Top Crack Repair and Brace Scalloping and Reglue on the Martin Guitar

I have a lot of details to attend to on this Martin restoration.  Had a meeting at work yesterday and during the meeting, made a list of all the stuff to do.

First up is this boo-boo that happened while removing the bridge pad.  There are actually two cracks, and this is the smallest.

Fortunately it's a reasonably tight break and it's fresh, so no dirt has found its way into it.  It's a little ironic that a lot of acoustic guitar players freak at the sight of a crack, but generally they're easy to repair.

I'm using Titebond on the two cracks.  I'd like to try hide glue on this sort of repair, but I'm not confident enough that I'd have time to align the crack properly, so Titebond it is.

You know the drill - spread the glue on, gently open the crack to get glue in the seam, wipe off the excess, and clamp, tape or otherwise align the crack so it's level while the glue dries.

These cracks fell in the latter category.  I supported the top from underneath with a brace bracket, but I needed a bit of weight on the top.  So I just used these hammers and they worked well.  Maybe not the most elegant way to do this, but it was efficient.

I should point out that the hammer on the right - an 'Engineer's hammer,' was just back from a demolition project at Toy Making Dad's house.  

From demolition to a delicate guitar top - this hammer does it all!

I wonder about the term 'Engineer's hammer.'  Does that mean it's a hammer an engineer uses when the stuff he or she designed just doesn't quite fit?

Another victim of the bridge plate removal is the uppermost of the two tone bars that run across the guitar just below the bridge.  You can see it here just hanging on.  I was actually going to just reglue it, but it fell off.

And this was a good thing, because I was thinking about scalloping it a bit anyway.

There is a lot of debate in the acoustic guitar world about scalloped braces.  In short, scalloping is the process of removing some material from a brace to give it a different shape, thus removing some of its mass.  Depending on the location of the brace, it can affect the tone of the guitar - generally it will deepen or 'loosen' the bass.

This is the brace off the guitar.  You can see where it got whapped with a removal tool during the plate removal.

This is a typical unscalloped Martin brace.  A lot of pre-war Martins had scalloped braces, as do their current vintage series guitars.  But Martin stopped scalloping braces post-war.  Since the pre-war guitars have a stellar reputation for tone, some builders and repair people (and hacks in their basements...) try scalloping.

In my case, I figure what the heck.  It's only one brace, and I wanted to clean up the whap mark anyway.  And I did find that tapping the top with the brace off entirely as well as with it in place gave a different tonality - definitely more bassy.

This is also an excuse to try out my new chisels.  These are German-made, and holy smokes, are they amazing.  I used a Japanese water stone to sharpen them and they cut wonderfully.

I chiseled a bit of material off, and then used 150 grit paper to do the final shaping.

The two deep 'scoops' are what I scalloped out.

The brace is made of spruce and it was light to begin with.  My guess is it will make a small difference in tone, hopefully for the better.  After all, this is a TONE bar.

Here we're almost ready to glue it back in.  I did a lot of test runs to make sure I'd get it lined up exactly from whence it came.  And, in a daring move, I'm going to use hide glue for this.

While the glue is heating, I used a heat gun to get the area warmed up as well.  Note the blue tape - it marks the location for the bar from the top.

I was thankful for the hole in the top too - I was able to look through the hole into a mirror inside the body and line up the brace that way as well.

After the glue is on, the brace positioned, I put an adjustable brace support between the brace and the body.

This is the view via the soundhole into the mirror.  The support fit against the brace tightly, and I also put the hammers to the top (now that's a mental image...) to help keep the brace snug until the glue dried.



The Complete Martin Guitar Restoration Saga
Restoration begins
Repairing heel break
DIY chisel for bridge plate removal
DIY bridge plate removal iron, Pt.1
DIY bridge plate removal iron, Pt.2
Steam removal of bridge plate
Bridge plate removed
Tongue brace removal
Crack repair and brace scallop (This page)
New bridge plate Pt. 1
New bridge plate Pt. 2
Patching hole in top
Final fitting of top patch
Installing carbon fiber rod
Fret removal
Fingerboard crack repair, Pt. 1
Fingerboard crack repair, Pt. 2
DIY fret bender tool
Refretting Pt. 1
Refretting Pt. 2
Tuner shaft repair
Neck reset - dovetail fitting
Measuring neck set with DIY jig
Gluing the neck with hide glue
Tortoloid Pickguard
Fitting bridge pins
Brace reglue
Making bone saddle
Making a buffalo horn nut
Restoration completed