tempus

Does it matter if i paint and then apply a protective epoxy coat or does monokote have and advantage? I am referring mainly to the horizontal and vertical stabilizer and the control surfaces. I tried paint and epoxy and it seems to give good results.

loopnspin

Hi tempus,

It probably wouldn't matter if you used paint and then epoxy instead of monocote or any other plastic iron on covering. The biggest advantage to using plastic iron on covering is that it is very lightweight versus paint and epoxy. You will be adding considerable weight to your plane by painting and then sealing with epoxy. Also the epoxy will probably discolor whatever paint you use.

Just remember, the lighter these planes are, the better they will fly.

Jeff

FLYBOY

My Feedback: (11)

I hope you are talking epoxy paint? I wouldn't paint a plane and then put a layer of epoxy on it. Huge weight and nothing else gained. If you are going to paint, prime and paint, that is the protection, if you are going to cover, just cover. The covering is the protection. I don't understand the painting and then epoxy over the top. I have never seen that done. Doesn't sound like a good way to do it. Maybe I missed what you are saying, I hope.

tempus

The epoxy applied would be ordinary 12 minute epoxy thinned with alcohol so that a very thin coat can be applied. This works very well as i tried it already.

FLYBOY

My Feedback: (11)

What is the purpose of the epoxy? Are you using it for fuel proofing?

loopnspin

Hi again tempus

It seems you are determined to try this paint and epoxy combination. So I say, go for it. Do yourself a favor before you proceed though. Get an accurate weight of your fully assembled plane before you do the paint and epoxy thing. Then when you are done, weigh it again and see just how much weight you have added. I am guessing that it will be a considerable gain (even thinning the epoxy).

In your original posting you only mention that you are considering painting the horizontal and vertical stabilizers and control surfaces. What are you covering the rest of the plane with? If it is an airplane with a lot of open framework, it will have to be covered with something. Painting items such as cowls, landing gear, and wheel pants is quite popular. What you are doing or considering doing with the paint and epoxy is not. Mainly because of the extra weight it will add to the aircraft. And as I previously said, the lighter these planes are, the better they fly.

I find myself wondering where you got this idea anyway. I have never heard of anyone doing this.

Jeff

tempus

I got the idea after fuel proofing the fuel tank area with epoxy thinned with alochol. This was suggested by some members of my flying club. Later I got to thinking why not paint and then fuel proof the surface in the same manner as I did with the fuel tank compartment. And the rest of the plane is surfaced in monokote. I'm only trying the control and stabilizer surfaces. The paint i used is ordinary car paint obtained from my local car parts store.

FLYBOY

My Feedback: (11)

The mixture in the fuel compartment makes the fuel not soak into the wood. The covering on the tail does the same thing but at a much less weight factor. You can prime and paint the tail, and it will do the same thing. Adding epoxy over the top does nothing but add weight.

I would re-think it if I were you. It is really pointless and you will screw up a good plane. Every ounce of weight you add to the tail, you have to add about two to the nose to counter it because the arm is longer to the tail from the CG.

They guys had you do the tank compartment, because that needs to be done along with the firewall. Doing it to the tail is not good. Let the paint or covering do that. Anything else is just extra weight.

ElectRick

My Feedback: (2)

I agree with the other guys. I have never heard of applying epoxy, thinned or otherwise, over a painted surface on a plane, except the firewall area. You can get away with this area because it really needs heavy-duty fuelproofing, and it's not a large area and won't really adversely affect overall weight or balance.
If you've used Monokote on the rest of the plane, I'd strongly recommend using it on the tail surfaces as well. It is fuel proof by itself, way lighter than any paint system you could apply as a beginner, and as long as you take reasonable care to clean the day's oil accumulation out of the hinge areas and along seams, it will stay looking good and stuck securely for a long time.
What kind of paint were you planning to use? Is it enamel, polyurethane, lacquer, or what? All of these are already fuelproof by themselves. Enamel is not as resistant because it dries kind of soft. IMHO, auto parts store spray cans are not the way to go for glow powered planes anyway. If you HAVE to use them, a coat of clear polyurethane would work better and be lighter as a fuel proofer coat.
Stay with the Monokote. Anything else would be screwing up majorly.

Rick

GeraldO

My Feedback: (2)

Enamel is not fuel proof. This is especially true for Krylon. I just completed painting a big Four-Star 120 with Krylon because I read that it is at least gasoline-proof, and I'm running a gasser engine.

Well, it turns out that gasoline (or glow fuel for that matter) takes the krylon off about as fast as paint remover. Now I'm faced with having to fuel proof the entire paint job that I've spent countless hours on.

It looks to me like a thin coat of clear epoxy may be a good solution. All the clear hardware store polyurethanes state that they will cause a yellowing over very light colors, so that's right out since I have white areas on the paint job.

Besides, I would like to see some hard data to support the belief that epoxy is inherently heavier for the same cured film thickness. It is my opinion that epoxy would be no heavier than any other clear coating assuming you can apply it in the same thickness. Also, the long curing time for the epoxy should give it a superior gloss.
Finally, if the epoxy is thinned with denatured alcohol, that should make it compatible with most paints without attacking the base paint. I tried some of the clear spray polyurethane over a test sample of the Krylon and it attacked the paint severely causing very bad wrinkling.

I would spray the thinned epoxy on with a automotive type touch-up gun. Just be sure to clean the spray gun out thoroughly immediately after. Don't let the epoxy cure anywhere in the gun because it will never come out after that.

loopnspin

Some people must like flying bricks.

GeraldO

My Feedback: (2)

Some people are incapable of intelligent discussion.

Since you admit you've never heard of this being done before your assumption that it weighs too much is baseless.

ElectRick

My Feedback: (2)

GeraldO...do you ever wonder why practically NO ONE has heard of or used this epoxy-over-paint method? Surely there is a good reason...don't ya think?
Perhaps Krylon isn't fuel proof, but it's probably not enamel either. If it's a quick-dry paint formulation, it's likely acrylic lacquer. There are a variety of enamel formulations in spray bomb paints out there. There are acrylics, alkyd, latex, epoxy, and various synthetic enamels. Black Baron Enamel is fuelproof. I have read that several colors (not all) of Rustoleum enamel are fuelproof. Dupli-color automotive clear engine enamel is supposed to be as well. I do know Krylon isn't meant for glow fuel, at least not as a finish coat. Otherwise, we'd all be using it as a finish coat since it is relatively cheap, compared to epoxy enamels, which ARE fuelproof. I was generically referring to epoxy enamels in my post, not the cheapo acrylics or alkyds.
Bottom line, I still think that if an epoxy topcoat were to be used, it would be best to spray a two-part epoxy, or a catalyzed automotive paint that is DESIGNED for such use, like the HobbyPoxy paints and PPG automotives. Most epoxy glues that I have used don't set hard, unlike epoxy paint. As for yellowing, no epoxy glue I have ever used has remained clear after exposure to sunlight for a few months. Automotive paints have UV stabilizers added in. Epoxy glue doesn't.
There are solvent-based polyurethanes and water-based polyurethanes. You might have had better luck with a water-based one than one out of a spray can. Testing compatibility first on scrap before committing paint to model is invaluable, needless to say.
If you feel like the epoxy glue thing would work, a simple test can be done. Mix some up, thin it, spray it over Krylon, and see what you get. Might be interesting to weigh the piece before and after the process. Of course, after it sets, you're stuck with the results, good or bad.
I personally don't have the time to waste in my hobby trying to use products for purposes for which they weren't designed, risking questionable results. I prefer to use the right materials, and get it right the first time, with predictable, repeatable results.
Just My Humble Opinion. Your Results May Vary.

Rick

GeraldO

My Feedback: (2)

I sprayed the 4*120 wing this afternoon in the manner I had described. The recipe is as follows: West Systems 105 epoxy resin mixed 5:1 with #206 slow hardener. This was then thinned 50/50 with denatured alcohol. The spray gun was filled with a total of 4fl oz of the mixed epoxy. The epoxy was sprayed outdoors in 75deg temperature. A light fogging coat was built up until a uniform high gloss wet coat was acheived. At this point I had used about 1/2 of the mix or about 2fl oz.

The thing to remember here is that the alcohol all evaporates leaving only a thin coat of epoxy. So that means the entire 1200sqin wing (top side) was covered uniformly with only 1fl oz. of epoxy.

And yes, I weighed it before and after. Total weight gain was 0.75oz (21g). This works out to a weight of .09oz/sqft or 0.8oz/sqyd, about the same weight as tissue paper.

It remains to be seen how duarable the finish is but I have to believe it will be at least as good as any other clearcoat would be. The West Systems epoxy is not glue and it does not turn yellow.

Also if I were to use an automotive style paint, I'd have to add plasticizer to keep it from getting too hard and brittle. This model is covered in Sig Koverall fabric and it needs a flexible paint. Just because a paint is good for car bodies doesn't make it suitable for model planes. I've personally painted many cars and am quite familiar with a lot of different automotive paints. These paints are not made to be lightweight or to have any of the requirements of models in mind.

I'd love to have been able to use Hobbypoxy but in case you didn't notice, it's no longer made and hasn't been for some years. What good is it to suggest paints that aren't available?

Don't assume that just because you haven't heard of something being done that it must be wrong. Isn't it possible that you don't know everything? It was from listening to the Know-it-alls on this board that led me to use the Krylon in the first place. It is now obvious that they didn't know what they were talking about. If people would stick to giving advice on what they have experience with instead of stating guesses as though they were facts, there'd be a lot fewer disasters like this to need fixing up.

ElectRick

My Feedback: (2)

I might not be a Know-It-All, but I know enough to get my planes painted.
As in most everything concerning paint, the best decision as to which kind of materials to use is dependent on the specific application. The question specifically stated the intended use of "ordinary 12 minute" epoxy (as in glue) to spray on the model. West Systems laminating epoxy resin is a different animal, as everyone knows, and was never mentioned until now. The response I gave was in regards to this given information. Reading back over his post, there is a lot of specific information which is missing which can have a direct bearing on what the recommendations left by others should have been. For example, the type of surface to be painted, whether over some other covering used to seal the wood(fabric/silkspan/glass cloth), or bare/sealed wood, etc., whether the fuel was to be gasoline/glow, etc. Not to mention obvious things like whether the plane was already heavy, how big the airplane is, etc.
Automotive paints are widely used and quite popular in painting R/C aircraft. Radio South R/C even sells it custom mixed. It's the PPG Concept urethane paint line. So what if a plasticizer has to be added? Just add it, no big deal. Admittedly, not everyone has the $$ for automotive paints, and they are more often seen on large, gasoline powered craft, pattern ships, or jets. I have used Imron and PPG paint myself on a few pattern aircraft with outstanding results. Again, paint choice depends on the specific application in mind.
My mention of HobbyPoxy was an "example". Of course I know it's been off the market for many years, but K&B has a new line of epoxy paints that are available. Maybe it was a bad example, but it is a well known one, available or not.
So, before this thread becomes a "urinating contest", I will say to you, "good luck" with your idea. It's your plane to do with whatever you wish. I wouldn't do it that way, but that's my own opinion. I wouldn't have used Krylon, either, not without testing it first on something besides my plane. Since Krylon labels don't say "for model aircraft use", that tells me to test first. That is just common sense.
How about reporting your results with the West resin back to us in about 6 months? If it works, maybe someone else could benefit from the experiment.

Rick