Hello all

I have commenced construction to my World Models Super Frontier 40. I am wondering about fuel proofing. How? do I fuel proof the tank bay and engine bay.

Thanks

Simon Kennedy

Several things will work:

Epoxy thinned with alcohol (works very well and is really messy to apply)

Finish cure epoxy which is thin to begin with is another good option.

Both of the above will flow better if heat is applied with a heat gun. It also shortens the cure time.

Polyurethane paint and Rustoleum paint are two other options. Easier to apply and do the job really well. These paints dry in 24 hours or so but don't cure (reach maximum hardness) for up to a week or more. Alcohol and/or nitromethane will melt them quickly if not allowed to cure properly before use.

EXCAP232

You can color the thinned epoxy with model enamels if you like. Just a drop.

One of the quickest and most effective ways is very carefully apply thin CA. This is how I fuel proofed when I built with balsa, the glue spreads and soaks in beautifully. The draw backs to this is ventilation...this gives off a tremendous amount of CA fumes. I would always do this outside.

Thanks guys

This is much appreciated


Simon Kennedy

I am not positive......... but from all I have read, CA in not fuel proof. Maybe what I have been reading and hearing was the "more than 15% nitro" content. If you use CA, I would definately test it on some scrap first.
... lownslo

if you get fuel on something and its cleaned up in a resonable time ca maybe some what fuel proof but that and epoxy won't let you go back and sand without a lot of difficulty(in case of a repair) i've been useing for the last few yrs. the pactra paint the guys use for the cars it soaks down in the wood but it still sands easy and glue will bond
to it.i've had both gas & glow sit on this and it still didn't remove the paint,also its fairly cheap and dries to the touch in about 5 mins.
roy

I apply 2-3 coats of finishing epoxy in the engine and tank bays. Balsarite works too.........

I use CA to tack down the edges of trim that's coming up due to fuel...and that's usually the only piece of the trim left stuck to the plane a year later I've also used CA to fuel proof ever since I got my hands on the stuff. I don't read much, so I guess ignorance is bliss, as it's never failed me yet!

Just read another thread which says that ca debonder primarily contains nitromethane. If that is true, then using ca for fuel proofing has a serious drawback as fuel contains nitromethane ? Please correct me if I am wrong..........

If I had to guess, I would thing Tattoo was meaning exhaust type of fuel rather than raw fuel. Exhaust residue probably contains little or no nitro_bob

You've got a point there Bob. Unless you accidentally spill or leak fuel but again the amount may be too little to cause much damage.

CA will do the job for 50 flights or so, but then, the planw will probably last for 30-40 flights without fuel proofing at all. I expect my models to last for 3-4000 flights, and generally they do.

I mask off and spraypaint the engine compartment with gray equipment primer ( a buck a can at your local hardware store). Then I sand lightly with 400 to knock off any rough edges. This step is not just to make it look pretty. Any stress fractures that develop in the engine compartment will show up clearly as white balsa streaks in the gray primer.

Next, I mix up a small batch of 15 minute epoxy. I thin it to the consistency of pancake syrup with DENATURED ALCHOHOL which is probably sold as Methyl Hydrate if you are in Australia. DO NOT use Isopropanol or "rubbing alcohol" from your druggist shop, as it will interfere with the cure of the epoxy.

Apply the thinned epoxy to your fire wall and the surrounding engine compartment using a good quality artist's brush. I use a 3/4" brush which allows me to do a very neat and clean job.

Clean up the brush with more denatured alcohol. If you are slow, and the epoxy starts to cure before you get the brush completely clean, use ACETONE to clean up the brush. Acetone, applied to a clean rag will also clean up any epoxy you accidently dripped onto the model. It will not attack most covering materials, but it will ruin peel and stick decals.

Care and attention to details like this are the difference between a model that survives for a season and a model that sparkles for years.

Thanks for telling me not to get Isopropanol alcohol as i was looking for it yesterday but luckily the hardware store didn't have it.

Has anyone flown the super frontier or come in contact with one. The fuel tank supplied is 380cc. My engine is an OS 46LA. The instructions recommend a 200cc tank. Should i change it?

Thanks again

Simon Kennedy

What is the difference between denatured alcohol and rubbing alcohol ? A while ago, I used IPA, I think that's rubbing alcohol, and the epoxy did take a very long time to cure but it did evetually. Any chemist here ?

I am far from a chemist..... but one of the differences is water content. Denatured supposidly has none. Rubbing alcohol has a certain percentage of water........lownslo

OK, so it is only Denatured Alcohol that can be used to thin down epoxy, not Rubbing Alcohol. I almost used rubbing al the other day.

If I use 30 min epoxy and want to fuel proof the tank area, how thin do I want the epoxy to get? Should it be like water then painted on? or how much thicker than that?

I guess you could use rubbing alcohol.... it will just take a lot longer to cure. In my mind.... I just can't see adding WATER to the mix. I get denatured alcohol in the paint dept. at Wally World, Home Depot, etc., and it costs about $3.95 per quart. It lasts such a long time... so I just buy it. I also use this to clean covering edges before adding repair patches etc. I even dump a little of this in my clean-up "brew". I did notice that rubbing alcohol comes in 2 different percentages. (about 70% or 90%). I usually like to keep the 90% handy when I am gluing with epoxy. I ALWAYS seem to get a gob of epoxy on my fingers, so I use this cheaper stuff just for cleaning my fingers that I don't contamimate coverings, clothes, etc.
Again...... it is NOT written in stone about not using rubbing alcohol...... but why not get the best and feel more confident with it?
As far as how thin to make the mixture.... I make mine as thin as I can, WITHOUT LOSING CONTROL and have it run all over. (the viscosity maybe something like pancake syrup???) The thinner it is, the longer the cure time. .... lownslo

If you could GET pure isopropanol, that would be fine, but the drug store variety is ALWAYS cut with water.

It is, as others have said, the water that interferes with the cure. Sometimes you can make rubbing alcohol work, and sometimes you just end up with a gloppy mess, so it's just not worth it, especially when you realize that denatured is cheaper anyway.

Last I checked, denatured alcohol was 2.50 a quart at the paint store, and isopropanol was 3.25 for a PINT at the drugstore. So, there is no cost savings in buying rubbing alcohol.

Oh and by the way, I do keep isopropanol on hand because it does a great job of cleaning up my hands when i get epoxy on them, and is not as toxic as methyl hydrate.

About the consistency of pancake syrup.

Resist the temptation to brush it on with a cheap "flux brush", 'cause they shed and get hairs all over the airplane. Get a real artists brush and use that. As long as you clean it quick when you are done, you can use the brush again and again. I also use thinned epoxy and an artists brush to apply fiberglass tape when needed.

ctdahle what you are saying is that regular epoxy is fuel proof? How about polyester epoxy? I have a few boats made of the stuff and am worried about the fuel eating away at them.

Seems to be. I just use Devcon, or hobby shop brand/Bob Smith Industries 15 or 30 minute epoxy for everything. It is completely fuel proof. I even use it to fuel proof the fuel bottle well in my flight box, and have left an inch or so of fuel standing in the well with no damage to the epoxy. Even Fox Missle Mist (I had an old can of it around that I use in the 049 jobbies) doesn't effect it.

I don't keep polyester surfacing resin on hand because I am horrible at fiberglass lay up and so I don't build from glass anymore, but when I did use it, it worked just fine for fuel proofing. Messy to deal with though.

I was reading another post about fuel proofing and they made it sound like the alcohol was used with the epoxy to make it fuel proof. But I see now that epoxy IS fuel proof, and the alcohol is just used to thin it down. Thanks for clearing that up!

Isopropanol is Isopropyl Alcohol, also known as rubbing alcohol. Usually bought in drugstores or even grocery stores. WalMart sells it for about 2$ per quart, give or take, in 70% and 91% varieties. (The rest is water) It's available in my local market for slightly higher prices. Denatured alcohol is usually Ethanol (grain alcohol) with additives to make it poisonous. Sometimes Methanol is used for the denaturing. Methanol is wood alcohol and is poisonous. I have used Isopropyl to thin epoxy and have never had problems curing. I add only a few drops of alcohol per ounce of epoxy(10 or 15) and it thins nicely. I don't know but would assume the water evaporates when the epoxy cures as it gets hot. Generally when fuelproofing the tank compartment or engine bay I used Polyester resin. It's somewhat thinner than epoxy.

Nice write up Jim ! I have lab grade IPA which is >99%. I wonder where the term "rubbing" originated from ? Anyone ?