Painting Hull; Lessons Learned

[hriehl1]

Just acquired a 1968 DS1... great shape, but original black gelcoat had too many scrapes and was too faded to bring back (hours with rubbing compound were fruitless). Decided to paint the hull (Mauritius Blue) this autumn.

Chose Interlux Perfection 2-part polyurethane with Interlux Watertite epoxy filler, Interlux PrimeKote primer and Interlux thinner. Probably 35 hours and $175 invested resulted in a job I'm very pleased with as a first effort. I was happy with the Interlux products, though I'd guess other 2-part products would be comparable. 1 Quart each of primer and paint just made it (2 coats primer, 2 coats colored finish).

Lessons Learned

1. Believe what's been written that a successful job depends 90% on preparation. When you think you're done sanding... sand some more. Then when you're sure you're done sanding, sand some more. The flaws I have are 90% due to imperfect surface prep (mostly residual primer streak marks I didn't fully sand out). This stuff is THIN and won't fill-in any surface flaws, it'll highlight them.

2. Do not even think about hand sanding the whole job. Regretfully, I did and it cost me probably 8 to 10 extra hours, sore shoulders and a few imperfect spots on the hull. After the first coat of primer, I gave in and bought a random orbital sander for $40. It worked so well I went back and sanded thru the primer to correct the few epoxy patch flaws my tired shoulders had glossed over. I'm very glad I did.

3. The 3X sandpaper discs really do last far longer than regular discs... more than 3 times longer, I'd say.

4. Thin coats really are better than thick. Temperatures were in the 50s, and I thinned my first coat of primer somewhat less than the 20% called for because it just seemed SO thin. Mistake. The first coat of primer had notable stroke marks that took a lot of sanding to level-out (didn't get 'em all). Because of the cooler temperatures, I thinned the second primer batch >25% with much happier results.

5. For primer and paint, I used the roll-and-tip method, working alone. Cool temperatures kept the leading edge plenty wet to do it solo. For tipping, I used hi-quality ($12) china bristle brushes. Given how costly the Interlux thinner is, I didn't bother cleaning the brushes after each coat... I threw them out. Next time, I'll tip with $2 disposable china bristle chip brushes and save the $12 brush for just the final coat.

6. Instructions said use a solvent-resistant foam roller. Practical Sailor magazine said they got better results with solvent-resistant mohair rollers. I used mohair and was very pleased.

7. When they say tip with a dry brush, that's what they mean. First primer coat I loaded up my tipping brush with paint to dab under rub-rails and got the brush saturated with paint, making it tip poorly and causing drips and streaks. Subsequent coats, I really kept it dry (painting cardboard to unload it occasionally) and the tipping process was much more successful while still covering adequately under the rub rails.

8. Finish coat instructions said no sanding necessary between coats if applied within a couple days, but Casey's book emphasized one should wet sand with 320 grit. Don't know how it would have been if I hadn't sanded, but I did and I'm quite pleased with the final result.

Given all the labor involved with a topsides job, I'd encourage anyone to spend a little more and use the premium 2-part polyurethanes over anything else (1-part polyurethanes, enamel, etc.). The reputation that they're hard-to-use is way over-stated and Don Casey and Practical Sailor both state that these finishes will last with high gloss at least 5 and as many as 10 years where others are lucky to give 3 or 4. And the gloss really is impressive!