Category: Coamings

Cockpit Coaming

The Flatfish design has cockpit coamings that extend forward of the cuddy bulkhead and form the sides of the cuddy top. The port and starboard coamings meet at a mitered joint just aft of the mast. I made the coamings from African mahogany boards planed to 5/8″ thickness. The forward sections of the coamings are significantly curved and twisted. The coamings are each about 16′ long, so I scarfed shorter boards together to make pieces sufficiently long.

I began by making a pattern out of 1/4″ plywood pieces. The bottom edge of the coaming makes a jog at the cuddy bulkhead. Forward of the bulkhead the coaming lies atop the foredeck, and aft it forms a wide backrest for the cockpit seats. The jog at the bulkhead provides a starting point for fitting the patterns.

Fitting a plywood pattern for the starboard coaming. Note how the pattern rests on the edge of the foredeck forward of the bulkhead, and jogs down aft of it. Also, there is a considerable twist in the forward-most part of the coaming. I’ll attach another piece of pattern stock for getting the coaming’s shape as it proceeds back to the transom.

Given the 5/8″ thickness of the coaming and the degree of curvature in its forward section, it requires steam bending. I made a form that would impart both bend and twist using a plank of nominal 2″ thickness to get the bend, and mounting cross pieces that would set the twist. The cross pieces were attached with saddle joints, so they were easily removed and reversed for making a mirror-image coaming.

I made a bending form for steaming the coaming stock to match the shape and twist of the coaming’s forward section. I’ve installed brackets to keep it in place on the barn floor. (The form is set for bending the port coaming. Simply reversing the cross pieces resets it for bending the starboard coaming.)

When I was deciding how to cut the mahogany planks for the coamings, it turned out that the scarfs would have to lie forward of the cuddy bulkhead, in the region where the coaming would need to be most highly curved. I wasn’t sure that the epoxy I used (West System) for the scarf would maintain its strength at the steam temperature, but it did so. I was careful to place a clamp right over the scarf when I secured it on the bending form.

The after section of each coaming is relatively straight so it does not require steaming.

Starboard coaming steamed and clamped in place on the form. The after end is being pulled downward by a line outside the barn. The scarf in the coaming is right under the clamp in the middle of the picture.

Except for the winding bevel on the bottom of the coaming where it lies on the foredeck, I left all other edges somewhat over size so that I could drive the fasteners, then mark the coaming’s final profile, then remove the coaming and do the necessary trimming before fastening it for good. I used 3M 5200 (mahogany colored) in the joints.

Coaming in place forward of the cuddy bulkhead. I’m using a line at the after end to impart enough bend to get a good fit in the area near the cuddy bulkhead. And the coaming’s after end is still a little long; it needs to be trimmed for a mitered fit where it meets the transom.

Cutting the miters where the coaming joins the transom requires care. I made a reference mark well forward in the cockpit, and a corresponding reference mark on the coaming piece when it was in the position shown in the photo above. Then I measured the required length of the coaming, took off miter angles with a bevel gauge, and transferred these onto the coaming. I made the first miter cut a bit long, tried the fit against the transom, and removed a bit more, repeating the process until I had a good fit.

Fasteners have been driven in the starboard coaming but I’ve not yet trimmed it to its final profile. I’ll mark it for trimming, then remove it, trim it, and do the final installation.

I didn’t do the final installation of the coamings until after I’d canvassed the foredeck. This makes for a much neater job: otherwise the edge of the canvas would have to abut the coaming, rather than be concealed under it.

Both coamings are refastened aft of the cuddy bulkhead. I am ready to trim the forward ends for the mitered joint where they will meet up. This forward mitered joint also requires considerable care to do well. It helps that the joint will lie on the boat’s centerline. You need to get the compound miter angles right so that the outward tilt of the coamings is correct and at the same time ensure there will be a tight joint where the coamings meet. Once the miters are cut properly, a piece that lies inside the “V” of the joint is used to provide secure fastening of the mitered joint. This piece is just visible in the photo below.

After a few preliminary coats of varnish and installation, the coamings are looking very handsome!

Near the transom, the upper edge of the coamings has a very sweet curved profile, a fine detail in Nat Herreshoff’s design.

Over the years I’d read quite a few articles about how to make coamings for the Herreshoff 12 1/2 footer, and I approached making my own with some trepidation. I adapted what I’d read to what I thought would work best for me, and proceeded deliberately. My process worked very well and I didn’t have to re-make any parts!