HVLP Paint Sprayer Recommendations

On Thursday, March 15, 2018 at 9:50:15 AM UTC-5, wrote:
Jeff, here are a few tid-bits I have picked up over the years, small compressors that are working hard are going to give you water drops spitting out at the gun. We have had success using a large desiccant dryer in line and a mini desiccant dryer at the gun, but we're using a large compressor with 50 gallon tank. Keep an eye on the balls.........when your blue balls turn red, stop emediatly and let things cool off.......yes, we're still talking about painting! Never spray dope when it's raining......or you will trap "blush" on the surface and it will never go away. I use a cheap HVLP gun from Home Depot and throw it away after a few jobs. If the gun starts spitting, turn the air pressure down..........these guns want no more than 40 psi. Feel free to email me with any issues, may be able to sort things out.
Have fun,
JJ

Thanks, John. First time I've heard that blue balls is a good thing! ;-)

When you say "dope" are you speaking in generalities? I'm using the Poly-Fiber system, and so are the other folks at TSA who are working on recovering/refurbishing gliders. I may experiment with the Stewart System in the future, as I have an ultralight project ongoing, as well.

Also, the compressor we have in our shop/paint booth is a large volume one (stands vertically about 6 feet tall--is that 50 gallons?) While the line has two filters, there are still moisture issues, based on the finish that the other person who is refurbishing an old glider is getting. When I go to the shop, I regularly open the urge valve at the bottom and let the water spray out.

These issues really have me leaning toward buying an HVLP system. You mentioned that you buy a cheap one and toss it after a few uses, which is kinda the Harbor Freight approach, but I have read that the cheap guns do not have a consistent pattern. Apparently, your experience is different? I'm aware that you've been doing this kind of work for a very long time (you're a legend! I once owned a Libelle you repaired long before I owned it), so I'm not questioning your judgement or skill. I'm willing to spend up to about $500 on a system if it will do a better job for me. In the overall scheme of things, that's pretty cheap. All-in-all, I want to end up with a good looking, durable, long lasting finish, and I'll pay the extra $$ necessary. I like to save money where I can, but often, you get what you pay for.

Sorry, I guess I rambled a bit, but thanks for the info.

Jeff

For years I kept adding filters and drain traps, but kept spitting water droplets after spraying for a while. Finally figured out that when the compressor is working hard, the moisture is in vapor form and will never get trapped in any filter or drain, but when the pressure is suddenly released at the spray nozzle the air is cooled and water droplets form..........same principal as your refrigerator works on. The best long term solution is a refrigerated air dryer if you want to spend $500 or more. There are desiccant systems available for less, that do the job, but require constant monitoring and changing the desiccant. Harbor Freight stuff is too cheap, but I find guns for $65 to $100 bucks work quite well. A good painter is constantly monitoring flow, fan and pressure. In fact when approaching an area where excess paint may cause a run, I simply lower the pressure that reduces the amount of product I'm applying without the need to adjust flow or fan. Good lighting is a must as is a very clean spray area.............one bug will ruin all the prep work!
Cheers,
JJ

One of our club members fabricated a nifty water quencher. He had a coil of copper tubing made that fit nicely in the bottom of a 5 gallon bucket. Compressed air was routed through this tubing, which sat in the 5 gallon bucket, buried in ICE. At the end of the copper tube was a big water trap and then the line going to the paint gun. All that hot humid air coming out of the air compressor was cooled down, any moisture condensed and then trapped. We also put an inline trap at the gun. Same philosophy as the refrigerator water trap mentioned.

Stewart Systems does not recommend Turbine systems, this was tested and found to be true by another club member. It is also a water borne paint system, and as such is incredibly sensitive to moisture in the line. We have learned that the hard way on the three gliders (So far) that i've been involved in refinishing with the system.

On Friday, March 16, 2018 at 2:38:34 PM UTC-7, Tony wrote:
One of our club members fabricated a nifty water quencher. He had a coil of copper tubing made that fit nicely in the bottom of a 5 gallon bucket. Compressed air was routed through this tubing, which sat in the 5 gallon bucket, buried in ICE. At the end of the copper tube was a big water trap and then the line going to the paint gun. All that hot humid air coming out of the air compressor was cooled down, any moisture condensed and then trapped.. We also put an inline trap at the gun. Same philosophy as the refrigerator water trap mentioned.

Stewart Systems does not recommend Turbine systems, this was tested and found to be true by another club member. It is also a water borne paint system, and as such is incredibly sensitive to moisture in the line. We have learned that the hard way on the three gliders (So far) that i've been involved in refinishing with the system.

A refrigerated air dryer will cool the air to about 40 F, lowering the dew point to at least that by condensing the moisture out. The air is then passed through the condenser, elevating it back to room temp or so, now relative humidity will be quite low. The bucket of ice will do the same thing (for awhile) but you want keep from having a low spot in the coil of tube, a bit of a problem to work out. The reason is that water will condense and puddle in the low point at low air flow, they blow through in a slug when air flow increases. This is the same reason you want the air lines overhead, rather than under the floor. I've had to abandon the air lines under the floor of my shop for this reason.

If you look for a little while, you can get a refrigerated air dryer on ebay for about $200.

On Friday, March 16, 2018 at 6:51:50 AM UTC-7, wrote:
one bug will ruin all the prep work!

That's what you get for painting the glider after it's built. We paint them before we build them, so the bugs end up on the inside.

--Bob K.

I’ve been using a $200 HVLP knock off for years for Polyfiber and Ceconite. No complaints at all. Just make sure your air is dry. I just have a drop down drain for water and drain my compressor regularly.

The Wix Aquachek spin-on desiccant filter looks promising for intermittent use. Around $100 for the installation kit and one filter.

On Friday, March 16, 2018 at 6:51:50 AM UTC-7, wrote:

...Harbor Freight stuff is too cheap

For final finish, maybe. But I've found that the standard $16 purple gun ($10 when on sale) is perfect for spraying the vinylester we use as an in-mold primer instead of gelcoat. I generally get three good sprays out of them, and then relegate them to backup duty or the parts bin.

For the polyurethane topcoat, the auto body shop down the road uses whatever they use. Probably pricy.

--Bob K.

Anyone used the 3M Accuspray gun? Seems like a great tool for spraying gel coat and polyester topcoats. Spray head is disposable and they come in 3-4 diameters. I am going to try one