Painting Equipment

(splatting this across multiple groups in hopes of finding someone who knows)
The Problem:
I want to set up a small paint booth for painting model airplanes. I'm
cheap, so I want to start collecting equipment for it bit by bit as it comes up for sale on Craigslist &c.
This will be for model airplanes, so the actual spraying will be far more intermittent than for (say) a car -- in fact, the worst-case painting job would be if a fender from a car project accidentally found it's way into the booth along with some primer (I dunno how _that_ would happen :-).
I used to work at a shop with a paint booth, so I know all the procedures. But I was just a peon, and it was a long time ago, so what I _don't_ know are things like what capacity compressor do I need, do I really need an HVLP gun, what sort of exhaust fan is recommended, etc.
Currently I'm only planning on using airplane dope, which is basically butyrate lacquer that's formulated to stay flexible so it won't crack when it's painted on fabric. I may eventually branch out to multi-part paints, but I doubt it -- I really like dope finishes, and I don't like the amount of hassle necessary to dodge toxicity with the fancier stuff.
I'm thinking that I want to get an automotive touch-up gun (a regular- size automotive gun is way bigger than necessary). But what capacity compressor? It's looking more and more like I need something significantly bigger than what you get to go with an air nailer -- is this correct? Do I want to look for anything special (beyond explosion proof) in an exhaust fan (I have a room in mind, and am planning on just poking a hole in the wall for the fan)?
Thanks.
--
www.wescottdesign.com

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Depending on the size of your models, would an airbrush make more sense?
--
Cats, coffee, chocolate...vices to live by

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On Wed, 11 Nov 2009 12:19:24 -0500, Ecnerwal wrote:

Too small. Didn't make that clear -- think 30 to 80 inch wingspan.
--
www.wescottdesign.com

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wrote:

My favorite spray paint guns....
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber† http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumberf871
At least for smaller stuff. Smaller than a VW or Bridgeport.......
Gunner
"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster
Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton
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Tim Wescott has an excellent solution. I do plastic models. For flying models you will need a larger paint booth. Make one yourself with a large cardboard box. Use a downdraft design. Mine has an 8 inch box fan from a heavy iron computer. The fan is mounted on the table top of a cabinet made from a heavy iron computer stand (printer 40 lbs weight!) The air is drawn downwards into an enclosed chamber formed by the printer stand's legs. The air is exhausted through two furnace filters. When the cardboard box is messed up just put on a new box, any suitable size, with a hole cut for the fan.
If you have the space and don't mind the noise get a contractor's compressor of at least 5 hp. I really love the air tools as they are so much lighter, easier to use, more versatile and cheaper. You can also use it to spray paint too.
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Is the air filtered before entering the chamber as well?
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Well, it should be filtered both ways. 'In' to the chamber for the ultimate finish without any dust in it, and the 'out' filters are paint pads to keep the paint out of the fan blades, but - Go look at the paint booth at an auto body shop, study the details, and you start to understand the scope of the problem...
I would just rig a simple "open" booth to catch the overspray, and don't worry too much about dust. Because a closed booth gets complex and expensive real fast. If you are going to have a person step inside an isolated room and spray around volatiile materials (ranging from flammable to explosive when atomized during application) you HAVE to follow the same safety design constraints.
It has to be non-combustible construction in case of a flash fire, and not easily collapsed on top of the painter and work by the pressure wave, so a lot of temporary methods like draped visqueen plastic over furring strips is OUT. You need a way out, you need explsion-proof lighting (or the fixture outside the room shining in through a sealed window), you need to design against static buildup that could ignite the fumes...
You could build a little paint booth at home, but the project would eclipse the model you are painting. It would work with a freestanding sturdy frame of 2X4 studs with light sheet-metal screwed on the inside, and a Lexan window on top for the outside light fiixture. Prehung house door or two for egress hung opening out, and ball-spring latches only so they can pop open to release the blast overpressure.
You need pro-grade fire extinguishers ready at hand, strategically placed, and enough of them to handle the volume of materials. And a garden hose in case that still isn't enough.
Your exhaust fan motors have to be outside the airstream, and make sure the static can drain from the blower wheel/blade. And ground the sheet-metal walls, and the hook or table the work sits on, and make sure static can drain away from the paint gun...
If you spray two-part catalyzed paint, you have to use real non- combustible paint pads on the exhaust system. (Not just furnace filters.) These paints get hot as they cure, and you don't want your paint booth to spontaneously combust on you.
And no spraying any exotic aircraft paints with nasty solvents that'll kill you (like DuPont Imron) inside any booth without a full postive pressure respirator rig. Bought, not cobbled together - there are places to scrimp, this isn't one of them.
--<< Bruce >>--
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Very good information, you are knowledgeable and safety minded! I think I'll just spray in the open and put up with the dust because all that trouble is bull shit. Thanks Bruce, MK
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Experts probably have a better solution, but here's what I used for painting...um...maybe 30 Pinewood Derby racers.
My spray rigs were two airbrushes -- a cheap Badger "spray can" for laying on primers, and a double-action Badger airbrush for finishes. I sprayed inside of a cardboard box about 2 feet on a side, with big windows made of Saran wrap taped to the sides. These were for shining a couple of desk lamps into the box, and for viewing the inside. I used Saran wrap because the paint makes a mess of them pretty quickly. Keep the roll of Saran and the masking tape handy to replace them.
I sprayed the inside of the box with two coats of lacquer to settle the dust. Then I took an old hair dryer, the kind with a separate hose, and stuck the hose through a hole in the box to keep a positive pressure inside the box. I taped an air-conditioner filter over the hair dryer's intake.
Cut two holes in the box for your hands, and tape two oversize rubber gloves to the holes. I used some orange ones I got from Home Depot, extra-large so I could get my hands into them.
I was going for cheap and effective, rather than efficient. <g> It worked great; I completely eliminated dust motes in the paint, although you have to run it a few times to work the dust out of the dryer, etc. I still use it from time to time. It's gotten as stiff as plywood from all the paint. I've had to replace the rubber gloves when they got too stiff.
You wind up with some paint spray leaking out with this setup, so I lay out a lot of newspaper around it. But if you just let in enough air from the blower to barely keep the pressure positive, it won't blow around too badly.
Oh, regarding going cheap -- I use a spare tire with the Badger "Propel" valve for painting indoors. I fill the tire periodically with my portable compressor. It doesn't get much cheaper than that.
--
Ed Huntress



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Make your own compressor and set up paint booth as described above : refer sub section: Airbrush tips and techniques etc
which includes amongst other items:
Airbrush Pressure - How much is required Airbrush talk, art, painting, illustration, auto graphics, crafts Airbrushing Tips - Golden. Buying and Using an Airbrush Compressor for airbrush - How to DIY ex fridge #1 Compressor for airbrush - How to DIY ex fridge #2 Compressor for airbrush - How to DIY ex fridge #3 at Alan's Hobby, Model & RC FAQ Web Links http://homepages.ihug.co.nz/~atong /
regards Alan T.

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If you are using AC powered fans, compressors, lights etc. you'll have to work to code (electrical, health and mechanical).
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N Morrison wrote:

An explosion proof fan motor such as a restaurant grease fan would be nice.
--
Andrew Muzi
<www.yellowjersey.org/>
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Have you considered the Critter spray gun? It's bigger than an air brush and works just fine on my intermediate size projects. Clean up is a snap and, as it uses mason jars for the paint pot, saving left over paint is easy. Amazon has them for $40 w/ free shipping. Details and review here: http://www.woodcraft.com/Articles/Articles.aspx?articleidi9 Art
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๏ฟฝDo I want to look for anything special (beyond explosion

Tim
Somewhere in my many years I wanted a small spray booth and thought about using a large cardboard box with a 4" dryer hose vented to the outside. I thought that by pushing air into the room it would exhaust through the dryer hose and with it the overspray from the spray gun.
Then I saw a cardboard spray booth advertised somewhere. But at this time I simply did it outside in a open sided shed against a fence. Now I do it when the wind blows out in the backyard.
Harbor Freight sells a nice small spray gun that can be hooked to a compressor. Next time I use mine I will use a short flexible hose with it to avoid the attendant clumsiness of a close attached QC coupler and will attach the hose to a larger airline.
Bob AZ
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Tim... Look up the Krebs cordless sprayer. I found it in a Woodworkers supply catalog. Made in Switzerland. Don't know if it would spray dope or not. Warren
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There are airbrushes and airbrushes. Some are only good for painting hairlines for photo touchup, good ones can have needles and nozzles changed to handle a wide variety of work, the one I'm familiar with is the Paasche VLS. You can get fairly large paint bottles for that and it doesn't cost an arm and a leg. A small compressor will work, the air has to be DRY, so budget for a good water trap or dessicant trap. HF has some suitable compressors, their airbrushes suck, though.
If you go with a car touchup gun, that'll take 3-5 cu ft/min or so, that's about the tops that a 115 compressor can do. The touchup guns will handle maybe 3' square surfaces, they don't spray a very wide pattern. A $10 one from HF will do for shellac and varnish, what I mostly use them for.
Stan
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Tim,
I have had good luck with tools from Harbor Freight http://www.harborfreight.com . I use their #94734 air compressor ($139.99) 5.0 CFPM@40PSI with their 86-7VGA Detail spray gun (13.99). I have painted several models and 2 pair of car bumper covers with this equipment and have no complaints. I use automotive acrylic paint obtained free as leftovers from a local body shop and I use clear water based polyurethane as a clear coat because it has proven to be fairly fuel proof. On my electric models I use automotive clear coat which works well. If I had it to do over and could afford it, I would go with a 2 stage air compressor like #99918 ($1799.99) 18.7 SFCM@100 PSI with a HVLP detail gun #45001 ($23.47). I have used an HVLP set up and prefer it, but the cost, is prohibitive.
I do not have a spray room for painting - I use my car port. Because the automotive paints dry very quickly, I have had few problems with dust settling on the finish. The few times it has happened, I have sanded the blemishes out with 1000 grit paper and then put on the clear coat. When the clear coat has been damaged, I have found that sanding and polishing works well to remove any blemishes.
Randy

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Tim,
I also use a cheap Harbor Freight air brush for spraying trim colors, though I do have to be careful to mask off ALL areas I don't want overspray on. FWIW, I have also used this compressor with a paint tank and different gun to paint a house and I use it with a brad nailer in my cabinet work. A Harbor Freight staple gun has also been very helpful when I did some upholstery work.
Randy

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