So in this blog, we’ll talk about surface prep of the bottom and the barrier coat. It is imperative that the surface is completely clear or all residue, oil, or old paint as the new paint will not adhere correctly or even at all. Nothing is worse than having to haul your boat out mid-season to make repairs. Been there. Done that, Paid the bill for it.
So, assuming that the paint is mostly gone, now we get into the fine surface prep. For this I used #80 grit sanding discs, and went over the entire bottom. At this point, when all the paint is off, it’s time to look at and fix any defects in the hull. It’s difficult to look at the bottom and see the issues when it’s all one color, especially white. Some ‘Old Salts’ would use a can of black spray paint. They’d cover the area that needed improvement with the paint, then sand away until it was flush. If paint was left over, it’s not flush. Others use strong work lights at various angles to highlight the imperfections. In any case, walk around it very slowly. Carefully inspect the surface. Do it several times. Run your hand over it if you’re not sure. The more time you take doing this, the less time you’ll spend sanding off paint when you try to apply the barrier coat. Barrier coat and bottom paint is not cheap.
Clean the hull thoroughly. Rinse it with water, let it dry for a day or two. Then use the cleaning agent specified by the paint manufacturer. It pays to buy it all from the same company, because they know how it will interact. Mixing paints and thinners and cleaners from different companies is bad juju. Don’t do it.
Now to tape. Tape everything you don’t want paint on. I suggest at least a 1” wide masking type tape, but wider is better. The wider the tape, the more wiggle room you have to make mistakes. As for the type of tape, there are some tapes that work better than others. Do not use the green tape named after the amphibian. It leaves a residue that is a bear to take off. Take your time on this too. Any place you miss; the paint will cover.
Barrier coating your hull prevents water from seeping into the fiberglass and creating blisters. After making sure your hull is smooth, clean, and taped, you can use whatever product you like. I used Interlux® Interprotect 2000E, so that’s what we’re covering here. I bought two of the one gallon kits, one gray kit and one white kit. It’s a two-part epoxy based barrier coat. When you mix the two parts, it begins a chemical reaction that generates heat. Some folks call that “kicking off” or “cooking”. It’s only good to apply for a short time before it cures. After that it becomes a solid, and it’s permanent. On everything. So use it or lose it. It comes in a two-can system; three quarts’ paint, one-quart hardener. If you have a smaller boat (less than 30 feet), do yourself a favor; get one 2.5 quart and one 1 quart graduated mixing buckets with lids from a hardware store for each gallon of paint. Separate each gallon of paint into two halves before mixing. Leave half in the original cans, put half in the buckets with lids (1-1/2 quarts of paint in each can and bucket, 1 pint of hardener in each can and bucket). That way you have 2 coats from each gallon (two quarts total each) separated, that can be mixed and applied at different times. You should not recoat in the time that it takes to harden. If you can see your thumbprint in it, it’s not cured. If you have the paint divided into two parts for each component, YOU can decide when to use each coat. I would also suggest using Interlux® 2316N thinner for each two-quart mix, per manufacturer’s specs. It gives you a little extra time with the mix before it hardens. Use a foam roller designed for the paint. You can spray it, but there will be overspray and loss to any wind. You can change the time it takes to solidify somewhat by using it during sunny warm days (for faster cure) or cool overcast days (for slower set up). If you have the time to let it set up slow, do it. Then you can use all of each coat. Let it sit a day before re-coating, more in colder climes. I used 4 coats of the 2000E, alternating colors (gray, white, gray, white). The gray covers the white hull nicely; you can see easily where you have or have not painted. Then the white covers the gray nicely and so on. There is also an added benefit. If you ever have to sand the paint off, you can easily see if you get down to the 2000E, and how many layers you have gone through as well.
The next installment will be the application of the final bottom paint.
Written by: Steve Bayless
Port Sanilac Marina
(810) 622 -9651