Playing With Boats

With the bottom shaped, it’s time to get everything we’ve built so far set up on the strongback.

The plans show a baseline above the midships frame and the bulkheads that represents the top of the strongback. Using this, temporary legs are cut from scrap and fastened with drywall screws. The frame and bulkheads are plumbed and aligned on the strongback and the legs are fastened to cross-cleats.

The stems are fastened to the bottom with screws and glue.

The bottom/stem assembly is placed on the frame and bulkheads and carefully aligned. The bottom is then glued and screwed to the frames and bulkheads.

The stemheads are extra long, extending beyond the sheerline. When the boat is turned upright, these will each be trimmed and shaped into a pleasing curve. In the mean time, the height of the stem and the height of the legs on the frame and bulkheads affects the curvature, or rocker, of the bottom. When the bottom is fastened to the frames and bulkheads and the stems are pulled down tight to the strongback, it introduces a (very slight, for this particular boat has almost no rocker) curvature.

At the moment, the edges of the bottom are square, just as they came from the bandsaw. The bulkheads and the frame, however, are angled so the planks must meet the bottom at an angle and the bottom must therefore be bevelled. How do you find the correct angle? By playing “connect the dots,” or rather “connect the bevels.” Where a bulkhead meets the bottom, you can lay a straight piece of scrap along it and see how much wood must be planed off to make the scrap lie flat.

If you do this at each intersection, and also where the stems meet the bottom, you will have four known points on each side to guide you. The bevel “rolls,” or changes between each of these, so your job is to join these areas up with a fair curve to create this rolling bevel.

Here are four of the most useful tools for doing this kind of work, and in fact four of the most useful tools in a shop that builds traditional small boats. From left to right, they are: a jack plane; a low-angle block plane; a bullnose rabbet plane and a low-angle spokeshave. In the backgound is an awl, useful for clearing chips and shavings from the throats of the tools.

The next pieces to be added are the sheer clamps, which define the upper edge of the hull. These are important elements that join the sheer plank, decks and stems together, so they’ll be gotten out of white oak. I couldn’t find any stock long enough, so I ripped a shorter piece of white oak and scarphed it together with epoxy, using an 8:1 angle.

Ripping this long, flexible piece takes careful preparation, so I’ve made some temporary supports to hold before and after it passes over the saw. As usual, the preparation takes about 5 times longer than it does to make the actual cut. Once the sheer clamps are ripped, they are planed to the final dimensions.

The clamps fit into pre-cut notches in the bulkheads and frames. At each stem, they must be cut so that the planking will flow smoothly off them and on to the stem bevel. This is pretty easy at one end, using a bevel gauge to lift the correct angle and cut the end of the clamp. At the other end, though, the untrimmed end will be in the way of an exact measurement, so it requires some careful thought to cut the correct angle at the correct length.

With the bevels cut in each end, the sheer clamps are screwed to the frame, bulkheads and stems.

Everything is now in place for planking, where we’ll pick up next time.

Until then. . .