Friday, August 2, 2019

Centerboard, rudder and spars

Since the boat is right side up, I had to lift it off the ground by at least 45 cm (18") to fit the CB and put it in place when it was fully finished. I did it with the help of two people and several bricks (first photo). The CB pivots around a 6 mm (1/4 inch) bolt. The rudder needed a pivot bolt of its own so it can be lifted with a line. Gudgeons and pintles attach it to the transom. The tiller I made from pine lumber, and its jaws from two 12 mm pieces of plywood. There is a pivot bolt attaching the tiller to the rudder top, so the tiller can move up and down as needed, especially with the outboard I plan  to use.

Sandwiching lead shot inside the centerboard without mixing it with glue proved very ill-advised. The shot was small, and the gluing of the plywood layers was not tight enough, so the shot was swishing around inside.  I was force to prize the layers apart, not an easy thing given how strong epoxy is. Then I mixed the lead with latex caulk and reglued the CB. The result was an imperfect lamination that made the CB too thick to fit in the CB trunk without getting stuck. The next inevitable step was to use an electric planer to remove a couple of millimeters from one side of the CB. Not something I would recommend except in extremis. In any case, it was done with a lot of flying shavings and some gouging, but after sanding, a little puttying and more sanding the CB was ready for more work.

The work in question was fitting a block to a corner of the CB for raising and lowering it. It involved cutting a semi-circular piece off the top forward corner and chiseling channels for the two stainless steel straps that are bolted to the CB on one end and the sheave at the free end (photo). Both bolts had to be cut very short to fit inside the 24 mm-wide CB trunk. Another sheave is fitted on the corresponding corner of the CB trunk for the lifting/dropping line. Because of the extra 4.5 kg of ballast and its leverage, the fittings needed to be sturdy. The 2:1 purchase from the blocks helps. The CB was coated with epoxy but no paint or varnish, since it will be invisible and protected from UV rays. Fitting the CB into its trunk and putting in the pivot bolt were tough: imagine being on your back with a lead-weighted CB on your chest, under a boat on bricks that could come tumbling down on you, trying to thread a quarter-inch bolt through three holes that need to be precisely aligned. My wife watched over me just in case. I'm happy to say that the CB and its raising and dropping bock and tackle system were fitted well and work fine (third photo).

Before I finished assembling the CB block system, I made the spars. The mast I made from a 4 m long (13' 1") piece of fir, 75 mm (3 inches) square. As in previous times, I cut the corners off at 45 degrees (this time with a hand-operated rotary saw since I don't have a table saw) to make an octagon. I went surprisingly well. Then I used an electric planer and a palm sander to make the mast round. The sprit I made by laminating two 4 m long boards. I had to extend it to 4.3 m, which I did by gluing a lumber extension between two plywood jaws. The latter form a shallow slot for the snotter, the improbably named line that holds the sprit up and adjusts its tension. Planing and sanding turned the sprit approximately round too. Both spars are visible in the next photo.

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