Boatbuilding Blog

September 4, 2008

Photo Essay – Installing the plywood cabin top trim

Filed under: Building - Cabin — tomlarkin @ 10:12 am

(Or – why boatbuilding takes a long time :-))

For the last few days I’ve been adding the trim pieces to the rear cabin top. These act as reinforcements and rain gutters. All of Sam’s roofs have them. This is a short essay describing how they got installed and finished.  Here’s the cabin top before this work started:

Before the trim pieces

First, I cut out the parts out of half-inch plywood, and radiused the edges with a plane and sander. Then I epoxied and screwed them into place onto the cabin top. After the epoxy hardened a bit I smoothed a thickened epoxy fillet along all the edges so the pieces make a smooth transition to the roof. I let the epoxy cure for a couple of days, then rounded the outside edges with a power plane and a random-orbital sander, finishing with a longboard to keep the lines straight. Small sanders tend to make a wavy edge.

Here it’s all sanded, ready for glassing. Note how solid this is – with the trim piece, this is 1 1/2 inches of solid marine plywood:

Sanded and ready for glass

I draped the glass cloth over the top and smoothed it out:

Dry glass cloth ready for epoxy

Then I wetted out the cloth by pouring a quart of epoxy on top and spreading it around with a plastic spreader, rolled it smooth, and squeegeed the surface to remove any raised areas or bumps. I made sure to add wet epoxy to the edges because the plywood edge-grain really absorbs a lot of epoxy.  I let it cure for a few hours:

Epoxy & glass curing

I trimmed the glass off the bottom edge with a razor knife and rolled on a layer of gray-tinted epoxy. This is to start filling the weave of the cloth:

First filler coat

After the first filler coat set up I rolled on another. The glass weave is mostly filled now, so I can sand it later and not sand into the cloth.

Second filler coat

Now I will leave it alone for a few days to cure. Then I’ll sand the whole surface, fill any indents with fairing compound, sand the fairing compound, and coat it with epoxy again. When the whole cabin is done, the epoxy gets sanded one last time, and the surface gets a couple of coats of epoxy primer. When this is sanded smooth, I’ll apply the finish paint. Then I can install the handrails that mount along the edge of the roof.

These steps have to happen to almost every part that makes up the boat. It takes a long time!