It may not be obvious from some of the photos, but right now I’ve got a long slot cut in the bottom of the boat. Since Tammie Norrie will be sailed, I need something to counteract the lateral force of the wind on the sail. I’ll use a centerboard for this function. The centerboard is pivoted so that it can be raised when on the trailer or when rowing, or lowered when sailing. The centerboard case is a glorified box that holds the centerboard.
On Wee Lass, the centerboard case was permanently glued to the boat, as was everything else. The thinking was that if it was permanently glued in, it would never leak. Hurricane Ike had something to say about that. I was able to sorta-fix the leak by globbing in some epoxy at the joint between the case and the keelson, but the case still leaks. Not enough to sink the boat, but enough to be a nuisance. So the lesson learned is that the centerboard case on Tammie Norrie will be screwed and sealed to the keelson with bedding compound, but it will be made removable so that if repairs are ever required, they can be more easily done.
Despite being a glorified box, the centerboard case has a surprising number of parts. The plans give the layout of all the parts, but to minimize the risk of cutting parts the wrong size, I lofted the case full size on a piece of MDF.
Not only are the sizes of the parts laid out, I also indicated what material the parts were. The spacers that go on either end of the case are made of fir, as are the bedlogs, which will be used to screw the case to the keelson. The remaining parts are made of cherry, to match the remaining furniture on the boat. I also indicated the location of Stations 4 and 5 on the lofting. These stations will fix the horizontal location of the case.
Milling out the parts went quickly, and generated a lot of sawdust.
The plywood sides of the case are also cut out. The plywood is the same material that was used to plank the hull. When cutting the ply, use a fine tooth blade to reduce the splinters; I also scored the cross-grain cuts with a utility knife prior to cutting to also help reduce the splinters. My ability to cut a straight line with a jig saw is non-existent, so I cut a little proud of the line. The bottom edge of the panels is a factory edge of the plywood, so I know it’s straight. The two sides were tacked together with small finishing nails and the top, forward, and aft ends were finished to the line with a block plane and sanding block.
The interior of the case will be impossible to get to once the sides are glued together, so now the sides are sealed with two coats of clear-coat epoxy. The interior edges of the spacer blocks get the same treatment.
This is a test fit to make sure the centerboard will actually fit inside the case. The spacer blocks are clamped onto the case side, and fortunately, there’s enough clearance for the board. The centerboard was made some time ago, and has been waiting patiently. The leading edge of the board is oak, chosen for it’s ding-resistance. The remainder of the board is fir. After shaping, the board is coated with fiberglass cloth and epoxy.
It’s a little difficult to tell what’s going on in this picture. The pencil line on the hull and the piece of tape on the keelson mark the location of Station 4 on the hull. The bedlog is 7/8″ square fir. It has the location of Station 4 marked from the lofting, and has the case side temporarily clamped to it. The bedlog also has the location of the pivot hole marked; that will be drilled later after the box is assembled.
This is a dry fit before any glue-up. The centerboard case matches the slot I had cut in the hull, and the centerboard will fit inside the case, with the exception of the upper corner which you can see sticking above the case. Later, it will have a dowel handle that I can use to raise or lower the board. The rails are also clamped on to the case, and are intentionally long. Two thwarts (benches) will be screwed to the rails, and will provide rigidity to the case as well as giving myself and the crew a place to sit. One thwart will be located flush with the aft edge of the case, the other just forward of the case. You can also see from the photo that I’ve got the bedlogs screwed to the keelson. Each log will have five screws. It will be difficult enough to drive the screws due to the high sides of the case, so before anything is glued together I marked the location of the screws and pre-drilled the holes.
In the final dry fit I screwed the bed logs into the keelson, and then to make sure the sides were in their proper place with each other, I screwed some temporary drywall screws on either end.
Finally the case sides can be glued together. The drywall screws help align the case sides with respect to each other, the clamps hold the sides together while the epoxy cures.
I’ve still got some final work to do on the case. I’ll take care of that next time, and will also make the floors that are installed next to the case.