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Boat Painting Tips

On October 14, 2016, in Builder Tips, by Gayle Brantuk

By Ken Schott

(Reprinted from the Boatbuilder Forum, August 9, 2016 – “Boat painting is a puzzle for newbies”)

I’ll post my views on spray painting, if it might help you.

Urethane paint is chemically a type of paint, a true urethane paint dries with a chemical reaction (the hardener) whereas enamel paint is air dry by evaporation of solvents. Automotive paint is just spray painting, as opposed to roller/brush painting.

“Paint system” is the type of chemical paint you choose. A “system” in automotive paint can be old school lacquer, alkyd enamel, acrylic enamel, urethane, poly-urethane, or epoxy. With any given ‘system’ you use the compatible solvents, primers, topcoats, sealers, clears, pertaining to that system.

For your boat paint ‘system’, I would choose one that is a 2-part system. That is, the paint itself, plus, an amount of hardener added to that. This is what makes it a chemically drying system. Some systems may have different names like hardener, converter, activator, etc.

Question: It’s the small things I miss, like which cleaner/thinner to use to clean the surface before painting.
Answer: You don’t need any. Cleaner/thinner is for removing old wax, contaminants or gook BEFORE you begin a re-paint auto paint job. Since you have a new build, you have not waxed it, used it, got it dirty, nor anything that requires smearing some kind of solvent on your project.

Not all solvents evaporate 100%, and may leave behind worse contaminates than you wish to remove. Heaven forbid if the rag you are using is not 100% pure, then you are smearing the rag contents all over your virgin paint job. Screw the chemicals wiping.

Comment: ..removing runners and correcting imperfections when the first layer of primer is hard, wet sanding slightly with grit 600..
Response: Why are you using 600 grit on primer? 600 is for pristine auto-show paint jobs, not for us fishing/working boats. 360 grit, even 320 is good enough for a work-a-day paint job. I have even top coated 220 with an activated alkyd enamel. 600 is just extra work not required, especially on primer.

What are your so called “runners”. Did you get a run in your primer? If you’re describing what I think you are, do this:
Spray your surface, or move your light source, from such an angle that the fresh sprayed paint is between your eye and the light source. Look down into the paint surface as the spray is going on, you should see the wetness of the spray reflected in the light. You have to keep moving to maintain the exact reflection of the light into the place where the spray is going on. When it looks wet, that is enough paint, keep moving. You can tell by looking at the reflection whether it is dry or wet. if it is wet, move on, adding any more will ‘run’

Sanding — use a block for all your sanding. if you use a bare hand for sanding, you will not get a truly flat surface. Use some kind of sanding block, a really soft wood like balsa is good. A hard rubber flat block is good too. Bring your build up in paint layers of different grits–wet sand all the way, Yes, you can dry sand, but wet sanding is faster, less dust.

Let’s say your first heavy primer coat is dry, work out all imperfections in 180grit, prime again and block it out to 220, or 260 grit. Prime again, block it out to 320/360 grit. Apply your topcoat–you will likely be happy with this as is.

Believe it or not, the top coat actually likes 320 grit better than the finer grits. Something about the coarser teeth of 320 vs 600, the top coats flows better in the drying process.

Catalyzed paints may sometimes react with high humidity. My luck and success has been as follows:

  • Never work paint (topcoat quality finish) in afternoon falling temperatures.
  • Never work in really high humidity like rainy, foggy, dank days.
  • Always work your best paint finishes in the mornings, as temps are on the rise.
  • Never let wet paint get fallen dew on it, or fog.

For your fishing boat, a 2-part urethane solid color finish is all you need. NOT the base coat/clear coat system. You need a single color, 2-part, system.

I try not to use any rags at all, they are actually just a liability for introducing dirt and solvents.
If you wet sand with potable water, you have just exposed a pure, raw, clean, paint surface. There is absolutely nothing else you can do with a solvent rag to expose a pure, raw, clean paint surface. Read the directions on the paint can, if it does not specify to solvent wipe, then avoid that. Read the paint can label, and determine your ‘recoat time or ‘recoat window’. This is the time allotted to recoat without sanding, wiping, or doing anything else to get a positive adhesion.

Sanding with 2000 grit then polishing is an option, not a requirement. If everything goes well, and the sun the moon & stars all align, then you will be happy with the final outcome. However, if a fly, mosquito, or something gets stuck in your topcoat, you got an option to sand him out with 2000 grit and buff him.

Same with small particles of dust & lint. Let them cure dry, and buff them out. Most of the dust lint in a top coat comes from you. I was always fighting dirt/lint, and it didn’t go away until I put on one of those plastic overhauls, dust hood, and so on. Like I said, paint in the mornings, when the grass & environment is heavy with dew, there is no dust in the air early morning. Air gets dusty after lunch when the sun dries things out. Then after lunch air gets hot & humid, (paint dries too fast to work) and humidity gets higher.

Editor’s Note: The Glen-L Forum is a treasure trove of helpful information and it costs nothing to be a member.

In looking for photos of the author of this article, Ken Schott, I came across a great interview we took of him back in 2011 about his Double Eagle build–great action shots of his boat too:

Double Eagle by Ken Schott

Ken Schott’s Double Eagle from the 2011 Gathering of Glen-L Boatbuilders in Tennessee.

Ken Schott & Gayle Brantuk

Ken Schott & Gayle Brantuk

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