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From a Bare Hull:  Cabin Trunk Carlin (Page 2)

Test Fitting and Sizing the Curved Carlin
The laminated piece, as it came from the mold, was covered in a large amount of glue squeezeout on both sides, so my first step was to clean up the curved beam with a borrowed power planer (handheld) and my sander.  With that done, I measured for a centerline and then moved the piece into the boat, where I clamped it in approximately the correct position with the forward edge tangent to the last full-width deck beam and the sides supported on top of the forward bulkheads.

The next step was to properly align the two sides of the piece so that they were the same distance from the edge of the hull on each side, measured at the forward bulkheads.  After a few minor adjustments it was even, and I made some reference marks.  The carlin was designed to sit on the bulkhead for added support, but I had to cut notches out on each side to allow the carlin to sit at the appropriate height--equal to the height of the underside of the eventual deck sheathing, or the same as the tops of the deck beams.  To determine this height at this location, I ran a string from a previously-made mark on the amidships bulkhead, which correlated with the proper height, forward to the first deckbeam and clamped it tight.  Then, I measured down from the string a distance equal to the height of the carlin.  With this mark, in conjunction with the marks indicating the inside and outside edges of the carlin, I made the appropriate cuts in the bulkheads.  Then I made a plumb cut down the bulkheads to trim some excess from the inside edge, as the bulkheads should be even with the inside of the carlin, and the way the physical pieces ended up was slightly different than how it ostensibly should have been on paper.  Slight modifications such as this are par for the course in a seat-of-the-pants type of construction.

Next, I had to figure out where to cut the curved piece so that the remaining carlins--those that define the edges of the cabin trunk and cockpit--could conjoin properly.  What I wanted was a smooth, flowing curve on the inside edge.  To determine where this joint should be, I mocked up a carlin with a length of scrap pine.  I clamped the pine on top of the after two bulkheads, aligned with some marks I had made earlier showing the location of the carlins,  and then worked on bending and forming the forward edge so that I could create the flowing curve I was after.  

Bending the pine here and there with clamps, I eventually pulled it into a pleasing shape that satisfied what I was looking for, so I made some marks on the top of the carlin.  Bending, observing, and adjusting took the better part of an afternoon; it's these tasks that seem to be slowest, with the least visual progress, but they are critical to the overall look and ultimate construction of the various components, so I never rush the process.  Knowing the second (starboard) side should be more or less identical to the port, to to help me locate the same spot on that side I made reference marks where the carlin passed over the forward bulkheads, so that I could use it as a known reference point for measuring.

This photo show the "tangent" line that I created with my pine template.  For observation purposes, please ignore the line of the pine board to the left of the forwardmost (lefthand) orange clamp, as this position has nothing to do with how the board curved.  The tangent line is located approximately in line with the lefthand clamp in the picture.  With a little vision, one can see how the carlin line (which, in this view, is the defining edge of the cabin trunk, once built) should sweep cleanly forward (left) and merge neatly into the curved forward section of the carlin at approximately the lefthand clamp

When I was happy with the curve I had created, I traced the board onto the carlin beneath, and removed the various pieces, bringing the curved carlin down to the bench to make the final cuts.

To make the cuts for this joint, I built a small jig from three pieces of 3/4" pine.  Using the tangent mark on the curved carlin as a guide, I staggered the three pieces of pine (each representing one of the laminations of the eventual carlin) in an appropriate manner so that the end of the first (inner) piece ended up in the proper location at the tangent line, and the outermost (third) piece ended up flush with the outside of the carlin.  The overlap for  each piece ended up at exactly 2".  I screwed the pieces together and marked out the stepped shape, first on the port side and then on the starboard by flipping the jig over and remarking on the other side.  I used my jig saw to cut out the stepped shape on each side.

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