Help removing bottom paint

imthewalrus

Recruit
Joined
Aug 14, 2008
Messages
3
I've been trying to remove the bottom paint on my 21' fiberglass Chris Craft with limited success. I've tried West Marine's paint remover which didn't seem to do much and I've also been trying to sand the remaining paint off with an orbital disc sander using 60-80 grit discs. It's extremely slow and I'm going through discs like crazy since they only last a few minutes or so and then are no good.

Is there an easier way? How about sandblasting - is that safe or would that hurt the gel coat?

Thanks!

Ronnie
 

arks

Lieutenant Commander
Joined
Nov 7, 2002
Messages
1,929
Re: Help removing bottom paint

Sandblasting does the job but can easily damage the hull gelcoat. I know of a couple marinas that still do bottom sandblasting, but most have switched to soda blasting- it uses baking soda as the blast media. Soda removes the paint but is not nearly as coarse as sand- even very fine sand. Do a Google search and you'll see a short video about soda blasting.

If you have most of your bottom paint already off, try some open mesh sanding pads- they don't clog as fast as regular paper discs.
 

Sorrento25

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Joined
Apr 7, 2008
Messages
2
Re: Help removing bottom paint

Try a pressure washer. Depending on the quality of the original surface prep job and the thickness of the application it can work quite well. When sanding start with a coarse paper like 80 and move around quickly with a light touch. The paint warms and softens easily clogging the paper.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: Help removing bottom paint

Ronnie, Here are two ideas: First of all Sandblasters have a variety of media to use to blast with. I have heard that the best for bottom paint is walnut shells of the appropriate courseness. The gives a matte finish, w/o any damage. Find a blaster with some experience. He should know which to pick.

Second choice is more unproven, but might be worthwile. There is replacement nozzle for a pressure wiasher. This nozzle has a hose that you can stick into a bag of blasting media. You then blast the bottom with a mixture of sand and water. No dust, and easy cleanup. It is not as powerful as sandblasting, which is just what you want.

You may need to experiment to fingure out the best media.
 

proshadetree

Lieutenant Commander
Joined
Jul 19, 2008
Messages
1,887
Re: Help removing bottom paint

Try air craft remover it about the strongest stuff iv seen.
 

Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: Help removing bottom paint

Went thru the same ordeal early this summer.

Tried the pressure washer, sanding, scrapping etc with no success. Took hours to remove a small area. The stuff is incredibly hard and sticks like sh!t to a baby diaper.

In a desperate measure I decided to try the heavy duty gelled paint & varnish stripper. It is thick enough to stick to the hull without dripping off. I applied a heavy coat with a 3" paint brush and applied more as the bottom coat sucked the stuff up. After about 5 minutes, I was able to CAREFULLY just scrap the mush off the hull with a 3" putty knife. Washed it thoroughly with water afterwards. I found thru experience I needed to grind/round off the corners of the scrapper to prevent gouging the gel coat.

I worked in strips about 6" wide x 2ft long. Applied the remover to the next section and let it "work" as I scrapped off the previous section. Did the entire wetted hull surface with about 3 litres of remover and took about 4 hours for a 16ft deep V hull.

Wear glasses and rubber gloves with long cuffs. The stuff burns when you get it on the skin.
 

mohawk317

Recruit
Joined
Apr 24, 2008
Messages
3
Re: Help removing bottom paint

Just my 2 cents. I just walked in from the same problem 'exactly". I found the answer. My boat is a 1987 and I'm going through the same thing. I treid everything , I mean everything. I busted my a-- and will probably die soon from inhailing all the dust. The answer is ' a benzomatic propane burner and a spackle knife'. I am so happy its working for me. Try it. Just heat it up until it turns black and bubbles's a little , then scrape it off. Good luck.
 

imthewalrus

Recruit
Joined
Aug 14, 2008
Messages
3
Re: Help removing bottom paint

Hey, thanks everyone for the great tips! As it turns out, I was informed that the old paint is hard bottom paint and that since I will be re-coating it with hard bottom paint (West Marine Bottom Shield), I don't need to remove it...doh! :redface:

So, I've left the rest of the old paint on and just went over it with 60 grit sanding discs to smooth everything out some. Am I ok to slap the new paint on or is more prep needed?
 
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