Wrestplank: Trimming to size

The jagged back edge of the wrestplank was cut off using a tapering jig at an 8 degree angle, and the right-hand side was cut cleanly, resulting in a width of 770 mm: the first cut I've made to establish a final dimension in this project. This is about 1/2" more than the original, which allows me to add an extra pair of strings in the treble so the highest note (c''') will not be lost when the keyboard is transposed to the right.

Next, I cut a 20 mm rabbet along the underside of both the left and right edges, extending halfway through the thickness of the wrestplank. The rabbets will receive support blocks (basically 10 cm planks stood on edge) that hold the wrestplank up from the bottom, allowing room for the keyboard to slide in. The height of these blocks defines the depth of the interior of the instrument, as the liners must end up at the same level.

Below you can see the underside of the finished wrestplank and the rabbets, one of which is not visible due to the camera angle:


Here is a dry-fit of the left support block in its rabbet:


The joint between the wrestplank and its supports must be very strong. I'll put about a half-dozen 3/8" dowels through the wrestplank from above and sideways through the block to firmly pin this joint together.

Animals?

This afternoon when I stepped into the garage to continue the project, I was unable to locate my earplugs. I had two foam earplugs connected by a plastic cord to keep them from getting separated. When I finally found a trace of them, only the plastic cord remained.

My conclusion is that during the night, some animal got into the garage somehow (it was closed), sniffed the tasty earwax on the earplugs, and simply ate them (!) leaving behind the cord that connected them. The cord ends looked neatly snipped as if by scissors.

Yes, I know it sounds gross, but everything is food for something in this world.

Baseboard: Making the breadboard edge

After picking up a rabbeting router bit set at the Home Depot, I cut a half-inch wide tongue on the front edge of the bottom. Next, I ripped a strip of leftover red cedar to a 1" width and, after a bit of trial and error, routed into it a groove to match the width and thickness of the tongue. Here's a photo of the pieces, dry-fit together:


This strip is known as a breadboard edge and is used on large panels such as tabletops to hide the end grain. Here it provides a suitable surface for gluing on the case mouldings that will come later as a decorative embellishment.

Note that the bottom and breadboard are both still oversize at this point, so they need not be of identical length. The pencil tick on the light-coloured board (slightly below the X on the breadboard) marks the cutoff point that will establish the final width of the baseboard.

Baseboard: Trimming the front edge

After my two workers finished cleaning up the dried glue, I took the baseboard outside and sanded both faces with 100 followed by 150 grit paper. I used a random-orbit sander, which also helped to take out a few very minor irregularities in the joints between boards. Both my father and I agree that our work joining up the boards was very good: the sander needed to dwell on only a few spots to get everything level.

Next, we clamped a straightedge along the front, making sure it was perpendicular to the long side, and crosscut the front edge straight with a handheld circular saw. The process of biscuit joinery allows some slight sideways play in the boards when they're glued up, so the ends of the boards are usually a few millimetres away from being in a perfect line. As long as you cut the ends off, all is well and a straight edge is restored.

Additional personnel

This morning, as I was finishing my coffee, I heard activity downstairs and discovered my father, of his own volition, scraping dried glue off the joints in the bottom assembly. My mother was feeling for roughness and pointing out places he'd missed. So it seems I now have a supervisor (my mother) and an employee (my father). Thus far neither has said anything about salary...

Baseboard: Gluing together

All the boards making up the bottom were jointed cleanly on one edge, ripped along the other edge and jointed again. The final orientation of all the boards was decided upon and all were pencil-marked to make sure they didn't get flipped onto the wrong face or turned end-for-end by mistake.

The boards will be joined with glue and biscuits, which are little football-shaped splines made of beechwood that go into slots cut on a board's edge with a special power tool.


Biscuits help reinforce the joints and make it easy to align the edges during glue-up. Without biscuits the boards, slippery with glue, would slide around quite a bit while the clamps were being put on. An advantage of biscuit joinery is that minor bowing of the boards along their length can be taken out: the biscuit slots are all cut at the same position measured below the boards' upper faces, so the faces are all pulled into the same plane during assembly.

To start with, the four right-hand boards were glued up:


After this assembly sat in the clamps for a few hours, the remaining two long boards were glued on:

Wrestplank: Gluing together

The wrestplank (or pinblock) is also an important structural component in all harpsichords. Not only must it hold all the tuning pins tightly—although not so much that they can't be turned when the instrument is being tuned—but it must resist the pull of the strings and not get dragged backward towards the tail of the instrument.

The original Trasuntino has a walnut wrestplank 1.75" thick. Quarter-sawn wood would be helpful here, because its grain orientation allows the pinblock to expand and contract in the same direction as various other structural parts of the instrument.

Walnut doesn't seem to be available anywhere quarter-sawn, or perhaps only by special order, but that's not a problem. My friendly harpsichord maker told me to just saw up a bunch of slabsawn strips, stand them on edge and glue them up that way. Here are the raw materials:



The net result will be a block made of 2"-wide sections standing on edge. After planing to final thickness, the block will be covered with a veneer of soundboard material, as often is the case with many instruments, so the patchwork appearance of the multiple strips will be completely hidden.

I glued the strips up with polyurethane glue, which is quite strong and supposedly won't "creep" (i.e. shift slowly under prolonged stress) like conventional woodworking glues. This was my first time using it. It seems to work well, but has this habit of foaming dramatically as it cures. Not long after clamping everything, this beige sauce-like stuff starts oozing out of all the joints. It's supposed to scrape off easily when dry. I glued things up in two sets to start out:


Note that the leftmost set has strips of different lengths. This wrestplank is trapezoidal, not rectangular, so one end is wider than the other. It was more economical of material to not make all the strips full width. I used the same technique as I did for the baseboard in making these strips, by laying them down on the drawing right onto the outline of the wrestplank.

The final glue-up of both sets of strips:

By the way, the polyurethane glue does indeed scrape off when dry: a chisel seems to be the best tool to get it off, but it took a fair bit of work. You can see from the photo immediately above that I learned to apply it more sparingly the second time around. The squeeze-out I experienced the first time was a bit much. I have to say I'd be leery of using this glue on joints that would be easily visible in the finished product because the foam spreads out sideways much more than squeeze-out from regular glue.

After scraping the glue off, the wrestplank was planed on both sides to its final thickness, and the left edge was cut cleanly. I've left it long on the right side for now.



A straight taper will be cut along the back edge.