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What is the best / easiest method for removing multiple layers of ablative bottom paint from a sailboat hull?

I have acquired a sailboat which has 3-5 layers of different bottom paints. I want to get back down to the base layer and put a fresh coat of paint on the hull. I have used a pressure washer to knock off loose chips, used an angle grinder for some, but it's really too labor intense and it cuts into the original gelcoat (which isn't too big of a deal), and it creates more dust then I really want.

Is there a tool or stripper that makes removing this material faster?

The hull is fiber glass, and based on the age of the hull, I'm forced to assume it is setup with polyester resin.

  • What is the hull made of? Certain compounds may have an adverse affect on the hull and degrade it's integrity if you plan on stripping it. A thoughtful answer is dependent upon this information. – Citizen Jan 5 '16 at 3:08
  • @PaulD Added more details of hull materials. – Escoce Jan 5 '16 at 16:35
  • I'm voting to close this question as off-topic – Wills Jan 7 '16 at 7:10
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Here is a Youtube link for "Fast bottom Paint Removal using Walnut Blasting".

You could also try the following steps:

There are several ways to take off many paint layers, and what you ultimately decide on will depend on your budget, the boatyard’s rules and your boat’s current condition.

Method 1:

Sanding the boat’s bottom is the dreaded chore that most boat owners will face at some point. This is definitely a case in which having the right tools will really make your job easier. Using a vacuum sander helps keep most of the dust out of the air, producing a much cleaner work environment. Many boatyards also require them. Prices for a random orbital sander with a vacuum port range from about $60 for a Ridgid brand to about $450 for a top-of-the-line Festool. You’ll also need to buy a Shop-Vac-style vacuum.

You’ll want to sand down the bottom with 60- or 80-grit paper until the excess paint is removed and the bottom isn’t overly textured. Be careful not to damage the gelcoat. Most boatyards in the United States have strict rules about how bottom jobs are done and may require a ground cover or a tent around the boat from the waterline down to capture the dust and debris.

Method 2:

A quicker way to remove many layers of paint is through high-pressure blasting with either soda, sand, or a special glass material shot at the hull. It’s effective and faster than sanding, but it’s also not typically a do-it-yourself project. If having your hull blasted is something that you’re considering, do your homework and find a reputable blaster. Also check to see if your boatyard allows it. Expect to pay about $35 to $45 per foot for professional blasting.

Soda blasting is what many boat owners choose for bottom-coating removal on fiberglass boats because it’s less abrasive than other materials, though if you have a steel or aluminum hull, you can probably go with sand blasting. If the project is done by a skilled blaster, the soda will take off coatings down to the gelcoat or barrier coat—if it’s in good condition—without damage.

After soda blasting, the surface is typically too smooth for bottom paint and must then be sanded with 60- or 80-grit sandpaper. Before covering with new antifouling paint, wash the bottom with water and let it thoroughly dry. According to Mike Morgan from Chesapeake Blasting Service, “Most boats can be blasted unless they have serious issues with the gelcoat or fiberglass. If this is the case, they should be peeled and a whole new bottom applied.”

Method 3:

A chemical paint stripper is another way to remove paint buildup and is the method of choice for some boatyards since there’s no dust or noise and the residue can easily be contained. Paint stripper is relatively easy to use—you brush it on with a paintbrush, wait the recommended time, then remove the resulting goo with a scraper—but it can be a time-consuming process, not to mention a messy one. A ground cover is essential, and you’ll need to discuss the debris disposal with your boatyard.

When choosing a chemical paint stripper, be sure to check that it can be used on your particular hull material, and expect to use 5 to 6 gallons for a 45-foot sailboat. Paint strippers work best when not used under direct sunlight, as the chemicals need to stay moist to work. After the old antifouling paint is removed, you’ll still need to sand the bottom with 60- or 80-grit sandpaper to rough up the bottom for paint.

(Source of above points)

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So after all is said and done, I called a sand blaster, but they wanted too much money to blast my small hull. Like $1000. I could buy my own equipment to do the job for that price, but I didn't want to spend the money either way.

My neighbor told me he had a blaster I could use, and when I looked at it, it was just another pressure washer. Well he said this one is a lot stronger.

Anyway, I used his pressure washer and holy cow what a difference. His pressure washer blasted the paint right off. There are still some spots, but to be honest, it really did the job. What he leant me was a generac 3100 psi 3 GPM gas powered unit.

It worked great and only took a few hours to strip the paint off the whole hull. Now all I need is to let it dry out so I can shop vac up the debris from my driveway.

I just thought in case anyone wanted or needed to know that a powerful enough pressure washer does the trick.

Bear in mind that it can and will strip the barrier coat and dig into the fiberglass if the spot is weakened, but considering I am looking to repair and restore this hull, that's just fine by me, if it comes off then I want it to come off so I can lay new glass and epoxy up and make it stronger.

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