Question about epoxy resin chemistry..

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.

Larry LaBeau just completed his Delta a year ago, and had a lot of
success using premade panels. Hmmm...get a stronger, pin-hole free skin
without all the work, smell, or exposure to hazardous chemicals. Great
idea in my book. He bought his panels 6yrs ago. If you look at a
manufactures web site, you'll be inundated with choices, all only
slightly different.

The thread I read here occured in 1994, and it discussed how brittle
resins were and that some 'new' developments were making resins tougher
vs just harder. It discussed how West Systems was not a good laminating
epoxy, even though Aircraft Spruce sells it as a laminating epoxy.

In fact, every place you look that sells epoxy says that every
formulation is the perfect solution for everything. Just a lot of noise
and practically no signal. I go to the EAA meeting and mention "resin
system" and really get noise. If you try this, be ready to duck the
flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs
chicken soup soaked paper napkins. I get the impression that very few
know anything other than what their kit specified, and are arguing from
the 'my choice must be the best, else I'm an idiot' perspective.

I'd like to make these skins once, and not have a lot of regrets in
5yrs. I want to pick the BEST sytem, not just a good system. But as
far as I can tell, the stuff that Lowe's has on its shelf is no
different than the 'aircraft' epoxies, except in the lower price. I
find VERY little difference in the mechanical properties of the
different resins, but a LOT of difference in prices. Either I'm missing
out on something, or a lot of people are getting taken for a ride. At
this point, I'm assuming the former.

Where can I find recent information other than sales brochures? More
importantly, does it really matter? Is the stuff at Lowe's so much
stronger than what's required that it just doesn't make sense to spend more?

I forget who said it, but answers are easy. It's asking the right
questions that's hard. Right now, I'm at the point of not even knowing
if there is a good question to ask.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber