It's time to dismember the instruments! I have never taken apart a violin-family instrument before, but I've done so with guitars, to varying levels of success. The most important thing about taking apart an instrument is patience, and evidently, I still don't have enough of it, as we'll soon see.
The first thing I did was remove the fingerboard from the viola. Blessedly, it was only weakly attached with hide glue (like they're supposed to be), and it came off nearly instantly after I wedged a few palette knives into the bottom seam. Gently. I didn't even have to apply heat or steam.
(That photo is staged; I'm holding the fingerboard on with my thumb, because it had already popped off before I had a chance to take a picture.)
Now to remove the neck. The cello neck had been held on by basically nothing, so it came right off without teaching me anything. I needed some guidance. This article is helpful for illustrating the removal of a violin neck: https://www.andrewcarruthers.com/replacing-a-violin-neck/. It's rather daunting in its professionalism, but at least showed me how to saw the joints around the neck. So that's what I did:
You can see that my saw could only handle cutting about 2/3 of the way through the joint on the side without risking cutting into the back. I used a SharkSaw, a pull-saw with a very thin kerf that you can get at Ace or wherever, and the teeth don't go all the way to the tip. I assume a fancy Japanese pull-saw might be built more conveniently.
This video shows several interesting things about removing and replacing necks: https://www.youtube.com/watch?v=BXi7RuOtcgk. At about 8:00, there's a demonstration of a fairly terrifying method for actually getting the thing off after the joints have been freed, but it was the only specific method I could find, so it's what I did. And it worked without much damage. The heel pulled up some splinters from the heel block, but that's easily leveled out later with a chisel.
You can see that there's some garbagey filler material between the ribs and the heel block, and the button didn't have a good join with the back of the heel, and also the button has large areas of wood filler (the tan discolored blotch in the middle, to the left of the center line). So we see that I'm not dismembering an instrument of quality, which is comforting.
Here's a shot of the removed neck:
Now it's time to take the fingerboard off the already-removed cello neck. Easy, right? WRONG. In my more or less limited experience, removing a fingerboard is either extremely easy and fun, or extremely hard and bad, with nothing in between. The cello experience was hard and bad. First, I couldn't open the seam at the top or the bottom at all; it seemed welded shut. (The nut came off easily, like it was supposed to, but that was the only easy thing.) Then, when I finally managed to open it a little bit, I made no progress--not with heat, not with steam, not with muscle. The photo is of the application of heat while the palette knives are wedged under the top seam.
I don't know exactly why it was so hard; possibly this joint didn't use hide glue, but rather Tite-Bond or another wood glue. Or it might have been the much greater surface area of the join, compared to that of the viola. In any case, I lost patience after the better part of an hour, and, dear reader, I made a bad mistake: I tapped a chisel into the seam. This did crack open half the glue joint at one go; but it also caused the fingerboard to flex too much, because it was still strongly attached at the other end, and so it splintered some in the middle where it was under the most stress.
OK, maybe it's not so bad?
It's bad. I was able to glue some of the pieces back into place afterward, but let this be a lesson to you: don't lose patience. Meditate, turn on some light music, smoke weed, do whatever you have to do. If your fingerboard doesn't want to come off immediately, just set aside an entire afternoon to tease it off, gently, excruciatingly slowly.
Anyway, here's a picture of the pieces that will eventually become the Adapted Viola:
The next order of business is to create the hybrid neck. This should have the profile of a viola neck, but the length of a cello neck (or even slightly more). Inspired by the first article I linked in this blog post, I ambitiously decided to go for a V-shaped mortise and tenon joint, for maximum surface area.
Here, you can see where I measured for the combined lengths of the necks, based on the necessary scale length, and laid out the shape of the cuts. The "fun" part is next.
Here, I've roughed out the cuts, in anticipation of filing and chiseling them to their final dimension. It looks like I overshot on the left, but it's actually right on the line; the tip actually goes down further than what I laid out. Anyway, I'm not a fine carpenter by any means. I'm a dilettante-level luthier. But rough initial work can be compensated for, with hours of careful fiddling.
(As a matter of fact, the phrase "hours of careful fiddling" can also accurately describe the microtonal string music of Marc Sabat... and I mean this with the utmost respect!) (I suppose the phrase also conveys what's in store for me as I learn to play this instrument.) If I were to do this again, then I would take two lessons from this experience. First, rather than attempting to cut these joints freehand and then painstakingly shave them to a perfect fit--which did, indeed, take hours--I would use a table saw with an angle jig. That would get me a lot closer to a perfect fit on the first pass, and I'd only have to account for a wider kerf in the overall neck measurements.
Second, for this instrument specifically, I would not use such a strong joint as this: it's not actually necessary. The string tension is a lot lower than a violin or a viola, so the joint could be more like a common guitar headstock joint (a "scarf joint"):
This could be achieved on a table saw or even a chop saw with zero cleanup--very much worth it in terms of labor. And if I were truly worried about the strength of this joint, I'd put a pin through it and call it good. In fact, before I strung up this Adapted Viola, I was indeed worried about the strength of my V-mortise joint, because I couldn't quite get an airtight dry-fit before gluing it up... so I put a pin through it. Pictures of that later on.
Hilariously, almost all of my clamps were at my dad's house when I decided to glue this thing up, so I decided to jerry-rig it rather than waiting until I could pick them up. This involved clamping the pieces of the neck to a board which I knew to be flat and straight... using shims that I screwed to the board.
There's a piece of wax paper under there so I didn't glue the neck to the stabilizing board. I used Tite-Bond for this joint, instead of hide glue, because a) it is slightly gap-filling, and I wanted to accommodate my still-slightly-bad joinery; and b) it's a lot stronger than hide glue, and this joint doesn't need to be reversible. I mean, for God's sake, if this joint fails, the merciful thing would be to just make a better neck and replace the whole thing.
The astute observer will also note that I screwed the two pieces together across the joint, with an actual screw, in addition to clamping the pieces sideways. This served two purposes. First, to assist in immobilizing the joint and maintaining an accurate alignment. And second, the hole I pre-drilled for the screw (please pre-drill your screw holes!) will be enlarged later to accept the oak pin. It's a real belt-and-suspenders approach. Perhaps this actually weakened the joint instead of strengthening it, but since all of the woods involved are hardwoods and I left a decent margin, perhaps it didn't hurt.
Dennis Havlena, whom I adore, and who infected me with the instrument-building bug when I was a teenager, would probably have left in the original screw. It's up to you just how "hobo" you want this instrument to be.
The next article will be about shaping the neck profile, setting the neck into the body, and my misadventures with varnish. Then, the final article will be about preparing the fingerboard and marking all the microtones. As a final note, I wanted to show you a picture of the length of my conjoined neck compared to the original cello neck:
The top of the cello neck is held right against where it was cut. You can see that the cello neck was originally only about an inch shorter than the combined neck. All this work for an inch of length, and the right size of pegbox! Does that make me a size queen?