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The 10 painting commandments of carvel hull preparation

by Doug Raymer

It seems that in the life of almost every wooden boat owner that eventually that beautiful spring morning arises, and the owner decides that the old girl needs a fresh coat of paint. But first, she’ll need a little sanding.

So the owner goes to the tool shed, gets his trusty swirl-o-matic disk sander, slaps on a 40 grit disc, and begins creating a flume of dust, resembling that of the Mount St. Helens eruption of 1980.

When the dust finally clears, he’ll notice that the disc sander has left behind zillions of swirls, gouges, and divots, which will only be more noticeable after painting. Hmm, he says, “I know how to fix this, I will take a belt sander to it, that will flatten her back out.” So, he fires up the belt sander and begins to go heel, toe, heel, toe, as if making an attempt at line dancing. And, hey, that is exactly what is now imprinted on the side of his hull - heel, toe, heel, toe dents from the heel and toe of the belt sander.

This texture will really clash with the previous disc swirls. And don’t believe that primer and paint will hide it, because it won’t.

Here are some guidelines to go by that you may find helpful:

1.   Do not use a dust mask - use a respirator. There is a good chance that you will be sanding off lead paint, and a dust mask just does not cut it. Marine bottom paint contains copper cyanide.

2.   Use eye protection - even though cleaning your goggles is a hassle it is much easier than cleaning your eyes.

3.   Wear appropriate clothing to keep dust off of skin and out of pores.

4.   Keep kids and pets out of area. Buddies won’t be a problem, since most of them will only want to be on the boat, not working on it.

5.   Keep area clean of potential trip and fall obstacles and other accidents waiting to happen.

6.   If your boat is already fair enough just buy a flexible flat board and some 100 grit paper from Fisheries Supply (Fisco) in Seattle Washington (1-800-426-6930). Wash and clean the boat, let it dry completely, and give it a good scuffing. Wipe dust off with solvent. You may need to wait a few days for the minerals in the solvent to evaporate before painting. (Check your brand - because if not dry it will evaporate through your paint, leaving blisters).

7.   Never strip down to wood unless absolutely necessary. But, if you have a boat that fits the above description, you will have to. Do not use a paint remover. The paint will act as a depth gauge, hence, there will still be paint in the low spots.

8.   Use a random orbital sander only. Don’t buy a hobbyist type of light duty random orbital either. This is tough job and you will beat the bearing out of it in 20 minutes or so. No kidding! I have done it. I like the Dewalt 6″ - model DW443. Also, don’t use an orbital that uses the hook and loop (Velcro) type pad and disc. What happens here is the little hooks on the pad can’t hold up to the grip of a 40 grit disc, it rips them off, and nothing will stick to it. I don’t care how careful you are, this will happen. So, by using the adhesive stick-on discs you’ll save time and money.

9.   On a hull that has a lot of paint and damage to the wood I start out using a 40 grit disc, sanding away a plank at a time, until the low spots that are still holding paint are very faint, if not gone. Then, go over he whole job with 80 grit. This is the time to do any patching of cracks, fix bungs, putty over any fastenings, etc. Polysulfide works best on a cracked plank (boat life) as a crack will act like a seam swelling and shrinking with or without moisture. Deep gouges = epoxy with a sandable additive or sanding dust; fastener holes = wood putty. All the above patching can be gently faired with 80 grit. However, I have found that with putty it is easier to use 100 grit because 80 grit may take out little chunks that will only have to be touched up again. So, it easier to fill and leave for the 100 grit sanding.

10.  I don’t know if other guys use this method, but I do it this way and it works out good. Get out the old flat board, no whining now, you’ve already done the hard part. Stick on a piece of 100 grit, and start sanding in the direction of the plank until it looks good. It should have no lumps or bumps, all of the little scratches should go in the same direction — horizontal. These little scratches are what hold the primer to the wood. Much like a farmer who does not make his rows go down hill, instead he makes the rows go across the hill to hold water. This is the same way your boat will hold primmer to the wood. Using a finer than 100 grit sandpaper will make the wood too smooth and the paint will not stick to it.

Rotten‘Zine thanks contributing author, Doug Raymer, All Wood Boats, P.O. Box 193, Rockford, WA 99030