Good fuel proofer?

[Doc J]

Hi Lads - I am taking a break from designing gliders and I'm doing a control line F2b stunt model - of my own design needless to say.

Thing is I have been away fro it for so long I'm out of touch.

Soooo...can any of you more knowledgeable chaps point me ago a good clear coat fuel proofer? I'll be using 10% nitro so it needs to be a good one.

Any help grateful received!

Couple of pics of the drawings etc below.

Cheers and thanks - Doc J.

 

[Konrad]

I've found that only catalized epoxy really is fuel proof, like to 65%. There are other finished that hold up fine up to 15% nitro. 2-stage urethanes like DuPont Nason works great, so does Klass Kote but a bit $$$. Non- catalized Urethanes are poor and leave a yellow tint.

If starting from scratch the classic butyrate dope over a few layers of nitrate dope should hold up fine against 10% nitro. I think Butyrate dope will hold up to 25% nitro. But it needs the teeths of nitrate dope underneath. I wouldn't use any of the dopes as a clear coat.

If clear coating don't forget to draw panel lines, real old school!

 

[kenh3497]

I've found the automotive urethane paint to be "more than enough " fuel proof unless you run 30%+ nitro. I use house brand paint and have had no problems.

Ken

 

[Hank]

I have used Minwax polyurethane spray from the can. The new version of spray does not yellow. I left it to cure for a couple of weeks before exposing to glow fuel. I have not flown the plane enough to determine long term wear. But so far after 8 flights no problem.

 

[joefly]

I use finishing epoxy mixed with 50% alcohol and brush it on. For firewalls, I first paint it with craft paint with a matching color and then finish it with the above mixture.

 

[Hank]

Update on my previous post. The polyurethane spray has not held up in the area immediately exposed to 15% nitro exhaust. The less exposed areas are fine. So I will have to try something different in that area.

 

[Konrad]

Nothing will hold up to the heat of the exhaust being directly aimed at the paint. One needs to try to keep a 5mm air gap around the muffler. If one can't then one needs to use a heat shield, preferably an unpainted heat shield. Again if looking for a long term finish with Urethanes one needs to use 2-stage urethanes.

 

[Hank]

Nothing will hold up to the heat of the exhaust being directly aimed at the paint. One needs to try to keep a 5mm air gap around the muffler. If one can't then one needs to use a heat shield, preferably an unpainted heat shield. Again if looking for a long term finish with Urethanes one needs to use 2-stage urethanes.

Hi Konrad. Thanks for the info. Can the paint under the 2-stage urethane clear coat be non-fuel proof paint?

 

[Konrad]

Yes. That is the main purpose of a clear top coat. That is to protect the base or undercoats.

Do test for chemical compatibility. Make sure the urethane doesn't lift the base coat.

 

[Hank]

Yes. That is the main purpose of a clear top coat. That is to protect the base or undercoats.

Do test for chemical compatibility. Make sure the urethane doesn't lift the base coat.

Will be looking for 2 stage urethane for top coat. I think the Rustoleum spray paint is enamel, but not sure.

 

[noarf4me2]

..........just use Elmer's thinned a little , its fuelproof when completely dried. Everyone wants to used these solvent based things.......white gliue works just test it yourself..

 

[CherokeePilot]

I've brushed epoxy on my firewall and then bonded some aluminum foil for the visual effect of a metal firewall prior to bolting on the motor mount. Then brush epoxy around any holes cut thru the firewall for additional sealing protection. Silicone sealant is good when passing fuel lines thru wood also..

 

[Hank]

That's interesting!! How transparent is the diluted white glue when dry?

 

[Txmustangflyer]

Dad always used a good epoxy..so have I.
Edit: a 15 minute epoxy diluted.

Formula dad taught me was mix the epoxy with its hardener then add the equal volume of rubbing alcohol to the mix so it's 50/50 alcohol and epoxy. Makes it brushless, and it soaks into the wood kinda like thin ca.
Seen a guy use body undercoat paint on his firewalls...to me that's a a couple extra ounces of weight that's just not neccesary, but on the flip, I don't think he had an issue with oil soak either lol.

 

[Txmustangflyer]

In the past I've used a good epoxy, mixed 50/50 with isopropyl alcohol to thin it so it can be brushed on ..always seemed to work.

 

[Txmustangflyer]

I will say on the current one, I was going to try some aluminum tape (similar to flitemetal) and see how that works. If it sticks well, helps keep some heat away from the electronics and batteries, etc...just not sure if a coat of epoxy underneath would help or just be overkill.

What y'all think?

 

[Joe Garfield]

On my most expensive and favorite models I used DuPont 2-stage urethane clear coat.

 

[Txmustangflyer]

Just cuz my curiosity got the better of me...Thanks Konrad (your fault)

I went surfing for alternatives. I found a fuel/glow proof 2 part epoxy resin paint called Klass Kote.
24.00 bucks for half pint, another 24 for the (side b) hardener. Mix and brush.

https://www.klasskote.com

Now, it's pricey, but the claim it's fuel proof, and low and behold, comes in warbird colors

I would think that a half pint of side a and a half of side b would be enough to fuel proof a firewall.

 

[Konrad]

Fuel proofing the finish is a bit tricky as it needs to flow out, have a good bond and shine and not yellow over time. Diluted hobby adhesive epoxy doesn't cut it. Diluted epoxy can help seal the engine compartment but to fuel proof the models finish I find its performance rather poor. Catalyzed epoxy and catalyzed urethane paints have been the best fuel proof finish for me. But these are often dangerous products for the hobbyist to be using.

Klasskote works great and is what I use in my QM40 and Q500 racers. It has also held up to 65% nitro fuels used in the defunct F1 class of racer.

Please heed the danger warnings with any catalyzed paint! in the 70's Dupont's Imron paint put me in the hospital for 3 days and I was suffering the effects for 6 month (neurological and respiratory distress). I was using a full face respirator but not a pressure suit (later this would be recommended by Dupont)

 

[Txmustangflyer]

Youch...