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Why coat the inside of a fuselage with epoxy?

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Why coat the inside of a fuselage with epoxy?

Old 04-05-2007, 12:43 PM
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Tommygun
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Default Why coat the inside of a fuselage with epoxy?

I've noticed that on many swap meet aquired airplanes, the builders for some reason elected to paint the inside of the fuselage, radio compartment and all, with epoxy. What are they trying to accomplish with this technique, other than add weight?
Old 04-05-2007, 12:50 PM
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WacoNut
 
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Default RE: Why coat the inside of a fuselage with epoxy?

They are fuel proofing the inside of the tank compartment and radio compartment to protect it from fuel in case of a leaking tank or fuel line or from exhaust oil residue. I always fuel proof my tank compartments but that is as far as I go back.
Old 04-05-2007, 01:16 PM
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Kaos Rulz
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Default RE: Why coat the inside of a fuselage with epoxy?

DITTO
Old 04-05-2007, 02:24 PM
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Default RE: Why coat the inside of a fuselage with epoxy?

I have a stupid question if you fuel proofe one are so that fuel cant saturate into it and its an inclosed space wotn it just keep mooving aorund till it find un protected wood? so you may aswell not fuel proof...\


hope you understand what im talking about...
Old 04-05-2007, 02:42 PM
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Default RE: Why coat the inside of a fuselage with epoxy?

When you fuelproof the tank area you coat the entire area with epoxy so that if the tank should leak into the fuel compartment it should not go any further than the tank area as fuel will not (under normal conditions) soak through epoxy. Same with the engine compartment.

When I paint the engine compartment to match the covering I ALWAYS paint first, then put a thick coating of 30-minute epoxy over the paint. All you need is epoxy for the fuel area no one will ever see it so no need to paint.
Old 04-05-2007, 03:00 PM
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Default RE: Why coat the inside of a fuselage with epoxy?

I have a stupid question if you fuel proofe one are so that fuel cant saturate into it and its an inclosed space wotn it just keep mooving aorund till it find un protected wood? so you may aswell not fuel proof...\
Well, you might have a point. But if you fuel proof the firewall and the tank area, you pretty much took care of some areas that take a lot of stress during flight, if the fuel finds unprotected wood to soak into, it better be in an area where the stress is not so high, or the repairs are easier.

Rafael
Old 04-05-2007, 06:32 PM
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Flying freak
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Default RE: Why coat the inside of a fuselage with epoxy?

true while the front of the plane is nice a protected you just mooved the fuel back into the radoi campartment and around the wing where repair is infact esier but i wouldnt want fuel around my servos rx or battery or evan worse would be if it weeks the woddd around the wing hold down dowls then what..?pull out of a dive and you loose the wing (dame that would suck)


I think for this sort of idea you would have to have several littler (like 1/64) holes drilled on the fuse to allow fuel to porr out the bottom of the plane if it ruptures....
Old 04-05-2007, 07:05 PM
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Default RE: Why coat the inside of a fuselage with epoxy?

I had a tank to leak a few years ago. Since then, I coat the inside with epoxy and drill a 1/16" hole in the tank compartment.
Old 04-05-2007, 07:06 PM
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Default RE: Why coat the inside of a fuselage with epoxy?

question was answered advice given was correct you want to use a different idea go ahead but in the 50 plus years of r/c flying don't you think that the ideas that work remain and those that did not are never passed on.
Old 04-05-2007, 09:27 PM
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Default RE: Why coat the inside of a fuselage with epoxy?

I fuel proof as much of the inside of the fuselage as I can. I guess if you used epoxy it would add a little weight but if you were to use a waterbased polyuerethane stain or several coats of clear dope the weight gain would be almost nothing. I have been usseing a red devil clear stain for my last several models it is easy to apply, dries fast and looks much nicer than painted on epoxy. Fuel-proofiing the inside of your plane takes so little time there is no reason not to do it.
Old 04-06-2007, 08:43 AM
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Steve Collins
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Default RE: Why coat the inside of a fuselage with epoxy?

I have used Hayes tanks for years and have never had a leak with one of them, even when pressurized by a Y.S. 4-stroke. I don't fuel proof the tank compartment because, with the Hayes tank, there simply is no need for it.
Old 04-06-2007, 10:24 AM
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Rodney
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Default RE: Why coat the inside of a fuselage with epoxy?

Over thirty years of building and flying RC, I have found it always pays to fuelproof the inside of the fuselage if you plan to keep the airplane for a long time. Sooner or later, I don't care how good the tank is, you will get a fuel spill inside the plane. Not only do I fuelproof the inside, I also am one who drills a hole in an appropreate spot to drain any gross fuel leak out the bottom of the plane. This gaurds against that time when the fuel line breaks at the tank mouth or similar problems and your refueling proceedure pumps a few extra ounces into the bottom of the fuselage. The added weight, even if you use epoxy is muniscal, probably much less than 2 ounces. The epoxy serves a second purpose, it greatly strengthens any joints in that area, especially firewall to fuselage.
Old 04-06-2007, 10:39 AM
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RCKen
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Default RE: Why coat the inside of a fuselage with epoxy?


ORIGINAL: Flying freak

I have a stupid question if you fuel proofe one are so that fuel cant saturate into it and its an inclosed space wotn it just keep mooving aorund till it find un protected wood? so you may aswell not fuel proof...\
This is a very valid point, but it brings up something that a lot of people have missed. If the tank was the only thing that was in that area a leak would do just what you said here, it would simply flow to a different part of the plane. But think about the normal installation of a fuel tank. In most planes the tank is padded and held in place with foam. So what happens when you get a fuel leak? The fuel first soaks into the foam, and won't start flowing to other areas of the plane until the foam is completely saturated. This can actually take quite a bit of time before that happens. But until that happens you will have fuel soaked foam touching the wood of the fuselage. If the wood isn't sealed the fuel will simply wick from the foam into the wood, and now more fuel leaking will simply move from the foam to the wood and continue to spread from that point. But on the other hand if you seal the wood the fuel won't soak into the wood.

Trust me, I have seen the results of what happens when fuel soaks into the wood. The end result is usually a destroyed plane. My case was an Ultra Sport 60. I was doing an outside loop when the wing simply separated from the fuselage, the wing fluttered gracefully to the ground and the fuselage turned into a lawn dart. The post mortem revealed that leaking fuel killed it. I had missed an area of wood around the F-2 former when I was coating it with epoxy to fuel proof it. A leak in the fuel tank allowed fuel to soak into the foam and then into the wood in the area that I had missed. This soaked into the joint of the fuselage former and the fuselage, which softened up the glue used to glue it in place. The stress of the outside loop simply pulled the former out of the fuselage. It came out of the fuselage cleanly. Apparently the the leak had been going on for awhile, and the foam was soaking up the fuel so there was no indication on the outside of the plane that would indicate there was a leak. Yes, I did miss the fact that they foam was fuel soaking when I was inspecting the plane after flying it. But then again, how many of us actually check the foam around the tank?? Well, I do inspect now because of this happening. Oh well, live and learn!!

Hope this helps

Ken
Old 04-06-2007, 11:33 AM
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MinnFlyer
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Default RE: Why coat the inside of a fuselage with epoxy?

This is also why it's good to fuel proof the radio compartment. If the fuel leaves the tank area, the first place it goes to is the radio compartment.

With a low-wing plane it will leak out and you will see it. On a high-wing plane, you;ll see it the next time you remove the wing.

In either case, as long as the radio compartment is fuel-proofed, the leak will be detected before it can get passed the radio compartment.

Lightfoot's idea of a hole in the floor of the tank compartment is a good one.
Old 04-06-2007, 04:48 PM
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da Rock
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Default RE: Why coat the inside of a fuselage with epoxy?

And you don't have to use epoxy.

Polyurethanes are often a better choice. Lighter, easier to use.

And one detail that's been missed up to now............ Very often, either epoxy or paint adds measurable strength to the structure. When you grasp the front of your airplane and jam the starter onto the spinner, where do you grab it? Yup, right where that "fuel proofing" is. I've built consecutive models of the same design. The ones that didn't have the "fuel proofing" inside often felt soft when I grabbed the nose to start them. The ones that had been strengthened didn't wrinkle their monokote or anything.

There is often more than one benefit from the old, established techniques.

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