soundboard decorations

My spraypainted-paper technique is going to work, but I think I will go with metallic gold instead of the "hammertone copper": the latter just looks too brown, I think it won't have enough contrast with the soundboard wood (which turns much darker and redder when finished -- which is going to look nice!).

And here are my bridge blocks, drying: still in a long strip, not diced-up.  I've covered the top surfaces with several coats of polyurethane.  Next, I will hammer in the nails, then cut up and sand the individual blocks, and glue them to the soundboard.  Having the tops pre-finished will allow me to tape them up to keep the finish away from the nails, as I spray-coat the soundboard itself.  Originally I was going to hammer in the nails after all the finishing, but my concerns over splitting have changed this sequence.  Chances of splitting should be reduced by doing all the hammering while the blocks are still in a contiguous strip; and if splitting does still turn out to be a problem, I'll be able to change course without having already glued the blocks down.

the bridge blocks

So, I am planning to use a very unusual design for the bridge on this instrument.  I am now very glad that I've built this monochord, because it is allowing me to uncover and correct problems with my design, before I commit changes to the real instrument.

Most harpsichords and similar instruments use a single curved piece of hardwood for the bridge.  This works pretty well.  Usually, the builder just calculates the correct lengths for all the C notes on the soundboard, forces the bridge to pass through those points during the shaping process, and then the rest of the points on the exponential curve just kind of end up more or less where they should be, using the "curve fitting" of the bent wood itself.  It's not deadly accurate of course, but probably close enough, I've never heard of anyone asserting that the notes in between the measured points ended up noticeably wrong, on any real instrument.  (The only obvious problem would be if they were too long, because then the strings would break when brought up to pitch; other than that, errors in position would only lead to very subtle changes in tone quality.)  Another probably-insignificant-in-practice issue with the curved bridge, is that when there are pairs of strings per-note, one of the two ends up being slightly longer than the other.  Again, as long as nothing wanders over the safe maximum length, there is no real problem here -- though in this case, I have heard some people assert that they can hear the difference caused by the different lengths.  This would be very hard to pin down, because another factor probably has a larger effect on the tone in most instruments, which is the plucking position on each string: this is nearly always different for the two strings in a pair.  Having a difference in tone is not necessarily a bad thing, of course, as long as all the tones blend together well.  Many times, the two strings of a pair can be turned off and on separately, allowing the player to get different tones for different parts of the music.  Thus, some might argue that maximum tonal contrast, not minimum, is the right aim.

In addition to setting the correct lengths for the strings and coupling their vibrations into the soundboard, the conventional curved bridge has some other secondary effects, which may or may not be important.  For one thing, it leads to a relatively large amount of coupling between strings of different notes.  On traditional harpsichords, most of the notes will be damped (forced silent) at any given time; but on my pandalon, it will be possible to lift all the dampers at once, thus allowing strings to vibrate sympathetically with each other.  A one-piece bridge would probably enhance this effect.  Also, it's important to recognize that the one-piece curved bridge provides a tremendous amount of straightening and stiffening guidance, to the soundboard.

But I'm not using a curved bridge.  Instead, I am using small individual blocks of wood, one for each pair of strings.  Thus, there will not be as much coupling between notes.  And the stiffness of the soundboard will have to be maintained entirely through other means (I have fitted some braces, we'll see if it's enough).

Each block carries two nails, which provide the string terminations.  Well, actually (I'll have to post a link here when I find it), someone did a study and it turns out that the slight difference in length between the horizontal-plane termination of the string, provided by the nail, and the vertical-plane termination, provided by the point behind the nail where the string rests on the wood of the bridge (the "peak"), is quite critical to the tone.  Larger separations between the bridge peak and the nail, lead to softer attack, longer sustain, and less fundamental in the harmonic structure.  Of course there's a sweet spot, certainly less than 1 cm, which varies due to innumerable factors.  Out of a hat, I picked a distance of around 0.25 cm, as much because that's where I could best drill the holes as out of any tonal concerns; but I could have made the distance smaller, close to zero, and after reading this paper I chose not to do that.  One thing I could do with my monochord, is experiment with other distances, but I am so far satisfied with the tone quality I'm getting.

Of course, my bridge design looked really good on paper, in theory; but once I started building the monochord, I could see just how narrow the bridge pieces would really be.  1/2", to be exact.  1/2" wide sections of 3/4" quarter-round oak molding.  So, they look like tall quarter-slices of lemons, standing on their cut edges.  The tallness has always been a concern to me: would the sideways force of the strings, which make a 15-degree turn at the nails and then proceed to the hitching point, put too much torque on these pieces?  So far, answer seems to be no, the Titebond is amazingly strong when a good glue joint is attained.  However, the other factor which the narrowness brings in, which I somehow didn't forsee despite its obviousness in retrospect, is that I've pretty well done everything I can to make these blocks as likely to split as possible.  Two long nails, side by side, penetrating almost all the way through a narrow slice of molding, right near one of its faces.  If it were't hardwood, there wouldn't be a chance in the world of this working.  But now I see how poor oak is, as a choice for this.  I should be using something with a very dense and "closed" grain: I think maple might qualify better.  Of course I drilled pilot holes, but they are significantly smaller than the nail diameters, both because that's the available choice I had, but also because I want the nails to be very tightly gripped by the wood, I don't want them coming loose with vibrations and humidity changes, etc.; so I am expecting to significantly compress the wood fibers as I tap in the nails.  But how not to split the wood?  Well, I have revised my order of events, in processing these bridge pieces.  I was originally going to cut them up first, and then hammer in the nails.  Now, I plan to hammer in all the nails while it's still a single strip of molding, and then dice-up the pieces.  Even so, they might split after some time, being under constant strain from the fiber compression near the nails.  So, I am planning to "size" the side faces of the blocks with glue, during the operation where I also glue the blocks to the soundboard.  If this fails, well, I guess I'll try maple or some other variety of wood, next.  I might also try impregnating the wood with polyethylene glycol ("PEG"), which my woodworking reference suggests is a good treatment for making small wood parts like this more stable and easy to machine.

first sound! (in a way...)

Here, I am marking out the bridge positions on the soundboard, using a "ruler" I marked off on these steel rods taped together (material from the pedalboard project).

The string lengths are all based on the scaling (maximum tension before breaking) suggested by the string manufacturer.  I don't have a reason to doubt the value, but it would feel a little funny to start stringing up the final instrument without having any experience with this new iron wire.  It'd be a drag to have made some error of a few percent way back when, which I then propagated through all my calculations and stringing charts: I might see each string snap in turn, as I tried to tune it up to pitch.  This wire is notoriously fragile anyway; I'm used to strong steel guitar strings (and they also break!).

To check out the tension situation, and also to test several of my design ideas which have never been tested, I built a "monochord".  Actually, it's a duochord, replicating the two-strings-per-note disposition of the real instrument.  I sized the length for E4 with this iron wire, which is the high E of a guitar, and will be the middle note on this 49-note keyboard.  54-some-odd cm, i.e., only about 10 cm shorter than a guitar E4, which is strung in steel.  The iron is supposed to have a much lower breaking tension than steel, about half, and so the fact that the optimal length for E4 is so close to the guitar scale, shows how far guitars are tuned below their breaking tension.  I.e., I'm going to be operating these fragile iron strings much closer to their breaking point, than guitars...  (Actually, to estimate steel max tension relative to the "harpsichord" string materials, I use the high G4 of a 12-string guitar, which is the highest pitch I know of being strung at 65 cm.  And they sound pretty good!)

I also wanted to test out my bridge and nut design, based on quarter-round oak molding.  More and more, I see that oak is not the right wood for anything on an instrument, even though it has been used in the past.  It is strong and yet machines easily, but the grain is too coarse and uneven.  On my bridge pieces, the molding will be diced up into narrow chunks, 1/2" long each.  Thus, they will be taller than they are wide, so stability and the torque of the string tension, pulling sideways as it does, are of concern.  Also, I think, splitting is so much of a concern that drilling the pilot holes for the bridge pins may not be enough.  Maybe I should "size" the bridge pieces with glue, before finishing.  Or maybe I should give up on oak and find some other hardwood in a convenient shape, such as maple.  I don't have a definite answer, but now I can play with the monochord and ponder these matters...

Glad I tested this out!  I tried to use the same narrow-guage brass-plated nails for my hitch-pins, as I am using for the bridge and nut pins.  But the hitch-pin takes a lot more force, and as you can see, the poor thing bent right over as I tried to bring it up to pitch.  I'm glad to correct this once, rather than 49 times.  A slightly heftier nail seems to do the trick; although the ones I have in that size are not brass-plated, so I may look for some which are to keep a consistent look to everything.

You can see that I am using "double stringing", which refers to the string passing around one hitch pin and folding over to provide both strings of a pair.  The tradition with harpsichords has been to tie a loop in the end of the wire (a minor art in itself), and give each string its own hitch-pin.  But I have seen double-stringing in many other places, where it seems to work fine, including in pianos under way more tension, and in my little 15-note zither, where I can verify the somewhat-amazing fact that the two halves of the string can be tuned to entirely different pitches, without interacting or "slipping".  In the pandalon, the two halves will be at the same pitch, so I think I'm OK.  And stringing the instrument will be significantly easier.

With the monochord tuned up to E4, I can press it against the soundboard of the real instrument, and get a reasonable semblance of how its own E4 may sound.  All the signs are good.  The sound is reasonably loud, louder than I might have hoped.  It is delicate and harmonically-rich, similar to a harpsichord or a guitar, *not* similar to a piano (which is a good thing).  And when the monochord is pressed firmly against the soundboard, the sound no longer seems to emanate from the monochord itself: instead, the locus of sound seems to migrate to the larger sound hole.  So the soundboard is active, and it seems to be doing what it is designed to do -- perhaps even more effectively than my carefully-managed expectations might have expected.

drilling the wrestplank and nut pilot holes

I drilled pilot holes in the wrestplank: about 1/8", where final holes will be 3/16".  I hope that the pilot holes, done on the drill press, will suffice to guide the hand electric drill, so that I don't have to use the drill press for the final holes, once the wrestplank is glued into place and coated with finish.

I marked the holes with Sharpie, through a paper template.

I plan to use these little brass nails I found, called "escutcheon pins" (if I remember the spelling right), for the pins on the crowns of the nut and the bridges, which will form the crucial termination points of the "speaking lengths" of the strings.  The plan is to drill pilot holes in the nut and the bridge, using the drill press for nice vertical holes, and then to tap the nails in with a hammer; hopefully the fit will be just the right tightness, to not require glue and also to not split the wood.

The problem was, the nails were smaller in diameter than any of my drill bits: like with most regular sets, I can go down to 1/16".  Below that, they usually start using other measurement units for the drill diameters, and, it seems, they become a rare specialty item.  What, you people never had to drill a small hole?  All the "usual suspects" had nothing below 1/16" -- even places with Dremel tools and small hobby-type drills and such.  Fortunately, someone reminded me to check Hardwick's in the University District of Seattle.  It was a little obscure even there, but I found a set of small drill bits, and then the staff very helpfully were able to locate a tiny chuck in a different part of the store.  The drill bits are weird, they are coated with abrasives, for drilling through tile and stone, but they seem to go through wood OK without clogging up; indeed, the abrasive coating seems to let me "keep on trucking" and drill straight through even though the spiral grooves are fully clogged with wood shavings.  (They had a more-expensive set of bits that were regular steel, but I thought I'd try these first.)

The drill press has pretty poor mechanical stability, and between that and the two chucks, there was significant oscillation at the tip of the drill bit: it was not properly centered, even after much fussing and adjusting.  However, the drill bit was so flexible, relatively speaking, that it had a strong tendency to wander, which I suspect would have been a problem even with perfect centering.  The oak molding I'm using for the nut and the bridges, is quarter-round in shape, so at the line of the pins, I am drilling on a slight slope.  Wander-city for drill bits.  So, it was necessary to make pilot holes (for the pilot holes), which I did with the corner of a small screwdriver.  Once guided by the starter holes, the drill bit flexed enough to go right where I wanted it.  Still, for the many similar and more-demanding drilling tasks coming up in the construction of the action, I think I will need a smaller and more-precise drill press of some sort, for these little bits.  Perhaps just a hand-cranked drill built into the right frame.

Now that it's drilled, I can glue the nut to the wrestplank.  The whole thing will get sprayed with finish, and then I will tap in the crown pins and drill out the wrest-pin holes to their final diameters.  (I hope that the finish doesn't clog the tiny pin pilot holes so thoroughly that I can't hammer the pins into place; at worst, I might have to re-open the holes using the hand-drill: a whole lot of tedium but not the end of the world.)

The pandalon will have 49 notes, meaning 98 strings and 98 tuning pins.  The tuning pins come in sets of 100, so handily enough, there are just enough extra left over (if I don't mess some up!), so that I can build a "monochord", to test out all the aspects of my bridge and nut designs, test out whether I can get away with double stringing without tuning problems, as I believe I can, etc..  This "monochord" will have two strings (a "duochord"?), tuned in unison, just like the real instrument will have.  I'll be able to verify the actual breaking tension of the iron wire I've got, and I'll be able to hold it next to an electric guitar and get some sense for how well this wire will activate a magnetic pickup.

perimeter established

So now I have all of the sides glued on.  There are a couple areas that need additional gluing, probably with this hypothetical filler compound of glue and sawdust, which I have yet to try.  And I will have to fashion thin wedges of wood to glue into some voids, where my cut wandered in trimming the frame.  Most concerning is at the wrestplank end of the spine timber.  I hope I can fashion a tight-fitting wedge, glue it into the void next to the wrestplank, while gluing the wrestplank itself into position, and using the clamping to correct some of the outward cupping on the bottom of the spineside case plank: all in the same operation.

Before gluing in the wrestplank, I will drill holes in the nut for the pins (nails), and attach the nut.  And I will drill pilot holes for the tuning pins, with the drill press, so that I can drill the full-size holes with the handheld drill later on; I could probably maneuver the drill press to work on the wrestplank after it's glued into the frame, but I hope to thus avoid doing that.

Here, the pieces are just placed in position, in the frame.  You can see my relatively-narrow 2-inch gap, between the wrestplank and the soundboard.  As I am designing the action, I can see it will be tight to fit this spacing.  At this point, I could still choose to make it wider, by fitting spacer blocks when I glue in the wrestplank: ugly, but I think it'd be strong in the right ways.  But, I want to try to target a 2" gap.  This will allow the action to still work with higher notes than I have here, such as instruments with a 4-foot choir (a set of strings 1 octave higher on each note).

The two elements that need space in the gap are the strikers, and the dampers.  The dampers will be vertical wires, passing through holes in a narrow rail, and bent into loops at the top to which felt will be glued.  These come from underneath and press against the strings.  The damper rail will be closest to the soundboard, in the gap.  I'm pretty sure I can build it to occupy less than half of the gap, probably about a third overall, max.

So the strikers will have more than an inch of front-to-back space in the gap, which seems like it ought to be enough.  However, there are complicating factors.  The strikers on this action will necessarily be quite tall, something near 2" (which brings in a host of concerns in itself, as to stability and dynamic behaviour vis a vis the different guide systems in the action -- but presumably I will somehow solve all this and make the strikers work right).  Since the motion of the key is circular, centered on a pivot-point something like 12" away from the striker, the striker moves through a shallow arc, and thus needs more than its own size worth of clearance, towards the front (wrestplank side).  And given the intentional "looseness" of the guide situation, the strikers will need more clearance generally, to ensure no-contact with other elements.  (Unlike other early "tangent pianos" where the strikers moved vertically in harpsichord-like guides, in my action design, the strikers are more or less firmly associated with their keylevers, and follow their motion: the guides for the strikers are attached to the keylevers.)

And the real complicating factor is, the moderator stop.  This is a little strip of cloth, felt, or leather (haven't decided which material yet, will probably have to try them on the real instrument before deciding: just hope I don't decide I want all the types available as separate stops!), which can slide into position between the strikers and the strings, thus softening the tone of the bare-wood strikers.  The effect is as if the strikers themselves were covered with the moderator material.  It's important that the moderator fabric not touch the strings, except when and where a striker has been keyed: when playing with the moderator active, the strings still have their full sustain time, it's just a softer initial excitation; this is in contrast to the "buff" stop, where the strings themselves are muted and have a much-reduced sustain time.

Doing without a full set of tone-modifying gadgets is simply out of the question for me, in-style or not.  So the question is, how can I fit the moderator into all this?  Specifically, where will it "stow" itself, when not in use?  The obvious design for the moderator is a long rail or rod, with the fabric attached along its edge and protruding to one side.  The rail itself does not pass through the path of the strikers, but it moves up close to the strikers, so that the fabric is in their path, or it moves farther away "somewhere", so that the fabric is out of the way of the strikers.  The simple plan would be for the rail to slide horizontally (or move through a wide arc, approximating a horizontal slide), so that when not deployed, the moderator would be taking up its full width of space next to the strikers, in front or in back.  However...  The moderator can't slide to the back, because that's where the dampers are.  (Original pandalons didn't have conventional per-note dampers, so if I were sticking to that exact design concept, I wouldn't have a problem here, but like I said, every possible gadget...  The per-note dampers are particularly important to me: I want to be able to play with articulation, and also to play with the dampers off.  Not many instruments prior to the piano (which has its own problems of course, or I wouldn't be here) gave both options in one instrument, but we don't have to be limited by the past to learn from it.)  And to the front, i.e., between the striker-zone and the nut, will be the rails of two other stops, the buff and the bassoon.  I'm not positive, but I don't think there will be room to park the moderator in the space that remains.  So, I'm considering making the moderator swing through an angle of 90 degrees, and slip down in between the strikers and the dampers, in a vertical orientation.  I think there may be just the right amount of room for the required arc of motion to do this, since the strikers in rest position sit well below the strings.  We'll see, there's plenty of time for me to pull together the exact design of all the stops and gadgets, because I will finish building the full basic instrument first, before I start on these other things.

Pretty pointy.  I recently had the opportunity to see if the instrument will likely fit in my friend's car, an early-2000's Toyota wagon.  It will be very convenient if I can fit into this very-typical vehicle, and conversely, it will be very inconvenient if I can't!  The car was parked at my apartment the other day, so we carried out the big piece of plywood you can see standing up off to the side (at the bottom of the photo).  This will become the lid of the instrument, and it is already cut to the rough outline, so it's a good representation of the footprint.  And, with all the seats down, we found that the lid piece fits very nicely in the car -- although, given our driver-on-the-left country, it fits best upside down!  I guess that won't hurt anything...  Presumably the real instrument will be encased in a "sleeping bag" I'll make for it, stitched-together out of blankets.

However, we weren't figuring on the additional length of the keyboard and action, which (I'm pretty sure) will extend the length even farther than any of the current wood.  I'm planning to make the action easily-removeable anyway; perhaps it may be necessary to separate the action from the instrument, every time I want to move it somewhere.  Maybe that's better anyway: there may be reasons I don't want the action to spend hours bumping around in the back of a car, while in the upside-down position.

more case sides... (and a link)

Have you ever seen the Wallace and Gromit movie, one of the original short ones, name escapes me, the one with the evil chicken; but it has a "chase scene" involving a model railroad.  At one point, Gromit is headed towards a dead-end of the track, balanced atop his toy train car, so he grabs a box of extra track segments that just happens to be there, and starts laying down new track in front of his car, at lightning speed, routing the track precariously around table legs, etc..  F'in clever, as good as the best of Looney Toons, IMHO.

But anyway, to make a short story long.  I feel like Gromit, but in extreme slow motion.  One segment per day, at best, given the 24-hr minimum drying time of this Titebond II glue.  And they don't lie, it's at least that; especially when I seal the bottom of the joints with Duck Tape, so that I can do the gluing without laying out a huge tarp under everything (and probably walking through it): this limits airflow, and the portions of glue bead in contact with the tape will still be wet at least 12 hours later, when most of the other glue has at least dried to a pliable, rubbery state, or beyond.  It'd probably take 48 hours or more to fully dry, if I didn't "rip the bandaids off" and accelerate the drying.  I doubt that it is good to have such a differential in drying rates;

maybe I could find a way to mask with paper or something, which would have some air permeability and/or glue absorption.

Here, I've just laid the soundboard on top, to see how it's gonna fit.

Shorter "bentside" piece: one more to go, the cheek piece.

Fitting each successive piece (other than, of course, the original two long pieces, which didn't join to anything initially) has been a repeat of the painstaking iterative grind-to-fit operation.  This lets me know that there isn't a square angle or straight surface anywhere on this rig!  But at least it will all look like it fits together.  Fitting the lid, when that time comes, may be something of an art: I highly doubt that the top edges of all the case lumber will be truly co-planar, though I hope they are close.

As I finish up this step of adding the sides, next steps include: pre-drilling and fitting the wrestplank, pre-drilling and fitting the nut and bridge pieces (the nut in my design is a single strip of oak molding, but the bridges are short segments of molding, all diced up, one piece for each pair of strings at a given pitch); and then I'll be ready to start the finishing process on the case.  As in, spraying it with polyurethane finish -- the overall project won't be anywhere near "finished".

I have decided to spray all exposed surfaces with polyurethane, both inside and outside of the soundbox.  So this presents something of a challenge, as to masking and ordering of operations.  (And I say "spray" because it's a good quick verb that is less ambiguous than "finish", but in fact I'm not positive, I might use a brush for at least some of it.)  I'll have to spray the inside of the soundbox, and the back side of the soundboard, with both areas properly masked where they will glue together.  Then glue the soundboard in place: I think I can do that process before the first polyurethane is fully dry, i.e., perhaps after 24 hours.  Then, the outside surfaces can be sprayed, again maybe 24 hours after gluing the soundboard; however, I may have to position the case different ways to hit all the surfaces, so more than one session may be required.  Anyway, after 3-5 days of that, the whole thing will then need to sit and thoroughly dry: which may take another solid week, judging by my prior experiences with this type of finish (under conditions of better airflow).

None of this can be done in my apartment!  Nor is there space outside.  The outdoor-air-exposed basement hallway where I did much paint and finish drying for projects like the pedalboard, does not have enough space to fit this pandalon (I checked), without being seriously in the way of the other residents.  This is a real issue, for this "cottage industry" concept.  I use a minimum of harsh chemicals, where possible, but here there is no way to escape a process which is simply not compatible with indoor living.  My solution will be to borrow a friend's garage space.  Others undertaking a project like this will have to solve the matter for themselves; I considered ways to do it "on the premises", like constructing a special-purpose "tent" or shelter, so I could store the instrument in the backyard for the days of drying (or I also considered the roof...).  But, between humidity and vandalism, I'm happier having it on my friend's property, assuming that the plan works out.  This will be a first chance to assess how much of a pain in the ass it is to move this instrument, as well!

Oh yes, and about the soundboard.  Original plan was glue-n-screw.  Then I got all fancy with no screws on the case sides, so I wondered if the soundboard would look bad in comparison.  The usual approach is the "go deck", which I don't have... but maybe I should...  But anyway, I think I have a good solution here, and critically, given the two-part finishing process I outlined, it's one I can execute up at my friend's house, in between polyurethane coats.  (Of course, my "portable go-deck" would also fit that bill, but it has yet to be built -- or even fully designed! -- yet.)  Glue-n-nail.  I think I can find some nice-looking brads, brass or copper looking, and space them quite a bit more closely than I was going to do with the screws, and it'll look not-bad.  This will also give me a design-coherent way to delineate the positions of all the braces, which I want to do, so that I can analyze their effect on particular notes and such.  I also plan to put some decoration around the sound-holes, astrological symbols and such; I will make these in metallic finish, to match, or at least to correlate with, the brad colour.

But the greatest amount of decoration will be the painting on the underside of the lid.  My artist friend has offered to do a painting for this, which I am thrilled about.  I won't have her start until I'm sure the instrument is worthy, however!  The rest will be mainly finished in clear polyurethane, letting the blonde colour of the wood come through.  I want it to look relatively plain, a simple "proof of concept" implementation of my ideas, so that the design and the mechanism are easier for interested people to see and understand, without a lot of distraction.  Except for the lid painting!

As for the wrestplank, and the bridges.  I will drill small pilot holes at the positions of the tuning pins, before I glue the wrestplank into the frame.  Thus, it'll be easier to use the drill press to get these holes vertical (I'm not attempting to give the holes a back-angle, as is often done; I just want them to be consistent).  Then, I'll glue the wrestplank into place, and finish it with polyu.  And then, I'll drill out the tuning-pin holes to their final diameters, probably using the handheld electric drill.  Thus, the sides of the holes will be raw wood, not finished (which is necessary for the right kind of friction on the tuning pins).

I will drill small pilot holes in my oak moldings, with the drill press, for the bridge "pins".  Small nails, in my case.  Two moldings, one for the nut, one to become the bridges.  After drilling the bridge molding, I will dice it up into individual segments; then I will glue the bridge segments into their places on the soundboard, 

All this before the polyu, so that there is good Titebond conditions.  After the polyu has fully dried, back at the apartment, I will install the nails into all the holes... and then, I'll be able to begin installing the strings and the tuning pins, which will be one operation.  Wow, sound!  A ways to go yet, but it's in sight.  I'm now quite confident that the tone will be adequate, and less confident but still *fairly* confident that the structure will be strong enough, and won't just collapse immediately or within days, of coming under tension.  Just from my instincts, my "tapping tests", and my general visceral sense of how strong the structure feels, now that I can physically interrogate it.

Oh yes, and about that link.

http://www.si.edu/Encyclopedia_Si/nmah/hdmake.htm

This page, among other things, makes me think that good tone is obtainable from a simple design employing plywood.  My aim is really just to create a hammer dulcimer with a keyboard.  The construction techniques and materials don't have to be the same as were used in 17th century harpsichords, to still sound good.  I hope...

fitting the tail-piece

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.