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Old 30-07-2021, 22:17   #1
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Removing old anti-foul bottom paint. Thread?

I can't find the thread I'm looking for, it must be here somewhere...

What's the quickest way of removing old, thick, patchy bottom paint? I have the boat at home and there are no issues with dust or noise, etc. I've tried an abrasive flexible disc on a grinder, but this seems to be too uneven and before you know where you are you are through the gelcoat. I've tried a belt sander, but this didn't seem very effective on the old antifoul, but very effective on the gelcoat again, unfortunately. I've tried a wood chisel by hand, but this will take forever and will still need sanding afterwards. I've already waterblasted with a good high pressure washer - some little amount of the looser stuff came off. I haven't used a soda-blaster as I was hoping for something that I could do myself (money is not a non-issue, to say the least). I am hoping to give a couple of 2 part barrier coats prior to applying the antifoul.
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Old 30-07-2021, 23:03   #2
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Re: Removing old anti-foul bottom paint. Thread?

I spent about 5 days with a young hired hand and a circular sander removing 30 years of built up bottom paint on a 38-foot monohull. It was not the most efficient but it also didn't dig into the gelcoat like a bad blasting job that I had tried on a 20-footer once.
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Old 30-07-2021, 23:26   #3
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Re: Removing old anti-foul bottom paint. Thread?

Try using some paint stripper to soften the antifoul and just scrape it into a bucket for disposal. You might use quite a few litres of stripper and several coats. But the method is way more friendly than using noisy, dusty power tools. Turn on the radio and enjoy the results.
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Old 30-07-2021, 23:31   #4
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Re: Removing old anti-foul bottom paint. Thread?

I watched this recently and wondered if it was worth a go for a one off job. Dewalt also do a similar attachment widget:

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Old 30-07-2021, 23:44   #5
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Re: Removing old anti-foul bottom paint. Thread?

How about one of these for the keel, its a Tercoo rotary blaster:

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Old 30-07-2021, 23:50   #6
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Re: Removing old anti-foul bottom paint. Thread?

Jeremy if your not going to pay for soda blasting or a light sand blast then you just have to suck it up and do it manually. These Sandvik scrapers work pretty well and produce good results.
I have also used an antifoul paint stripper that you put wax paper on top after you have spread the gel. The results were ok.
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Old 31-07-2021, 00:56   #7
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Re: Removing old anti-foul bottom paint. Thread?

Wet sanding with an compressed air rotary sanders. It is a truly horrible job.
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Old 31-07-2021, 01:09   #8
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Re: Removing old anti-foul bottom paint. Thread?

following...

i spent about ten days with a circular sander on the belly of a 47' monohull a few summers ago... and it was a very tough, not-so-satisfying job. and, even though i wore a mask(s), ended up coughing for three weeks.


whatever you chose, chose high-quality protective gear too
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Old 31-07-2021, 10:58   #9
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Re: Removing old anti-foul bottom paint. Thread?

I am doing my boat now, and it is perhaps the nastiest job I have ever done. Summer heat in 90s doesn't help.



Blasting is one way to shorten the task, but keep in mind that it is not cheap. The blasting and all the dust/mess mitigation put the price for my 33' at close to $2000. After that you will need several epoxy barrier coats, then 2-5 new topcoats of a high quality bottom paint. For me that would be prohibitively expensive -- I estimate $5 - $7K.


So I have opted to scrape the loose paint, sand and feather the edges, prime the bare spots with some left over paint from the last time, then roll on 2 new topcoats.



Unless you can pay someone to do it, you will have to just suck it up and take your ass-whipping.
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Old 31-07-2021, 11:15   #10
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Re: Removing old anti-foul bottom paint. Thread?

Sea Hawk stripper works really good. Depending on how thick you put it on the stripper can remove all layers at once. It removes all types of marine coatings, not just bottom paint. Usually you can buy it on Amazon or ebay for a lot less than a marine store.
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Old 31-07-2021, 19:35   #11
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Re: Removing old anti-foul bottom paint. Thread?

Several years ago I removed gummy vinyl bottom paint from a trimatan using a seven inch air powered grinder with 26 grit fiber discs. I wore a mask and maybe snorkel and kept a hose aimed on where I was grinding to cool it off. If you use discs (and holder) with large holes in it, you can easily see when you are thru the paint. The high volume of water kept it cool and one disc lasts for ever.
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Old 12-08-2021, 02:30   #12
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Re: Removing old anti-foul bottom paint. Thread?

A bit of report back.... I've had a fair bit of assistance from an electric wood planer. You have to resharpen the blades regularly though. And it kicks up the same amount of dust as a sander. After planing the worst off, then an orbital sander. Not sure if it's the best way yet, as I have still got 70% to do.
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