jmurphy18

Folks
I have read the posts to thin the epoxy to fuel proof the wood under the tank and the fire wall. How do you do this???

Thanks

d_bodary

My Feedback: (85)

Acetone or denatured alchohol 50/50 mix or until you get it thinned to your preference.

da Rock

Acetone is cheap and easily found at any hardware or home improvement. A quart is usually only a couple of dollars. Read the label and you'll see that it is epoxy thinner. It's also excellent to have around to clean CA smears off monokote. It's also good to soak CA dispenser caps when they plug. They come clean with no effort when submerged overnight.

If you don't have any Denatured Alcohol, then you can find it at the same hardware or home improvements. But why buy it when the Acetone is almost as cheap and Acetone is made to do the job you want to do. And alcohol isn't. I just bought 4 little bottles of paint to finish the pilot figure that's going into my P47 and those cost me more than a can of Acetone and a can of Denatured would have cost.

Now, about thinning epoxy to fuel proof............................
Do you plan to build more than one model in your life, or is this your last one? I thought so.
Buy some Finishing Resin Epoxy. Use it to fuel proof. It is designed to work perfectly for what you want to do. You won't have the problem learning how much thinning your epoxy needs, nor will you ever screw up a model with thinned epoxy that won't cure for you. Or alcohol thinned epoxy that winds up rubbery after a couple of days.

First choice would be to use Finishing Resin.
Second choice would be to thin 30-minute epoxy with acetone.
Every other choice sucks.

To thin epoxy, first mix it thoroughly. Make doubly sure you mix the right amounts. Add about half the volume of Acetone and stir. If it's not thin as you wish, add a very little more acetone and stir.

Don't try this with 5-minute and if you're going to use 15-minute then do a test application first to learn how much you can handle and how it acts.

bruce88123

Actually you don't need more than a few drops of thinner in the epoxy to do the job. Additionally you can usually do the job on a firewall without adding any thinner at all. Use 30 minute epoxy and use your covering heat gun to warm it up after getting it on the firewall. Then spread it with a throw away brush. Still work quicky because the heat will accelerate the curing time. Usw all that thinner the others were talking about and it may never cure and just stay gummy.

piper_chuck

My Feedback: (12)

In addition to what Bruce said, even if it does cure, the thinner will make it porous, which is the last thing one wants when fuel proofing.

jmurphy18

Thanks Guys! What I am trying to do right now is under the fuel tank. I did get acetone but I will use very little as Bruce said. I don't have the heat gun yet so I will have to order that tomorrow along with the irons.
I will try this tomorrow afternoon after our cookout.

RCKen

My Feedback: (9)

For fuel-proofing I prefer to not thin the epoxy with an outside chemical. The reason is because if you get too much thinner the epoxy will not cure properly. The thinner actually changes the chemical composition of the epoxy and it's possible to get too much in it. I prefer to just use heat to thin it with. Use a disposable epoxy brush and put a "blob" (highly technical term ) on your work area and use your heat gun on the epoxy. It will thin out the epoxy to a consistency of water and you can then brush it over the area you want to fuel-proof. Just make sure that you use 30-minute (or higher) epoxy because heating it will shorten the cure time.

Hope this helps

Ken

piper_chuck

My Feedback: (12)

Got a hair drier? They can get the epoxy warm enough to thin it well.

rxAxilleas

hi the finishing resin doesn t need acetone or alcohol?
thanks

piper_chuck

My Feedback: (12)

Finishing resin is significantly thinner than the formula used for adhesives.

jmurphy18

Thank you very much everyone!!!! Thanks for the explanation Ken. I will wait and order my heatgun and then do the task. Why hurry This way I can do the jpb right.

bruce88123

Finishing resin is NOT a structural adhesive. It's primary use is to apply fiberglass covering.

Rodney

RCKen has given you some very good advice. You can also put the 30 minute (or longer) epoxy on with a putty knife and then heat it with your heat gun after it is on the balsa. As it heats up (do not get it so hot it bubbles) you will see it suddenly wick into the surface. At that point remove the heat source. Not only does this fuel proof the area covered, it also strengthens the joint between the firewall and the rest of the plane. To often, this part--the firewall--is not well attached on some ARF's.

opjose

One minor problem with Acetone, is that it can melt some plastics.

It thins epoxy MUCH better than Alcohol, but I've had it affect some plastic parts.

I tend to use alcohol as a result.

jmurphy18

Thanks again. I ordered my heat gun and irons and they should come by the weekend. So I hope to do this part of the project by then.

bruce88123

Just in case then notion strikes you ----- don't use the irons to spread the epoxy.[:'(]

jmurphy18

LOL, my name might be murphy, but I will leave that one

Sport_Pilot

Which is why it works so darn good for fuel proofing![sm=wink_smile.gif]

bruce88123

I fully agree. Just wanted any newbies to realize it had very little actual structural strength.

da Rock

Some epoxy is green. Some is yellow. Most is clear.

Some surfacing resins will provide good structural strength since almost all epoxies rely on bonding the fibers of another component in the layup for the major proportion of the strength of the result. Some surfacing resins have more fillers to provide better finishing results. Some have wax that surfaces as the epoxy cures to provide a shiny, slick surface. Some don't.

Z-Poxy's finishing resin can be used with layers of glass cloth or CF to strengthen rubbery cowlings, something you often get in ARFs nowadays. Do the reinforcing layup inside the provided cowl and decide for yourself is "surfacing resins don't provide structural strength." And if it's applied to wood that'll soak it up, it's going to make that wood lots stronger. For example, the cowl hold-down blocks supplied in my H9 P47 were a very stiff but fiberous wood. It was obvious the wood would probably not hold the cowl screw without splitting. Brushed on Z-Poxy surfacing resin was drawn into the end grain. It was ready for a second coating almost right away. Three quick coats and those wood blocks cured to be like steel blocks. OK, cast iron blocks. Didn't appreciably affect the weight either.

And the firewall's plywood absorbed lot's less, but every exposed ply was greatly strengthened, as were all the joints. And the surface is obviously stronger and stiffer.

As for how much acetone to use to thin..... None for finishing resin. But for 30-minute? Add a little and see if that's enough. If it's not....... hmmmmmmmmmm

I flew the P47 for the first flights today. It got a couple of pieces of wood glued into the cowling and some overlooked fuel proofing in the firewall and inside the fuselage last night. The finishing resin went on and in last night. It worked like gangbusters today.

Almost every technique works for someone. You just gotta pick the ones that suit you. And be smart enough to make them work for you.

Black Arrow

All the posts that mention heat guns and acetone makes me think that it might be worth mentioning that acetone and it's vapor is extemely flamable.

jmurphy18

BA, yes very much so. I intend to use heat only to thin as Bruce, Ken and other have pointed out to me. I returned the acetone due to it's flamiblity.
You have not lived till you worked around MEK in a vapor degreaser [:'(]

bruce88123

You're not still using MEK are you?[:@]

jmurphy18

Heck No! That was 25 years ago when I was a jet engine mechanic apprentice. Did not take me long to learn MEK was NOT your friend. That tank would take your breath away in a hurry.

bruce88123

Sure did clean good though.