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.
--
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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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On Fri, 20 Nov 2009 08:45:32 -0800, Bruce L. Bergman

Good advice, Bruce. Painting, especially with today's paints can be VERY dangerous. It can also be illegal so my advice would be to check with the local authorities as to what you are allowed to do. In Californicate that would be very little without professional equipment and all kinds of permits.
I've been off the group for a while. Got tired of all the political crap. Doesn't look like much has changed. How are things with you?
Jim Chandler
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Ferchrissakes, a good disposable overall, gloves and the correct filter cartridges will cope with Isocyanate catalysed paints. I've only sprayed a couple of gallons of the stuff over the last few weekends and I haven't died yet.
PS positive pressure masks are banned in some parts of the world, because you can't guarantee there will be no recirculation. Go figure.
Mark Rand RTFM
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On Sat, 21 Nov 2009 01:22:51 +0000, Mark Rand

Selective corner-cutting is encouraged in r.c.metalworking - but you have to understand the problem before you go 'Off the reservation' for a lower cost solution. You look at what is required for a commercial operation, then you find a way to do the same thing without spending a bundle doing it.
Like the lights - If you put a cheap sheet of polycarbonate plastic or laminated glass, you don't need an explosion-proof light fixture.
The booth doesn't have to be all metal - it just has to be non combustible enough to not catch fire easily, and fairly sturdy so a flash fire from the solvents doesn't collapse it on top of you. Other than that, feel free to improvise.
It could be a permnanently built room on a house or garage, with drywall walls - but you have to provide a blowout panel or two in case you get that flash fire. Removing the door striker and using a simple ball catch lets it pop open.
And you always work with the EXIT door to your back so you have a clear egress path - you don't want to go through the fire to get out, that's bad form.

Yes, and I know a finish carpenter who used to make big bucks painting airplanes. And those exotic paints screwed him up something bad, even with a respirator - he has hand tremors that were funny when Don Knots filmed "The Shakiest Gun In The West" but aren't fun at all when you have to live with them the rest of your life.
He had to walk away from the paint booth and develop a totally different craft. Luckily the tremors don't keep him from doing a great job at finish carpentry.

They can make the perfect safety system. But if it's implemented and used by a moron who puts the pump (and it's fresh air intake) inside a cloud of the compromised atmosphere...
Think first about what you are doing and WHY you are doing it, and you won't make stupid mistakes like that. If nothing else, you read down the checklist in the instructions for the PPV Pump every time you set it up. And when they get to the line about "Make sure to position the unit well away from the exhaust outlet of the spray booth"...
And it's a lot easier to ban something than try to legislate that all workers have to use their brain and follow the instructions.
--<< 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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wrote:

If you're not fussy about finish quality, a cheap import jamb gun will suffice. If you want consistently excellent results, go with Binks, DeVilbiss or Sharpe. Sharpe's D-5-55 detail gun takes about 4.1 SCFM. They also offer a mini-gravity feed HVLP, the MGF. It takes 2.9 SCFM.
Your vent fan should probably be capable of at least 2000 CFM.
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On Wed, 11 Nov 2009 16:22:15 -0600, Don Foreman wrote:

Jamb gun = detail gun?
That's an expensive gun, I'd have to save my pennies for a lot longer to get it than to get the Sears detail gun (which is, I assume, a cheap import). You're telling me I really need to spend the bucks, right?
--
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wrote:

Not necessarily. I'd say try one of the cheap ones first. They're so cheap they can be regarded as disposable, and you just might find one "good enough" for your jobs and materials. Harbor Freight (and others) sell a knockoff of the Binks detail gun for about $20. I've used it for lots of ho-hum little jobs like bicycles. I reserved the Sharpe for base-clear jobs on automobiles where the paint costs north of $100/gallon. I also have one of the HF gravity feed HVLP guns that go at various sale prices. It works quite well with thinner material like lacquer ... and probably airplane dope.
BTW, the prices I saw on Sharpe were jaw-dropping. I didn't pay 1/4 of that 15 years ago. A local supplier of auto body supplies sharply discounts Sharpe around June when the Vo-Tech students graduate, so that's when I bought.
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Tim Wescott wrote:

For what your looking for you could use a small HVLP touch up gun. You can get them with small paint cups. For the booth itself it depends on if you want a permanent item or a temporary one. Since I doubt you will be painting I would build a temporary unit out of cellotex style foam. Make a simple frame of wood and attach the foam to it. Hinge the sections and you could make it fold flat. For the vent unit you don't need something exotic. You want a fan that moves the air well. To keep crud out you can use furnace type filters set into the foam walls. Light can be had from a couple fluorescents in the corners. Compressor would be a decent 3-4 HP unit with a 20-30 gallon tank. (larger tank is better but not really needed). Oil free would be good BUT they are usually very loud. Oil bath types are generally quieter BUT you MUST install a filter to keep any oil/moisture out of the line.
You will also want an airbrush, they work great for wheel pants, decal setting solution, and doing detail painting.
--
Steve W.

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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.
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Andrew Muzi
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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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