Friday, April 2: I finished trimming the sheer yesterday for the right level and angle. Seeing the finished hull shapre for the first time was a special pleasure. The boat has sweet lines, a function of the sheer, stern and stem rake, and the high tucked bottom at the stern. Why are most boats built now so completely lacking in asthetic appeal? Beats me.
Today I started on the centerboard trunk. I laid a sheet of plywood on the floor, used one edge as the plan's baseline (actually the baseline minus 9": no need to waste wood unnecessarily), followed the plan offsets to locate the level of the chine at the station sectons, which enabled me to find the level of the chine at the ends of the centerboard trunk slot cutout. I measured and drew where the top of the c.b. trunk should be, and followed the notes on the plans to draw the ends of the trunk. I used a long piece of molding to draw the curved bottom edge of the centerboard trunk where it is supposed to meet the top of the keelson. That gave me the profile of the c.b. trunk.
All this drawing is the same as traditional lofting, but by doing it on the pieces actual material saves a step and is one less chance to screw up. As it was, I had to redraw the aft end several times: thank goodness for gum erasers.
As a final check, I drilled a pilot hole in the centerboard where the pivot pin will be, and drove a small nail through the board and into the pivot pin point of the centerboard trunk drawing. Then I swun the centerboard around the pivot to make sure that it had clearance at both ends. It does, but as I suspected I will have to find a way to extend the board below the top level of the centerboard trunk to get it all the way down. Some kind of pivoting handle will be needed. The plans do not suggest anything.
I put the plywood panel on sawhorses and cut it in fourths. Then I screwed the piece I had drawn out to a second piece underneath. I screwed them together at the ends, where they will need to be screwed into the spacer piece (king post) later anyway. Then I cut out both both pieces together with a circular saw. Even sawing both 12mm pieces at once, the circular saw could cut along the gently curved bottom line. I left 1/16" for trim at the top and ends, and 3/4" at the bottom. I will scribe the bottom line so it fits against the keelson, whether its profile is the same as the plan or not. When I set the double side pieces into the boat, the bottom line matched... well, see for yourself:
Not a bad fit, is it? In other words, the boat is shaped just like the plans say it should be.
Looking around online, it seems that about 1/8" is the right side clearance for the centerboard inside the trunk. Too little and the board might stick. Too much and the board can vibrate or flop around. But since the board and the inside of the trunk haven't been covered in fabric yet, I don't know how thick to make the end pieces. So before closing shop for the day I measured a sample piece of wood and then epoxied a little fiberglass to both sides. When that cures, I'll recheck the thickness and will see how much additional space is needed.
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