Wednesday, May 14, 2008

Varnishing the Interior

It was now time for the most visible effort I was going to make - varnishing the interior. As I've mentioned, I hope I've learned some lessons from this to make the next boat go even better. I'm not sure I could have learned these lessons any other way, however.

I had also put some time pressure on myself: It was now the end of April and I wanted to have to pram ready by the time warm weather in Colorado arrived. Also, I set a date to have a cook-out at our house where the guest of honor would be the Pram! The date of the cook-out would be May 18. I started varnishing the interior on May 9. Since I started on the week-end, and since the varnish I was using (Schooner by Interlux) could be reapplied in 12 hours, I was hoping I could varnish and sand on the same day. This proved to be true, although varnishing took over two hours and wet-sanding took over an hour.

The first coat went on pretty well. I realized that planning the varnishing was going to take some work. I was using the varnishing technique described on the CLC website, namely using a foam brush, applying in one direction and then going back over it in the perpendicular direction, always going from "dry" to "wet". This works great in a small patch, or where an adjoining section will be completed soon enough where you can blend the two sections together before the first begins to get tacky. And that was true of the exterior transoms. But what about the interior bottom? It was too big to do as a single section. I wound up doing a quarter of the bottom at a time, going around counter-clockwise. Unfortunately, by the time I did the fourth section, the first section had begun to set and it was impossible to join the two without leaving brushmarks or a double-thickness of varnish. This is a problem I never did figure out a complete solution to. I suspect I needed to thin the varnish even more than the 10% I was doing. Of course, that has drawbacks too: runs on the vertical surfaces would be even harder to control. I don't know what the right answer is other that using a sprayer and spray booth (I have the former, but not the latter).

I also managed to nearly drive us out of the house after the second coat. Up to the second varnish coat, I had always varnished right before bedtime. By the morning, the odor in the house wasn't too bad (have I mentioned I was building and finishing in my basement?). I had also installed a ventilation fan in my shop that vented directly outside. The second coat, however, went on in the early afternoon. It had also gotten cold outside, meaning closed windows and a running furnace. My wife was really regretting getting me this boat at this point. Luckily I had only one more coat to go and I put it on a night.

The second coat had developed a problem, however, that I hadn't seen before: It had many tiny hairs or threads embedded in it. If I didn't figure out what caused it I was in danger or ruining my third and final coat. What was strange, was the mast, which I had varnished immediately prior to interior, showed no signs of this problem. Before I started the last coat, I switched back to a shop cloth that had worked earlier. I was fastidious in wiping down the boat after the final wet-sanding.

After two coats of varnish

So, with much trepidation, I began the last coat. The first section went well, no sign of the evil threads. Then, on the second, adjoining section, they reappeared! At this point I realized the problem. Immediately prior to the thread appearing, I had just varnished underneath the mast step, a place that was very difficult to reach. I must have missed wiping the sanding debris out of there. I quickly tossed the brush and grabbed a new one. Problem solved. Every time after that when I started seeing anything suspicious in in the varnish, I replaced the brush.

In the end there were only a couple of mistakes in the final coat: a spot on the middle seat that I didn't apply enough varnish that didn't blend well when I went back over it and a sag on an upper (near vertical) panel. I consoled myself by saying I could always sand and recoat at any time.

After three coats of varnish

Almost done! I just had to assemble and attach the rudder, attach the oarlocks, and rig the sail.

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