Justine’s cuddy top is supported by four deck beams that in turn are supported by cleats fastened to the inside of the coamings. It also gets support from the deck beam atop the cuddy bulkhead at station 12. The cleats are 3/4″ mahogany and have essentially the same curvature as the coamings to which they are fastened, so I was able to steam-bend them using the same form I used to bend the coamings. The cleats are notched to receive the ends of the deckbeams, and they also serve to make more room for driving fasteners at the edge of the cuddy’s plywood deck.
I’d read several articles about deckbeam curvature over the years but didn’t fully appreciate the subtleties until making Justine‘s cuddy top. From the Flatfish construction plans it would appear that all the cuddy’s deck beams would be cut to the same curvature, so that’s what I did initially for the cuddy top. Once I tried setting the deck beams in place, the result was not pretty: viewed from the side, there was a distinct dip in the cuddy top’s profile. A straightedge placed at the centerline of the deck beams and forward to the point where the coamings join showed a big gap on the forward-most cuddy deckbeams. The cuddy top’s profile should be straight or perhaps even have a bit of a crown, not have a dip. (The same is true of the foredeck, but because of the trajectory of the Flatfish’s sheer line, the foredeck profile is pretty straight even when all the foredeck’s deck beams are made with the same curvature.)
What to do? I actually tried trimming down the forward part of the coaming a bit but quickly realized that would not be a good solution, so I built the coaming back up. I realized I’d need to make a new set of deck beams, each with its own curvature, such that the deck would have a straight profile. I’d have to calculate the curvature required for each of the deck beams. This required measuring the span of each deckbeam, and the intended height of the cuddy top’s crown at that deckbeam location. With that information—chord length and height at mid-chord—you can calculate the radius of each of the deckbeams. I made the new ones and the cuddy top’s profile was nice and straight.
The cuddy top is 9 mm marine plywood, and it’s got a enough curvature that I was a little concerned that it would not be easy to spring into the correct shape as I drove fasteners into the deckbeams. I started a row of fasteners along the boat’s centerline, and worked outward, spacing fasteners about 4″ apart, and had no problems. I first drove all the fasteners into a piece of plywood that was a bit oversize, scribed a line around the perimeter, then removed the plywood and trimmed it to size.
I painted the underside of the cuddy deck and then installed it, again using some 3M 5200 along the joints with the deckbeams and coaming. The edges of the plywood were treated with epoxy to help prevent any water from working its way in over Justine‘s lifetime.
I laid canvas in Titebond II, used a squeegee to smooth it and work out excess glue, and stapled the perimeter around the edges of the plywood.
After painting the canvas, the only remaining detail to finish the cuddy top is installation of half-round mahogany molding pieces over the three edges of the plywood deck.