Four Part Harmony

Looking back, the last time I put anything up about the guitar project was back at the end of October! I have been working on it some since then, although the major progress has just come in the past couple of weeks or so.

Since building the side bender, I had to spend a bunch of time getting the sides, back and top down to the appropriate thicknesses. The sides had to get to ~.085 inch, the back to ~0.090 inch, and the top to ~0.100 inch. It’s amazing the amount of difference that actually exists between those measurements, especially with the different species of woods. I ended up doing most of the thicknessing with a random orbital hand sander…not necessarily the best way in terms of keeping everything uniform, but I think it worked OK. I used scrapers quite a bit too, for smoothing things out. I actually thicknessed the sides almost exclusively with the scraper (lots of work!).

I checked my progress along the way with this little thickness caliper that I made.

I’ve been too nervous to actually bend the sides yet, so I distracted myself by moving onto the bracing on the back. I got to use the go-bar deck a few times, and everything seemed to work pretty well.

The first step was to glue a narrow reinforcing strip along the center seam of the back.

Next, I cut the brace blanks from a billet of spruce. The brace billets that I have are nice quartersawn stock. I used the bandsaw to cut them roughly to the proper dimensions, then planed and sanded them to true up the edges. The back of the guitar isn’t flat, but actually has a slight spherical radius to it. I use a radius sanding dish to get the braces to match that contour, and then clamp everything up in the dish.

I glued up the braces 2 at a time. This photo shows the back two braces already glued on, and the front two being clamped up. When I did the back two, the glue squeezed out everywhere, and I ended up with a big mess to deal with the next day. I did better with the front two.

Once the braces were all glued in and cleaned up, I set to work with a chisel and plane to carve them down to their final dimensions. This was the fun part. It took some getting used to, as I’m still very new to the idea of woodcarving. But by the end I felt I had a feel for it, and I think the final shaping turned out pretty well. I may have to take them down a bit before I finish everything up, as I tried to err on the side of caution, so I think I left them a bit thick. In general, the lighter you can keep things like bracing, the better the acoustic properties of the instrument will be. The challenge is in balancing that lightness with stability. I read somewhere that the theoretical ideal instrument should be just on the verge of imploding upon itself.

Another shot of the back bracing. After getting everything finished up, I cut the outline of the guitar out (leaving about 0.5 inch all around at this point).

And here’s the “finished” back, all cut out and actually looking kind of like a guitar! When I get a chance, I’ll start on the bracing for the top, which will be significantly more complicated.

Oh, and here’s a picture of Anna hanging out with me in the workshop. She asks to come down at least once a day. She likes to sit on the workbench, play with the measuring tape, and collect wood shavings mostly. Papa’s little helper!