I am redoing a plane that has some large lead weights epoxied to the firewall. I really need to get these off. Any sugestions as to how to disolve or soften up this stuff without tearing up the firewall!!!

Use your heat gun. It will make the epoxy soften up and you can remove them.

.... and then use acetone to remove small amounts that will be left. When finishing up a new plane acetone and a rag will remove the glue prints and clean it up nicely. Then go over the plane with a coat of automotive wax!!! <G>

Ernie

Thanks for the help. I think that will do the job.
Mike

With all due respect for previously submitted opinions, I submit that cured epoxy does not soften under a heat gun, and cured epoxy will not be affected by acetone at all. Having worked with this stuff (epoxy, polyester, vinylester resins) for years, both small scale, (models), and large scale, (boat building), I have never heard of such a process as you describe. Acetone is an aggressive solvent, and it will clean up uncured epoxy, but once the stuff has cured....forget it; and as for a heat gun....you can make it hot, very hot, and with enough heat you may even succeed in making it burn, (not recomended)..but you will not soften it like a thermoset plastic. The only way to remove cured epoxy is to cut, or grind it away. Cured epoxy is infinitely harder than the balsa, or plywood to which it is bonded. It will be the wood that will be much more abused by the application of heat and chemicals. Without actually seeing the weights and how and where they are attached, my guess would be to use a hacksaw blade or jewelers saw to cut them away as carefully as possible. Perhaps a Dremel tool may help. The firewall will most certainly be abraded somewhat in this, but carefully done, the plane will survive the operation.

I put the heat gun to the epoxy holding the lead on the firewall. It got nice and soft and a gentle pry with a flat blade popped it right off. A little more heat and a small putty knife took the remains of the epoxy off the firewall. So it does work and was very easy to do. No damage to the plane at all. I didnt try the acetone tho.
Mike

I think Capt Jim was right. Epoxy does not melt. You must have come up against some hot melt adhesive from a glue gun. I'm glad U got your airplane fixed, though. I'd rather be lucky than good.

Jim, It wasnt hot melt, it was 5 minute epoxy. I put the stuff on myself. I agree, I would rather be lucky than good. I do appreciate the info.
Mike

As I read of his success, I was astonished. I was thinking uncured resin, poor bond strength, etc...I didn't think of Hot Glue !! That stuff does kinda look like epoxy. Well now...we've all learned something here tonight.
Thanks for your insight.

stgrlee,

epoxy is interesting stuff. Just what it does depends largely on the type - like slow cure, cold cure, 5 minute - the brand and how well the proportions are maintained and mixed.

If you don't put in the correct amount of hardner, it wiull stay rubbery or maybe even not cure. Too much and iut gets brittle, while losing strength.

There are only two ways to get it off:
1) cut it off
2) fry it off with a torck, grinder or something else.

If you just heat it and it pops off, that makes me thing that it wasn't stuck on so well in the first place or had a less than ideal mix of hardner and resin.

You're double lucky. It never separated when you didn't want it to. Yet it came right off when you wnatedit gone.

Anybody that lucky can fly my plane anytime!

To all who have read this thread I have personally removed fiberglass cloth that was put on with epoxy by using a heat gun. Just get it very hot and start pulling, it will come right off with minimal damage to the wood. This was from a glassed wing center section.

I dunno, Capt Jim, I guess he was lucky. If he says he put the weights in with 5 min epoxy, he was there and I was not. I am bumfuzzled. My only conjecture is that the epoxy went in with imbalanced or un-mixed components, and never cured fully. If there were significant amounts of residual unreacted molecules in the matrix then it would probably be gummy.

Either that, or everything we know is wrong.

And also, I wouldn't argue against sucess. This episode has apparently worked out well. I have heard many of the horror stories and so I know that working with resins can be difficult and frustrating. As previously posted, different formulations, quality and age of the products, temperature and humidity conditions at cure, and of course the human element in the mix, can contribute to some odd results. I have just about eliminated using resins in models, in favor of good quality CA. In a meeting with a "ZAP" factory rep, I learned that the bond strength of CA is actually much greater than our old friend the epoxy. I now use it on high stress areas such as firewalls, wing center sections, including glassing the center section with light cloth. A bit more costly to be sure, but fast, convenient, and secure. The caveat is to avoid using the kicker. Each little spritz will significantly weaken the bond strength. I use the nice thin parachute rip-stop nylon with thin CA to reinforce the inside of those cheap plastic cowls, wheel pants, etc. It works like magic, stopping all the usual cracking and tearing. Well, I guess I'm getting off topic now. Thanks to all contributors to this thread.

Interesting thread,

Epoxy will soften with heat, I use a hot-knife (old pencile type soldering iron with xacto blade) to rempme hinges and such. Also low heat gun for other areas like firewalls. Epoxy is used to seal the normal lawnmower metal tanks, using my converted iron I can simply take the cured epoxy out.

The main differance in marine use is formula, and impregnating gass. You can get it hot enough to warp or mold, but You can burn it around the edges of a hull fracture and have glass strands left behind. And the patching is blended with the original form.

Builbing plugs and molds with epoxy and polyester bases has many variables not seen in the boat industry, as a normal rule.

Mixers, pumps and chopper guns call for differant formulations, The 5 min or 30 min type does not require.

Ex Sarasota bay and miss it"

Heat will soften epoxy so that you can remove an item. I have repaired golf clubs for years and the accepted method for the strongest epoxies is HEAT. For both steel and fiberglass shafts. Temperature variables are critical. Two much heat and the epoxy and shaft come apart. However, in some support of Capt Jim, golf clubs are not balsa airplanes. It takes quite a bit of heat to break the epxoy bond on golf clubs so there is a good chance that you may ruin the wood if not careful. HOWEVER, if you can control the airflow to a specific spot, heat will soften epoxy. The best way to do it is to bring the temperature up slowly to epoxy breakdown point which is around 250-300 degrees depending on the epoxy.

JB weld should not be affected by heat so much as regular epoxy. That is why we don't use epoxy on muffler or mousse can applications, right?

Ernie

Try it. It works. I am building a full scale plane too. It is right in the plans from Rutan about painting it white, because the suns heat will soften the epoxy and deform things. That is why we oven cure epoxy products. Once it hits a high temp, it will take that temp again to soften it. Don't mean to blow you out of the water, but facts is facts.

Not only does heat soften the epoxy for removal, it softens it so that you can take a composite wing that is warped, heat it and then hold it in a new position and the epoxy or resin will take a set in the new position.

The AMA 424/428 guys have been doing this for years!

Try it you'll like it.
There's a write up on wing warp at Darrol Cady's site:
http://www.darrolcady.com/Racing_Inf...tips-tech.html

Many different blends, many different properties. Many soften with heat, and most of the more comman types used by modelers are not glo fuel proof. They are very glo fuel resistant. CA is also not fuel proof. Any body that thinks different can prove it, to themselves, simply by coating the inside of their favorite planes fuel tank with their favorite brand of epoxy. Let it cure. Happy dead sticking. Why does it work on firewalls as protection from fuel? "All" of the fuel components do not stay on the surface long enough.
Ed M.