Day 7: Creating the soundboard bracing

Creating bracing for the soundboard:

Today was all about creating the bracing for the soundboard. This is a detailed process, and there’s a set formula/layout to follow. Altering this formula will have a profound effect on the distribution of the sound across the soundboard, thus altering the sound/tone. It would be a good experiment to make different bracing on other guitars made from for the same shape/material and see how the sound differs, but for my first attempt at an acoustic guitar, I’ll stick to what physicists believe best.

Today I got through the X braces, and the Lower Arms.

There’s a lot of fiddling involved.

Firstly, cut and the braces to size, width, height, then sand them to the correct thickness.

There is also a trick to sanding the bracing. Later down the track the soundboard will be attached to the sides of the guitar, and to create a good sound chamber, there should be a slight curve in the soundboard. The bracing needs to help structure this curve. To do that I needed to sand a slight curve in the bracing. I placed a piece of sand paper, sandy side up on the template of a soundboard, then I sanded each brace by running the brace along the sand paper in the direction that it will be located on the soundboard.

The X braces were a little more involved because you have to chip out a section in their centres so they can cross over each other and lock into place.

I ruled up the positions to glue the bracing onto the soundboard.

When gluing the braces to the soundboard, you need to place the soundboard into the soundboard template. The template has a slight radius/curve on it, whereas the soundboard is flat at this stage. As you glue and clamp the slightly-curved bracing to the soundboard, slowly it pulls the soundboard into a slight curved shape.

The gluing process stresses me out (more so than using a BAND SAW!), as it doesn’t take long for the glue to set, and once it’s glued, it’s glued. It was awkward trying to clamp the bracing onto my guidelines on the soundboard; one end would shift while you fastened the other, all the while I was running out of time as the glue set. Tick… tick….. tick…….

Once the glue has set I measured and marked out peaks and troughs onto the individual braces.

The bulk of the shape is chiseled, and planed off. It’s bizarre when you cut little slits into the wood with a Japanese hand saw, then bash the pieces out with a chisel and hammer. It feels like I’m abusing the poor guitar. But it has to be done, being careful not to ruin the soundboard.

Once I got the main shape of the bracing, I then sanded it smooth, using a piece of sand paper over a bottle to get the rounded shape in the bracing. There are some tight spaces in there….

I then planed off the edges to create peaks on the bracing.

This is followed by a final sand.

This will be sanded down furthermore, when the guitar body is built, as I will be required to “tune” the soundboard by removing weight from the bracing later. But for now, the bracing is done.




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