Hi Guys,

If I want to use epoxy for fuel proofing the engine compartment should I thin it before brushing it on? If so how do I thin it?

Thanks in advance

G'day John,
I personally use Zpoxy finishing Epoxy, for my fuel proofing, it is thin like warm honey & about the same colour.
But when I need to thin epoxy resin, I use a small amount of methanol, I mix my own fuel so I have plenty, & I also use methanol for clean up.
But denatured alcohol will do the same thing.

Isopropyl alcohol will work also, IF you get the 91% stuff from the pharmacy. That cheap 18% stuff is 82% water, and water is what you DON"T need mixed in your epoxy.
Denatured alcohol works great - your local hardware store should have it on the shelf.

I use 30 min epoxy , unthinned and then use the heat gun to flow it out.

As stated above you can use alcohol to thin it, IF you are careful. The problem here is that if you get too much alcohol you will change the chemistry of the epoxy and it will never set up and you'll be left with a gooey sticky mess. I do what Moondoggie said. Use heat. Mix your epoxy up and put a small "blob" of epoxy on the wood in the area you want to cover. Then heat it with your heat gun. The epoxy will thin out and flow on the wood. Use a disposable epoxy brush to paint the wood with the heated epoxy. I prefer this method to thinning as the heat will turn the epoxy to almost a water consistency and it will soak into the pours of the wood much better than if you thin it. When you do this make sure that you use 30-minute (or higher) epoxy because when you heat the epoxy it will reduce your curing time. If you use anything less than 30-minute you won't have time to work the epoxy as you heat it.

Ken

I've used both 70% isopropyl and the 91% stuff. They both worked but the 70% took a long time to dry. I've also used Synasol which is denatured ethyl alcohol. I liked the denatured alcohol the best.

What Ken and Moondoggie said. I've seen to many messes with people using alchohol as a thinner plus; when it does seem to kinda work, the coating is weak and not very durable.

If you need to thin epoxy use ONLY denatured alcohol OR acetone for thinning. DO NOT EXCEED 10% by volume when thinning. This will provide an epoxy that USUALLY dries in 72 hours.

Want to get by with something that's probably already in the bathroom closet, use the isopropyl alcohol. Keep in mind that it already contains an appreciable amount of water. 71% is at least 29% water. When epoxy is thinned with water.... uh, rubbing alcohol, it sets up too quickly for the water to make it out of the resin.

Denatured alcohol contains no water and is cheap and readily available. Alcohol absorbs water from the air, so keep the lid on and that won't happen.

Acetone says right on the can that it's made to thin epoxy resin. It's priced about like denatured and is found in the same places: hardware stores and home improvement stores. Acetone can also be used to wipe away CA that has run onto monokote and dried. Nothing else does that.

When thinning with any of these, it doesn't take much. If you thin to brushing consistency, the water causes the epoxy to cure with holes in it. So if you're using the rubbing alcohol, don't thin very much and don't brush it out thin either. With the other two, any consistency and any coating thickness will be good to do.

There is also another solution. Epoxy surfacing resin is made to paint on. It works great as it is.

And another..... polyurethane paint, but it'll take a couple of coats and they'll have to dry and then they'll need to cure for over a week.

Thanks to all!
I love this site! So many people, so much knowledge!
I will try the heat method. I have a heat gun and wont have to buy anything else.......that will keep the wife happy


Thanks again
John

For those of us old (experienced) enough to remember it, I use a few coats of dope. What I like about it is it comes in colors so you don't have bare balsa showing.

Seems you've made your decision, but I'll throw this in anyway...

Go ahead and get a quart of Denatured Alcohol and Acetone anyway and keep them on the shelf.

Aside from using them to thin epoxy, they have a myriad of uses in this hobby - not the least of which is using alcohol to wipe your fingers after using epoxy, or acetone for removing CA.

You don't want to touch your eyes, nose, mouth, etc if you have the SLIGHTEST amount of that stuff on you.

I am in complete agreement on the heat method. That's all I do and have had excellent results. One thing that's always bothered me is the fumes ... they are not terrible from a smell perspective, but are probably not the best thing to be breathing eithter. Outside of that, you'll be happy with the heat gun method I imagine.

Good luck!

-MA

I use West Systems Epoxy which is already thin by its nature and stronger than most hobby store epoxy.
I got into using the West Systems with my other hobby, high power rockets. Some of the airframes had to be fiberglassed to withstand the strains of flight. ie.. extreme G-forces and transitioning through transsonic into supersonic flight.
Until a couple of days ago I thought West Sytems was only available in 1/2 gallon resin and 10.6 oz. hardener (it is a 6 to 1 mix) but my local marine has much smaller sizes.
I bought the 10.6 oz hardener, because I was out, for $30. might seem expensive but it will last me several years.

I have a hard time finding denatured alcohol but I found out that methyl hydrate works really well. I tried isopropyl alcohol from the cupboard but found out that it is watered down way too much. Mix the 2 parts of the epoxy really well first and then add a very small amount; about 2 drops and mix really well. If its not enough you will know almost right away. A little alcohol goes a long way. The epoxy mix should be thin to almost water like consistency then your ready to go. It does take at least overnight to dry so suggest that its the last thing that you do the model at night.

i use spray can clear for cars. works really good just suff up the wood with some 400 grit then spray away.