Digging into Bottom Paint Removal

Posted by Darrell Nicholson at 01:03AM - Comments: (4)

March 4, 2014

Keeping chisels sharp can save a great deal of work over the long haul.

If you are looking at your hull and thinking about stripping back all the bottom paint and perhaps applying a barrier coat, here are some practical tips on getting it done quickly using a paint stripper, with the least amount of pain. Before you embark on this project, you’ll want to look at our recent article on estimating the amount of work that is required, as well as our in-depth report on chemical paint strippers, which looks at the best chemicals to use. This article, redacted from PS Technical Editor Ralph Naranjo's extensive report on removing paint in the March 2009 issue, looks exclusively at the tools and techniques that add some mechanical umph to the chemical paint removal process. If you have your own specialized tools or techniques for this tedious work, we'd appreciate your input.

Paint removal using a paint stripper is a little like dental work in that there’s no one perfect tool and getting the job done usually requires a tray full of devices—from multiple scrapers to sanding tools and sanding discs.

Power tools need to be used carefully to avoid putting deep gouges in the gelcoat.

The arsenal of hand-scraping weapons used during our test of paint strippers ranged in caliber from a lightweight, extra-thin and narrow scraper sharpened to a knife’s edge to what old shipwrights referred to as a “slick.” This heavyweight king of the chisel family was kept sharpened with a whetstone and had the mass to plow into thick paint buildup and peel the substrate evenly. Drag scrapers utilize a pulling motion, and the key trick-of-the-trade is keeping a file handy to regularly sharpen the blade.

The downside of scraping paint from a surface goes beyond the drudgery and sore arms and shoulders associated with such toil. The real drawbacks are the nicks and gouges that result from even a slightly misaligned scraper. When the paint removal is completed and the surface has been thoroughly washed and inspected, it’s time to repair the scraper damage with an epoxy filler. This is done at the same time blisters in the laminate are repaired. To reduce the potential damage from scrapers, you can round the scraper corners and be very careful when a chisel is used for heavy-duty paint removal.

Sanders

We found that Fein’s 120-volt AC random orbital vacuum-assist sander is a double-barrel winner. Not only is it a vigorous, efficient sander, but the dust and residue collection system is superb. Even so, we did need a conventional disc sander to tackle the really tough stuff, and not having Fein’s version of this tool, we were content with using a medium-duty, two-speed Hitachi sander/polisher—a tool for many occasions.

A heavy and powerful Bosch grinder is an aggressive option, but it needs to be used with a deft hand and would be good for removing coatings from a steel hull.

Sanding Discs

Heavy-duty sanding discs used on soft pads transmit considerable torque, and conventional “Stikit” type adhesive-backed discs often fly off soft pads like sharp-edged Frisbees. To solve this problem, 3M (www.3m.com) and others have switched to backing discs with an attachment system called “Hookit.” This three-dimensional securing system provides a Velcro-like connection between the disc and pad. Even 36-grit “paint buster” abrasive discs stay stuck to the pad. When it comes to less abrasive grits, the product from 3M was a favorite. Fein offers 150-
millimeter diameter discs with a hole pattern matched to its soft pad. These abrasives are expensive, but they allow the vacuum system to work at its optimum level.

Here are a few tips that can help you save time in your bottom-paint stripping enterprise.

  • A file and a whetstone for sharpening scrapers are the bottom stripper’s best friend.
  • Heavy-duty rubber gloves, leather work gloves, and disposable latex gloves are a must. A hat, eye protection, and particle mask round out the required safety gear.
  • The choice of drag scraping or push scraping depends on the hull contour and your body position.
  • A small stool and step ladder can make the job easier.
  • Roll on the paint stripper using a thick-nap roller and a wide dabbing brush.
  • Use masking tape to help hold the stripper covering—paper or plastic—in place.
  • Remove blistered and flaking paint by first dry scraping, and then attack more reluctant areas with stripper.
  • Lightweight, back-vented coveralls effectively balance the need for heat dissipation and skin protection.

If the paint-stripper process seems too overwhelming, you may want to consider hiring someone to soda-blast or peel your hull. In our review of soda-blasting services, we got a first-hand look at how these operations work. In the end, we determined that the price of this service was well worth the time (and back muscles) saved.

Comments (4)

Scraping with a carbon steel scraper requires as much sharpening as scraping. Use a carbide scraper instead and sharpening becomes a once a day,or less,chore.

Used carefully the carbide scraper will remove bottom paint many layers think in one pass. A friend and and I removed paint from the bottom of my 33 foot boat in two 5 hour days using carbide scrapers and and a Porter Cable orbital sander. We did very little repair requiring damage. Some light sanding was required prior to applying the barrier coating to remove the final traces of the old bottom paint.

We scrapers used were a 1.5" and 3/4" wide. The 1.5" model was $16. I bought the tools at Home Depot. They are also available online at several easy to Google sites. I have used these tool for many non boating tasks and love them so much I have given

The scrapers were also used to smooth the barrier coat prior to applying the anti fouling paint.

I would never consider using a push scraper/chisel on fiberglass except where a pull scraper or sandpaper couldn't do the job adequately.

Posted by: BillR | March 10, 2014 11:19 AM    Report this comment

Forget all this and use dustless blasting - high pressure water combined with finely ground glass. No dust, finite control of the amount of paint removed. Used in auto body shops to remove finish coat but preserve the primer coat. Far less hassle than soda blasting.

Posted by: BRIAN L | March 6, 2014 5:39 PM    Report this comment

I have stripped my bottom twice. I used just a pull scrapper and a random orbital sander. The pull scraper takes off the loosely adhering stuff and the machine does the rest. Buy plenty of sandpaper and don't wait too long to change disks. You will also need several masks certified for lead paint removal.

You can't go too cheap with the sander but my $50 Porter Cable seems good enough. The Porter Cable allows the attachment of a vacuum hose and has holes in the disk to suck away the dust. I am sure the $450 Fein tool is a lot better.

After sanding you will want to apply Interlux Interprotect 2000 or its equivalent because it is impossible to avoid sanding off some of the blister protective gelcoat.

The idea of using a chisel is frightening. I also experimented with a chemical stripper. I sounds good and there is less physical labor. The downside is washing the stuff off makes a huge mess that is difficult to contain and won't earn you any points with the yard manager. Scrapping the softened paint off combines the worst of both methods. For sure, you will need multiple applications of the stripper.

The yard asks that I use a HEPA filter on the vacuum which is pretty expensive. I found a particle separator that saves the filter. Dust Deputy from Oneida Air Systems. I saved a couple of bucks and used my own 5 gallon drywall bucket. It paid for itself in the first day. http://www.oneida-air.com/category.asp?Id={CC6B6F2A-E3D7-4F18-A53C-B5C357DFE131}

Posted by: BARRY N | March 5, 2014 3:32 PM    Report this comment

I am using a Bosch 1250 6" random orbit sander. The price is half of the Fein sander, it has a normal and aggressive (oh yes!) mode and the tool body is closer to the work surface which makes handling easier. But I still have it hooked up to a Fein vacuum with the automatic on/off feature. No other vacuum beats those. Buy German tools if you want to get the work DONE.

Posted by: BERNHARD L | March 5, 2014 8:33 AM    Report this comment


Add your comments ...

New to Practical Sailor? Register for Free!

Already Registered? Log in

Forgot your password? Click Here.