I am at the point of mounting the engine on my Top Flite Piper Arrow. Should I Fuel proof the firewall now or what until I finish building the kit? The instructions say nothing about fuel proofing at this time. How and what should I fuel proof the firewall with?
Thanks
Chopper Man

they make several different things that accomplish the task of fuelproofing i think most are listed under building supplies on tower hobbies.
I always used 30 min epoxy thinned with up to 50% alcohol. works great spreads good and also helps to reinforce the firewall from the front side. if you mix a bit much you can fuelproof/reinforce the backside of the firewall and fuel tank compartment also.

As far as when to fuelproof, that's a decision of your choice. Most of my kits i fuelproof right before covering. if you get a bit of runout from the engine compartment you just sand it down when it dries.

ditto:
exept for mine is 6 min epoxy and "denatured alcohol" thats what the old guys always told me at my old club.
Raf-

Is there really any reason I should even mount the engine mount/engine until the kit has been completed and the firewall fuel proofed? Thanks for you help
chopper man

As I'm stuck helping my wife, I've been thinking about this fuel proofing. Should I paint the firewall first (using Ultracote paint) Than put a layer of thinned epoxy?
Thanks
chopper man

I always fuel proof the entire inside of the tank compartment. Usually use 30 minute epoxy (no thinning with anything) by spreading it on as thin as I can then gently heating the entire area with the heat gun. This makes the epoxy very thin and it penetrates every nook and cranny plus cures somewhat faster when heated. Just do not heat it so hot that it bubbles, just enough to make it run easily. I also drill a hole in the lowest part of the fuel compartment to let that inadvertent problem of split line, ruptured tank etc. to have a place to drain and alert me immediately to a problem if and when it occurs. I usually get one of these after a model has been in service a few years and I get careless about replacing a tank or fuel lines. When Hobby Poxy paints were available, that was my favorite fuel proofing item. I understand that Klass Cote does the same job just as well but I have not yet tried their paints.

I just completed an UltraSport kit that was covered in ultracote.
I got a most excellent tip from "PiperChuck" to use a product called BalsaRite.
BalsaRite is a liquid that you brush on your un-covered airframe, it seals up the pores in the balsa fuel-proofing everything at the same time. I use 3 coats on the firewall, and fuel tank areas or anyother area that might be exposed to fuel.
The other great advantage to this product is that it reacts with the adhesive on the covering you will be using, making the covering stick much better to the wood than if there were no BalsaRite applied.

My recommendation is to use BalsaRite both as a fuel proofing agent and also to assist in the covering of your model.

Let us know how your model turns out.
Ryan

Thanks for the tip. I'm about 75% complete on the build. I'll post pictures in order to get your opinons. Thanks
chopper man

Is there really a difference between thinned 6 or 30 minute epoxy for fuel proofing??

You can also use thin CA to fuelproof. Just make sure it covers good. Most of the time I will do two coats of thin CA just to be on the safe side.

dope and gloss fuel proofer for me [8D]

all over the firewall, and back about a half inch under the covering, if it has cheeks i fuel proof them all over, i generally don't bother with the inside, depends how careful you are with the pluming and tank testing

this depends on how you look at epoxy...it's been discussed in depth many time over on rcu

most people think the longer the cure time (of the epoxy) the stronger, more durable the bond will be. the shorter the cure time results in a more brittle finished product.

strictly for fuelproofing, i would say either one would work fine. but as i stated above, mine pulls double duty (fuelproofing and firewall reinforcing) so that's why i use 30 epoxy

How heavy is the BalsaRite? I'd imagine if you are putting this over your whole plane that the weight could matter.

I used about 4Fl. Oz. to cover an entire UltraSport 40 kit.
In my opinion I dont think it added much weight to my plane.
I see what you are saying about the added weight to the airframe.... I guess it depends on how sensitive the airframe will be to an extra ounce or two of weight.

Great product though,
Ryan

Can you paint over Balsarite? I would be using Hangar 9 paint. I've already used the Balsarite on the firewall for fuel proofing and now I just want to have the firewall match the rest of the planes base color (white).
Thanks
chopper man

Ive never tried painting over CoverRite.
I would test it on a scrap peice of balsa wood.
If I had to guess, I would say that it would work since it is sealing the wood like a primer would do.

Ryan

I'm going to give it a shot. Your right though, I'll try it on a test piece. I'll let you know if it works.
chopper man