Thursday, May 8, 2008

Priming and Painting a Backwoods Drifter

This week I've been in the process of prepping the Backwoods Drifter I've been building in my spare time for paint and varnish. This boat, which I'm building for a customer, was originally going to be delivered unfinished, but since he was not in a particular hurry for it, the owner decided to have me go ahead and do the painting and varnishing.

I had the first coat of primer on it a couple of weeks ago, before I went to south Florida to work on another boat. When I got back to it this week the primer was sanded and another fill layer of fairing epoxy applied to smooth out various minor imperfections in the fiberglass sheathing. I use a compound of about 50/50 phenolic microballoons and silica for this fairing mix. This makes a relatively easy to sand filler that is still hard enough to make a good substrate for paint.

After sanding this final filling coat down to 80 grit, I then cleaned the surface of dust and wiped with denatured alcohol before applying another coat of primer. The primer used here is Interlux Pre-Coat, a product designed to be used with the one-part polyurethane paint I'm using for the project - Interlux Brightsides. This primer comes in white or gray. I used the gray for this hull as it will get dark green topcoat. Below is a view of the primed hull. The interior at this stage coated with 2-3 coats of pure epoxy, and has yet to be sanded smooth for varnishing.

Yesterday I applied the first coat of finish paint, the Interlux Brigthsides in Sea Green. It was put on with a brush after first sanding the primer to 120 grit. This first coat is just a build coat to get a good base color. It will be sanded with 220 and overcoated at least 2 and probably 3 more times, using a foam roller for application. I was not worried so much about dust on the first coat, so it was done in the garage. For the final coats, the boat will be moved outside and painted early in the mornings when there is no dust in the air. The process takes time, as you must wait until the next day to sand and recoat. Instead of sanding this coat today, I turned the hull back over to work on the interior.

Sanding and varnishing the interior will take several days as well, as only one coat per day can be applied. The epoxy coatings must first be sanded smooth to 120 grit and since it is a clear finish, no fairing compounds can be used. It takes much longer than fairing the painted exterior. Because of the bright interior, all the fillets and glue joints are made with epoxy thickened with wood flour and silica, a mixture that is quite hard to sand when cured.

A high-build varnish does a lot to smooth out the surfaces over the epoxy as well, provided enough coats are applied. I use Z-Spar Flagship varnish for surfaces such as this that will be exposed to a lot of U.V. light. On a boat like this that will likely be stored inside or under some sort of shelter, 3 or 4 coats of this varnish will last for years. By the time the 3rd or 4th coat of varnish is done, the first coat of paint on the hull will be well cured for sanding and I can proceed with the final exterior coats.

Although it's dusty here, you can get some sense of how the hull will look with the dark green topside paint and varnished ash rubrails. The plywood is all BS 1088 Okoume, which also finishes out on the interior to a pleasing mahogany color. With any luck with the weather, I'll have all the necessary coats inside and out within the next couple of weeks.

More on the Backwoods Drifter design here.

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"A boat is freedom, not just a way to reach a goal."
Bernard Moitessier - A Sea Vagabond's World


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