Removing ablative paint

[bhartley]

After completely redoing the bottom on our Cape Dory 25D, I am finding myself having to take OFF the ablative paint along the water line and I am not having much success. I used Interlux Micron CSC as we do not haul our boat regularly (fresh water). The problem is my husband loves to scrub the waterline with a sponge while swimming and it has big white patches along the waterline after 1 1/2 seasons. Pyxis is out of the water now and I planned to sand off the top 10 inches of ablative paint and apply a hard paint before the coats of ablative so it would cover better. Except for the scrubbed areas, the paint has been great.

I have used 150 and 100 grit sand paper (with proper respirator) but it is very slow going. Pressure washer has done no good. I know if I just go ahead and roll on the non-ablative paint, it will fail immediately once we're back in the water.

Any advice? And getting the husband to stop simply isn't an option.

Spring is here in Georgia -- and we have water again! Launching shortly.

Bly

[Zach]

36 grit zirconium paper (the blue stuff) on a sticky backing pad. Put it on a 5-6 inch random orbital sander, or an 8 inch variable speed polisher.
The infamous Porter Cable 7335 with an aftermarket counter weight and backing pad... or a Makita 9227c get my vote for bottom paint removal.

Once most all the paint is off, switch over to 60 grit on the random orbital.

If you are going for a racing bottom... sand up and down, then make a flexible longboard out of 1/4 inch starboard, thin plywood... or whatever is handy, and put sticky inline paper on it.

If you are trying to use a palm style sander, or something that buzzes... its pretty much a waste of time at those grits. You can get 36 grit velcro backed stuff for the homeowner grade stuff, but they don't have the horsepower to make a decent show of it. Bottom paint is soft and gummy, you need a tool with the power to cut through it and throw the dust. If you are on a real tight budget, you can tilt the pad up in the air using the outer 3/4 of an inch or so to get most of it off... goes faster, stop just shy of the gelcoat and finish it off with the pad flat to the hull.

Good luck!

Zach

[bhartley]

Thanks Zach. I did as you suggested. I have also come to realize some of the paint "failure" areas were likely made worse by improper prep. The bottom needed a great deal of work while stripped. I finished by rolling on several coats of epoxy (not barrier coat). I must not have gotten the amine blush completely off in some places. The paint is so firmly attached on 90% of the bottom that I cannot blame anyone other than myself.

After lots of extra sanding, scraping and testing for quality adhesion, the bottom has been repainted with CSC only with two extra coats along the waterline. I may add one more before we launch on Monday. The paint has a 16 hour minimum before immersion so my decision better be made soon.

Thank you,

Bly

[sscoll]

If you're putting it in fresh water forget the ablative paint. You'll get the same amount of "fung" with or without that type of paint and that's about all you'll get in fresh water.

Steve

[Ryan]

FWIW, I am in the same water and after several conversations with the Interlux rep, he has convinced me to use Ultra hard bottom paint. Typical haul outs here are several years apart, nothing keeps the slime away, and with the hard paint, I can scrub it while in the water.

Will Pyxis be at Big Water again?

Ryan

[bhartley]

Ryan,

Yes, we are going to be back at Big Water. We have moved down to the C dock in about the same spot we were on B. We're due to launch on Monday. They're stepping the mast at noon.

We stayed with the ablative as it became obvious that the prep was the problem. The starboard side waterline had patchy areas -- and sanded off to smooth with no effort and the port side might have well been welded to the gelcoat. The poorly adhered areas were all sanded down and should fix the problem. I could have sanded for the next millenium and not gotten the good stuff off.

Are you in the water?

Bly

[Peter]

I don't know if it might be too aggressive for what you're doing, but there was a thread on carbide scrapers here that may help.
I swear by 'em :-)

[bhartley]

Peter,

The carbide blades were just the trick for removing the many layers of HARD bottom paint 2 years ago when she was taken down to gelcoat. The ablative paint wouldn't scrape at all. My only option was sanding (which is very unpleasant!). Once I determined that it was a prep issue, I feel comfortable putting the Micron back on.

Now only one more bottom to paint (already prepped) and we'll be sailing instead of doing yard work!

Bly