Cello reassembly

[Mark Wybierala]

Dipping my toe into territory never traveled, I'm putting together a cello. My guess is that this instrument sat in the truck of a hot car this last summer. There were few joints that did not separate. The sides had detached from the back and top, the neck block and the neck itself were both loose. I cleanly got the neck separated from the neck block. It's a decent instrument made in china with a solid top and reasonable quality materials. I've reattached the back to the sides and have the neck block secure again. So far, its been relatively straight forward with nothing being warped or distorted -- just cleaned off the old glue and everything fit quite well.

At this point, the back is secure to the sides and both the neck and the tail block are in place. What is left is to attach the top and the neck, and then deal with the back button that is fractured at the margin.

Should I reattach the top first and then deal with the neck alignment as one would with a neck reset or, should I attach the neck and align the neck as part of the top installation?

Generally, all of the joints came apart cleanly with a slight amount of damage to the neck joint when it gave way. Again, my guess is that the instrument was baked in a vehicle this last summer. Strung to pitch, it probably happened slowly over the course of a few hours with the instrument strung to pitch -- the strings and bridge were still in place when I received the cello. A nice process if someone ever wanted to totally disassemble a cello.

I'm tempted to reinstall the neck first. I've got a nice instrument size jig that'll let me align the neck angles while I glue and clamp the top.

Thoughts?

[Mark Wybierala]

More,
I've cleaned up the neck block pocket and the heel of the neck. Its a nice tight fit and the assembled unit (dry fit w/ no clamps) isn't as flexible as I anticipated. Again, I'm tempted to take advantage of the alignment without the top installed. I don't see a reason to install the top first since the clamping of the top may distort the angles without the neck being in place to notice or evaluate. My jig allows me to monitor the neck alignment when I clamp the top. I'm going to use a laser line to evaluated the in-line alignment and the unit is stiff enough to view the projection/end of fingerboard height. Everything looks really good.

[Rick Milliken]

Sounds like with the equipment at hand, you’ve covered what I’d be concerned about, the alignment of the neck when you attach the top. Interesting job!

[Mark Wybierala]

I gotta say that I've been real lucky here. I doubt anyone ever built a kit that went together so accurately.

After checking, double checking, taking it apart, testing my clamping method, and then checking alignment again, I glued the neck into the neck block without the top installed. I let the Titebond cure for three days and the alignment/projection is still right. Its a lot more of a solid structure than I anticipated with the top still not installed.

I built a jig for installing the top. As a result, I now own as many spool clamps as anyone. I purchased four 8' lengths of 1/4-20 stainless threaded rod, wing nuts and washers from McMasterC, and 250 1-1/2 X1/8" round discs made from 3-ply (ebay - cheap), stacked/glued/clamped and drilled them for spools. For the jig, there are 1/4-20 threaded inserts. The jig itself allows the neck and fingerboard to sit inside while I clamp it all down and I can inspect the neck alignment during clamping. I can also employ adjustable pushers to address places where the sides don't exactly align with the average perimeter of the top. I'll take it out of the jig on Friday.

25dec2019 003.jpg (68.08 KiB) Viewed 8841 times

[Fred Battershell]

Good job on that assembly jig! I've seen this type of jig used by a Brazilian luthier who makes violas da gambas. On my spool clamps,I fit clear plastic tubing over the vertical rods where they would likely come in close contact with the edges of the instrument to prevent damage to the edges.

[Mark Wybierala]

The end result was good but with a slightly less angle on the neck than optimal. I've seen far worse neck angles on new cellos and I can still employ a standard replacement replacement bridge. The cello was owned by a school and it was one of six that was presented to me for repair. All of them had challenging issues and 4 were repaired. 2 of them were not economically reasonable repairs. The school was happy with the results. Three weeks later I got informed that I can have the unrepaired instruments if I'd come by and pick them up. One is a Chinese economy student cello with the only decent part being the neck and it has a collapsed thin plywood top made from inferior material but the other is a German post WW2 cello made from delightful wood. Its really in bad shape with separated top and back and multiple splits on the sides but it deserves to be a project to practice my skills. There are stamps inside that make me suspect it was manufactured under some sort of American supervised economy recovery effort after the war but this is only a suspicion. Going to take my time with it cuz its cool.