Polyurethane on dope?

The most common source of polyurethane color spray may be found at many hobby shops. It's called Formula U. I have used it to paint a fabric covered plane. The weave had first been filled using nitrate dope, so I know that nitrate is OK.

The Formula U clear spray has a yellowish tinge, so you might want to use clear gloss Minwax with a detail gun for the topcoat instead. I find that the paint isn't fuelproof enough unless topcoated clear.

A big disadvantage of solvent based polyurethanes is the long time they take to dry. You need to wait about four hours between coats and at least 4 days before applying the clear topcoat. You should then wait at least a week before getting it anywhere close to fuel.

Jim - AMA 501383

Wan wrote:

A better way would be to mix the powder with some water base polyurthane for the sanding and sealer. Then there should be no compatibility problems with just about anything else you want to apply.

I am fond of automotive base coat/clear coat systems as you can ger ANY color including metallics and the newer color-shifting paints. It is more expensive, but with the right top coat, it will be nearly indestructible.

According to Tower, "Formula U" by Chevron has been discontinued by the manufacturer.

Thanks, Jim, Lyman. I am disappointed that "Formula U" has been discontinued. It does take a long time to set. Once set, it seems to be indestructable.

A Mr. funk responded directly after reading my post and said polyurethane may be purchased in many colors at any paint store. My friend and I went directly to a local Sherwin Williams and we were told this is not so. Mr. Funk also recommended that powder be mixed in thinned polyurethane as a filler coat. That sounds like a good idea.

Paul, I too have used and liked automotive paints called "Dupli-Color" for many applications. But maybe we should experiment to be sure their "clear top coat" is fuel proof? By using the right top coat, could you recommend which top coat it is?

Wan AMA 773188

On 10/5/2004 12:59 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

When using "Dupli-Color OR Duro" brand make sure the can states "Acrylic". Also make sure that the clear coat is the same as the underlying paint - i.e. Use acrylic enamel over enamel paint and acrylic lacquer over lacquer.

FWIW - The 11 oz spray cans of "Truck & Van" paint are labeled acrylic lacquer. The silver of this brand is a perfect match for SolarTex Aluminum/Silver and reasonably close to Coverite Aluminum/Silver coverings.

On 10/4/2004 8:53 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

I have had very good results using 2 coats of a water base polyurethane. My experience has been it is fuel resistant to 10% nitro (maybe more - all I use is 10% nitro fuel ), does not yellow with age and works well over MOST paints (latex and latex type acrylic enamels for certain ). To be sure if it will work with your paint do a test panel first. I like the fact I can get it in various degrees of "shininess" - satin, semi-gloss and gloss.

Thanks, everyone. Now we should take your suggestions and paint a few panels to see how fuel proof some combinations may be. These experiments will also show which paints are compatible.

While I have painted with various combinations before sometimes with good results, other times required stripping and repainting. I didn't want to experiment on my friend's plane because he had considerable time invested in building it.

This is the reason for my questions.

Wan

Any of the two part polyurethanes will be extremely fuel proof. I use the one that is used by many of the RC boat enthusiasts: House of Kolor. It is very easy to apply and is nearly indestructible.

indestructible.

I have had great results with Sherwyn Williams Ultra 7000. That was a while ago but I bet if you go into a Sherwyn Williams or DuPont auto paint store they will tell you which ones are best to use.

If you have a small compressor and auto detail gun, you can paint just about anything.