[NSRCA-discussion] epoxy question

Mon Nov 26 19:44:49 AKST 2007

Gents and Linda

For laying up work, that is fuselages, cowls etc I use LC3600 Resin. I
post cure at 80 Degrees C for 4 hours. I quite like this resin.

For wings I sand like crazy ( both sides) and seal with dope.
Honeycombed cores. Then I use West 105/207 for skins. Never tried to
post cure the wings, I figured this epoxy would not benefit from it (
i.e I had no data for it..so I didn't!)

Tom

________________________________

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Lance Van
Nostrand
Sent: Tuesday, 27 November 2007 2:48 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] epoxy question-I am back

I use the West system all the time but we use custom blends made up by
master Fowler for AeroSlave parts after all our R&D on the process
design.  West 205 hardener gives about 925 cps and the 207 gives about
750.  The thin stuff Gray is talking about is half that!
--lance

	----- Original Message ----- 
	From: Pattrnflyr at aol.com 
	To: nsrca-discussion at lists.nsrca.org 
	Sent: Monday, November 26, 2007 11:20 AM
	Subject: Re: [NSRCA-discussion] epoxy question-I am back

	I have built several wood racing boats with West System.  The
105/205 is for gluing and the 105/207 is for glassing and is much
thinner and easier to work with.  I glue the boat together with 105/205
and then roll on 105/207 for the final finish and you are done.

	Bruce Reins
	A Stock Hydro/Runabout
	15-R 

	In a message dated 11/26/2007 8:46:44 A.M. Mountain Standard
Time, lightfoot at sc.rr.com writes:

		West's 105/205 system seems to be a low viscosity epoxy.
It is a slow cure (8 hrs) so if you add solvent it should have plenty of
time to evaporate. I have only used it for sheeting, not glassing - yet.

		Jay Marshall 

		-----Original Message-----
		From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Gray E
Fowler
		Sent: Monday, November 26, 2007 10:23 AM
		To: NSRCA Mailing List
		Subject: Re: [NSRCA-discussion] epoxy question-I am back

		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.  " 

		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). 

		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. 

		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. 

		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. 

		1. Operator cannot operate a scale. 
		2. Operator has a crappy scale. 
		3. Operator added solvent anyway because thats how he
has always done it...since 1976 
		4. Operators basement is 100% realative
humidity..condensation on the wing. 
		5. Operator added "more" hardener to make it cure
faster. 
		6. Operator......(enter F/U here). 

		As you can see there is one common theme to all of these
possible problems, Operator, i.e. customer. 

		So if you are STILL interested please respond and Lance
and I will take it under advisement. 

		Gray Fowler
		Senior Principal Chemical Engineer
		Radomes and Specialty Apertures
		Technical Staff Composites Engineering
		Raytheon 

"Dr. Mike Harrison" <drmikedds at sbcglobal.net> 
Sent by: nsrca-discussion-bounces at lists.nsrca.org 

11/23/2007 01:57 PM 

Please respond to
NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>

To

"NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org> 

cc

Subject

[NSRCA-discussion] epoxy question

		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. 

		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.   
		2.  The properties of the epoxy are changed-it becomes
rubbery. 
		3.  Changing the properties is not an issue regarding
finishing the airplane(painting) 
		4.  Using thinned epoxy is fine for applying glass
cloth. 
		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.   
		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.   
		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.   
		8.  A second thinned coat of epoxy on the glassed wing
is .75 ounces each wing panel-1.5 oz total. 

		Pick your poison. 

		Later, 
		Mike 
		 _______________________________________________
		NSRCA-discussion mailing list
		NSRCA-discussion at lists.nsrca.org
		http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

		_______________________________________________
		NSRCA-discussion mailing list
		NSRCA-discussion at lists.nsrca.org
		http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

________________________________

	Check out AOL Money & Finance's list of the hottest products
<http://money.aol.com/special/hot-products-2007?NCID=aoltop0003000000000
1>  and top money wasters
<http://money.aol.com/top5/general/ways-you-are-wasting-money?NCID=aolto
p00030000000002>  of 2007.

________________________________

	_______________________________________________
	NSRCA-discussion mailing list
	NSRCA-discussion at lists.nsrca.org
	http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20071127/f09e242f/attachment-0001.html 