Strange lines on hull antifoul

[rognvald]

Well, LTC,
My opinion is: 1.) when they applied the bottom paint, the hull was still wet from a power wash(?) and you had poor adhesion of the bottom paint after a quick launch and no dry time which is why you see the shrinkage(strange lines) after it went into the water, or 2.) they used something on the bottom(chemical/soap, etc?) that disallowed the paint to bond properly with the substrata causing the paint to shrink. I've seen this, at times, when people spray paint enamel and the surface is contaminated or fiberglass a compromised surface. That's my three cents. If, however, it was painted before it went into storage, something was wrong with the paint or the process. I blame it on the application and/or the integrity of the bottom paint. If it were my boat, I'd completely sand off the offending paint and allow the hull to dry before applying new paint. Good luck!
Best, Rognvald

[rognvald]

One last thought . . .
It appears in pix #2 that another possibility is that the bottom was improperly sanded with a 40 grit sanding disc mounted on a non-foam pad(ie; hard rubber/plastic) that seriously gouged the bottom. I've seen this twice in boatyards employing clueless teens with hard mounted rotary sanders and aggressive grits. This could easily be determined if you can feel gouges in the bottom. Otherwise, my last post is my best guess.
Rognvald
Rognvald

[longtermcruiser]

Good thoughts but NOPE!
Hull was dry when painted (inside hall all winter).
We painted it and surface prep was the same as always,
Lightly hand sanding in spots before applying paint with a small roller. We have been doing the antifouling the same way for 34 years.
The paint was new and properly stirred. The same type of paint was applied as the previous year

[MicHughV]

Many years ago, I can relate this incident.

I had built my first boat back in the 70's, and prior to launching it, applied bottom paint.
Being as that I was a poor sailor with nary a dime to my name, I sourced some bottom paint as it was a "good deal"

I noticed right away that the paint was rather " streaky" despite my best efforts to stir it up, as the "solids" in the paint had settled to the bottom of the paint can. The end result was not a pretty sight and I had to do it all over again with newer paint.

Bottom paint is usually a mixture of chemicals in a liquid, and if this is not mixed properly can easily result in some parts of the paint thick with glommed up chemicals and other parts of the paint, not so much.

Once the paint is on the hull, it pretty much all looks the same, but parts of the paint will have the chemicals, while others don't. After some time in the water, the end result could look like the photo's in this thread.

When one says "properly stirred" that could mean anything. Stirred with a stick? or stirred with one of those long shafts with a small propellor blade on the end, attached to a drill ?

Just tossing out ideas and thoughts as I'm still of the opinion, the issue is with the paint and the application thereof and not any marine life.

[rognvald]

Originally Posted by longtermcruiser

Good thoughts but NOPE!
Hull was dry when painted (inside hall all winter).
We painted it and surface prep was the same as always,
Lightly hand sanding in spots before applying paint with a small roller. We have been doing the antifouling the same way for 34 years.
The paint was new and properly stirred. The same type of paint was applied as the previous year

Hi, LTC,
Then, the only answer is that there was a problem with the paint(bad batch) as mentioned above or something inside the building that caused contamination on the surface over the Winter ie; diesel exhaust fumes from a lift truck, engine, etc. that was run for extended periods over the Winter. My guess is that you got a bad batch of paint. So, wash, aggressively sand, dry, and repaint. Good luck . . . that's an interesting story!
Rognvald

P.S. Did you add anything to the paint during mixing? R

[rognvald]

One last thought, LTC,
Since all above comments are based on conjecture, why not contact the paint company and show them the pix. They might know immediately what went wrong. Good luck!
Rognvald