Martin 51 repair project:


February 7th 2017

One of my guitar instructors had this guitar on his wall. It was his mom's guitar that he was playing in highschool when one of his buddies ran in (over) with his car. It has probably been on a wall hanging for 20 years. He still is strongly attached to the guitar and would like to be able to play it again.

I offered to try and get it playable with the least amount of rework I can do. That is keeping as much of the original guitar, finish, age as possible but still have it be structurally sound.

Amazingly it is not in "that" bad of shape. The major crack on the top is repairable. THere is a small section of the x-brace that lifted cleanly over the crack. The tone bar has completely popped off. Just a thin shim of brace remains. With the large access port the repair to the top should not be difficult to do well.

I want to do a visible repair of the missing and cracked parts of the treble side. That is I would like to replace just missing wood with new wood. I still looking for any good idea to repair the wood but my Idea is to have a thin piece of bent mahogany (1 mm) backing the cracked but existing side. Then replace the missing side piece with a patched that is shaped to match the crack pattern. The patch would end up glued to the end bock, new kerfling and the backing patch under the remaining side and the top.

I will do all of the work with hot hide glue.

Here is where I am starting:

February 8th 2017

Thanks all, this is a O-15 not an 18 like I said above. I have the guitar on the bench so it looks like I might need to do a neck reset. I will do some research but I assume the 0-15 has a dovetail joint and I can find a gap a couple of frets below the body join.

The inside is really clean

I was able to get the top aligned. I glued the smallest crack working some hot hide glue in and then clamping. Luckily the the rims are pulling the top together so the joint is tight with no clamps. I am using a clamp on the top to align the two sides of the crack. Easy to get the clamps in!

March 1st 2017

Bit by bit I am making progress. I closed the cracks on the top and back and installed cleats to keep them closed. When looking at the pictures keep in mind that I want to maintain the history of the smashed guitar. I hope to cleanly install the veneer, but the old and the new wood will be obvious, maybe even outlined with black fiber purfling.

I made an insert that included a tongue to reinforced the intact but cracked area in the sides and kerfed linings to replace the missing linings and assure a good glue joint to the top and back. I was going to use a 1 mm cross grain strip, but could not find one long enough. Instead I thinned an orphaned side to 1 mm, bent it to shape, installed the kerfed linings than fitted and glued it into the guitar. It is recessed in about 1.5-2.0 mm to allow me to inlay a mahogany veneer.

A couple of orphaned sides to work with. I pick these up in the sale bins on the various tonewood sites. Often they sell a batch of unlabeled sides cheap

I made a cardboard template for the insert.

I bent the insert to the correct shape. It took a bit to get it to fit in the guitar. Once fitted I installed the linings and so reinforcement strips.

Instead of gluing all at once. I used hot hide glue to glue the tongue inside the cracked area. I made special shaped cauls attached to a spreader clamp to some what gently provide an internal backing. (sorry no pictures). I installed a few small cleats on the top and back to help me set the depth on the insert.

With all of the in place I was able to use hot hide glue to glue the insert onto place.

The small gap is where the back brace comes in. The kerfing was inset to the accommodate the brace.

The neck step is to make the veneer. I traced the shape onto some paper. I bend the side veneer to the correct shape. THen I had a nutty idea to put the template on the inside as it would be easier to cut out the shape. I say nutty because I did not flip the template so cut out a mirror image of what I wanted.

I took the veneer back to the bender and reversed the bend. I will redo the veneer though as it is not as smooth of a bend as I want. That is why I stopped tonight.