Spraying on Spar Urethane with a HVLP Sprayer

Anything to do with mechanical, construction etc

Spraying on Spar Urethane with a HVLP Sprayer

Postby jonw » Sun Jun 08, 2014 1:38 pm

Every few years I re-coat the woody sides of my teardrop with Minwax Helmsman Spar Urethane so the UV inhibitors in it will protect the wood from fading. I just did it so I thought I'd take and share some pictures in case it helps anyone else thinking of doing this.

I am by no means an expert at this. The first time I used an HVLP sprayer was when I built my teardrop and was unhappy with the finish on the sides from brushing. The second time was when I painted the aluminum on the roof as documented in my refurb journal (in my signature below). I've found with a little care and practicing on scrap wood or cardboard I got great results. You probably can too...

I bought the absolute cheapest HVLP (high velociy, low pressure) sprayer from Harbor Freight http://www.harborfreight.com/20-oz-8-cfm-gravity-feed-spray-gun-67181.html that happens currently to be on sale for $9.99. NOTE that it's coated with oil to protect it from rust so you have to clean it before first use with some mineral spirits, which is good practice for cleaning it after each use.

One thing about this model sprayer is it does not come with a wrench for removing the interior nozzle for cleaning and HF doesn't sell one even though the instructions that come with the sprayer says they do. I just used a large channel pliers to grip the outside of the nozzle to loosen it enough to unscrew it. I chewed up the outside of it a little bit but that won't affect it's performance and it will be hand tight and loosen-able going forward.

I recommend also purchasing a set of cleaning brushes http://www.harborfreight.com/5-piece-airbrush-cleaning-brushes-68155.html, a moisture filter http://www.harborfreight.com/disposable-inline-moisture-filter-68224.html, and a regulator http://www.harborfreight.com/160-psi-hvlp-air-regulator-68222.html. As you see you can get all of this for around $20 on sale.

I'd say that 50% of the stuff I buy at Harbor Freight turns out to be defective and I have to return it. The regulator turned out to be missing an O ring (I guess) so it never tighted up when attached to the sprayer and leaked air at the joint. Luckily I just removed it and was able to continue working as my compressor had a regulator. One thing I learned the hard way with Harbor Freight stuff is to always test your sprayer setup on the compressor before mixing up and filling it with material. Another good idea is to open and check out what you're buying in the store, as best you can...

The only big ticket item you'll need is an air compressor, but you should be able to borrow or rent one.

The actual spraying goes fairly quickly. The prep work takes me 1-2 days: wash the whole trailer, sanding (palm sander and by hand where it won't reach), wipe it all down twice to get up the sawdust (and pollen this time of year), and then masking all things I don't want sprayed.

Some tips:
  • don't use the HDX masking tape - it doesn't stick well and tends to peel off if you look at it
  • masking tape wont stick to any surface with silicon caulk on it. Cleaning any aluminum trim with Cameo aluminum and stainless steel cleaner remedies this
  • On a warm 80 degree plus day you wont need to thin your spar urethane at all. If cooler you might want to thin it just a little (like no more than 10%) with mineral spirits
  • Protect yourself, your clothing, eyeglasses and lungs with proper equipment. Most is pretty inexpensive but do get a good breathing mask suitable for working with chemicals
  • Make sure your car, dog, etc is not downwind...
  • Clean your gun immediately after each coat and/or use. Empty any leftover material from the cup and run a small amount of mineral spirits through the sprayer before dissembling it and cleaning all the parts and internals with mineral spirirts

Now onto some pictures:

All masked and ready to be sprayed:
Image

Me suited up and well protected:
Image

Checking sprayer adjustments on a piece of test cardboard:
Image

And finally spraying
Image

Image

In case you were wondering, I put 8oz (1 cup) of spar urethane in the sprayer cup and that was enough to spray each side twice (one coat). I'm waiting for the first coat to dry before applying another one. I'll try to take some picture of the final result, but from past experience it will be smooth and evenly coated without any brush marks or thick spots.
Last edited by jonw on Sun Jun 08, 2014 2:55 pm, edited 1 time in total.
User avatar
jonw
Titanium Donating Member
 
Posts: 525
Images: 163
Joined: Thu Oct 22, 2009 6:22 pm
Location: Marlboro, Mass.

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby BillZ » Sun Jun 08, 2014 1:59 pm

Very nice Jon!
I was thinking about getting some spray equipment myself. What gloss level of Spar Urethane do you use?
User avatar
BillZ
The 300 Club
 
Posts: 308
Images: 0
Joined: Tue Feb 16, 2010 7:39 pm
Location: College Park, Maryland

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby jonw » Sun Jun 08, 2014 2:53 pm

BillZ wrote:Very nice Jon!
I was thinking about getting some spray equipment myself. What gloss level of Spar Urethane do you use?


Thanks. I use the satin finish. I like the matte look in contrast to the aluminum (and painted roof).
User avatar
jonw
Titanium Donating Member
 
Posts: 525
Images: 163
Joined: Thu Oct 22, 2009 6:22 pm
Location: Marlboro, Mass.
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby martymcfly » Sun Jun 08, 2014 2:53 pm

I have the hvlp from Hf. I tried to use it to paint a car that I used to race at the local circle track. It looked like crap. I also have the siphon feed gun and I have had better results with that one. I realized that maybe I am a crappy painter. The last car that I raced, I painted with rustolium safety yellow with a roller. It actually turned out pretty good. It was also easy to touch up after any on track mishaps. With the hvlp, you really need a good in line water seperator.
martymcfly
Teardrop Master
 
Posts: 110
Joined: Tue Feb 25, 2014 4:53 am
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby jonw » Sun Jun 08, 2014 3:03 pm

martymcfly wrote:I realized that maybe I am a crappy painter.


There are definitely some tips and techniques that help a lot. There's a lot on the web and You Tube you can learn from (I did). Also I'd say it's critical to have the gun adjusted properly for pressure, flow rate, and spray pattern, which means spending some time and a little bit of material with your test scrap material.
User avatar
jonw
Titanium Donating Member
 
Posts: 525
Images: 163
Joined: Thu Oct 22, 2009 6:22 pm
Location: Marlboro, Mass.
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby jonw » Sun Jun 08, 2014 3:06 pm

Let me say also that it is much easier spraying paint where it's easy to see where you've missed and how thick you're putting it on, than urethane that is transparent.

I find I have to constantly check my work by looking down along the side of the trailer to see reflections of what is wet and what isn't. It somewhat requires a leap of faith, and understanding that you're better off with multiple lighter coats than fewer heavier ones that can run.
User avatar
jonw
Titanium Donating Member
 
Posts: 525
Images: 163
Joined: Thu Oct 22, 2009 6:22 pm
Location: Marlboro, Mass.
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby coyote » Sun Jun 08, 2014 4:54 pm

I used the same $10 buck H.F. Gun. I have painted cat. Transmissions for several years with one, so I bought a new one and tried it. I am by no means a painter, those transmissions never see the light of day again ( I hope). But, I got exactly what I wanted/expected. Just sand lightly, tac rag, paint, dry, light sand with 300, tac rag, paint again. Dave
coyote
Titanium Donating Member
 
Posts: 452
Images: 0
Joined: Mon Mar 04, 2013 4:20 am
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby nevadatear » Sun Jun 08, 2014 5:20 pm

Thanks, Jon, doing this is in the plans this year to Monstro. I hate the brush marks on him now.
Debbie (with Randy looking over my shoulder)
Our build thread: http://www.tnttt.com/viewtopic.php?t=41295&highlight=monstero
2009 Homebuilt woody, Kenskill inspired 5 wide
ImageImage
User avatar
nevadatear
Silver Donating Member
 
Posts: 2358
Images: 171
Joined: Mon Nov 10, 2008 2:37 pm
Location: No. Nevada
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby jonw » Sun Jun 08, 2014 10:35 pm

nevadatear wrote:Thanks, Jon, doing this is in the plans this year to Monstro. I hate the brush marks on him now.

Hi Debbie & Randy -

Unfortunately you'll not be able to completely get rid of the brush marks unless you take it down to bare wood and start all over, which I don't recommend. However you will visually lessen them significantly to the point where most people won't notice them unless they knew where to look. I can still see them on mine if I look closely enough.

I suspect over time with more coats they will continue to disappear.

See you at the IRG!
User avatar
jonw
Titanium Donating Member
 
Posts: 525
Images: 163
Joined: Thu Oct 22, 2009 6:22 pm
Location: Marlboro, Mass.
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby lfrazer98 » Mon Jun 09, 2014 6:00 pm

Thanks for posting this! I already ordered what you suggested and I look forward to when it arrives! I hope I can get a smooth even finish with this method. :)

Thanks!
User avatar
lfrazer98
Teardrop Master
 
Posts: 204
Images: 217
Joined: Tue Sep 17, 2013 6:25 pm
Location: New York
Top

Results after a single/final coat

Postby jonw » Wed Jun 11, 2014 1:50 pm

Well, just as I was about to spray on a second coat a breeze came up and was blowing around thousand of these things:

Image

Since the masking tape was peeling off I decided a single coat was going to have to do. Although another coat would have been nice the first coat was put on on two passes and coverage was pretty good, so it looks good and is well protected. There were a few of these fuzzy seeds stuck to the side in the urethane, but a quick light once-over with the scrubby side of a non-abrasive kitchen sponge (pictured below on the fender) removed them and any other imperfections without scratching the finish. You can see how smooth the finish is in the reflections.

The thing on the side in the middle of the picture is a bug *not* stuck in the finish - I guess he just wanted to be in the picture...

Image

And here's the same side from another angle. The mark in front of the door was a gouge made by the open window before I put in a bungee chord stop. I filled it with wood filler (couldn't find mahogany color) before spraying and although it is noticeable it is now smooth. If you look real hard on the panel to the rear of the door you can see some of the original brush overlap marks, but they are hardly noticeable any more.

Image
User avatar
jonw
Titanium Donating Member
 
Posts: 525
Images: 163
Joined: Thu Oct 22, 2009 6:22 pm
Location: Marlboro, Mass.
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby lfrazer98 » Wed Jun 11, 2014 4:17 pm

Looks beautiful!! :thumbsup: :applause:
User avatar
lfrazer98
Teardrop Master
 
Posts: 204
Images: 217
Joined: Tue Sep 17, 2013 6:25 pm
Location: New York
Top

Re: Spraying on Spar Urethane with a HVLP Sprayer

Postby oakinteriors1 » Thu Jul 03, 2014 5:51 am

I have been using a Binks model 7 since the 70's, spraying lacquer (Which cost $125 back then)
.....But a few years ago I bought the same gun you have posted here.....I have used it on a few projects and my build viewtopic.php?f=50&t=57906 ......I'm No painter by trade most of my stuff goes into new homes unfinished.....But if I was the Binks is in the cadalac comparison category in every aspect....
We had a Northern tool store open up here recently and they have a nicer gun for $65...http://www.northerntool.com/shop/tools/ ... Av_F8P8HAQ
User avatar
oakinteriors1
Silver Donating Member
 
Posts: 297
Images: 1
Joined: Tue Sep 03, 2013 4:47 pm
Location: Bates City Mo.
Top


Return to Teardrop Construction Tips & Techniques

Who is online

Users browsing this forum: Google [Bot] and 10 guests