Cutting the soundboard, finishing the bridges...

 

October 12. A big step but not quite as big as I had hoped. At least the remaining path is clear.

First: sanded the pinblocks to 400 grade and gave them a final coat of Deft semigloss. When that was dry, I sanded the backboard and hit it with Minwax polyurethane.

Then I finished the treble and bass bridges. I almost had a disaster with the treble bridge. I was using the table saw to taper the tops of the bridges to be sure strings would clear the edges. Blade set at a 15 degree angle, rip fence to the right, bridge right side up. The bridge was confined between the rip fence and the blade. That was a beginner's mistake! I had fed the treble bridge through once, then reversed it to whittle the second side to match. About 80% of the way through, I let up on the feeding pressure to reach for the back of the bridge to pull it the rest of the way through the saw. The bridge kicked back, rising up and out of the saw as it moved. The blade ripped deep into the second side, scooping a very deep, circular scallop from the last five or six inches.

Fortunately, I had not cut the bridge blank to length and there was room -- just -- to cut three more holes and then lop off most of the damaged portion. The fraction of an inch I could not spare sanded down well enough, but there'll always be a mark I can point to. I spent an hour or more insuring that the dimensions of the new bridge would work, lining up the holes and bridge top with the nascent courses. I had to puzzle out exactly which pin holes went with which courses (should have done this long ago) and used a long wand of scrap wood as a surrogate for the strings. When I was sure the dimensions were OK -- that there was support for the treble courses at top and bottom and openings that aligned with the bass courses as required -- I recut the angles on the treble bridge. This time, the fence was on the left, the top of the bridge down, so that the wood was not pinched between the fence and the blade. Much better. Did the same for the bass bridge. Live and learn. Then I laid each bridge on its side, set the blade at 45 degrees, and took a pass that just nicked a furrow down the tops to hold the brass tube / bridge cap. Measured for the fiftieth time and lopped the bridges to length on the miter saw.

I made a jig to hold the brass tubes while I blacked the tonics of scales for both treble and bass courses. Then trimmed the treble cap to fit the new bridge. Tomorrow I'll likely run the bridge caps on the lathe to bring the unblacked metal up to a high polish. Yes, I'll practice on scrap bits.

I decided to stick with RD's design for the side bridges, so I cut the side bridges from leftover cherry. Went to Ballard's for #4 screws, washers, and two 1/16 inch drill bits. I don't like using screws. Everything else is just joined and glued. But I am not taking any chances with diverging from RD's notes at this point. I printed, aligned and attached the hole patterns then made something of a mess drilling them out. Not enough of a mess to redo them, but enough that it is not an aspect of the instrument I will show off.

This is not my day for detail work.

Lacquered and measured everything and then there was nothing for it but to cut the soundboard. I took several whacks at the right side. See previous remarks about not my day for detail work. Eventually, it was good. I inserted that side of the soundboard into its eventual home on the right side of the dulcimer and marked the left directly from the left pin block into which it will soon fit. That worked much better than just transferring numbers. I rough-cut the left side with the jigsaw and iintentionally left myself about a 3-inch finishing cut on the tablesaw. Sanded the edges down, sanded the top of the soundboard, then hit both sides with Deft gloss, two coats. Did that outside to prevent odiferous offense.

This is where we pick it up tomorrow: I'll install the side bridges. Measure the distance between them at top and bottom and calculate the locations for bridge braces based on those measurements. Glue the bridge braces in. Lay out and cut the sound holes in the soundboard. Apply one more coat of lacquer to the raw edges.

Drill the support hole. Install the pins, then strings, then we're done.

How far do I get tomorrow? Would love to be ready to install pins on Saturday.

 

Sanding mahogany plywood.

 

That iconic shape...

 

Layed out for a plausibility check. Side bridges
(black cherry), bridges (rock maple), soundboard
(mahogany ply), bridge caps (brass).

 

Detail: the player's end of the bass bridge and
bridge cap resting on the soundboard.

 

Take that thing outside if your're going to spray that
nasty polywhatsit all over the place...

 

The difference a proper finish makes.

 

Coming along...

 

 

You're on page 8

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