Polyurethane Paint Expert

[Alan Wheeler]

There are many don't's being suggested and certainly none are incorrect. All are very valid. However, different paints can tolerate different conditions. So it is always essential that you follow the advice given in the specs of the product you are using. Every product will have a max humidity, min/max temp, min dry time based on temp, min/max recoat times, curing time, type of thinner to use (if any) for the means of application, what application method is deemed the best for that product (some are hand application only, some spray only, some both) and most importantly for two pots the safety imformation on the product. Some, in fact most all (although I know of one that is not) have isocyanate in them and are deadly if sprayed. So special breathign gear is needed. Not just a special mask, buit a self contained respirator, which most ammatures will not have access to.

[Tnflakbait]

Originally Posted by Boracay

Has anyone any experience with those cheap ($39.95) airless sprayers using single pot polyurethanes?

It's not much more than the cost of a good quality brush.

I tried one of these things and couldn't get good flow. I ended up throwing it away.

[bill good]

Vantares
Yes it will stop fish eye.
Regards Bill Goodward

[Tnflakbait]

Originally Posted by Alan Wheeler

Not just a special mask, buit a self contained respirator, which most ammatures will not have access to.

Even when I am brushing I take special precautions. Outside the fumes aren't as strong. Inside, I use a scuba tank with a huka hose!

[SkiprJohn]

Aloha Charley,
I don't think the humidity ever gets below 50% here. LOL
JohnL

[northerncat]

if spraying with isocyanates get a sundsthrom mask with a chemical filter a dust filter and a prefilter after all you want to enjoy your sailing not your hospital bed
sean

[charley]

JohnL

I think you are right, I was thinking more for steel. I have painted steel outside when the humidity was on the high side and it looked like crap when done. Of course I think it could have been because we reached the dew point the night before, and the steel was still much colder that the outside air which causes condensation. We reach the dew point like twice a year here in AZ. But I have seen on several two part paint products to not spray if the relative humidity is higher than 50% I think it is closer to 65%.

Damn, you have it nice over there highest recorded temp 95 the lowest 52. Man if we could all cram onto those little islands over there.

[JohnnyC]

cburger,

The Interlux website gives these directions for sanding/buffing out a less than ideal "Perfection" finish.

http://www.yachtpaint.com/usa/genera...df/leaflet.pdf

The disclaimer at the bottom of the leaflet says:

" Note: due to the change in the integrity of the paint film which may take place as a result of this process, the buffed area may not maintain the same level of gloss as long as the rest of the boat."

So you may well be repainting, but perhaps if you can buff out the imperfections it will not be for a while. Looks worth a try at this point???

Good Luck. Please let us know how you end up solving the problem and how it works out for you.

John

[Alan Wheeler]

Steel is a difficult surface to paint in regards to Temperature. One thing that you can do, is to blow warm air inside the hull. A few fan heaters will suffice. Not a lot of heat is needed, just enough to keep the steel above the dew point of the surrounding air. Not practicable on any other surface as they are too insulative. External infra red heating is excellent though.
A few other tips. Although, please note that these are pedantic and not always practicable.
Always paint timber on a stable or even falling temperature. ie. afternoon, not early morning. This allows the air in the timber to stablize. Rising temps will cause small bubbles to appear under the paint surface as air escapes.
Ensure the paint has reached the same temperature as the hull. In other words, keep the paint in the same room as the hull so as both are similar temps.
Use just enough thinners to do the job. Keep the thinners consistant through multiple mixes. Consisitancy is a difficult one and a real key. Consistancy changes with temperature, so pour tests are the best way to achieve consistant mixes.
It is always better to do two lighter coats than one heavier. However, you also need to cover the surface so as it does not present a "chalk" surface. =ruff, no gloss.
Even if you have just a few square inches left to cover, ensure you cover it with adiquate paint thickness. Never try and make the roller or brush just make it. You need a consistant film thickness.
FOLLOW INSTRUCTIONS They aren't written just to give someone a job to write stuff.
One key instruction often missed is the "leave to stand" time for two pots. Often 10 to 20minutes is specified. It is essential to let this happen. It allows special long chain molicules to form. Without that happening, you can have issues with paint sagging, long touch off times, longer between coat times, poor gloss set and so on. Be patient.
Use good quaility equipment. Although 95% of the finish is in the preperation, 99% of the remaining 5% is in the application. You need god qualtiy rollers, brushes etc if hand applying, or you need good quality spray pots and air for spraying. Air quality is essential. So much so, I will list this seperatly
Air. It must be clean and dry. Forget the little "home depot" cheapy compresors. They simply can not keep up. The harder the unit works, the more heat it produces and the more moisture enters the compressed air. You must not have moisture in the air stream. A compressor capable of supply significantly more air than the gun is using is essential. The bigger the better. A good spin filter for removing moisture and any possible oil spots etc is essential. I use a large water seperator, followed by a 40u filter/seperator, followed by a 10u filter/sep, then a filter regulator. I drain the compressor tank regularly. Very high humidity may require a special dryer. If you see the tell tale little bubble of water on the surface when spraying, it's too late. There is moisture being blown under the paint film and it will never adhere properly.

Feel free to add more info to this, and I will look at placing our collective info in a "study hall" at the top of this page.

[seaclusion]

When I painted the deck, cabintrunk and flybridge I used Interlux Perfection. Two years later it is still as hard and shiny as when it was applied. I rolled it on but did not 'tip' after rolling. I used a high quality foam roller from Redtree called FOAM ROLLER PH. It is yellow, has almost inperceptable holes in the foam, and costs six to seven times as much as the cheap gray collored foam rollers. It layed on such a smooth coat that 'tipping' was not nescessary. For the places I had to use a brush, I used a premium badger hair brush like I would use for varnish work. The brushed areas came out alright, but the rolled areas look as if they were sprayed. The only problem I encountered was rolling an area that was angled directly at the sun. The paint seemed to get tacky after about two passes with the roller and the roller dragged. Of course, the instructions say not to paint in direct sunlight and I guess there's a reason for that.

Richard