Spray Painting Technique

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Spray Painting Technique

Postby bluemax » Fri Jun 05, 2015 12:00 pm

I am looking for opinions on how others have dealt with a painting concern I am about to describe. When painting a very large area, like an entire fuselage, what technique is used to cover the whole thing in one session, without spraying next to an area that has dried? I hoping I am stating that correctly. When you make a pass with a spray gun, that paint will stay wet for a period of time, but what if you can't paint quickly enough? Do you paint it from one end to the other, rotating the fuselage as you go, like you were painting a barber pole? Has anyone ever painted their entire fuselage in one go, or do most folks just mask it off and paint in sections? I know the solution is easier when more than one color is used, but what if it's all one color? I know that a slower thinner will increase the "wet" time, but it also increases the likelyhood of runs.. . . don't ask me how I know.

This was not a concern on the other two planes I have painted, as they had lots of trim lines where I could control the size of a painted area. I just don't an area dry prematurely, while I am coming back around to shoot the bare area adjacent to it. Do you just learn how to paint fast?

Incidentally, I am not a big fan of HVLP. I have a Citation 3-stage turbine and a Lexaire bottom feed gun. Although it has less overspray than a conventional sprayer, it does not atomize the paint as well. I prefer the results obtained with a conventional gun, even though it uses more paint, more overspray, and more precautions with the compressor. I think my HVLP is somewhere around 3 psi, and over 100 CFM, where a compressor gun is more like 30 to 50 psi, and only 4 to 6 CFM. A lot of folks call there equipment HVLP when it is not. If you're not using a turbine, it is not HVLP.
Max Rentz
Newark, Ohio

Highlander Extreme # 257
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Re: Spray Painting Technique

Postby SuperFly » Fri Jun 05, 2015 9:42 pm

Max,

I am by absolutely NO means an expert on painting. But I have a Axis Citation 3 Stage HVLP system, and have managed to paint my airplane with it. I can tell you, first, with the Lexaire gun, buy yourself a garden hose 1/4 turn inline valve. Available at any hardware store or DIY center.

http://www.aquabarrel.com/store/index.p ... cts_id=167

Install it between the main hose and the gun whip so that it hangs next to your belt clip. You can then adjust the air flow with that valve. No one told me that initially, so I made a mess. The 3M gun I had had an air valve built into it, Lexaire does not. Learned that one the hard way.

Also,if you have the 1.2 nozzle and needle set in your gun, turn the needle all the way in, and back it out about 1 1/4 turns. That is about where I have found the best results. The air valve above is about 1/3 open.

You also should thin the paint more than the compressor guys do. I am spraying Poly Fiber Aerothane paint, and it recommends 3:1 catalyzed paint to reducer. I have been advised that I can thin up to 3:2 if it is hot(by Poly Fiber themselves). I am usually less than that, but certainly over the 3:1. You have to watch for runs, as the paint is pretty wet. The turbines send warm air to the gun as it is compressed directly. Air compressors send cold air (high pressure to low pressure = absorb heat) to the gun. The warm air from a turbine tends to cause the paint to start to dry faster since its warm. Thus thinner paint is ideal.

I have figured out that when the manual says (poly fiber, others certainly vary with mfg) spray thin, they mean THIN. As I spray my first coat, it doesnt even come close to covering. But it does flow out and cover. I wait an hour, and do it again. They melt together just fine. Even several hours later. I have waited 4 hours between coats, and they melt together just fine. So now that I have made this short answer very long, yes, I sprayed the entire fuselage at once. And each wing entirely at once. Cutting it into parts will give you a hard edge that can be very difficult to deal with. If you are doing multiple colors, you could do it that way, but even then, they recommend spraying the base color, then the next day mask and spray the other colors, and pull the mask after a few hours so that hard edge will soften naturally.

Also, turning down the air will dramatically reduce the over spray. It doesn't go away, but it helps alot.

I am sure you knew a lot of this, but just wanted to share what I have learned... mostly the hard way.
Best,
Ben Schneider
Highlander #263 converted to SuperSTOL
N45FT Now Flying!
http://www.stolairplane.com
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