Tuesday, April 6, 2010

Octave Mandolin Build, Part 1

The Soundboard
Since we have discussed some of the jigs, patterns and tools, now is as good a time as any to describe the building of the Octave Mandolin.

To begin, I started with the soundboard. After cutting out its general shape, I sanded the top with 80 and 120 grit sandpaper. Then I remarked the centerline on the soundboard top and traced around the pattern that I made for the sound hole, being sure to line it up properly. After everything was marked up and looking decent, I drilled four starter holes using a ¼” Forstner bit inside the lines drawn for the sound hole. I then clamped the piece to my drill press table, inserted the coping saw blade, and cut it out the sound hole . . . being sure to stay at least and 1/8” of an inch inside the line. When complete, I placed a sanding drum in the drill press and sanded the sound hole to the line. Next time I will clamp a board to the table with a pre-cut hole a bit larger than the sound hole that I want to cut out. It will offer better support when coping. The pictures below record the order of the process:

The picture below shows the pattern placed back in the cut out, simply to double check the shape. It looks good enough for now, as there will be lots of sanding later.

After the sound hole was cut and sanded, I laid out the brace patterns and glued them on:

In the picture immediately above you can see glue above the left side of the sound hole. When I was coping it out the soundboard cracked ever so slightly. I about freaked out, but once I regained my composure I realized that it was very fixable. I simply applied medium viscosity CA (aka, 'super glue') to the crack on both sides of the soundboard, and then let it dry for a bit. However, initially I wasn't sure it would hold, so I decided to modify the bracing pattern. Kawalek's kit calls for three braces - the two that make up the 'x-brace' (which are radiused to approximately 12 degrees), and the short brace above the sound hole. But, following the mock-up canted top layout, I added two additional small braces (1/4" x 1/4") along each side of the sound hole for added support. Here you can see the radius of the x-braces:

Next, following the center line marked on the inside of the top, I marked a center line on the upper brace so I knew where to 'crown' it. I also measure in from the outside of the x-braces two inches so that the scalloped ends would all be the same. I then took the chisel and 60 grit sandpaper to 'em.

I recently read that some guitar makers will shellac the back braces for aesthetic purposes (e.g., John S. Bogdanovich's, 'Classical Guitar Making: A Modern Approah to Traditional Design'), so I decided that I wanted to do the same on this octave mando. But instead of screwing up the back (which can be easily seen through the sound hole) with a faulty shellac job, I decided to first try it on the soundboard braces (which can't be seen as easily). I taped around the braces using blue painter's tape and added a coat of shellac to them. It was a piece of cake. I just took my time and it all came off without a hitch.

The soundboard is almost completed. The next step will be adding a piece of binding on the inside of the sound hole . . . but that will have to wait for another day.

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