If you have been around the acoustic guitar community for very long you have no doubt heard of scalloped bracing. Brace scalloping is usually a topic of lively discussion between luthiers. Some swear by it and some swear at it. Personally I fee that it lends itself to producing a fine-sounding instrument.
Brace Scalloping – How Did It Start?: The art of scalloping braces is thought to have started with the pre-war Martin Dreadnought guitars – that is the guitars they built from the 1930’s through the early 1940’s. If involved only the 2 tone braces that run angular from the main X-brace to the edge of the guitar. The scalloping was a slight depression or carved area that gave the brace a look kind of like a suspension bridge, although not nearly that severe.
It’s not really known why C.F. Martin suspended the scalloped bracing process in 1944, but there is speculation that there was lack of manpower due to the war. Another possibility is that they wanted to make their guitar-making operations more efficient to raise profit. Finally it is thought that there may have been speculation that the art of scalloping weakened the guitar and increased the possibility of customer complaints, repairs or bad PR.
Be aware that when you do this you need to have knowledge of top stiffness and bracing integrity. What this usually means is that the bracing needs to be slightly larger in width, height or both to make up for the loss of strength.
What Does Brace Scalloping Do?: This is a question that is up for much discussion amongst luthiers. Since the greatest control that we have over the tone and volume in our guitars directly relates to how much the top plate will vibrate, then brace scalloping can have a profound effect on sound. After all, one of the features that separates a pre-war Martin from a post war Martin is the brace scalloping. It is thought that scalloping the top braces will place more emphasis on the bass response of the guitar. The only way to measure this would be to build 2 identical guitars, with wood from the same trees, buy the same luthier and in exactly the same way. That would be an interesting experiment!
How Do I Scallop My Braces?: As in all guitar bracing, most luthiers will rough-cut the braces to shape and then glue them in place. The final shaping, scalloping, rounding and smoothing takes place after they are glued.
What Are The Pros and Cons of Brace Scalloping?: Brace scalloping can definitely reduce the structural integrity of your top plate. After all the braces not only serve to shape the tone of the guitar, they also provide the needed structure to resist string pressure. So there is a balance that has to be struck between tone and structure. Of course one of the rewards of brace scalloping is enhanced top production of the guitar.