Epoxy/Alcohol mix for fuel-proofing?

On Sat, 17 Sep 2005 00:36:38 -0500, "Ed Paasch" wrote in :

Ooooh, we've had a long thread on this recently:

or

I don't use rubbing alcohol becaue it always has some water in it, and the water makes the epoxy a little rubbery.

I prefer to thin with denatured alcohol, if anything.

I do this if I have some leftover epoxy that I don't want to waste and some uncovered balsa that needs protection. I just slosh a little alcohol in the mixing cup until it seems OK.

We're not talking about a mission-critical joint here--just a first line of defense against fuel soaking into the wood.

Marty

First, don't use rubbing alcohol...it has water in it. Go get some Denatured Alcohol. It only take a very small amount of alcohol to thin the epoxy. Somewhere in the area of 10% . You add the alcohol AFTER you have mixed the epoxy.

I just use 3-4 coat of Balsarite, less weight. If you're going to use epoxy, go with denatured alcohol, as already mentioned, or acetone. Another choice is to just heat the epoxy a bit.

A good alternative is to use polyester resin as used for some types of GFRP - especially if you have some to "use up".

This material also makes a good adhesive - again if you have an excess from some other use. I have even mixed some for this purpose.

Malcolm

Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

First of all do not use rubbing alcohol for diluting the epoxy. Rubbing alcohol contains water which will make the epoxy rubbery.

What you need to use is either denatured alcohol or acetone.

I use acetone and thin about 10% by volume.

Yes, with the limitation that it doesn't cure over epoxy.

I have used denatured alcohol or 90% isopropyl alcohol mixed 50/50 with 30 minute epoxy. It paints nicely with a brush and soaks into the pores of the wood. I also used it on my startup platform that I built many years ago. It has stood up well. I had a fuel tank rupture that partially filled the tank compartment once. I poured the fuel out and wiped the compartment dry as though it was a kitchen countertop.

Brian

On second thought, it was 1/3 alcohol, 2/3 epoxy. Sorry about that. Just add the alcohol until it flows nicely onto and into the pores of the balsa. If it is too thick it will just be a layer on top that can later crack and allow entry of fuel.

Brian

Despite what all are saying, I buy 99% rubbing alcohol that mixes quite well with epoxy, doesn't cause rubbery stuff, brushes onto wood for an excellent fuel proof coating and is dirt cheap. I buy my 99% isopropyl alcohol at my local Safeway Supermarket in handy pint size bottles and I use it as an all-round shop solvent. I just add the alcohol to the epoxy with an eyedropper and stir to get the right brushing consistency. My wife loves it when I re-coated her wooden handled kitchen utensils with this mix. It forms an almost indestructible plastic coating that has withstood many cooking uses and frequent washings.

When you go to buy rubbing alcohol in the stores, it is usually somewhat less than 99%. More like 70% with the balance water. If you can find the

It will cure, but won't adhere well to epoxy.

Both resins are incompatible with each other in this way, but the cure is a chemical reaction and either mix, once cured is pretty inert if mixed in the correct proportions.

Malcolm

Suggest you check with a local drugstore. Back in July, I obtained a 16oz bottle of Isopropyl Alcohol (Anhydrous USP; not less than 99%) from a local CVS. They ordered it one day; had it the next. Cost was under $5.

Bruce

The percentage is listed on the bottle. I've been able to buy the high percentage stuff also, although I don't use it for thinning epoxy.

I have used vodka to thin epoxy with good results. Just don't drink it while building. the two don't mix well. Don't ask how I know.. Ken.

That's the ticket...

In article , "Six_O'Clock_High"

No personal experience on model aircraft, but on real ships: Polyurethane color resists fuel well. Has anyone tried that?

HTH

Marc

"Marc Heusser" wrote in message news: snipped-for-privacy@news.bluewin.ch...

Yes, I have used polyurethane off and on for glow model projects since it was first introduced in the early seventies. It is very good at resisting model fuel/gasoline/petrol.

It's only weakness is its susceptibility to sunlight. Fortunately, our models do not spend much time in the sun, so it is okay.

"The trick" with polyurethane coatings is to take ones time and ensure that the original coats have had plenty of time to cure. To me, this is very similar to using bytyrate dope. I'm speaking of the oil based polyurethane, for lack of knowing the proper terminology.

The water based polyurethanes are fantastic too.

Ed Cregger