Laminating the Coaming Lip
I make the lip of my coaming (the part that holds on the spray skirt) by laminating a stack of thin laminations around the coaming riser (the vertical part of the coaming). In this way I do not need to make a separate form for the lip, the riser acts as the form.
I cut a bunch of skinny strips to act as laminations. In this case I used four 1/16 inch strips plus a ~1/32" accent strip to make a lip about 1/2" (1 cm) wide. I cut the strips as thick as I can, while still allowing them to bend around the riser with out breaking. Thicker strips means fewer required, thinner strips means more flexible. The number of strips is decided by how wide I want the lip.
I used my power-feed to run 1/4" thick strips through the table saw with a zero-tolerance insert to cut the thin strips. The saw likes to eat these strips. I made a low, short fence out of another strip so the newly cut strip would (hopefully) fall free of the blade when the cut was complete.
I wrap some stretch wrap around the coaming riser to keep the lip from getting glued in place. I then butter up the laminations with glue and wrap them around the riser. I pre-mark the back center so I can get the alignment right. A bunch of spring clamps holds everything tightly in place.
After the glue cures, I strip off the clamps and re-mark the centerline. This mark at the bow is used to cut the length. I use a scraper, plane and sandpaper to clean up both sides of the lip. This clean up is why I did not just glue the lip in place initially, but you could do it that way to save some steps.
The lip is then glued permanently on to the riser. I use the end of a strip as a height gauge so the lip is at a consistent elevation all the way around the coaming. More clamps and a clean up of the squeeze out and I'm ready to let the glue cure.
After the glue cures and the clamps are stripped off, it is time to clean up the front where the two ends of the lip meet. If you are really careful with your fitting you could make this step unnecessary, but this is easier. I cut of the ends of the lip with a straight cut and then glue on another piece of wood to act as the front.
Then it is time to cut off the excess riser above the lip. I use a coping saw. I used a belt sander, plane and hand sanding to level off the ends of the riser, then sanded a nice radius on everything.
This radius allows the fiberglass to conform more easily and makes everything feel good. I have sometimes used a round-over bit in a router to do this, but hand-sanding works also.
I mask off everywhere I don't want fiberglass and protect the inside of the boat with some paper so drips don't mess up the interior finish. I will fiberglass up the inside of the riser, over across the top of the lip, down under the lip, and down the riser.
This will require "bias-cut" cloth or strips of fiberglass fabric cut at 45 degrees to the weave.
These strips are epoxied in to place. Generally I use a chip brush to wet-out the fabric, but a bent-over acid brush helps reach up under the lip.
When the epoxy starts to set up I trim off the excess glass with razor knife.