Paint Removal, Blisters and Delamination
We purchased a vacuum sander and lots of 40 grit sand paper. Vacuum sanding is the only way to go. It recovers around 90 to 95% of all the dust from sanding. Apparently someone at the boat yard sanded his bottom paint not using a vacuum sander. The next day his neighbor who had just finished painting his entire boat with awlgrip found the boat covered on one side with bottom paint dust. The boatyard had to pay to have the newly painted boat professionally cleaned. Now the boatyard requires all sanding to be done with a vacuum sander. You have to consider that bottom antifouling paint dust is very toxic and breathing it in can't be healthy. I also purchased two respirators, goggles and lots of latex gloves and use them constantly.
Porter-Cable 5" Random Orbital Sander and Fein Vacuum. If you have a lot of sanding to do you might want to consider buying a larger diameter sander.
Once I started sanding the bottom I immediately noticed that I had a great deal of difficulty trying to remove the thousands of barnacles embedded on my hull. Sanding them off was nearly impossible with 40 grit. I went down to 36 grit but the heavy grit paper bogged down my random orbital sander and got me nowhere. I stupidly tried $100.00 worth of chemical peel which removed most of the antifouling paint but didn't even touch the barnacles.
Chemical peel removed most of the antifouling paint.
Stubborn barnacles
I searched the internet for some leads for how to get rid of barnacles and came across an article that said muriatic acid full strength would do the job as barnacles are essentially a base so the acid would melt them right off. I purchased a gallon of muriatic acid at the local hardware store, put on goggles and protective chemical gloves. I had a water hose handy and used a garden sprayer set to a mild stream to attack the barnacles. Once the acid was applied to the stubborn things they bubbled right up into a yellow paste. I left the acid on for a very short time and rinsed it off with plenty of water from the garden hose. I was then able to scrape the remainder of the barnacles off using a sharp paint scraper. I did the whole boat in small sections. Muriatic acid full strength is very dangerous stuff. I went very slowly with the application of the acid. Because of the strong vapors muriatic acid gives off, I ended up wearing my respirator.
Once the barnacles where completely removed I sanded the bottom down to the gel coat primer. That is when I started to noticed a lot of blisters. They were in groups running horizontal from bow to stern from the water line right down to the keel. I ground out some of the larger ones and they were filled with fluid deep inside the laminate. Some of the fluid squirted out when I began to grind into the blister. I cleaned them out with Interlux 216 solvent, washed down the entire hull and let them dry out for a few days. I then gave them a closer look and saw the separation between the fiberglass laminate inside the larger ground out blisters. My neighbor at the marina had a moisture meter and let me borrow it. I took readings all around the boat. The deck and upper hull were fine but from the waterline down the meter pegged off the scale. Now everything I had read about hull delamination told me I had a major problem. I had been buying epoxy and fiberglass supplies for repair work on the deck at a local Annapolis boating supply center called Oceana. I mentioned my boat blister problem to the sales person at the counter who used to lay up fiberglass hulls and paint boats in the area. She said I should talk to a local person who professionally peels boats.
The first two pictures show large laminate blisters. The third picture shows very small gelcoat blisters.
A hull peel job from what I have read uses a machine similar to an electric
planer device that removes fiberglass laminate in layers. I called the
fiberglass peel technician and asked him if he wouldn't mind taking a look at
the boat and give me an opinion as to whether I needed to peel the boat or just
let it dry out and seal up the blisters, give it a barrier coat, new
antifouling paint and hopefully it would last for a number of years. The
tech looked at the boat and told me I had a severe blister and delamination
problem. Sealing up the blisters would still leave large voids between the
fiberglass laminate where water would seep back in and push out new blisters
again. The only way to properly repair the problem was to
peel off the delaminated fiberglass form the
waterline right down to the bottom of the keel all the way around the boat.
I will then have to wait until next spring with a cheap dehumidifier going 24/7
inside my boat cabin. Hopefully by then the moisture meter will read the
same readings on the bottom hull that I have been getting from the top of the
hull. So far the
estimate for the peel is $30.00 a foot x 30 feet maybe more if they have to re-peel the
hull in order to remove all of the delamination. Materials for the fiberglass
lay-up will run around $2000.00. I also contacted a person who used to
lay up fiberglass hulls professionally. I will contract her next spring to
run the job with my wife, son and me assisting her. She figures total time to
lay out two layers of biaxial to be around 10 hours. Having this job done
at a boatyard runs around $9000.00 for a 30 foot boat.
August 2006
Materials for the lay up ran close to $4500, paid labor cost ran $1200