Dave, Is it possible you are trying to remove VC Tar or similar?
Coal tar epoxy is the corrosion protection system we typically spec for steel sheets in a marine environment. Bluewater makes a bottom barrier coat for boats, but I suspect it's for commercial use on steel hull barges etc. If you're dealing with VC Tar as Joe and others have suggested, then misery loves company. I am the final stretch of the same project. For me the tar was softer, it smelled terrible and was still somewhat tacky in warm temps. After much trial and error I settled on two techniques that worked for me. 1. Chemical stripping - I used Citristrip and a glass cleaner <https://www.homedepot.com/p/Anvil-4-in-Glass-and-Tile-Scraper-GTS-ANV/309996591?>(4-inch wide razor blade) in lieu of a putty knife. With the razor blade (lots of replacement blades), and a little practice, i was able to peel off two or three layers of paint at a time and leave a smooth fair surface. On the tar, i was able to get between the tar and gel coat without gouging the hull. My boat was raced by the original owner and had a decent bottom, but had suffered from paint build up. While this sounds tedious, it minimized the fairing and longboarding. The rub is the stripper needs the temps to be close to 60-F (15-C) to work and needs to sit for at least an hour or two. If you're in direct sunlight or windy, you'll want to cover the stripper with plastic. You want to avoid letting it dry out. (Another boat in the yard didn't use plastic, but just mist the gel with a water bottle to keep it from drying out.) With the citristrip, i was able to apply it and leave it overnight covered with plastic and then come back to scrape it the next day. It seemed to work up to about 3-layers of paint. 2. Mechanical Removal - Unfortunately, I counted 12 separate colors of bottom paint before getting to the tar, i'm located in the NE and with a hard launch date, i had to use a mix of chemical and mechanical removal. The only system that worked for me without destroying the hull shape was a 6-inch random orbital sander using 80-grit Mirka Abranet pads. The Mirka are a mesh pad and do not clog with the tar as long as your dust collection system is decent. I used a home depot dust stopper <https://www.homedepot.com/p/Dustopper-HD12-High-Efficiency-Dust-Separator-HD12A/315749552> separator before the shop vac. It is stupid expensive for what it is... but it really works and saves your shop vac filters. I could get 10 to 15 minutes out of the Mirka pads. I've gone through close to 30-pads in the project. I tried using traditional 36-grit pads but they were dulled after about 5-minutes. Also tried the Bahco carbide scrapers. Those worked well for level surfaces (e.g the rudder that you drop and put on saw horses) but it was tough sledding to work on your back under the hull. If you do go that route, bevel the edges of the blades and you won't gouge the hull. If you're still here, a few other lessons I learned the hard way. Managing heat on the pads was important. The Mirka pads do not insulate the hooks from heat. So you'll absolutely need to use pad protectors. If you don't, you'll melt the hooks on your sander and your disks will be flying off the sander by lunch on the first day. I lost a few days waiting for new parts when this happened to me... I also found lighter pressure on the sander worked better. Letting the pad spin faster allowed it to chew more of the material away. Easier on the shoulders too. Switching back to the stripper, I applied with a chip brush. Someone in the yard pointed out that i should only be brushing in one direction. Most have a wax in them that helps prevent drying out. Applying in one direction certainly helped increase the working time of the gel. Being dutch, i was able to wash the chip brush in hot water and used one brush for the whole job. Best of luck with the project -- cheers, matt C&C 27 Mk V EDUAM RYC, NJ On Mon, Apr 5, 2021 at 8:51 AM Della Barba, Joe via CnC-List < cnc-list@cnc-list.com> wrote: > I think this might mean coal tar epoxy barrier coat, which is nice until > it starts coming off ☹ > > > > Joe > > Coquina > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu
Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
