low cfm HVLP sprayers?


     Most of the talk about HVLP that work with smaller compressors points to Harbour freight. But they don't exist up here. Any chance any of the branded products might work with a 4.5 cfm 40 psi compressor? I've seen some talk about a Porter Cable unit but it offically requires 8 cfm.
A local place called Princess Auto sells a couple of guns that sound interesting. One claims 3.5 cfm average 13.9 continous. Does that really mean it's a 13.9 gun ? With 3.5cfm only if it's turned off 75% of the time? The second gun claims 6 to 8 cfm. The discussion in the archives is that it's possible to get by with less then the stated air requirements. Anybody think that's nuts?
FWIW I'd like to spray shellac and enamel. If it handled Latex so much the better but it's not a big issue. Usually nothing bigger then a bookcase. Not very often either.
Thanks Nick
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Hi Nick, Your 4.5 cfm compressor has what duty cycle? Unless it is a very expensive one it probably has a D/C of 50% or less which means you should only run it at about 2.2CFM for extended periods. How large is the tank? How much can you spray before the compressor comes on? The CFM of guns are likely optimistic. Use the high end of the range. If you cannot keep a wet edge when spraying (because you have to wait for air) you can create a real mess. And varying air pressure will give you an interesting effect too. If you go to the Canadian Woodworking Magazine forum and ask you will find some guys that have experience with the guns you mentioned. IIHO you are not likely to be very happy using a small compressor. YMMV, JG
Nick Zentena wrote:

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It's an eight gallon tank. Not sure about the duty cycle but I'll check the manual. The way I understand it is something like this:
With a small piece you can stop the gun every so often and let the machine catch up. So hopefully with something small like a bookcase it might be okay. A car wouldn't work-)
I'll surf over to the magazine forum.
Thanks Nick
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8 gallons is approx 1 cu. ft. at 40 psi, it will hold the equivalent of 2-2/3 cu ft _at_atmospheric_pressure_.

with a 8 gal. tank that will be _really_ often.
How long does it take the compressor to fill the tank to the point of shutting off, *STARTING*FROM* zero pressure? This will tell you what the 'actual' capacity of the compressor is.
for the sake of argument, let's say it take about 3 minutes. This works out to roughly 1 cu. ft. /min at atmospheric pressure.
lets assume you have found a gun that needs5 only 5 cu.ft/min at atmospheric pressure. the entire capacity of your tank gives you about 30 seconds of spray time. In which period, the compressor has been able to provide another 1/2 cu. ft. worth. so you get a grand total of 36 seconds of spraying time. Now wait 3 minutes for the compressor to recharge the tank, and you can spray for another 36 seconds. WOOPS! forgot about the 50% duty cycle. make that 3 minutes for the compressor to recharge the tank, and another 3-1/2 minutes for the compressor to 'cool off'. or roughly 36 seconds of painting, every 7 minutes.
But wait, it gets worse. the HVLP gun probably specs it's air requirements at something _above_ 'atmospheric pressure'. If it needs air at a mere 15psi, cut the 'painting' time to somewhat less than half the number above. You'll get about 17 seconds of painting time, and then have to wait the same 6-1/2+ minutes before you can paint for another 17 seconds.
If the specified air requirements are at a higher pressure, things get EVEN WORSE.
Not to mention what happens if it takes _more_ than 3 minutes to fully charge the tank.

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The short answer is that your compressor is not suitable for spray painting.

True - it would not work on a car. It may not work on a small piece either. Painting depends upon a lot of variables that your posts indicate you are trying to overlook in the interest of summing a complex issue up into a simple statement. I understand that - it's sort of the nature of trying to get your hands around something. So - while there are things I would try to shoot with your compressor, given the right gun, the right paint, the right weather conditions, etc., it is simply safer to sum it up and say that you don't have enough compressor.
It would also be safe to say that I would only hook a gun to your compressor as an act of desperation. I'm not trying to be critical with that statement, I'm trying to give you an honest answer. Do yourself a favor if you're looking to get into spray painting and invest in the equipment that will do the job. You'll be so much happier if you do.
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You have to be careful with the archives and read them for what they say Nick. The discusssions in the archives speak with some very specific context. Do I think it's nuts that one can shoot with less than the high rated CFM? No. I paint a lot and I know that it can be done, but as has been pointed out, that depends upon a number of variables as indicated in the fullness of the archive discussions.
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Rockler has a low pressure HLVP sprayer on sale now for 79.99.
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HLVP?? I'm guessing that's a misprint. Wood mag. reviewed the Rockler unit. Didn't give it high marks. I've been pleased with plenty of Rockler merchandise but I don't think this one will make it.
Max
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Bought one day before yesterday. Sprayed to rooms with it so far.

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Ya know, as much as I've sprayed I just can't imagine spraying the inside of a house. Just don't seem right. So, tell me - how did it come out? How about such things as the amount of prep-time before spaying and the amount of clean up time after, compared to rolling and cutting in with a brush. How much spray filled the room while you were spraying? Feel free to add comments.
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Popcorn ceiling. Sprayer is the best way to deal with that. Roller and pad for the rest of the room. With the HVLP, not much paint mist or overspray. Covered carpets in plastic, lights in plastic bag. Worked well.

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D'OH!!!! (smacking self squarely upon forehead with heel of hand...). Of course. Had it stuck in my mind for some dumb reason that you meant you sprayed the entire room. Sometimes the mind seems to get stuck between gears somewhere...
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Logical assumption as I didn't specify.

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