Quick Finish for Balsa for Sport Panes

LAST EDITED ON Aug-12-02 AT 07:55 PM (CDT)

LAST EDITED ON Aug-12-02 AT 07:34 PM (CDT)
What's a Quick Tough Finish for Sport Planes?

I am recently returned to the CL fun. The change in available materials has caused me to rethink finishing techniques for fun fly and (gee I wish they didn't) crash models.

Twenty five years ago I did quick finishes on profile balsa with finishing resin (one coat after smooth sanding and tack cloth) and one coat of hobby poxy brushed straight after the mix of A and B. The wings monokoted on bare wood. The finish was smooth and slick and impervious. As many of you know Hobby Poxy is long gone. (I called Petit Paints and the testy technician made it clear that they were out of the Model Airplane Business for good. ) The resin filled the balsa and also made for a strong center stick. (My Buster built back then, which I am flying these days, has been nosed in at speed many a time and patched and flown again... I think the Philly Flyer are sick of looking at its multi-hued covering.) Never a fuselage crack. I got hep to resin years ago when a I tried to hammer a mark into a bit of resin set up in a paper cup. Forget it. Never a dent. The traditional guys in the club led me to try dope again. Friday and Saturday I must have put on 15 coats filling the grain (sanding with 400 between applications) of a Flite Streak. I just used clear and realize talc probably would have done the job more efficiently. Three coats of color on top of that made a shiny surface, so I thought OK, but next to the old Buster things looked somewhat different. The grain of the Buster was actually more slickly filled with the one coat of resin and one of Hobby Poxy and nothing eats into Hobby Poxy.

The traditionalists in the our club who use dope usually cover everything with silkspan, now, yeah, that looks great, but it ain't quick and takes a lot of building skill. (Which I'm willing to work on). So what to do now that is quick and dirty and strong, impervious to fuels, and looks good.

What do you guys do out there do now to finish knock around models without much hassle. I am looking for a finish with the structural strength and durability of resin and Hobby Poxy. Balsa's still king for me, I just love the aesthetics of these structures, so at least here I am not asking about foamies.

You can get Z-Poxy finishing epoxy for your base coat, and it will be about as good as the old Polyester stuff (which you can also still get at auto supply stores for fiberglass work).

I then use Nitrate Dopes from Aerodyne, or Floquil colors for my color coats, and then a sprayed coat of clear epoxy over-all.

The top coat epoxy I have been trying out isn't quite as forgiving as Hobbypoxy was, but works. It is the stuff they use for decopage, table surfacing, and other thick, clear, tough work. It can be thinned with alcohol or dope thinner! Or, you can get epoxy thinner in the section of the paint store that deals with epoxy recoating showers and bathtubs. Thin it only enough to spray well.

The problems I have had were when I got too eager on the topcoat, and it would fish-eye. Put it on really light, let it flash-off, and then a second light coat to let it flow out. Nothing more, or it will start crawling around rather than leveling.

Any chemists out there know what to add to epoxy to get it to level out like the good old stuff?

Some might cringe, but here it goes.
1 sand it good.
2 some sort of plastic film on the wings.
3 light 'glass and thinned epoxy on fuse.
4 one coat of auto high build primer.
5 sand.
6 Paint with thinned Rust-oleum (with mineral spirits).
7 sand.
8 Finish coat.
9 Done.

The 1/2 ounce glass cloth works well with either dope and talc or finishing resin/Z-poxy. Fills fast and sands out slick. Then Rustoleum. Or I am about to try Dupli-color rattle cans from Wla-Mart.

Keep it going. Great. Is that thinned rustoleum brushed on? Can it be sprayed in the usual way? Is Z-Poxy model airplane stuff or a civilian commercial product. Is it strong like polyester resin or more a base coat filler?

I recently read on a can of Sig polyester resin that after a coat of automotive primer, dope can be applied. Anyone try that? I like the idea of a thinned clear epoxy top coat or two, after the dope. That's the spirit. A finish you can abuse at the field (for years) and wash off when you get to it, let's say Wednesday after the weekend fly and doink sessions.

Thanks to all.

D.

Z-Poxy is model stuff, should be easily ordered if your LHS doesn't have it.

The thined Rustoleum is the stuff in the 1/2 pint and quart cans. I use a automotive style touch up gun to apply the stuff. Although I am going to try a HVLP gun. Good luck to you. Let us know what you do on your plane and how it turns out? OK? Steve D.

You might look into Minwax Polycrylic. Brush and sand a couple of coats, then paint. It's water cleanup, no smell, dries overnight. I just had a trim tab to seal, so it was perfect, and I used an acid brush (aka epoxy brush). A quick rinse under the faucet with no detergent made the brush like new the next day. It is not supposed to be fuelproof, but if you can put some polyurethane or spay can Rustoleum over it, it will be good. I would not use anything but Brodak dope over any kind of silk, silkspan, etc. Just a lot easier to repair decently. Steve

Check out www.rccaraction.com/MA/how_to/latex1.asp
Household latex paint. I've tried a couple of samples and plan to use it on my curent profile project. It's very light weight, sands well dry (wet sanding doesn't work!) and when covered with a clear coat is very glossy. I'd like to hear from anyone who has tried it.

LAST EDITED ON Aug-15-02 AT 06:34 PM (CDT)

>(wet sanding doesn't work!) and
>when covered with a clear
>coat is very glossy. I'd
>like to hear from anyone
>who has tried it.

Ron;

Very interesting. I am curious as to what clear coat you used. Also, did you use automotive primer? How did you handle areas like the wing with open bays?

Please, fill us in. Also, if you have any digital pics as to how it came out, I am sure that we would all be interested.

Thanks for pointing out the article.

>Keep it going. Great. Is that
>thinned rustoleum brushed on? Can
>it be sprayed in the
>usual way? Is Z-Poxy model
>airplane stuff or a civilian
>commercial product. Is it strong
>like polyester resin or more
>a base coat filler?

Took me a while to catch up here....Z-poxy is made by the Zap glue people. Available at hobby shops. Hard finish without the stink of fiberglass. I think that a little auto primer and wet sanding gives you a terrific base. Rustoleum rattle cans do fine if the first coat is dusted on and allowed to flash off, followed by a medium coat. The only pain is that it runs pretty easily. Nils uses a heat gun to gently flow runs away.

Regarding latex paints, it is my understanding that Polyurethane goes over everything except latex...it never dries. There are not many thingss that go over Polyurethane, either. Be sure to test the combinations before you commit your model to it. Steve

>Regarding latex paints, it is my
>understanding that Polyurethane goes over
>everything except latex...it never dries.
>There are not many thingss
>that go over Polyurethane, either.
>Be sure to test the
>combinations before you commit your
>model to it. Steve

The MAN article on latex is vague regarding final clear coats, saying "If, however, you are using a glow engine, you’ll need to protect the finish with a clear epoxy or polyurethane top coat after it has dried fully." According to Steve's message you could get into trouble with polyurethanes, which I believe are made in both water-based and solvent-based types. I emailed Roy Vaillancourt, the article's author, for more specifics, such as brand names for final coat products, and will post his reply if/when I receive it.

Hofacker, sounds like you had good results with the clear you used. Can you tell us what it was?

I think for some of us the ultimate goal is water-based and fuelproof all in one can.

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

I use the clear coat with crosslinker & swear by it.
I have used it over Tru-Test Easy Color latex.
You have to let the latex thoroughly dry.