Spraying varnish / marine enamel

[TK1]

Hi all,

I have asked this questing in the finishing forum to get their opinion, but thought I'd ask the learned souls in the boating bit as well...

I am looking for a compressor to spray varnish finishes, and sometimes marine enamel, onto kayaks/canoes. So don't need a huge one capable of hours of work, just something that will spray for 15-20 mins at a time and at a consistent rate to allow a spray varnish finish.

Do others use spray guns for finishing? Any type/brand recommendations (at the cheaper end of the scale!)?

Or any hints/tips particular to boat-building when spraying finishes?

Thanks,
Darren

[m2c1Iw]

Hi Darren,
I use a really cheap and I mean cheap compressor it was actually sold for use with a brad nailer so the CFM and tank are tiny. I hooked up a LPG cylinder to add some reserve but to be frank it is not suitable for spraying certainly not your standard size gun. I get away with it by using a Star gravity feed gun it's a Mini S-106T these guns spray about a 50-60mm wide patten so not so good for big areas but good for small stuff. Like always there is a difference in quality depending on what you spend and spray guns are no exception. I involved with a crash shop and we use star guns mainly as they have proven to be good value for money. The gravity feed runs on lower pressure and tend to have less over spray.
I thin varnish and enamel between 10 and 15% which seems to get me a good finish particularly with varnish. It leaves a nice smooth finish which I find impossible with a brush and it's heaps quicker.
That said have you read Miks hints on enamel application I have followed his advice and found for enamel by using a small foam roller and if I thin about 10% I don't even need to tip off the end result is as good as I can get with the gun and nearly as quick with a lot less messing around. For spraying you need to think about dust control and some way to exhaust the fumes and don't forget some good PPE.
I think you need at least 7CFM and 30 ltr tank for hobby type work but if buying the el cheapo you will need to add a water trap and filter so look around some times the slightly more expense units are better value in the long run.

Good luck
Mike

[RossL]

I use a 17cfm, three-cylinder compressor to power a range of different guns. The ones I use most often (almost exclusively) are Star gravity-fed HVLP guns with 1.3mm and 1.7mm tips. The other favourite is a Star gravity-fed touch-up gun with 0.8mm tip.

Despite the 17cfm classification, I find the machine only just keeps up with the gun on a hull-spraying job, and I have FOUR water traps in the lines.

For what it is worth, I very rarely spray, even though I'm working professionally. With every passing year I spray less, and brush more. Rolling-and-tipping is a very effective method for large areas where wet-edge is a problem (it was 39 degrees in my workshop last week). For a canoe hull, brushing with a high-quality brush should be adequate, with rolling and tipping a possibility.

Use the best paint you can get, and become familiar with the properties. I keep a log-book of thinning ratios, application methods, ambient conditions etc.

One of the biggest yards in Europe (specialising in super yachts) uses brush application exclusively, saying that it is the only way they can get the finish quality that their clients demand. The teams are divided into three (very close together) first applying with vertical strokes, the second spreading with horizontal strokes, and the last tipping-off vertically.

Ross Lillistone

[Boatmik]

As an alternative ... I use Brushing or rolling only.

Some of the paints are so self flattening when rolled straight out of the tin these days even without tipping. Funnily enough they are not the cheap ones. Had particular success with Brightside enamels.

Varnishes I never thin except for the first coat and never would consider spraying anyhow ... I have professional car spraypainters in tears from trying to spray yacht varnish.

With two pots there is often a "brushing thinner" that is distinctly different from the "spraying thinner". Makes a huge difference to use the right one for your application method.

Remember whatever application you use the elbow grease in the sanding is what makes the difference.

MIK

[TK1]

Hi,

Thanks for the feedback guys. Looks like I jsut saved myself a couple fo hundred dollars :2tsup:

I'll stick with the brushing I guess, based on professional opinion. My only spraying experience is from models with hobby enamals - did a good job with those, but don't want to screw up a boat. Given the professionals and those with more experience say to stay away, I'll just have to improve my brushing technique and experiment a bit.

I use the Brightside or Epiglass enamels, and did have good results with the first 'yak. Just thought spraying may be quicker and easier to get a smooth, gloss finish. But seems brushing and tipping (if required) is the way to go.

Thanks for the advice.

Regards,
Darren

[m2c1Iw]

I use the Brightside or Epiglass enamels, and did have good results with the first 'yak. Just thought spraying may be quicker and easier to get a smooth, gloss finish. But seems brushing and tipping (if required) is the way to go.

Thanks for the advice.

Regards,
Darren

Hi again Darren,
Just a suggestion give the small foam rollers a go for enamel. I don't know of suppliers over there but I came across this (http://www.unipro.com.au/) company that might be able to supply otherwise a chandlery or boatbuilder.

The roller are what's called superfine dense white polymide they are about 25mm dia and roughly 100mm long.

Experiment with thinning, do not load the roller too much and do a final roll out slowly trying to avoid bubbles. As Mik says the International Brightside product has amazing flow out qualities ( well to me anyway).

Cheers
Mike

[PAR]

I've done a fair amount of spraying, particularly varnish for "show" boats and the only trick, besides having enough reserve compressor volume for the equipment (which is typically quite a bit of CFM) is thinning the varnish enough to eliminate the "stipple" effect from the spray process. The amount of thinning is temperature and humidity dependant, so it'll take some practice to get it right.

Michael's correct in that with modern painting systems, you can get nearly spray quality with roll and tip methods, which is a lot easier.

On a similar note, Michael, I had the chance to use WR-LPU in very dry conditions yesterday and today (40% an less humidity). It was difficult to keep up a wet edge and I can see how you'd cuss a lot using it. I rigged up a room humidifier and this made a huge improvement in the "wetness" of the paint and I was able to keep the paint moving along nicely. It's so weird being able to hit it with a sander 5 or 6 hours later.

[Boatmik]

If you get bubbles when rolling with the brightside the roller is too wet. Keep extending out and the bubbles will disappear when it is spread out far enough.

MIK

[nickpullen]

If you get bubbles when rolling with the brightside the roller is too wet. Keep extending out and the bubbles will disappear when it is spread out far enough.

MIK

I just rolled the PDracer with White Knights epoxy enamel. I did some testing on this a while back with intention to paint a car using a roller and thinned paint, it comes out like glass. and once set, its rock hard!

I've done 3 coats on it now, Ill see how that holds up.