Removing top layer of bottom paint - SailNet Community

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  #1  
Old 10-27-2011
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Removing top layer of bottom paint

A couple of years ago the previous owner had the whole bottom done with black Trinidad SR. They just added a couple of coats to what was there already.

The problem now seems to be that the top black paint layer is flaking off in places, and has the odd bubble in it. Not to be confused with true blisters, it's water getting under the badly-adhered top layer.

I can only assume that the bottom wasn't properly prepared before painting.

Soda blasting 20 layers of paint off seems a bit drastic. Is there a process, apart from sanding which isn't allowed, which can just remove the top layer and get down to sound paint? Can they soda blast lightly?
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Old 10-27-2011
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Find out if you can wet sand onto a tarp.

Alternatively sail down to the Caribbean and almost every yard dry sands.
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Old 10-28-2011
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Quote:
Originally Posted by MarkSF View Post
I can only assume that the bottom wasn't properly prepared before painting.
Bingo.
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Quote:
Originally Posted by Fstbttms View Post
Bingo.
Do you have any recommendations having seen it recently? I haven't seen it since the haulout in March.
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Quote:
Originally Posted by MarkSF View Post
A couple of years ago the previous owner had the whole bottom done with black Trinidad SR. They just added a couple of coats to what was there already.

The problem now seems to be that the top black paint layer is flaking off in places, and has the odd bubble in it. Not to be confused with true blisters, it's water getting under the badly-adhered top layer.

I can only assume that the bottom wasn't properly prepared before painting.

Soda blasting 20 layers of paint off seems a bit drastic. Is there a process, apart from sanding which isn't allowed, which can just remove the top layer and get down to sound paint? Can they soda blast lightly?
The current issue of Practical Sailor has an artical on soda blasting vs other methods. From what I understand soada blasting is pretty gentle on the gel coat, more so than sanding. The article indicated that soda blasting in general is quicker than sanding although I just got an estimate from my yard in Maine to have 30' botom stripped, sanded, barrier coated and painted that was better than expected from reading the article.
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If you can't sand, how about using a soy-based stripper? Lay down a tarp to keep the mess contained, and you're good to go.

On the lighter side, it is easier to remove just the top layer of bottom paint than it is to remove just the bottom layer of topsides paint.
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Several years ago when I bought my boat I spent a month of weekends with a soy based stripper and scrapper removing about 3/4" of built up ablative to the gelcoat.

Then a lot of repair, and sanding before epoxy barrier coat.

I would suggest removing as much built up layers as you can then see what the condition of the bottom is before moving on to new bottom paint.
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Seafevers bottom had many many many layers of paint over sound barrier coat after much wasted time i found a Home depot 3" carbide tip paint scraper removed the paint with a bit of pain WITHOUT doing any damage to the barrier coat

After some cleaning i laid down about 3 more gallons of barrier coat and a gallon and hafe of micron extra it has gone through a season issue free

It made the least mess at the lowest cost as the soda blaster was about 2K and it was worth the 4 to 5 days to me to spend 0K








I have seen plent of soda work and its pretty hard to be all the selective under a tarped boat in a snow storm of bottom paint and soda
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If a dirty bottom slows you down what do you think it does to your boat
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Last edited by tommays; 10-28-2011 at 10:08 AM.
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Old 10-28-2011
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Quote:
Originally Posted by MarkSF View Post
Do you have any recommendations having seen it recently? I haven't seen it since the haulout in March.
Do you have any idea of how many coats of paint are on the hull? I'm no expert on applying anti fouling, but I suspect that probably just scraping the flaking areas until you get to paint that is properly adhered would do the trick.
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Quote:
Originally Posted by Fstbttms View Post
Do you have any idea of how many coats of paint are on the hull?
No but I suspect it's a large number
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