Four Part Harmony

Hello again gentle readers. I’m continuing to make progress on the guitar project. Here’s the big accomplishments for the past week.

Let’s see, I had the rosette all glued up, so I was able to go ahead and cut the soundhole out and start in on the bracing for the top. As I have a tendency to do, I’ve made some slight deviations to the plan set I’ve been working from. I had been reading some things about a bracing design that Martin used on their 1930′s and 1940′s dreadnought guitars. Martin created the concept of an X-brace, and used it to make guitars that were strong enough to withstand wire strings. Their early designs were very lightweight, tonally responsive, etc. etc. They are the stuff of legend.

As those guitars aged, however, some of them began to show signs of buckling and distortion of the top, issues with neck set, etc. Also, with the need for production came a need for sturdier, more reliable construction. So they shifted the positioning of the braces away from the soundhole bit, according to some at the expense of some acoustic and sonic characteristics. This became the standard for guitars in production settings, sacrificing tone for stability (or so it is said). Of course, they also had plenty of high quality red spruce and brazilian rosewood to make guitars with, which are in short supply these days…that might have had something to do with it.

All this is a long-winded way of saying, I decided to use the forward shifted X-bracing setup. I figure, I need all the help I can get in terms of the acoustic properties of the instrument. And if the thing suddenly explodes 5, 10, or 20 years from now, at least I’ll likely know how to fix it.

As with the back, I cut the brace stock from a stick of spruce. Rough cut on the band saw and then planed to width and height. I also sanded the bottoms of the braces in a radiused dish. The top will have a 28-foot radius. It’s very slight, but it does add a noticeable amount of strength. I had to do these braces over the course of several days. Here are the first few, rough cut.

And here they are being glued up. I chose to do these first, so I could carve them without the big X-brace in the way. Also, this way, I was able to tuck the carved ends of these braces into the X-brace.

In this picture, the big X-brace has already been glued in, and now the last few braces and the bridge plate are being glued in. You can see the first braces have roughly carved to shape.

And here is the top, as done as it’s going to get for now! Carving the braces took quite a while. Carving away material from the braces is actually one of the most significant things that affects the tone of the finished instrument. Books have been written on the subject. The general idea though, for someone like me who doesn’t really know what they are doing, is to frequently pick the top up and tap it and listen to the tone. As material is removed, the tone changes, and at some point, you hear a good sound and you’re done. Sounds easy! But it’s pretty subjective, especially when you have nothing to use as a frame of reference. Mine right now sounds kind of “tight”. Not really “ringing” much, but it does have some resonance. I may end up doing some more shaping of the braces, but for now I think I will leave them, and trust that I’ve done all that I need to.

With this step mostly done, I’ll probably focus my attention back on getting the sides ready. I also need to begin the neck carving process.