How to match a compressor with an HVLP paint gun

[Jonboat2Bassboat]

Saw the following article on line. Just got an HVLP paint gun to use with my 20 gal, twin piston, belt driven painting compressor. Compressor puts out 9 SCFM@40 PSI and 7.5 SCFM@20 PSI. Gun requires 6.5SCFM@40 PSI but 7.2SCFM@40 PSI for continuous use. According to the 15% rule in the formula below this compressor should work with this gun. Any thoughts? Am also using an inline desiccant and air filter.

Instructions.

Read the owner's manual of your HVLP paint gun for the specified CFM@PSI measurement the gun needs to function properly. The useful thing about HVLP paint guns is that they can run on relatively low pressure, but you must make sure to select a compressor that is within the pressure range of your gun. Normally, this is quoted as CFM@30PSI, 40PSI or 90PSI (example: 25CFM@90PSI).
2
Contact a few compressor manufacturers' help desks for more information regarding CFM ratings for your HVLP paint gun and some of their compressor options. Have the CFM rating for your paint gun available, and ask specifically if the compressors' ratings are similar to the ratings you are looking for. If they are more than 15 percent different, find a different compressor or manufacturer.
3
Find the highest possible CFM rating that your HVLP paint gun will be running on (this can normally be found in the owner's manual as well). Multiply the highest CFM rating by 50 percent. Add this number to the total CFM required. The number you come up with will be the highest rating of air compressor you should be looking for, as CFM ratings within 15 percent of this number will allow you to run your tools without over-taxing the compressor.
4
Check to see if your HPLV spray gun can operate on the CFM rating you determined in Step 2 by either testing a gun/compressor setup or by contacting the manufacturer of your paint gun and compressor manufacturers to inquire as to their compatibility. If you are satisfied that your compressor rating will provide the type of performance you are looking for, determine your budget and begin shopping around for the best deal on an air compressor within your specified CFM rating. Remember, it doesn't have to match your specs exactly, but it should be close.
5
Purchase the compressor and try the gun out on a small project to see if the spray looks satisfactory. If the compressor cannot handle the gun, now is the time to return for a larger model (since your compressor should still be under warranty).
Tips & Warnings
As a general guideline, an HLVP paint gun will require 25CFM@50PSI to spray a clean coat of paint. Look for a compressor in this range at the minimum.

 

[Jonboat2Bassboat]

HVLP and paint additives

HVLP and paint additives

Getting ready to paint an aluminium boat with Rustolium. Have Alumaprep, Alodine and tons of 150 to 320 sandpaper to prep the surface. Bought two HVLP paint guns, one the Graco 3900 from Lowes for $150 and the other a Husky Pro conversion gun HDS model from Home Depot for $100.

Which one to use? Leaning towards the Husky as the paint gun seems much better made and durable where the Graco feels more like a small, cheap plastic vacuum cleaner.

Additives and cleaners. Have ODORLESS Mineral Spirits, Lacquer Thinner and Penetrol. Paint says to thin with Mineral Spirits but have never found "safe" paint products to work well. Plan to find some "real" Mineral Spirits unless someone says this "safe" stuff will work well. Also have Penetrol for mixing paint as paint guy at HD mentioned it as an alternative to Mineral Spirits. Any thoughts?

Have Laquer Thinner to clean gun during and after painting. Was told it will work better that paint thinner.

The boat has some areas under the gunnels that need to be painted but are hard to get to and tedious to sand by hand. Anyone think the existing paint on an aluminium boat can be treated with a sanding de-glosser without harming the aluminium?

 

[ondarvr]

Re: HVLP and paint additives

Re: HVLP and paint additives

Use whichever gun you like better.

Compressor sizing is a little tricky, but even a small one will let you paint the boat, if it can't keep up you just stop spraying for a minute.

 

[Jonboat2Bassboat]

Re: HVLP and paint additives

Re: HVLP and paint additives

Use whichever gun you like better.

Compressor sizing is a little tricky, but even a small one will let you paint the boat, if it can't keep up you just stop spraying for a minute.

Thanks. Keeping the conversion HVLP. Plumbing in 20 feet of 3/8" CPVC with a water filter and a drain to keep the paint dry. Added a descant in line filter so should be all set.

 

[Bob_VT]

Re: HVLP and paint additives

Re: HVLP and paint additives

Have you ever used one before? Te rustoleum is kind of thick even when thinned so, the largest nozzle (or one that is used for primers) should be used. You also have to regulate the air with the trigger pulled. My HVLP I believe needed to be 30 lbs psi at the tip with the trigger pulled.

HVLP works best at 90 degree angle to the work.

Go lightly since rustoleum loves to orange peel.

Be sure to have plenty of paper towels and clean that gun asap.

 

[Yacht Dr.]

Re: HVLP and paint additives

Re: HVLP and paint additives

Dont ever short change yourself on Air .. rule #1 of spraying.

Test your gun out with Water .. just like your going to spray your boat ( spray spray spray ). If your compressor does not keep up..get a bigger one. ( flush the gun out with acetone after your water spray ) ( If your gun gaskets cant handle acetone ..then get another one ).

Cant expect a cheap gun to give you perfect results .. so dont be too hard on yourself when you cant lay it like glass(ish).

YD.

 

[bryanwess2000]

Re: HVLP and paint additives

Re: HVLP and paint additives

Not trying to be an a** but why not take the guns back and buy some better paint like 2 part single stage urethane. Check out some of the hotrodders web sites to see the paint jobs they get with cheap HF paint guns or buy a used devilbiss. You'll probably need more air to drive a hvlp gun to not get major orange peel. I've gone through stripping and painting an aluminum boat and wish i had had a larger compressor and went with better paint like mentioned above. There's too much labor involved to use sub par paint. My 20yr original paint on my starcraft looks better than the enamel I put on my sylvan. I did a good job on the sylvan but it's not mirror like the urethane on my starcraft nor is it as durable.

 

[Jonboat2Bassboat]

Re: HVLP and paint additives

Re: HVLP and paint additives

Thanks for the input. I thought about going "first class", thought about it a lot. Even went to a marine store and bought Interlux primer and paint. What I am trying to do is make a 16 foot Polar Kraft Bass America boat out of a 16 foot Polar Kraft jonboat. If I had known how expensive this project was going to be, even going on the cheap, I wouldn't have done it. A 2005 used 16 foot Polar Kraft Bass America boat sells for about $8000 in Maine. I will have about $5000 into this one, $3000 purchase price 6 years ago and $2000 to rehab it on the cheap now. I think it would have been wise to sell my boat as is for around $2K, maybe less, and put in an extra $6 to $7K for a much better boat.

I sort of thought about the above but the mechanic inside me wanted to do the rebuild. Besides several people have done Jon to bass boat conversions so knew it was doable. I know it won't come out looking first class but hopefully will be a good second class, maybe third. Might keep it or sell it in the spring and get the Bass America boat I wanted in the first place.

Again, thanks for the input. After gutting the boat and getting into the details of paint, paint guns, compressors, carpeting etc, going first class just didn't add up for what I was trying to do.

 

[Woodonglass]

Re: HVLP and paint additives

Re: HVLP and paint additives

Have you seen the results that some of the paint jobs on here using the Roll n' Roll technique. From 3ft away you would be hard pressed to tell them from a Spray job. High Gloss and smooth as a Baby's bottom. Painted with Acrylic Enamel Paint with an added Hardener Cost is less than $100 bucks. Check the last link in my Signature below. You can do the same for your boat and get a first class, DURABLE finish.

 

[bryanwess2000]

Re: HVLP and paint additives

Re: HVLP and paint additives

I wasn't trying to discourage you from using enamel it's just alot of work stripping and painting an aluminum boat. I've gone through it
myself and used some BM p22 with hardener and its a nice hard glossy paint but it'll never be as glossy , durable or UV resistant as a 2 part urethane/polyurethane. The local auto paint supply has nason fulthane for ~$120 /gal including hardener and reducer it's supposed to
do well with roll and tip application. Thats what I'll be using if I repaint my superfisherman as it already has urethane on it.
I totally understand trying to stay on budget I was the same and if your going to end up selling to upgrade I would keep costs to a minimum. I happened to find the boat I actually wanted for a steal in the middle of restoring my sylvan and now lack the motivation to start back on it. I was just trying to show you could get a throw away gun or roll and tip and end up with a better paint job for what you've spent on the guns you have. Good luck on whatever you decide.

 

[Jonboat2Bassboat]

Re: HVLP and paint additives

Re: HVLP and paint additives

Well that is food for thought. I have already spent $80 on non returnable Rustoleum primer and custom mixed paint but do not want to do this job over again. Will look into the paint you mentioned.

The Rustoleum Marine metal primer says not to use primer below waterline but plan to anyway. Several guys have used this primer and a least some must be using it below water line with success. One thing is I live on a 200 yard wide fresh water river in Maine. The boat usually goes into the water in the spring and gets taken out in the fall. I mention this because another poster here, Woodonglass, has a great painting system that works IF your boat is only in the water only a few days at a time. I need something that will last the entire season, season after season.

 

[Woodonglass]

Re: HVLP and paint additives

Re: HVLP and paint additives

You are correct. If you don't plan on leaving the boat in the water for more than 2-3 weeks at a time and it's fresh water. The Rustoleum Paint or Majic Paint with the added Hardener can yield great, durable results with a roller. Here's an example of a Rolled on Finish by one of our iBoat members. No kidding this was done with a Foam Roller.

 

[Yacht Dr.]

Re: HVLP and paint additives

Re: HVLP and paint additives

You are correct. If you don't plan on leaving the boat in the water for more than 2-3 weeks at a time and it's fresh water. The Rustoleum Paint or Majic Paint with the added Hardener can yield great, durable results with a roller. Here's an example of a Rolled on Finish by one of our iBoat members. No kidding this was done with a Foam Roller.

Yea but This pic is not typical of a first timer DIYer roll out jobby.

Any paint system can look like this if you know and use the right application.

Just dont expect a foam roller with rusto to turn out like this pic on your first ( second or third ) time trying. Its not realistic.

YD.

 

[Jonboat2Bassboat]

Re: HVLP and paint additives

Re: HVLP and paint additives

Thanks for the input. Time is getting short so plan to prime tomorrow with Rustoleum Marine primer. Could not find the Nason acrylic enamel in my area but will look for something similar. If can't find it will spray the boat with the X-O Rust mentioned earlier. Like the idea of an inexpensive acrylic enamel but what the local NAPA had was Sherwin-Williams acrylic enamel at $180 a gal with hardener and reducer.

 

[Jonboat2Bassboat]

Re: HVLP and paint additives

Re: HVLP and paint additives

Wow! Great looking boat. Can you add hardener to Rustoleum? If so I would do that in a heart beat.

 

[Jlawsen]

Re: HVLP and paint additives

Re: HVLP and paint additives

Your compressor is right on the edge of not keeping up and that will frustrate the heck out of you. A 60 gal is about the minimum I'd run (I have an 80) and feel pretty safe. Ideally if your going to run thick or catalyzed paint you want to go to a pressure pot system but that can set you back at least a grand.

When I did my Tinny a couple of years ago Interlux was pushing me into a pot system but I finally just went with the roll and tip and was very satisfied with my first time effort. Good foam rollers and Badger Hair brushes were what made it happen for me.

 

[Woodonglass]

Re: HVLP and paint additives

Re: HVLP and paint additives

Yea but This pic is not typical of a first timer DIYer roll out jobby.

Any paint system can look like this if you know and use the right application.

Just dont expect a foam roller with rusto to turn out like this pic on your first ( second or third ) time trying. Its not realistic.

YD.

Uhmmm, that's not exactly true!!!! There's lot's of examples on the forum of Rustoleum Roll n' Roll Boats that have Excellent High Gloss results like these. Lakelovers is one, Drewpster is another, and the picture posted of TailGunner's was a "First timer" too albeit this paint is Interlux. Using the Hardener in the Rustoleum or any Arylic Enamel Paint Really enhances the Gloss as well as the hardness of the paint. Works with Rolling and with Spraying.

 

[Jonboat2Bassboat]

Re: HVLP and paint additives

Re: HVLP and paint additives

Thanks for the input. It has been comments read here about compressor size, SCFM@PSI specs HVLP paint guns that helped me understand paint atomization. Your comment about my compressor being "right on the edge" is well taken.

There is a compressor / gun formula on line (think I posted it here) that says take 1/2 the guns continuous SCFM, (7.3 ) add it to the intermittent SCFM (6.5 at 70% duty cycle) times 85% to see if the compressor will work with the gun at a given PSI. For me, adding 1/2 the max (3.65) to the min (6.5 at 70% duty cycle) gives 10.15@40. 85% of that is 8.63 and the compressor puts out 9SCFM@40PSI, so yes, right on the edge.

Did a little testing. Opened a valve at the end of the air hose to simulate painting. Can spray for 58 seconds before the compressor comes on. If continuously spraying the compressor shuts off 2:23 from when starting to spray. That's 58 seconds spraying and 85 seconds with the compressor on for a duty cycle of 59%, well within the 70% duty cycle. The 220 VAC motor on the compressor is rated for continuous use, but it does get warm. Spraying intermittently is 58 seconds spraying but only 40 seconds recovery for a duty cycle of 40%. I COULD spray continuously but think a safer method is to spray intermittently and wait 40 seconds every minute for the compressor to recover. This is the first time painting a boat so don't know how much of a PIA waiting 40 seconds is going to be. One thing for sure is it beats buying a 60 gal compressor for a one time use and hopefully spray painting will look better than the roll and tip method.

Thanks for your input.

 

[ricohman]

Re: HVLP and paint additives

Re: HVLP and paint additives

I think you need a bigger compressor. You do not want to be waiting for air pressure while the paint is flashing on one side of the boat. I agree with the comments on using hardener with your paint but you have to remember the the VOC's (isocyanates) are deadly and have serious long term health effects.
The only safe way to paint with hardener is a proper full face continous flow respirator. Painting outside and downwind ain't going to help. If you do not have the PPE to paint safely then roll it on.
I use a 80 gallon 12.5 cfm/100psi and I find it adequate for HVLP.

 

[wellcraft-classic210]

Re: HVLP and paint additives

Re: HVLP and paint additives

Second that on using hardener if its available / Otherwise rustoleum is soft and it will scratch very easily and need to be touched up fairly often. (ask me how I know or look at my trailer )
I have used a 3m respirator with the organic vapor cartridges numerous time with good results / I just make absolutely sure its seals on my face-- ( no beard / correct size/ strap tension set / etc ) / if you smell paint stop as something is wrong.
The key to using a foam roller with rustoleum is thinning the paint significantly -- I would still use a respirator even though it does make less fumes than spraying. Lots of web site showing how to do this with good result / spraying is a lot less labor.

Just my opinion - hope it helps