Barrier coat

[RichCarter]

I just finished putting on a barrier coat and thought I might send something out about my experience. I would guess that most of us who haven’t already had the process done must be contemplating a barrier coat. Our boats are aging to the point where the gelcoat is failing. In my case, I had minor blistering over the years, a dozen or so would show up each season when the boat was hauled. This by itself didn’t concern me. There were signs of spider-web cracks in the gelcoat. It was difficult to evaluate what was going on under there, but I feared that more serious damage would result if I didn’t address the problem. Bottom paint had laid up in coats over the years. Even though I use ablative paint, the previous owner had used cheap stuff. It had flaked off unevenly and left the bottom with a mottled texture. I had plans to leave the boat out of the water for a season so it was a convenient time to fix it.

If you’ve ever tried to remove your bottom paint, you know what a miserable job it could be. I hired a soda-blast company to remove the bottom paint ($2k). They did a very good job. They removed the bottom paint and carted off all the waste. They even moved the jackstands and cleaned under them. This left the bottom with a pink tinge. I spoke to the guy who did the job and asked his opinion on how to proceed with the barrier coat. He suggested sanding the bottom with 80-grit paper to make sure the epoxy would stick. I had plans to fill and fair the bottom anyway, so a light sanding didn’t seem an issue.

Close examination of the bottom showed dozens of small and medium sized blisters. It also showed hundreds of tiny pin-sized holes in the gelcoat along with spider-web cracks in various places on the hull. The entire hull wasn’t that same. There’d be an area that looked perfect and another area with pinholes and another area with spider-web cracks. I filled the larger holes with West epoxy. There were too many pinholes to even consider addressing them. I’d have to let the barrier coat fill them. There was no way to address the cracks. In areas that showed them, there were hundreds of cracks. Hopefully, the epoxy will repair them.

I used an orbital sander to buff the bottom. I had to be aggressive near the boot-stripe because I had raised the water line by about 2 inches. The old boot-stripe was never removed. Sanding the bottom was a terrible chore. It took about 10 hours, much of that time with a heavy sander at arms-length. Much of that time was spent trying to smooth-out places where I’d patched a blister. I did it in one weekend. It left the bottom with a clean white color.

I chose Petit Protect rather than the Interlux product. I’ve had very good luck with Petit products over the years. Since their product was less expensive than Interprotect, I went with their barrier coat. I used a foam roller and applied 1.5 gallons of epoxy in the first coat. The roller was purchased at Home Depot. I had issues with the roller foam separating from the spindle but I was able to work around it. The epoxy went on with an orange-peal finish. I suppose this is OK for the first few coats, but I wanted the final finish to be smooth. I found that a 6″ paint brush worked better, but you only get one coat per brush at $12 each. I applied up to, but not touching the tape. I don’t want the tape to be glued to the hull. The boot-stripe is above the water line anyway so there is no reason to put the barrier coat up that high.

Subsequent coats were difficult to apply because the stuff was all the same color. It was hard to see how much was applied. I later found out that Petit sells the same product in a white color. I wish I had known that. Alternating colors would have made the job much easier. In all, I applied four coats of epoxy for a total of six gallons, two coats on the first day and two the second day. According to the label, I had to sand the bottom before applying the first coat of bottom paint because I had missed my window. Once again I had the damn sander out at arms length, but I only buffed the finish this time for about an hour. I applied one coat of green Petit Hydrocoat for the first coat. One gallon just did the job. I’ll apply two more coats of red, but the remaining two coats will be a bit thicker. My neighbors must think I’ve lost my mind. Every time they drive by the house lately, the boat bottom is a different color, red, pink, white, gray, green, and finally red.

This is the first time I’ve used a water-based bottom paint. I’ve heard good things about the paint. Application is easier since it just washes up with water. I’m using a 6″ painters brush for application and find that it leaves a much smoother finish than a roller. Since its a water-based paint, I can get more than one coat with a brush. After I’m finished, I’ll move the jackstands and do under them. I’ll probably only get one coat of epoxy under the jackstands. Its too much of a pain to mix three small batches.

The total cost for this project came to about $3k and I’ll have about 60 to 80 hours into it. I had to pick my weather according to the instructions on the label. I had a lot of trouble getting the bottom paint to fill the pinholes. I’d brush over an area and it would appear smooth only to find pinholes reappear. I got them eventually filled. If I were to do this again, I’d hire someone to help. I don’t trust anyone to do it right unless I’m there. I’d try to apply thicker coats so that three would complete the job. This would be two coats on the first day and one coat the morning of the second day. One person could do each side of the boat. Timing would allow applying the first coat of bottom paint that afternoon without sanding. There is no time window for application of subsequent coats of bottom paint.

I don’t know precisely how much surface area the boat has. My best guess is about 400 sq-ft. This works out to just under two-gallons/coat. Its hard to apply the epoxy thicker than 4mils/coat without sagging, so expect to waste about a quart or two with each coat.

Rich
BlackSheep #47

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