Painting the bottom

With the skeg attached and epoxy hardened, I applied another coat of resin to the entire hull and started sanding in preparation for painting the bottom.   Did I happen to mention I hate sanding!

This is the first pass with 80 grit discs, using a random orbital sander.  The epoxy turns white where you sand it which helps show the high and low spots.  Coating with resin is not like paint.  The resin does not flow out and create a nice level surface.  Also, on the sides, the resin tends to sag because it takes so long to harden.  You get waves of thicker epoxy near the bottom of the sides. 

As you sand some more, the finish gets smoother.  However, I found I still had some pock marks (as a golfer I call them divots) which were lower than the surrounding surface.

This is the side, which will not be painted but coated with clear varnish to create a stained wood look. [This is called finished "bright", which means the wood shows and is not painted.]  These marks would show when you look along the hull.  I either had to do more sanding or fill these divots.  I was afraid to keep sanding as I might go through the epoxy and hit the finish so I rolled another coat of resin on the sides and resanded.

The bottom wasn't as critical as it would be sitting in the water and not show.  So, I went ahead with masking off the water line to paint the bottom.  You may ask how do you know where the waterline is?   It is actually marked on the plans, but I didn't use it.  For one thing, I wanted the bottom paint to cover the plywood seam at the bow of the boat, so the line had to curve. (A true water line would not curve.)   In addition, I had a flaw on one side that I wanted the bottom paint to cover.  So, I just measured enough down one side to cover my flaw and eye-balled a line from front to rear.  I did the same on the other side and then connected at the transom.  Here are some shots of the masked line prior to painting.

You can see on the second picture how the line follows the plywood to cover the seam.  A true waterline would be level around the whole boat and not look like this.

I painted the bottom with three coats of System Three WR-LPU paint in Mercer Green. This paint is water based linear polyurethane paint to which you add a crosslinker which increases the film toughness.  It is pretty nice to work with because it is water based.  It doesn't smell and cleans up easily.  I didn't thin the paint because it looked pretty thin in the can.   I rolled the paint on with a 4" foam roller.  The roller creates lots of little bubbles in the surface which you must smooth out by lightly brushing with a foam paint brush. This is called the "roll and tip" method. The paint dries pretty fast (20-30 minutes) so you can only do a small area at a time to ensure you maintain a wet edge.     I really like the color and it came out pretty nice.

You can apply a second coat as soon as the first one dries, which is about 1 hour.  I was able to put all three coats on in a morning before it got too hot in my garage.
Next up is painting a white bootstripe and then covering the entire hull with clear gloss varnish.