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<DIV><FONT face=Arial size=2>Gray,</FONT></DIV>
<DIV><FONT face=Arial size=2>I think the problem is trying to develop an epoxy
to please all issues. I would say the issue here is to develop an epoxy
that will aid in laminating a glass cloth to balsa that is very light.
There are already a host of epoxys that serve our other needs, ie layups for
parts, vacuum bagging, adhesives, etc. So what I am looking for in
particular is an epoxy that can be used to laminate 1/2 oz cloth to a wing for
2oz or less.</FONT></DIV>
<DIV><FONT face=Arial size=2></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 11:34
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=sans-serif size=2>Mixed viscosity is about 250
centpoise at 77F. Glass transisiton is about 128F. But can be increased to
165F......IF it is cured or post cured at 160F. A Tg of 109F is not possible
in an epoxy without the application of about 210F heat. Any manufacturer that
tells you otherwise is either ignorant or a liar.</FONT> <BR><FONT
face=sans-serif size=2>A 128F Tg DOES NOTmean degredation of the epoxy itself,
it means where structural strength is lost and this is reversable.</FONT>
<BR><BR><FONT face=sans-serif size=2>Gummy is the result of water or bad mix
ratio. If you apply during high humidity the top surface can be sticky, This
is just the very top of the cured epoxy and does not affect the structural
integrity, yet is a pain for us. There are chemicals that I can formulate in
the blend to make the cure less sensitive to this problem. </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>"Mike Hester"
<kerlock@comcast.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>11/26/2007 10:50 AM</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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<DIV align=right><FONT face=sans-serif size=1>cc</FONT></DIV>
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<DIV align=right><FONT face=sans-serif size=1>Subject</FONT></DIV>
<TD><FONT face=sans-serif size=1>Re: [NSRCA-discussion] epoxy
question-I am back</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'm interested...what kind of viscosity and what will be the
transitional temp? Most of the resins I have run across for this purpose have
a transitional temp that is really too low. If you take a temp reading of your
plane's surface in the summer time, some of the darker colors can approack 190
degrees f. On a wood fuse this can mean bubbling, delamination etc.
</FONT><BR><FONT size=3> </FONT> <BR><FONT face=Arial size=2>What Id like
to see is a transitional temp of at least 190+ and a viscosity of around
200cps. One that actually cures HARD and not gummy without reducer.</FONT>
<BR><FONT size=3> </FONT> <BR><FONT face=Arial size=2>I'd buy it by the
gallon =)</FONT> <BR><FONT face=Arial size=2>-Mike</FONT> <BR><FONT
size=3> </FONT> <BR><FONT size=3>----- Original Message -----
</FONT><BR><FONT size=3><B>From:</B> </FONT><A
href="mailto:gfowler@raytheon.com"><FONT color=blue size=3><U>Gray E
Fowler</U></FONT></A><FONT size=3> </FONT><BR><FONT size=3><B>To:</B>
</FONT><A href="mailto:nsrca-discussion@lists.nsrca.org"><FONT color=blue
size=3><U>NSRCA Mailing List</U></FONT></A><FONT size=3> </FONT><BR><FONT
size=3><B>Sent:</B> Monday, November 26, 2007 10:23 AM</FONT> <BR><FONT
size=3><B>Subject:</B> Re: [NSRCA-discussion] epoxy question-I am back</FONT>
<BR><BR><FONT face=Arial size=2><BR>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><FONT size=3> <BR></FONT><FONT
face=Arial size=2><BR>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><FONT size=3> <BR></FONT><FONT
face=Arial size=2><BR>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><FONT size=3> <BR></FONT><FONT
face=Arial size=2><BR>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><FONT size=3> <BR></FONT><FONT face=Arial
size=2><BR>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><FONT size=3> <BR></FONT><FONT
face=Arial size=2><BR>1. Operator cannot operate a scale.</FONT><FONT size=3>
</FONT><FONT face=Arial size=2><BR>2. Operator has a crappy scale.</FONT><FONT
size=3> </FONT><FONT face=Arial size=2><BR>3. Operator added solvent anyway
because thats how he has always done it...since 1976</FONT><FONT size=3>
</FONT><FONT face=Arial size=2><BR>4. Operators basement is 100% realative
humidity..condensation on the wing.</FONT><FONT size=3> </FONT><FONT
face=Arial size=2><BR>5. Operator added "more" hardener to make it cure
faster.</FONT><FONT size=3> </FONT><FONT face=Arial size=2><BR>6.
Operator......(enter F/U here).</FONT><FONT size=3> <BR></FONT><FONT
face=Arial size=2><BR>As you can see there is one common theme to all of these
possible problems, Operator, i.e. customer.</FONT><FONT size=3>
<BR></FONT><FONT face=Arial size=2><BR>So if you are STILL interested please
respond and Lance and I will take it under advisement.</FONT><FONT size=3>
<BR></FONT><FONT face=Arial size=2><BR></FONT><FONT size=3> </FONT><FONT
face=sans-serif size=2><BR><BR><BR><BR>Gray Fowler<BR>Senior Principal
Chemical Engineer<BR>Radomes and Specialty Apertures<BR>Technical Staff
Composites Engineering<BR>Raytheon</FONT><FONT size=3> <BR><BR></FONT>
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<TD width="46%"><FONT face=sans-serif size=1><B>"Dr. Mike Harrison"
<drmikedds@sbcglobal.net></B> <BR>Sent by:
nsrca-discussion-bounces@lists.nsrca.org</FONT><FONT size=3> </FONT>
<P><FONT face=sans-serif size=1>11/23/2007 01:57 PM</FONT><FONT size=3>
</FONT><BR>
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<DIV align=center><FONT face=sans-serif size=1>Please respond
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<nsrca-discussion@lists.nsrca.org></FONT></DIV></TR></TBODY></TABLE>
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<DIV align=right><FONT face=sans-serif size=1>To</FONT></DIV>
<TD width="86%"><FONT face=sans-serif size=1>"NSRCA Mailing List"
<nsrca-discussion@lists.nsrca.org></FONT><FONT size=3>
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<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><BR>
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<TD width="50%"></TR></TBODY></TABLE><BR></TR></TBODY></TABLE><BR><FONT
size=3><BR><BR></FONT><FONT face=Arial size=2><BR>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><FONT size=3>
<BR> </FONT><FONT face=Arial size=2><BR>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><FONT size=3>
</FONT><FONT face=Arial size=2><BR>2. The properties of the epoxy are
changed-it becomes rubbery.</FONT><FONT size=3> </FONT><FONT face=Arial
size=2><BR>3. Changing the properties is not an issue regarding
finishing the airplane(painting)</FONT><FONT size=3> </FONT><FONT face=Arial
size=2><BR>4. Using thinned epoxy is fine for applying glass
cloth.</FONT><FONT size=3> </FONT><FONT face=Arial size=2><BR>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><FONT size=3> </FONT><FONT face=Arial size=2><BR>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><FONT size=3> </FONT><FONT face=Arial
size=2><BR>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><FONT size=3> </FONT><FONT face=Arial
size=2><BR>8. A second thinned coat of epoxy on the glassed wing is .75
ounces each wing panel-1.5 oz total.</FONT><FONT size=3>
<BR> <BR> </FONT><FONT face=Arial size=2><BR>Pick your
poison.</FONT><FONT size=3> <BR> </FONT><FONT face=Arial
size=2><BR>Later,</FONT><FONT size=3> </FONT><FONT face=Arial
size=2><BR>Mike</FONT><FONT size=3> <BR></FONT><FONT
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