I recently purchases a used C/L airplane and motor for $10. I knew it was finished in Formula 'U' paints. Aero Gloss' manufacturer says they no longer manufacture the 'U'. I found some color spray cans down at the local hobby shop and purchased them. I have finished planes using other dope brands but never Formula 'U'. If i'm not mistaken, Formula 'U' isn't even a dope. I could use some advice on using Formula 'U' for refinishing my model. Do they have a clear? Does it come in bottles so you can brush it on? Any advice or help would be welcome. Thanks. Dave G.

Formula U was a polyurethane paint. they haven't made it for quite a while, I think. If you found some, I would expect it would be bad, and stay away.

For refinishing, I'd try to remove as much of the old as possible, and test compatibility of whatever I was putting "over."

Good luck,

Phil

Formula U was terrible stuff in my experience. Very heavy, took forever to dry. Get it off and use good old dope.

What Philip said.....

I tried some of it a couple of years back when it was still on LHS selves. It was still being stocked at the time, so you'd expect it to be "good". Near as I could tell, it was bad back then. So I'd bet any you happen to find would have been bad back when it was first put on the LHS self, and hasn't gotten any better.

I'm attaching a chart of what finish goes over an original finish. It's sort of a chuckle that it appears that Aerogloss won't go over Formula "U". Nor will Butyrate. Everything else seems to go over polyurethane.

Are there any covered open areas (like the wings), or is all the exterior wood?

BTW, if you're in Minneapolis, you've got the home of KlassKote just down the street. They are the only source I know of for 2-part epoxy paints for models.

I've seen a couple of refinish jobs done with epoxy. Both were spray jobs. No brushing anywhere. And they looked excellent.

The only problem I had with Formula U was that higher nitro fuels took it off. If it still sprays from the can it is OK. I have several cans of the stuff but haven't used it in 15 years.

Thanks for your help. If I read your chart correctly, I could put nitrate dope over the polyurethane 'U', and then put Butyrate over that. I don't want to go to 2 part mixes, the plane isn't that spectacular. If my idea is functional, it is a choice between Sig and Brodak dopes. Let me know if you think this will work. They plane is an old one and the covering over the wings (with open areas, not all wood) is tore in a couple of bays.

Yup, according to the chart, that'll work.

To refinish, you need to clean the surface and lightly sand it. I've cleaned the surface with soap and water and a soft brush in preparation to repaint, and discovered the finish look good enough to fly, and wound up not repainting. But whatever may happen, it's a good idea to wash the plane first.

After I washed that plane, I wiped it down with denatured alcohol. That's when it looked better.

You need to get the oil and dirt off. That's why I used soap and then alcohol.

If you do happen to find Formula U, stay away from it. I recently sprayed a set of floats for my plane with a can of "u" about a month ago; ran out about half-way through the project, went back down to the LHS only to find out "they no longer produce or stock it." I caught pure hell trying to figure out compatibility. And to top it off, the finish really looked like doodey, and I'm no rookie. I had the misfortune of tearing up one of the floats, only to discover the formula u DID NOT stick to the underlying primer...in fact, it peeled off with a pocket knife blade like a banana peel. STAY AWAY FROM IT!!

Never tried to dope over any poly. Have used many gallons of both nitrate and butyrate. If you are determined to repaint this machine, maybe you might review Jerry Nelson's 2-part water based paints.

http://www.nelsonhobby.com/paint.html

Agreed that Form. U was some bad stuff.

Thanks for all your advice and wisdom. Now it is a choice between Brodak and Sig. I will try to stay away from Aero Gloss as they are starting to reduce their variety. I plan on brushing the dope on after I clean the surfaces, so I do not care if it is available in spray can or not and I do not have a ventilated area in my home to set up a spray booth. The odor from brushed on paint is so strong I can only paint with the windows open and a fan blowing. That limits my painting season here in Minnesota to about 5 or 6 months (when I should be flying). The rest of the year is construction weather. Have you had any experiences with these dopes (as far as I know they are both dopes). Both are available by mail order but Brodak is not available in the stores while SIG is. I heard of some stories about finishes cracking or yellowing with age, but I didn't hear any Brand Names mentioned. Not to belabor the point, but which would you recomend? I think I have used Aero Gloss all my model building life (about 45 years) whenever I painted. I have some experience with SIG and it seems to work OK. Some of the local guys use Brodak but they have spray booths. Any opinion or suggestions would be welcome.