greenland_coaming

The Coaming Layup

In the hull design, I came up with a boat with a deck height of about 7 inches. That's pretty low, but I want a coaming height of 7 inches, measured at the rear of the coaming. This means that I need to recess the coaming. To complicate matters, the aft deck is flat across. This means that in order to achieve the recess, I need to fabricate a 'gutter' to house the coaming riser and lip.

The sketch of what I am attempting. I will mold the recess/coaming in one piece, using the kayak deck as a molding surface. Then, certain surfaces will be discarded.

Two saw cuts were made. The inner cut is the desired 16 by 20 inch cockpit opening, cut a little big to account for the thickness of the laminate. The outer cut is the dimension of the future "gutter". This cut is not complete; there are gaps in the saw cut to hold this piece in place during molding.

The height of the coaming must be determined. for most of the circumference, the coaming lip will start at deck height. At the sides, the lip was raised about 1/4 inch, to create more finger room to put on the sprayskirt. This is minicel foam used as the mold.

Next, the interior thickness of the coaming lip is determined; I used 3/4 inch. Shown is a wood caliper to gauge the 3/4 inch thickness of the tool. The minicel tool has been shaped to this thickness all the way around. Next, a bevel was shaped in the tool, to join 'deck level' with 'gutter level'. Lastly, all sharp corners were sanded round.

The finished tool, underside of deck

The tool was masked with blue masking tape, and then with clear packing tape. The epoxy will not stick to packing tape, but beware, it will absorb into masking tape.
I prepared strips of bias-cut fiberglass and carbon fiber cloth.

I had intended to vacuum-clamp the laminate, so there is plastic taped around the outside. This plan never worked out, as I had a bag leak that I could not find. However, the plastic sheet provided another benefit: the tension in the plastic sheet held the coaming lip in place during layup and cure. Each piece of cloth was wet out on a table covered in plastic sheet. Then, the wet cloth was tucked into the lip area of the mold, with the bag holding it in place. The cloth was then smoothed up around into the recess area of the mold. The laminate consists of: 1 layer of 5.8oz carbon twill, about 6 layers of 6oz fiberglass cloth, and a final layer of 5.8 oz carbon fiber twill.

After cure, the little gaps in the outer saw cut were cut with a knife. The coaming/riser/tool was taken out the bottom. Next, the tool had to be removed by breaking the cedar pieces, and pulling out the foam and masking tape.

The coaming/ recess was trimmed, sanded, and glued in. Later, the deck cedar was beveled to match the angle of the recess. 4 oz glass tape completed the installation.


	Two saw cuts were made. The inner cut is the desired 16 by 20 inch cockpit opening, cut a little big to account for the thickness of the laminate. The outer cut is the dimension of the future "gutter". This cut is not complete; there are gaps in the saw cut to hold this piece in place during molding.
	The height of the coaming must be determined. for most of the circumference, the coaming lip will start at deck height. At the sides, the lip was raised about 1/4 inch, to create more finger room to put on the sprayskirt. This is minicel foam used as the mold.
	Next, the interior thickness of the coaming lip is determined; I used 3/4 inch. Shown is a wood caliper to gauge the 3/4 inch thickness of the tool. The minicel tool has been shaped to this thickness all the way around. Next, a bevel was shaped in the tool, to join 'deck level' with 'gutter level'. Lastly, all sharp corners were sanded round.
	The finished tool, underside of deck
	The tool was masked with blue masking tape, and then with clear packing tape. The epoxy will not stick to packing tape, but beware, it will absorb into masking tape. I prepared strips of bias-cut fiberglass and carbon fiber cloth.
	I had intended to vacuum-clamp the laminate, so there is plastic taped around the outside. This plan never worked out, as I had a bag leak that I could not find. However, the plastic sheet provided another benefit: the tension in the plastic sheet held the coaming lip in place during layup and cure. Each piece of cloth was wet out on a table covered in plastic sheet. Then, the wet cloth was tucked into the lip area of the mold, with the bag holding it in place. The cloth was then smoothed up around into the recess area of the mold. The laminate consists of: 1 layer of 5.8oz carbon twill, about 6 layers of 6oz fiberglass cloth, and a final layer of 5.8 oz carbon fiber twill.
	After cure, the little gaps in the outer saw cut were cut with a knife. The coaming/riser/tool was taken out the bottom. Next, the tool had to be removed by breaking the cedar pieces, and pulling out the foam and masking tape.
	The coaming/ recess was trimmed, sanded, and glued in. Later, the deck cedar was beveled to match the angle of the recess. 4 oz glass tape completed the installation.