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Building Tips and technical articles. => Paint and finishing => Topic started by: Bootlegger on February 11, 2013, 09:56:43 AM
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Does anyone make polycrylic in an alcohol base? All I have seen is water based and I don't need to warp the balsa
when I use it.
Also can you use model dope over the alcohol based polycrylic?
Thanks,
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As far as I know "Polycrylic" is a brand name of a specific acrylic varnish made by Minwax. So there'll only be alcohol-based stuff if they decide to make it.
Don't let that keep you from searching for what you want, though. Just try to find the right generic name, and search on that.
I've done four planes now using Polycrylic as a base, and I've only had warping problems on one of them. They're all profiles, two of them hollow. None of the problems were with the fuselage.
The problem that I did have was with the most recent, a Fancherized Twister, where I got really enthusiastic about not getting any gaps in the center sheeting on the wing. Basically made it over sized and crammed it on while gluing it up, and compounded my error by not gluing it firmly to the ribs. As soon as I hit it with the Polycrylic, it swelled up. But, given what I saw when I tore it up and re-glued it, I'm not sure that it wouldn't have warped up on the first really humid day, even with a dope finish. Given my three successes so far, I think my one failure can be traced back mostly to the assembly.
I avoid dope first because I don't want have to manage the whole issue of toxic, flammable vapors coming off of my building project. I'm using Polycrylic second because I can waltz into Home Depot and get my painting materials rather than having to mail order them and spend a lot. It would seem that a paint product that uses any alcohol at all gets you right back to "flammable" and (even with ethanol, to some extent) "toxic", so I'm not sure you're gaining on that issue. Add to that the fact that unless your desired paint is available easily you're back to mail-ordering stuff. All in all, I'm not sure you'll gain much advantage.
And, if I could get dope at Home Depot for the same price as Polycrylic, I think I'd be figuring out how to arrange for better ventilation in my shop, and using that.
But I'm interested in hearing of your experiences!
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Thanks Tim, I am building a wing some what like Tom Dixon's "found foam" method, and used carpenter glue to attach the foam. I don't want to have the balsa curl up, or turn loose.
What method did you use for color, and is it fuel resistant?
I'm thinking about using auto base/clear coat for the color.
Oh, I am going to use poly span instead of silk span for the covering.
Again thanks...
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I use Rustoleum Gloss Protective Enamel in non-metallic colors. Based on things I've read here and my own experiences, you want to get exactly that -- flat colors, "Painter's Touch", metallics, etc., are all susceptible to fuel. Gloss Protective Enamel (both spray-bomb and brushed-on) aren't.
Pretty much every finishing decision I make these days is based on the principle that I'm going to crash it anyway, so why waste money on good materials? At some point my flying is going to get nicer, and I'll have to start paying for dope.
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and you know polycrylic's not fuel proof right?
I'm seeing some effects from this. If you just drive a screw through the paint, or otherwise violate the integrity of the top coat, and if this is done anywhere close to the engine or fuel tank, then expect to see signs extending up to several inches away that the Polycrylic is reacting to the fuel.
To date I've been solving this by the simple expedient of crashing my planes before it becomes an issue. Now that I'm crashing less, it'll start being a problem.
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Contact Randy Powell or Mark Scarborough who are this forum. You might check the thread at the head of this section by Randy Ryan.
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I have no idea how to color Polycrylic. I suppose you could use regular toners since they are largely inert and will mix with most anything. Mark S may know.
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I would consider any tinting of Polycrylic to be highly experimental.
There's a whole bunch of fine acrylic paints that are intended to be mixed. Were I going to experiment I think I'd want to start with one of those product lines rather than Polycrylic, which is marketed as a water-based varnish.
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FWIW, "Shellac" uses alcohol as a solvent. I seem to recall being told that the rest is some sort of powdered beetle shell, but don't take that to the bank! It is not real popular these days, but for centuries, it was the standard first few coats of stuff applied to raw wood surfaces, and most paints went over it just fine. That said, I would also suggest TEST PANELS! Also, I'm not at all convinced that alcohol would not attack polystyrene foam, not having tested the two. D>K Steve
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Steve! What did you do with yourself before you got married?
Trust me -- I've done the ethanol in styrofoam experiment many times, with various mixers.
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Nelson water based polyurethanes hold up well. It seems like were all in search of the ideal home center solution. I use Nelson paints with 45% nitro and no problems. It cost a bit but it works and it takes all the guess work out of the equation. The Nelson colors match Monokote better than any paints I've ever used. I'm not a big fan of the primer, but I've used it and it's thinned with alcohol. It's a water based epoxy. It sands beautifully. The clear is used extensively with the r/c crowd on foam and top coated in gloss clear or flat. This paint takes a bit of practice if being brushed but my results look excellent. I use a sponge brush and this paint will go a long way. Key points with any painting project and especially with a water based product is not to touch the surface due to oil contamination from your hands. Washing the brush out with soapy water is not recommended in my opinion as well if you decide to reuse. The soap which will not fully be removed from the sponge will further run problems due to the soap reducing the surface tension of water. I know it's convenient to use what's in the home center, but I know when I do my projects, the last thing I want to do is redo them. I prefer the nitrate as a base coat due to the same reasons as explained above as I don't want it to warp smaller thinner wood surfaces. Nelson paints won't work effectively with gray spray primers from auto centers. They also don't work well with butyrate dopes. Ken