1919 Gibson A-4 Mandolin: New Bridge & Crack Repair, Pt. 2

Continuing to repair cracks on the Gibby mandolin.

You may recall that four years ago I fixed the center seam crack. Guess what? It opened up again. Gently pressing down on the top revealed the crack had come unglued. I think the length of the crack meant it was under stress and glue just won't hold it shut.

So this time, instead of just gluing it, I figured I'd cut some cleats with my new cleat cutter and put them in there for a very solid repair.

First step was to make a bunch of cleats production line style.

I won't need all of these, but it's so much fun I couldn't stop making them!

Don't look at this picture if you're squeamish.

I settled on four cleats, and then drilled the access holes as I did on the last repair.

I wanted the cleats and the cauls to conform to the arch of the top as closely as I could make them.

So I taped some 100 grit paper over the crack. I used double-sided tape for the paper, and knocked down the tack a bit by putting it on my shirt and removing it a few times.

Then I sanded a few small blocks of pine for the cleats.

Here's one of the three cauls, showing its arch.

Maybe this is overkill, but I wanted to put as much leverage onto the top when gluing the crack and cleats as possible.

Note that I labelled each caul as to its location - top, middle, bottom. Each curve is a slightly different.

Then I put sandpaper on each caul and shaped the "top" surface of each cleat using the radius on the caul. The top being the side that will be glued under the crack.

Each cleat is numbered so it would match the correct location under the crack.

I wanted to ensure as close a fit of the cleats as possible under the crack - since the top is arched, I figured I'd arch the cleats too.

As with the previous crack, put the wire though the body, then slip a cleat on, then the brass tie block, and tie the block onto the wire.

I taped the cleats down so they wouldn't get tangled up. The wires are fairly long and I envisioned a mess inside the mandolin other wise.

Then apply glue to the crack and the cleats as usual.

Thread the wires through the cauls, then pull the cleats though, wind the wires around the tension tuners, wind them tight, and let the glue dry. Again I have waxed paper over the crack so the glue won't adhere to the cauls.

This made for a very solid repair.

You can see that you need a bunch of tuners for a long crack. I have an ancient Lyon & Healy parlor guitar in the repair queue with long side and top cracks, so I'll need to cook up a few more of these for that job.

I'll do the finish touchup on the mandolin in the next post.