FlyingGatsby

I need to fuel proof a piece of bass wood, can I think out the epoxy with 70% isopopryl alcohol?

exeter_acres

My Feedback: (2)

higher percentage is better....but yes you can

AmishWarlord

My Feedback: (5)

No, go get some denatured alcohol. Its mostly alcohol. Rubbing alcohol has water in it that will cause you problems.

FlyingGatsby

What kind of problems? I'm just fuel proofing.

Gray Beard

My Feedback: (-1)

Sometimes, not always but sometimes the epoxy will stay tacky if you use 70% alcohol, that is 30% water. Most of us use 91%. Same alcohol, just less water. Usually the 70% works just fine but it's that one time it doesn't that will make you start stocking 90% in your shop. Try it, if it is tacky clean it up with acetone and do it over, not the end of the world.

fledermaus

You can also thin epoxy with acetone, which is usually available with much less water. It evaporates more quickly however, so if you are taking a long time to get coverage the viscosity of the epoxy will change during application.

FlyingGatsby

Okay, I see. How much alcohol should I mix in?

dbacque

My Feedback: (3)

If you build regularly, you might want to just buy some 20 minute Finish Cure epoxy. It's already thinned out and works great full strength for what you're trying to do. Also works for applying fiberglass cloth. Just be sure that you don't try to use it as epoxy glue!

Dave

jester_s1

heat works to thin the epoxy also, and doesn't affect the curing aside from making it faster. I'd suggest 1 hr because of that.

Gray Beard

My Feedback: (-1)

About this much. TLAR. How thin do you want it. Jester just brought up heat, just mix some 30 min. epoxy up and heat it with your covering gun until it is runny enough to use.

JohnBuckner

My Feedback: (1)

Old habits perhaps die hard, I use plain old rubbin alcohol (so cheap) and it has never failed me for, well a really long time.

Heat does work also but my preferance is to not have to pull out and put away the heat gun when I can just drip a little 'Rubbin' with an old acid brush.

To answer your question drip one drop at a time in to the just mixed epoxie bubble untill the mix turns milky white and the mixture will freely drip off your raised brush.

The working time for brushing is short so more rubbin drips may be added to extend a little. For this reason keep the batchs small.

John

da Rock

If you already have rubbing alcohol around, yes you can use it if the epoxy is to fuel proof.

Water does weaken the epoxy mix so it's not perfect for everything however. Acetone is epoxy thinner. It usually says that on the can. It's also quite useful for wiping excess CA off iron-on film, or cleaning off a surface that needs an iron-on patch. It does not weaken the epoxy, so it's best to use thinning epoxy you want full strength from.

It's cheap.
It's better when strength matters.
It does other things for you.
It is epoxy thinner.

jaka

Hi!
Why not use 24 hour epoxy (that you use to cover wings/fuselages with ) instead! Flows like thick milk!

airraptor

My Feedback: (66)

Epoxy isnt 100% fuel proof. use a thin layer of epoxy the spray with acrylic clear coat to fuel proof.

Charlie P.

You shouldn't dilute more than 30%by volume.


Whatever you add to epoxy -thinning agents, c. silica, flocked fiberglass, wood dust, etc - ALWAYSmix the epoxy well first and let it set a half-minute (longer for the30minute &longer hardeners)to link before adding your adulterations. You will get much better results.

jmpups

My Feedback: (1)

The best product I could find to fuel proof aiplane engine areas and firwalls is Zap Finishing Resin. It has a much looser consistancy that brushes on like paint, fills in all the voids and goes alot farther than thinned exopy. Jmpups

TexasAirBoss

My Feedback: (22)

I prefer thinning 30 minute epoxy, especially for larger firewalls. But it will stay tacky for about 4 or 5 hours. It flows out and looks amazing. Best to do it just before bedtime rather than waste a day waiting for it to dry.

MTK

As you can see, there are as many opinions on this subject as there are modelers responding.

Short answer, for fuel proofing yes you can use it. Are 91% isopropyl (WallMart), acetone and/or denatured alcohol (Home Depot and Lowes) better for this? Yes they are because they leave a minimum of water behind, except they aren't really necessary for a simple fuel proofing application. Water will dry fine if the coating is thin enough.

How thin? I have used 1 part resin 1 part hardener and 1 part thinner (any of the above, I've used them all at one time or other). I mix the epoxy firts and let it sit for 10 minutes, then thin it

Some one mentioned heat and that's fine, but it could build up weight if not careful. Same for finishing resin, either epoxy or polyester.

I use epoxy paint, clear or colored depending on whether I have to match the plane's color. BTW, if you thin epoxy with any of the above, you may need two coats to fully seal the wood

JohnBuckner

My Feedback: (1)

Gatsby in my climate and the climate that I have lived in most of my life (of course I cannot speak for your climate) you do not even need to use the 91% rubbing alcohol, Yes the the 70% works just fine.

In my climate it is ridiculous to spend five times the money on the alcohol (denatured) when uneeded. Rubbing stuff is only a couple of bucks good grief give it a try, you likely may even already have some in your medicine cabinet.

This is not about strength, is about fuel proofing and that is the original question. It works great and can be done rapidly without much effort.

John

raptureboy

Ask an expert. http://www.seqair.com/skunkworks/Glu.../Thinning.html

eddieC

My Feedback: (2)

I use dope to fuelproof fuel tank areas, firewalls, and sometimes use clear to seal monokote edges and seams. Penetrates great. I have some 'Poly-U' also that is very good.

Gray Beard

My Feedback: (-1)

John, when the Walgreen's around the corner has it on sale all three percentages are the same price, 89 cents a quart. May as well buy the alcohol instead of the water. I agree, over thinking fuel proofing, something that simple. I just saw dope mentioned too, used that to do complete planes more then once. The complete Rascal when it was a solid balsa FF, the Dakota too. 101 ways to do something simple.

wally3185

My Feedback: (26)

I use Rustoleum oil based enamel , work's well, but takes overnight to dry (24 hrs).

fred985

why not just use old fashion DOPE,,,it drys in minutes and is totally fuelprof.??,,,

Yucholian

My Feedback: (7)

Why? I thought everyone on the internet (especially forums like this) are experts