Probably the most important fixture in the guitar building process is the Solera. This jig is used to establish the arch in the guitar’s top as well as the necessary angle of the neck in relation to the top. Basically it’s a guitar-shaped board with sections carved away to facilitate various shaping and assembly processes. A shaped clamping caul more or less.
I’ve read about these fixtures being made of mdf and solid wood but I chose 3/4 fir plywood. A previous attempt on birch ply ended badly as I discovered large voids just under the surface. While not as fine grained, the fir ply has much thicker veneers so I shouldn’t have any problems when removing material in the area of the lower bout.
Sorry about the poor resolution, I forgot my camera and had to use my phone. Here’s a pic of everything I needed: templates, scraper, flexible sanding block and radius plane. I also used an orbital sander in the final stages.
First I cut out the solera on my bandsaw. The shape of a guitar’s body is called the plantilla and can vary quite a bit from maker to maker. I’ll be using a plantilla taken from the guitars of Manuel Reyes. Roughly four inches of material is left outside the line traced around my body template. Add-ons for assembling the body are attached to this border to hold the sides during assembly of the sound box. The steel pin marks the center of the sound hole and will eventually be threaded for a caul which holds the top in place while gluing on braces and sides. I intend to mount a go-bar rig.
Next the area of the solera that will support the lower bout must be hollowed to accept the dome of the soundboard. According to the plans I purchased this doming should be roughly 2 mm. I’m not sure how much spring back to expect so I may go back later and take out more material when I am actually ready to start gluing in the braces.
Taking my time I planed and scraped a pear-shaped dish in the plywood. Frequent checks with a template ensured the recessed area was uniform and symmetrical across the area just in front of where the bridge will be. This point is also the deepest part of the arch and placing it in front of the bridge should help resist the tension placed on the top when the guitar is strung up.
Although the arch is slight, placing the straight edge of the template across the same area shows that it’s definitely not flat.
More pics soon as I refine the surfaces and get ready for the next step!