Both the spine-side 2x4 and the 1x6 were warped, in different ways. The long flat-sawing operation and the gluing-together process will, I hope, result in an overall composite beam which is strong and functional. But actually making it fit has been a challenge at every step. I can now see that to use this no-bandsaw, no-plane building technique, i.e., relying on the original lumber faces as much as possible, the management of the wood becomes critical; and I probably need to build some kind of special restraint-frame, a press, basically, for storing and curing lumber for the future projects. But anyway, I still want to make *this* collection of wood into a functioning instrument, if only to have a testbed for all the other radical ideas I want to develop, in the action and such.
I had already cut the miter plane into the spineside 1x6. Due to the cupping of the board, this plane intersected the wood in a broad gentle curve, like a bent sponge, rather than a rectangle. Just by a few degrees, but enough to put a noticeable sharp point extending out mostly at the bottom. I will trim or sand this off after the gluing; but the important thing was to have a straight vertical plane at the right angle, to attach the small tailpiece to.
I cut the tailpiece exactly "straight", i.e., vertical cuts at the proper angles, no attempt to compensate for any irregularity on the mating spineside face. I figured I'd make all adjustments by grinding down the already-glued-on long pieces, and if I ran out of "room" and the tailpiece became too short to span the distance, I could easily cut another one a little longer, since no mods were made to that piece.
The tailpiece and the "bentside" 1x6 mated just right, no adjustment needed; but then the mate to the spineside was pretty far off. So, with a long process of iteration, I ground down the face of the spineside 1x6, also grinding away some of the tailpiece 2x4, until I got a reasonable fit for the joint. I used a flashlight to judge where the "high spots" were as I was grinding, by shining the light through the crack from underneath. I used my "sharp tooth" handsaw to rough-away some large masses of wood, then I used my wood-block-backed hand grinding wheel (seen first in the pedalboard project) for the iterative process.
I got the joint about as close as I could, but still with a gap at the top. Then, while gluing it up, I used a second clamp to force the top edge of the spineside 1x6, which was cupped outwards, to bend more straight, and this correspondingly closed up the gap in the top of the joint. So as long as the Titebond holds... and if it doesn't, I have bigger problems than how this joint looks, anyway...
It's not exactly masterful craftsmanship, I can only aspire to that as I go, but at least it looks semi-reasonable -- and I think it'll hold the string tension, the critical thing.
It's been quite a dance, a long progression, in my notebooks and in the realm of my thought-experiments and ideas, as I have gradually evolved a notion of how stringed instruments like this should "probably" be built. My initial impulse was to attack the problem with "shock and awe", i.e., to overbuild in a number of senses. My first drawings show beams made of laminated lumber, 2x6s in some of the designs, which probably could be used as roof timbers in Solomon's Temple. Thus, I could convince myself that there was something I could build, out of materials I could readily get, which would be virtually certain to be able to handle the string tension. Also, at the time, I was not sure about string diameters and tensions; I knew, less than a piano, but that is a very wide universe!
As I have studied "failed" attempts to re-invent or improve upon the ancient instruments such as the harpsichord, I have realized that, at least for the sort of tone I am going for, it is crucial not to overbuild: a light and resonant structure is what's needed. And string diameters and tensions are quite low; it's almost "the thinner, the better", but of course there are opposing concerns to optimize between. So after all my research, I come around almost to my very earliest ideas, which derived from the guitar. I wanted to put a keyboard onto a set of strings with the same lengths and diameters as the same notes on the guitar.
The high E string of the guitar, or better yet, the octave G string on a 12-string guitar, these strings are very close to optimal in terms of length vs. tension, and (usually) diameter. The lower strings are compromised in different ways.
So, essentially, what's needed is a large guitar. Something with that level of strength to resist tension, and something with that basic nature of lightness and resonance. In a guitar, the "strong" parts and the "resonant" parts are pretty clearly segregated; in the typical traditional harpsichord, the strength is obtained by a box-type geometry, and resonance is provided by all sides and surfaces being relatively thin (not just the soundboard). In my current design, for this pandalon, I have sort of stuck with my laminated-beam notions, but the beams are much smaller in cross-section than I originally thought might be necessary; and I am counting on thin "fabric" (plywood) to contribute geometric strength. So this tends to segregate the strength and the resonance, more like a guitar than a harpsichord (arguably). Since the sides of my instrument are integral with the beams, they are very thick and will not radiate sound much. Knitting the beams together, I have used just about the thinnest plywood I could get, 3/16" (I was originally planning to use 1/4", and that fourth 1/16" really makes a difference!). I used this both for the soundboard (top face), and for the bottom face. So, the bottom, as well as the soundboard, should radiate a lot of sound. It certainly "taps" like it will.
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