[NSRCA-discussion] epoxy question-I am back

[glmiller3 at suddenlink.net]

I'd love to try some FowlerPoxy  (? GrayPoxy) for lamminating and finishing!
 
Put me on the list

George  Miller

---- Gray E Fowler <gfowler at raytheon.com> wrote: 
> 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
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