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What tips for fuel proofing

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Rocker11/10/2016 11:28:29
341 forum posts

Need to fuel proof my firewall and tank bay on my new model anybody have any tips on what to use besides the fuel proofers from the model shops (not sure they do what they do and are overpriced )For instance does varnish etc do the same job.I am sure there is some think out there that will fuel proof my model just has good has the commercial ones?

BrianB11/10/2016 12:00:59
31 forum posts
7 photos

Thinned epoxy finishing resin,totally fuel proof and easy to apply.Thin with a little meths and it brushes easily.

Don Fry11/10/2016 12:24:21
3814 forum posts
42 photos

Or even better use a 4 inch foam roller. Rollers straight to bin on completion.

Richard Wood11/10/2016 13:29:02
1081 forum posts
163 photos

A tank bay I once coated in polyurethane varnish 'pickled' a little from 5% glow fuel
from a tank leak.

As said above - epoxy resin is a very good fuelproofer & the finishing types are 
very easy to brush on.

Edited By Richard Wood on 11/10/2016 13:29:41

Tim Flyer11/10/2016 14:21:48
1008 forum posts
169 photos

I would second epoxy. Polyurethane is particularly unsuitable if you use high nitro fuels, even on 5% it will eventually deteriorate.

Tim Flyer11/10/2016 14:28:12
1008 forum posts
169 photos

One thing to remember with epoxy is that it often yellows in sunlight. If you are painting visible fuselage areas too its best to use the expensive clear coat two pack paints. . On my ARTFs I normally just epoxy everything under the cowling and tank bay plus inside and outside the firewall. It's easy to make an extender for your paintbrush if needed from an old bit of bamboo so you can reach into the fuselage.

Rick Tee12/10/2016 07:11:16
297 forum posts
20 photos

Exterior polyurethane varnish is completely fuel proof, apply 4 coats thinned 50% with white spirit 2hrs between coats and at least 4 days cure time. It does have a brown hue so only use inside the model. If you have had polyurethane pickle then I would suspect something was on the surface before you coated it or you're using water based which is not fuel proof.

Engine Doctor12/10/2016 09:25:00
2267 forum posts
25 photos

Hi try Clearcoat . I can thoroughly recommend it . It's made by the solar film people and it's very good.  I have tried all sorts of varnishes ,epoxy and two packs but now only use Clearcoat as it easy to use straight from the tin doesn't discolour and also easy to clean off with cellulose thinners if spilt. Use it on any areas that might get fuel contamination. Use it  before covering the model especially the engine bay, fuel tank bay and around u/c mounts etc . It's not very expensive goes a long way almost importantly , it works . It will also seal and improve the adhesion of your covering material and really does prevent any fuel creeping under covering. The only down side to it is that it has a strong smell when drying but does dry pretty quickly. Leave to dry overnight before covering . It can be thinned  by up to 10% without affecting it's performance . I use cellulose to thin it and have not had any problems. I use a thinned coat and allow to soak into any wood then a full strength coat . Hope this helps.

Engine Doctor12/10/2016 11:07:34
2267 forum posts
25 photos

I forgot to say that Clearcoat also works well against higher nitro fuels. I used it on a kyosho Majestic ARTF that powered by a YS 63 running on 20% nitro . It now ten years old , looks good and still not fuel soaked.

Tim Flyer12/10/2016 13:13:12
1008 forum posts
169 photos

Beg to differ Rick . I have found exterior polyurethane to be merely "fuel resistant" . In fuel soaked areas especially high nitro it can produce sticky goo. I certainly would not use it in engine bays. It also adds no extra strength like epoxy which cures hard and soaks into wood. Personally I use west systems 105 epoxy as I have a lot of experience using it on boats and it is a top quality product. Clearcoat would be good or any other 2 pack epoxy paint.

Edited By Timothy Harris 1 on 12/10/2016 13:15:04

chris larkins12/10/2016 14:03:52
183 forum posts
121 photos

I would second the use of epoxy finishing resin, on several models I have mixed in a VERY small amount of black paint and it then dries just like a coat of paint but still gives a tough fuel proof finish

Martin McIntosh13/10/2016 19:58:59
2901 forum posts
1062 photos

I agree that internally epoxy is by far the best, but what about the rest of the model? It can be used but for a good finish requires spraying on. Since the demise of Tufkote I have been searching for an alternative. A club mate of mine who is also a painter suggested Sadolin PV67 which is used for pub bar tops. I got hold of some. It comes in 1ltr tins, it smells the same, brushes on, gets mixed with hardener and dries very quickly in the same way as Tufkote. As far as I can see they are one and the same thing.

A bit expensive but you get an awful lot of it for your money.

robert chamberlain12/09/2019 22:40:04
121 forum posts

Hello, I was recently advised to use "water base polycrylic spray" as a fuel proofer here in the US. I found a really old bottle of "aero Gloss " fuel proofer from about 20 years ago which I regularly used back then, but I will bet it is no longer available. I have .recently used alcohol thinned 2 part epoxy for the job. All the paint I can fine says not necessarily fuel proof. Can finishing resin 2 part epoxy be used also? Just getting back into the hobby and over here it is all ARTF and no body know how to build anything. Much has changed in 20 some odd years! ------------Bob

Cuban813/09/2019 08:25:52
2638 forum posts
12 photos

To the best of my knowledge and experience from others, only two-pack epoxy paints will be proof against glow fuel, especially high nitro stuff.. My friend has invested heavily in proper spay gear and his models remain immaculate after much use. I always use finishing resin, brushed on, for firewalls and find that it never succumbs to the soaking from fuel and exhaust residue that usually finds its way inside the cowl.

As for paint, I didn't want to spend hundreds of pounds on decent spay gear and protective equipment that was only going to be used once in a blue moon, so I stick with Flair Spectrum/Spectra paints and Flair satin spray proofer - rattle cans. The secret is to really allow the paint to harden, at least four weeks in a dry and warm atmosphere (i.e indoors) and similarly, allow the proofer coat to go off totally by allowing as much time as possible, again in a warm and dry atmosphere.

I try to plan to have the paint and proofer indoors across the winter months. so the finish can be allowed tor cure over many weeks. Not always possible I grant you, but just allowing a few days or a couple of weeks for enamels to dry, possibly in a cold and damp shed or workshop (rather than cure) and then exposing them to even 5% fuel with have the finish feeling tacky in no time. Been there in the past. Enamels like Spectrum can effectively resist fuel and exhaust and remain hard, but only up to 10% nitro and again I must stress the need for as long a curing time as you can get in a dry and warm environment.

conrad taggart13/09/2019 09:16:58
80 forum posts
4 photos

Did a bit of desk research on this in the past and came across this very useful thread

Posted by Simon Feather on 31/01/2018 12:05:20:

One option is a spray lacquer. I have done this recently on a Seagull Zero where I wanted to matt down the very shiny ARTF, and although I have yet to fly the model (waiting for the better weather) the tests I did prior to committing were promising. In my case, I also needed something that would stick to film, and I found a couple of products that do seem to achieve this very nicely.

It depends whether you really need "fuel proofing" as you would use on the inside of the engine bay, or "fuel resistance" where it's fine so long as you clean up after flying and don't leave the model soaking in fuel residue. My tests certainly showed some products have good fuel resistance.

I did my tests by making a small balsa box, covering it in film, spraying it with the products I was testing, let it dry thoroughly and then put some neat fuel on and leave it for a couple of days. (I used Optifuel 5%).

"Let it dry thoroughly" is very important as the fuel resistance can take some days (or even weeks!) to kick in. I'd strongly suggest you do your own tests to satisfy yourself the results will be adequate for your use, and if you do use these products, leave it at least 2 weeks to dry before running the engine.

I've tried Autotek gloss petrol resistant lacquer from my local independent car parts shop at around £7 a tin, which is quite fuel proof - in my tests it marked, but the fuel did not dissolve it. It's quite shiny, and sticks well to film.

I used Rustoleum Polyurethane Clear Matt Finish varnish on my Zero. This gives a lovely semi-matt finish, it seems to stick very well to film, and my Zero looks fantastic now. It's also available as a gloss finish. It comes in 400ml tins, I used about 3 tins to do the Zero (68" wingspan). You can get it in B&Q at about £9 a tin. That's a silly price, I got my stocks from at £4.15 a tin instead! And Sprayster have lots and lots of other very useful things like grey primer at good prices.

My tests showed that the Rustoleum stuff will mark after a couple of days soaking in fuel, but it doesn't appear to penetrate. Here's a link to the product on Sprayster: **LINK**

Hope this helps - as I say, your mileage may vary, and do your own tests!



Don Fry13/09/2019 09:50:16
3814 forum posts
42 photos
Posted by robert chamberlain on 12/09/2019 22:40:04:

Hello, I was recently advised to use "water base polycrylic spray" as a fuel proofer here in the US. I found a really old bottle of "aero Gloss " fuel proofer from about 20 years ago which I regularly used back then, but I will bet it is no longer available. I have .recently used alcohol thinned 2 part epoxy for the job. All the paint I can fine says not necessarily fuel proof. Can finishing resin 2 part epoxy be used also? Just getting back into the hobby and over here it is all ARTF and no body know how to build anything. Much has changed in 20 some odd years! ------------Bob

Straight answer to the question, yes you can use 2 part epoxy finishing resin. And it's fuel proof. Thin it with isopropyl alcohol in preference to meths (better coating strength). Your side of the pond may use different names. The universal name for isopropyl alcohol is propan-2-ol.

Spray, brush, or radiator roller does. Read a safety quide before spraying.

Martin McIntosh13/09/2019 09:50:26
2901 forum posts
1062 photos

Water based satin Dulux Diamond Glaze works reasonably well on my war birds, three coats brushed on after thinning about 5% with water. This is invariably over Humbrol or Spektrum matt enamel. Not 100% with 5% nitro but only under the cowl gets affected.

Martin McIntosh13/09/2019 09:58:08
2901 forum posts
1062 photos

I tried some MRM spray on epoxy which can be mixed as gloss, satin or matt but only comes in very tiny jars so for the model in question I brushed the rest with finishing resin. Interestingly, they said thin with cellulose which actually works and unlike the other types of thinners mentioned does not affect the curing time. You can use up to 50%.

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