HVLP turbine setups are fine. most woodworking shops don't use them and instead rely on compressed air. i'm a cabinetmaker. i don't know what luthiers use but would imagine the more inexpensive small touch up guns would have plenty of fan for a ukulele. even large shops have gone away from compressed air HVLP guns connected to 2 gallon paint pots and instead use the gravity cup HVLPs auto painters use. SATA is great, i use iwata. the new set ups use shockingly small amounts of air and can be powered by a hundred buck porter cable compressor, hopefully set up with a filtration unit.
as good as the SATA &c stuff is i'm sure with investigation you can find a knock off for forty bucks.
The top level turbines are good. The smaller ones are a waste of time. I think the key concepts here are the difference between a finish, and an efficiently applied, high quality finish. It is not about fan size, per se, overall control of the volume of fluid, being able to deliver the volume you want, and proper atomization of this fluid is more where it is at, IMO. I do not want to be waiting around for the fan to put some finish on the surface. I want to move very quickly, and know that the surface is wet. A small touch up gun is totally inefficient for finishing ukes, though, arguably, it would work. If one wanted to, an airbrush could successfully be used to spray finish on an uke. The problem is in getting a nice sumptuous wet coat that flows well together all over the instrument. With a small gun, and an uke, say it takes 6 passes or maybe more to really wet one side of the instrument. ( I have seen exactly this scenario with a nice new Graco HVLP Gravity cup, fluid needle pulled well out, it was a smaller one) With a full sized, professional gun, with the fluid turned up, that same side could be sprayed (without control) in one pass, to sagging if you wanted. Turn down the fluid a little, or just don't squeeze the trigger quite as deep, and the side can be comfortably fully wetted in 3 easy passes, and maybe a couple blips on the triggger at the top or maybe the bottom of the instrument, depending on what your spray sequence is.
My introduction to Cardinal lacquer ( I have sprayed, literally, thousands of gallons of lacquer, and numerous different brands) was only recently, and on a small gravity cup HVLP, made by Graco. It was a smaller gun, that was purchased to be efficient on air, and run on a small compressor. This is a new gun, and nice. Even with the fluid needle turned way out, it just wouldnt let out enough lacquer to move as fast as I wanted to, as fast as I needed to to get a really nice wet flow. I was super pleased with the Cardinal lacquer, but it did not lay out like I wanted that time. ( it was the gun) For the situation, that gun works. The lacquer needs to be thinned when spraying through it. Next time was on my gun, 3 casual passes and the side was fully wet, continuing on it was easy to fully wet the surface, and by the time I made it back to the starting point, it was still wet and flowing well. ( Cardinal lacquer is possibly my favorite ever, I love how it feels) If it takes too long to make it around the instrument, by the time you meet your starting point, the lacquer does not flow all glassy back into itself, requiring more sanding where the little lacquer droplets sit on the surface of the already curing lacquer like the drips when you are at the beach building sand drip castles. Also likely, it does not put on enough finish overall, requiring more coats, more possibility of holidays, or thin spots. I want to see some finish going on when I make a pass. Touch up guns are meant for precise application, and feathering in to 'touch up'. They do work well for some small uses, or maybe dyes, other detail purposes, but for general spraying, they are inappropriate. That little Graco gun could be set up with a larger fluid tip, and needle, might need a larger air cap then, also, but then it would need more air from the compressor that powered it.
I have met many cabinet makers who do their own finishing. I have met very few who do not suffer their own finishing, and I have met none yet, who can come anywhere near the efficiency and quality of a professional finisher. Most can end up with a passable finish, IMO. Most cabinet makers I have seen only finish their own work. Spraying is a skill that will continue to deepen after many years. After you have sprayed 50,000 gallons, or lots more, of various finishes, that little gun probably won't seem so adequate anymore.
And again, sure, it is just a little uke, but... you will get a better finish if you can get the fluid on the thing more quickly, and correctly atomized. I like the fan set up to spray fast, and as much fluid as possible without being so fast as to make holidays more likely ( from being too cautious about runs, the gun set too fast)
For cabinet work, in homes, and anywhere where there are large surfaces to cover, I will choose the 2 gallon pot with an HVLP gun. It can be set to spray almost as fast as an airless, but with more fluid control. Having to stop and refill the cup all the time is slow, tedious, and inefficient. As well, the cup setup is more tiring, and cumbersome. Gravity cup HVLPs are efficient, and do a nice job. I cannot imagine any large shop ( someone who is spraying woodwork or cabinetry, all day, every day) using a cup. That is a waste of time on numerous levels. Spraying a car is a different story, a few cups filled will cover the whole car, and breaking the job into panels, clean breaks like doors, hoods, etc, this works fine. High quality gravity cups atomize well, and a re a little safer than a pot, as far as fine finishing goes ( not a problem with wood finishing) The main reason for the HVLP high efficiency guns is to comply with low VOC regulations, though the nice ones are excellent tools.
Sorry, but I have to pretty much totally disagree with what you just said, except that the new guns are nice. I would, however, be very surprised if I would be happy spraying lacquer on any air powered gun powered by a hundred dollar Porter Cable compressor. I have one of those compresssors, I use it for my pressure pot when connected to my HVLP turbine setup. Small and tidy. I have used a larger contractor ($500) Porter Cable compressor ( extensively) for running a spray gun, and it runs non-stop while spraying. For an uke, I guess this is no problem. That same compressor will not run a sander for more than a minute or so..
You do mention filtration, that is important, and not mentioned previously. My shop air is all clean, goes through a Sharpe air conditioner system. On the cheap, you can run straight off the compressor, into a vertical metal pipe of a large diameter, maybe 2". let the air come in about 2' from the bottom of the pipe, put a 1/4 turn drain valve at the bottom of the tube for draining the collected water and contaminants, and the clean air comes from the top of the pipe. The metal pipe is important, as it encourages condensation, and the larger diameter slows the air velocity, giving more chance for things to fall out of the air stream. Small inline air filters that screw to the base of the gun can be purchased from auto paint suppliers, and paint stores that cater to professionals, for about $10, and act as final insurance that air borne contaminents from the gun do not spoil the finish, unless you have untidy gun habits.
A good glassy finish right out of the gun relies on getting the fluid to the surface quickly and well atomized. Lots of it...
I have sprayed with some of those $40 knock offs, I wouldn't even take one for free.
In learning to spray, go learn from a professional finisher, like an autobody guy that has been doing it for their whole life, or a professional lacquer finisher. There are many ways to skin a cat, and some work much better than others....
lol
