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Which epoxy?

D

Desert Rat

Well Known Member
This is probably going to be another primer war, but I'm going to ask anyway;

I see west system as a frequent recommendation for epoxy, but then again, it's certainly not the only one out there.

I've used the 635 Thin epoxy system from U.S. Composites for quite a few boat parts and I'm familiar with that product and comfortable with how it works.

It's not UV resistant without a top coat, and has a temp range up to about 150f to 190f depending on a number of factors.

Is west system better in some way, or should I stick with what I know? U.S. Composites is quite a bit cheaper than West system, but that would just be a bonus, not a deciding factor.

Thoughts?
 
I use MGS L335 or L285 epoxy resin for fiberglass layups and anything structural and West System 105 for finishing that requires sanding.
 
The MGS 285 is an outstanding epoxy. This is the resin used in europe to build high-performance sailplanes.

In our composites shop we use the Jeffco 1307 LV (now sold as Rhino 1307). Available at Aircraft Spruce. It has essentially identical properties to the MGS 285, but quite a bit cheaper and more readily available.

Personally, I avoid West epoxy like the plague. I know it is widely used, but it is fairly expensive and has some serious short-falls. Chief among those is that at low temperatures, it can cold-inhibit so that it will never cure right. I've been burned a couple of times when temperatures in the shop dropped into the low 50s after doing a lay-up, and it won't cure. You can take it and put it in an oven at 150 for 3 hrs and it still won't cure, once it has cold-inhibited.

By contrast, I've had temps drop into the low 40s after a layup with Jeffco and it still gets hard as a rock.

For high-temperature applications, such as near the exhaust pipes on a cowl exit, we use PTM&W 2080, which requires a 150F post cure, but gives a 265F T_g. It is more expensive, but if you are going to paint something black and put it in full sun, this is what you want.
 
MGS for me

I agree with Steve. I use MGS for everything (at work as well) and stay the heck away from West. It also wets out much much easier.

I'll have to give Jeffco a try. I just checked Spruce and a gallon of MGS resin is not $287 (hardener not included). WOW, has that price gone up!

Thanks for the heads up on Jeffco Steve.

Laird
 
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I've been using the Jeffco epoxy that Steve Smith recommended. It's slightly faster to cure than the slow West epoxy and is easy enough to use. I weigh out my ingredients each time and would for the West stuff too, having had batches of that lost because their pumps failed.

Dave
 
This cool non-cure is real and serious.

scsmith said:
Personally, I avoid West epoxy like the plague. I know it is widely used, but it is fairly expensive and has some serious short-falls. Chief among those is that at low temperatures, it can cold-inhibit so that it will never cure right. I've been burned a couple of times when temperatures in the shop dropped into the low 50s after doing a lay-up, and it won't cure. You can take it and put it in an oven at 150 for 3 hrs and it still won't cure, once it has cold-inhibited.
Click to expand...

I have a heat wave in my canopy when this happened during the canopy installation and a layer did not cure. I think it was only 55-60F over night in my garage. I had to heat the syrup to get it off and accidentally heated the canopy in a small area. It would not come off w/o some heat. I was luck it wasn't all of it.

I did not notice until into Phase I. :mad:
 
Which Epoxy?

I have used many gallons of US Composites 635 Epoxy for various projects and like it a lot. Always had great results, good in hot and humid (Florida) conditions and I have some unpainted (interior) things that I made 5 years ago that look great. I have about a gallon of 3:1 that I plan to use for my canopy skirt. Learned a lot about working with epoxy from the Cozy Girrrls.

Stuart Grant
1953 Cessna 180 - Sold
2013 RV-12 Kit - Finish Kit underway
N412SG - reserved
 
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