the frame takes shape

I've started to lay out the design, on the bottom panel, similar to "Italian" construction (in that regard at least). I'm going with the two-line-segment bentside. I was going to draw the layout in CAD first, but instead I have ended up drawing it in real-life on the plywood, because that is how I can visualize it best: decisions about the angles and proportions, etc.. Then I'll have to carefully measure what I've drawn, lengths and angles, in order to do the lumber cuts; it won't be at all surprising if the measurements end up going into a CAD drawing after the fact: a little backwards, but what can I say!

(Just as an aside, I should note that I realized: I'm not doing something quite as offbeat as I thought, with the compass. I mentioned, I'm starting from E instead of the more-usual F; however, that is E based on A=440 Hz tuning, aka F in the "early music" community where A=415.3 Hz is the more-common consensus tuning. So, interestingly, I have found my way right to the compass which was often used, even though my materials (no brass strings) and design constraints (over 6' long OK, but no foreshortening) are different. Many times, instruments are made to transpose between the two by sliding the keyboard, but I'm not planning to do that with this one, made only for my own "rock and roll" use, I'm just going with fixed A=440 Hz tuning. My harpsichord will have a transposing keyboard.)

I've cut the oak plank I plan to use for a wrestplank in two, glued it up, and that is now drying; I'm making a double-thick sandwich of the 3/4"-thick planks, final thickness 1.5". Given the density of the grain, I am letting it dry for a "good long time" before unclamping. Seems like it might take a while for the moisture to find its way out of there (or redistribute, at least). I haven't worked with oak or other hardwoods much...

Fortunately, in addition to my drill press, I have access to a circular saw, configured as a "chop saw". It is able to cut angles up to 45 degrees away from a right angle. A couple of the lumber joints I had planned exceeded 45 degrees, so I redesigned the frame to eliminate these. It is better without them.

Here I've laid out the cut lumber, on top of the plywood back. Nothing is glued or fastened yet; the lumber will be held together with countersunk screws, just in order to firmly clamp the glue joints. Same goes for the bottom plywood and the soundboard (also plywood): sheetrock screws will be used to clamp the surfaces in place for gluing. As opposed to the "go-boards" used in conventional instrument-building: other than avoiding visible screws, it's not clear to me that the go-board approach has any real advantage, and it basically requires a proper woodworking shop, with an assembly table and a matching surface on the ceiling for the go-boards to brace against. Perhaps the go-boards (especially with an assistant or two) allow the soundboard to be clamped into place more quickly, which is a critical consideration when using traditional hide-glue, because it sets so quickly. I am planning to use synthetic adhesive with a longer setting time.

Before I glue the frame lumber together, I will need to carve away part of the top surface of the interior diagonal beam, to leave the soundboard free to vibrate there. About half of the beam closest to the front and to the spine-side, will not be carved away, so that part of the soundboard will be "masked off" and prevented from vibrating.

Also, I may fit one more smaller brace diagonally across the long tail section, and this brace would also be partially carved away on top. In my original design for the frame, I had the shorter segment of the "bentside" continue past the junction with the other two beams, ending at the spine-side. That portion of the beam would have functioned as the smaller brace and would have been carved appropriately. However, I realized that the beam did not need to continue in that fashion for strength reasons; the structure as you see it should be more than strong enough to handle the tension. I hope!

Also, the "spine" and "cheek" pieces, i.e., the parallel straight sides, will need to be carved for the wrestplank, which will be inset approximately flush with the top surface of the beams.

Finally, thinner and wider softwood planks will run around the outer perimeter of the frame, extending mostly above the top surface of the beams (which will form the bed of the soundboard), and extending downwards enough to cover the edges of the bottom plywood panel. These planks could be used to hide the screws fastening the frame together, but actually I'll probably use screws to attach the planks as well.