I read somewhere that epoxy can be thinned with alcohol and used to fuelproof a firewall?

How exactly is this done?

Thanks

Easy!!

Mix a good amount of epoxy. i usually go for about 1oz total. then add a few drops, only a few!! 2 or 3 drop max of Methyl Hydrate / denatured alcohol to the mix. and mix.

It should thin. do not use more than a few drops, as it'll weaken / break down teh epoxy, and increase cure time. if you use too much, the epoxy might take days to fully cure, and even then, it'll be spongy, like a sponge (full of holes too!!)

Nother metod it to warm teh epoxy when you mix it/ warming it makes it runnier, but eh cure time decreases. Put your mixing cup in a mug of hot water, and mix. the heatr should really thin it up.

Also, you can paint on teh epoxy, then blast it with your heat gun. that shoudl also make it run, and flow into all teh little nooks and crannies!

I find it the easiest to put it on the wood and then use a hair dryer.
Those are all great tips dr_wogz

I only have 6-minute epoxy. Would that work? Do you brush it on with a normal brush? I imagine you have to toss the brush afterwards.

Thanks

I have used the Methyl Hydrate / denatured alcohol and other types but prefer MEK short for Methol Ethyl Keytone which is the thinner recommended for thining Epoxy and other two part glues and paints. Locally available at most Home Depots and good hardware stores.

Alchol attracts mosture and causes a contamination of the matrix.

Heed the Warnings and other cautions as with so much or our products these days..

I have tried thinning 5 min epoxy with alcohol and was not satisfied with the result. You can get away with it for a small area but 30 min works much better.

WOW!! these responces came fast!!

Yes, the longer / longest cure time epoxy is always reccomended. Penetrates the wood more.

(We all shoudl have the three epoxies on your bench: 5 min, 15 min, and 30 min, or something close to that!! )

and yes, toss teh brush. you can get 'acid brushes' which are disposeable: hair in a rolled metal (tin?!) handle. Usually 3 for a buck..

Good to know about the MEK stuff. Will surely look into it. Just hope I can find it up here!!

I use epoxy finishing resin, as it is thinner. Squeegy it on with a playing card.

Use at least 30 minute epoxy. The alcohol is a "reducer". It makes the epoxy thinner. The object with any reducer, either paint or epoxy, is to get the stuff to the viscosity that you want. Then, it is the job of the reducer to disappear before the paint or epoxy sets up. In the case of the epoxy, the alcohol need enough time to evaprorte before the epoxy sets, or you wind up with a rubbery mess.

Do NOT use rubbing alcohol. It is normally 30% water and the water will not evaporate fast enough. Use either pure isopropyl alcohol or denatured (ethyl) alcohol. I mix it one part epoxy, one part hardner, one part alcohol. This is not real important, as long as the epoxy is slow enough setting to let the alcohol evaporate. Acid tinning brushes work well. If you are doing inside the plane, you can even bend them 90 degrees to get areas that are tough to reach.

You can wipe of the excess with wadded up toilet paper to get rid of any extra weight. No strength is involved so any excess is.. well.. excess.

You can also use watered down aliphatic resin (YELLOW wood glue). It is fuel proof when it dries. It goes on easy and weighs less when it is cured.

JR

throw out your 5-6 minute epoxy. It is crap. ALWAYS use at least 30 minute epoxy. Fast epoxy is weak, turns brittle, crumbles off, is heavy and a waste of money. If it needs epoxy at all, it needs good epoxy.

Also, I think thinning epoxy is a really bad idea. Many don't agree with me, but many do. Heat works great. Put it in a pan of warm water and in a minute or two it's plenty runny without messing with the chemical reaction.

[quote]ORIGINAL: CafeenMan

throw out your 5-6 minute epoxy. It is crap.


I agree, with one exception...USE ONLY DEVCON brand epoxy...it's expensive but its the best. The rest is crappy junk and not worth using.

That's My Story and I'm Stickin to it.

And let's not forget to use floor varnish (poly urothane) as a fuel proofer for woods (engine bays..) , or just paint the area with a known fuel proof paint such as Lustercoat!!

Hi,

When I want to fuel proof an engine or fuel compartment, I just buy fiberglass resin, mix, and brush it on. It works great and is cheap.

Hope this helps,

Wayne Miller

Ah, you got to love the Internet! Post a simple question, and within minutes you have a dozen mostly contradictory answers.

I'm one of those opposed to thinning epoxy. First, I tried it and it was a gooey mess (yes, I know others have a different experience). Second, the manufacturers recommend against it (but what do they know?).

I used to use epoxy resin exclusively. It seemed like the right stuff for the job. I had a big can, and it lasted for years. But I "loaned" the can to somebody, and it never came back, so I'm now in the same camp as Wayne Miller. Polyester resin is much cheaper than epoxy resin, and people say it's just as fuel proof.

The main problem with most epoxy (and some epoxy resins, I found out), is they don't like to be mixed in big quantities. Say you mix up 2 oz or so, and you're happily glassing the wing joint, and you look over, and the epoxy is smoking. The heck? You pick it up, burn your fingers, and realize the whole mixing tub is about 5 seconds away from being 1 super-hot solid mass of hardened epoxy. Trust me on this one, you're going to have a crappy glassing job. Use the right material for the job, I say.

Mike

The question was about fuel-proofing a firewall. Not about fiberglassing. Two entirely different things.

Polyester resin has it's place, but, anyone using it needs to realize that the surface is waxy after it has cured, and that in order to paint it or apply another layer of resin, the surface must be sanded. Personally, I don't much like epoxy as an adhesive. Glassing is another matter, as is fuel-proofing. If using an epoxy as an adhesive, it's not wise to reduce it, I agree with you there. When it comes to glassing, I prefer epoxy resin because it does not need to be sanded between coats. On the other hand, it sands like a rock when compared to polyester resin.

Knowing what to use and when to use it is half the battle.

JR

put yur epoxy on without thinning...hit it with heatgun (as stated above) and it comes out perfect...thats a good trick to get it in those hard to reach spots also cause it runs right in all the cracks and joints like water....

TinMan - That's what I do for the engine compartment. For the tank and radio compartment, I dumb in a couple ounces of Minwax solvent based polyurethane, slosh it around a bit and then drain it out - usually through the fuel line holes in the firewall.

Oh... I plug all the holes before I pour it in so I can turn the fuselage every which way without it dripping out everywhere. An acid brush helps me get it where it won't slosh.