Pulling all the pieces into one instrument, marking down the stars...

October 13. An early start and some critical steps.

I test fit the fully dried soundboard in the pin blocks; it fits great!

Mounted the side bridges. Marked the side bridges' places with masking tape and removed the soundboard. Flipped it over and drilled 1/8-inch holes where I intend to screw down the side bridges. I countersunk each with a 1/4-inch Forstner bit, then glued in a 1/4-inch brass washer. Measured the place of the first mounting screw, transferred that to the appropriate side bridge, and drilled a 1/16 hole there. Used a moderate amount of glue under the side bridge and then started the first screw. Drilled 1/16 pilot holes for 4 additional screws on each bridge. No problems: each side bridge is now held down by 5 brass #4 X1/2 inch wood screws countersunk into the back of the soundboard with a brass washer to distribute the stress (total area: 10 x .125^2*pi = 1/2 square inch). Glued area: 1/4x20 = 5 square inches. Everything on the back side is generously glued.

With the side bridges in place, the soundboard is easy to set in and take out of the pin blocks. Good! Slight misgiving: the holes in the left side bridge are just about flush with the top of the pin block. Be very sure to keep the strings low on their pins on that side lest the lifting vector rip the side bridge off the soundboard. If that happens, sand it down, put a cap on it, and run all strings over that bridge. Or put a brass bar on top and bolt everything down -- that could be done without unstringing (drill out an access port in the backboard if needed) if the problem proves real and is caught early.

I chucked the bass and treble bridge caps in the lathe with a live center in the tailstock and spun the 3/16 inch brass while pinching 400 grit silicon carbide paper around the bright bits. They were bright; they're brighter now. Then I coated the bridge caps with polyurethane to see if the polish can be preserved.

I rehearsed the cutting of the sound holes but the battery in the hand drill was almost dead. The spare was worse. While it charged, there was time to place the bridge supports. Get a cup of coffee and let's go do it...

Did it. A bit heartpounding, though. At the last minute I substituted much thinner shims. Glued everything down, verified measurements. Test fit a piece of plywood -- no contact with the braces! Pull out the braces and the shims. Put the original, thicker shims cut from the same back- and sound-board stock in at the last, last minute. Replace the braces. Much better. I've got scrap plywood laid across all three braces with about 20 pounds of stuff mashing down. Easier than trying for an adventurous clamping rig.

The fully charged drill cuts practice soundholes in scraps of the soundboard stock just fine.

After the braces were dry and solidly in place, I reshot the innerds and used the photos to work up a guide in Photoshop to be sure the soundhole design will work.

Freehanding the Pleiades... I scaled the photo and a diagram of the Pleiades to actual-size, 1:1 scale (with the dulcimer, not the Pleiades), then rotated the starfield until none of the proposed soundholes lay above braces or other innerds. The bottom left corner of side rail and pin block was my origin (0,0). Still in Photoshop, I measured the positions of all the stars and then applied x and y offsets to translate the coordinates relative to an identifiable spot on the soundboard (I made the lower inner left corner of the side bridge my new zero point). Then I transferred the numbers onto the wood, re-measured, re-re-measured. Then measured again. Go ahead, laugh, but two stars were out of place until the last check. Marked all the spots with bits of tape; looked at it for plausibiity. Measured again. Drilled pilot holes. Then drilled Venus (2-1/8 inch Forstner). Drilled the five bright sisters (1-1/8). And finished with the two faintest stars (5/8). The drill produced clean holes (whew) where I aimed to place them. Next we'll see if I really avoided the internals. If not, I'll deal.

OK, why wait? I set the soundboard atop the pin blocks and look: no braces! Success! To darken the rims of the stars, I experimented with my scraps full of practice holes. I tried linseed oil (not dark enough), boot black (too hard to control, bleeds over onto the visible surface), and settled on spraying flat black paint from the back side out through the holes to catch their edges without misting the soundboard.

Next: drill out the tuning holes and insert pins. Then string it up. Geraldine the mail lady left a Korg tuner (eBay) in the mailbox just in time. I also need to finish sanding the rails and begin rubbing them with boiled linseed oil. A test bit of cherry treated that way last night was nothing short of thrilling.

Thank you David Brakefield! Late tonight, I sanded the side rails and rubbed the first dose of boiled linseed oil into them. Wonderful! "Like a gunstock," indeed. I'll need to read up on this to see how much, how often, and how many times to apply oil (some, 1-2 hours, rub it in after applying; buff off whatever has not been taken up after 1-2 hours, repeat as many times as you like).

A small hitch, so to speak: while preparing to label the hitch- and tuning-pin holes for tomorrow's drilling pleasure. I confirmed my suspicion that I've drilled the hitch pin holes too deep, or that my hitch pins are not long enough. In any case, if I drive these to the full depth of their holes, they'll disappear. I could shim the bottom of the holes with... something. BB's? Very short screws or nails? Tiny dowels? Snippets of brazing rod? Solder? Sand? Think on this. Drill a sample hole to take to Ballard's.

Did supper, watched "Bringing Up Baby," then rubbed on a second application of linseed oil and hand rubbed the finish for 15 minutes or so. Wiped off the remaining oil rather than let it sit overnight (excess boiled linseed oil can get sticky, I read).

All the while I was thinking about those holes. The brazing rod will do the trick; it will offer substantial extra resistance even if that resistance could be overcome (by bending, by driving the rod into the maple or up beside the down-driven hitch pin), but it would put up a fight. I can always use multiple pieces. Make a jig: just a piece of hard wood that will let the hitch pin pass through readily but will not let it be driven any lower than I want it driven. But be careful not to scar the pin blocks -- maybe just use such a tool as a gauge rather than as a collar to be hammered through.

Still thinking about what do use to fill the bottom of the hitch pin holes. Aluminum foil, paper wads, soda straws (cut and slice them and roll the plastic tighter to make sleeves), paper rolls, trimmed shishkabob skewers...?

The answer is: [next page].

 

 

Treble bridge.

 

Poplar inlay in black cherry rail surrounding rock maple
pin block with black cherry side bridge and mahogany soundboard.

 

Polishing the bright brass between scale markers.

 

Found still life: top of the table saw as a workbench. Rehearsing
to cut the biggest soundhole, calculator for finding locations
of bridge braces (the faux "blade" in the upper left is actually
a bit of flashing left over from a telescope project; don't
let it worry you).

 

Rectified view for measuring soundboard decoration.
Two 1-1/4 inch oak dowels hold the pin blocks apart;
nearly vertical bar near middle is the treble bridge brace;
the two oblique bars at right are twin bass bridge braces.
Treble bridge sits directly above the treble brace; the bass
bridge sits in between the bass braces. Avoid all that when cutting out "Venus Among the Pleiades." (The inside
is simpler than it looks: some tricky shadows here.)

 

Marking down the stars.

 

Venus cut out, other stars marked by tape and pilot holes.

 

Soundboard, ready to use except for one last spritz of
poly to seal the edges of the newly cut Pleiades.

 

You're on page 9

Building: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Refinements, etc: 16 17 18 19