Bracing the Soundboard

Bracing the top of the guitar is the subject of great mystery and debate. Arguably, nothing affects the sound and tone of the guitar more than the bracing.
For this guitar I wanted the bracing to be light enough to allow for a clear note when plucked with a fingertip, but firm enough to maintain its sustain and volume. I chose to follow Martin's standard X-bracing guidelines, with subtle modifications to the placement of the lower face braces.

I used AutoCAD software to try a few different layouts and then printed the one I liked best, transferring the line work to the underside of the soundboard. This way I could better control the symmetry of the bracing, as well as the open / closed relationship of the X-bracing.

Below is a picture of the first bracing element I began with (according to the order in the book), the rosewood bridge plate (cut from a scrap from the back material). I sanded it down to .10" and sized it according to my final bridge design.

Next I cut and planed square all the brace blanks and glued down the upper face graft (top of picture) and the 4 smaller face braces (shown clamped).

Some people wait until all of the braces are in place to begin carving and shaping them, but I couldn't wait, so I adopted a "glue and carve as I go" sort of plan (carving braces is actually one of the most rewarding steps).

Here's a shot of the top sitting on the work board, showing all the little guys in place and carved. Notice I left the 2 sound hole braces taller than most, yet smaller than recommended by the book.
Here's a shot from upstairs down into my "workshop"....

According to the book, the next steps include dry fitting the X-brace (the most important one), gluing and shaping the remaining bracing and upper face brace (the one that bears the load of the fingerboard and soundboard torsion) and THEN gluing and shaping the X-brace. However, i chose to fit and glue the X-brace first, then attach the remaining braces. The X-braces are each carved first with a slight arch, so that when glued they impart a gentle arched dome to the soundboard. I felt that by installing this element first, I would then have established the arch of the top and could then make sure the other braces fit that curve, rather than compete with it.

(You can never have too many clamps, and get good ones).

LESSON LEARNED: Before carving the arches into both X-brace blanks, I mistakenly notched the lap joint first. Then I tried clamping one into a vice for carving, not thinking about the fact that I was bearing down on the end of the brace, and ultimately fractured it near the lap joint. I was able to wick superglue into the crack and clamp overnight, so it's fine now. In the future, I will arch first--fully supporting the length of the brace--then cut the lap joint.
Carving the X-Brace is a task that should be well thought out before beginning, as leaving too much wood will deaden the tone, but too little could result in an overly bassy guitar and/or a structural failure of the top due to the high tension of the strings (almost 200 lbs. worth).

LESSON LEARNED: Have a shape in mind, and stick too it. I began thinking I would "scallop" the X-brace a little (you can see my rough carving in the picture below). I introduced a slight scallop, then changed my mind and had to carefully feather my high points back into a gentle curve. I'm currently under the belief that scalloping creates dead zones at the peaks, and instead favor a more gentle parabola.

In the end I was very happy with my bracing. The top has a clean tap tone to it (but I really have no idea what I'm listening for...) and in general just looks freakin' cool. The 2 little diamonds toward the bottom are book-recommended seam patches to strenghen those regions. In the future I think I will omit them--I see no need for them there, so they probably only serve to deaden those spots a little...

Below are just some more pictures of my bracing (you can never look at too many bracing photos. Check out this link for pictures of factory bracing).

Close up of the X-brace lap joint and the "bump" wood patch. Most people use a glues soaked linen patch, but some (including Bourgeois) feel that the wood patch is stronger...