces of epoxy and add 2 ounces of thinner and
put it all on the airplane, you have added 4 ounces to the airplane.
</FONT> <BR><FONT face=Arial size=2>2. The properties of the epoxy
are changed-it becomes rubbery.</FONT> <BR><FONT face=Arial size=2>3.
Changing the properties is not an issue regarding finishing the
airplane(painting)</FONT> <BR><FONT face=Arial size=2>4. Using thinned
epoxy is fine for applying glass cloth.</FONT> <BR><FONT face=Arial size=2>5.
I have tried MEK(epoxy thinner), denatured alcohol, 91%alcohol, acetone.
My preference is denatured alcohol because it is the safest and most
economical, I think. I thought MEK would be the answer. It is the
worst of the bunch. </FONT> <BR><FONT face=Arial size=2>6. The
best way to glass surfaces is to thin the epoxy and apply as sparingly as
possible. A way to do that is to apply and wipe off excess with paper
towels. </FONT> <BR><FONT face=Arial size=2>7. It is almost
exactly 2 ounces to glass a wing panel complete, so 4 ounces for a whole wing.
About 2 ounces for a stab. Properly done wings and stab glassed
and painted is 2-2.5 times the weight of monokote. </FONT> <BR><FONT
face=Arial size=2>8. A second thinned coat of epoxy on the glassed wing
is .75 ounces each wing panel-1.5 oz total.</FONT> <BR><FONT
size=3> </FONT> <BR><FONT size=3> </FONT> <BR><FONT face=Arial
size=2>Pick your poison.</FONT> <BR><FONT size=3> </FONT> <BR><FONT
face=Arial size=2>Later,</FONT> <BR><FONT face=Arial size=2>Mike</FONT>
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