The soundboard is perhaps the most critical component in the overall tone of the guitar. Material (spruce/cedar), rigidity, thickness, and bracing all play a major role in the intensity, brightness and overall flavor/sweetness that the guitar will have. I am using cedar on my first guitar, since it is a slightly sweeter and darker tone. It is also a bit softer than spruce, which requires a higher level of attention to keep it from getting marred while working on it.
The first step in constructing the soundboard is joining the two mirrored plates to recieve each other perfectly. Then the plates are glued together with minimal amount of pressure. At this point, the plate is planed down to thickness. I attempted to achieve a final thickness of 0.11'', with a hair less towards the outer edges. It will take a long time to discover what effects thickness plays on the sound. It helps to tap the wood and listen to it while it is being planed down. There is a definite change in pitch and timbre as the plate becomes thinner, and a threshold where the resonance is destroyed when it becomes too thin. I didn't push it that far though...
After the soundboard is planed to thickness, the rossette is inlaid around the soundhole. This is documented in rossette.
Once the rossette is inlaid and the soundhole is cut out, the soundboard is ready to be braced. The soundboard needs to be braced so it could withstand the hunderds of pounds of tension exerted by the strings. The trick is too brace it in such a manner that will provide rigidity against the tension, but will also allow flexibility for vibration and resonance. This is probably the most subjective component in the guitar, where each luthier refines their own structure and form. Unfortunately, this is not in plain sight when one looks at a guitar. It is possible however, to go thru the soundhole with a dentist mirror and look at the bracings of a finished guitar.
I am bracing this guitar with a traditional Torres fan formation. The bracings are structured in such a way to withstand the tension along the axis of the strings, while allowing it to vibrate and resonate as much as possible. Even in this traditional formation, there are countless parameters that can be manipulated. I went on blind intuition, and will soon enough find out how I faired.
I spent a few days building these cam clamps, and saved a fortune. They are essential for instrument building, since they provide a very sensitive feel to the gentle pressure that they exert. I built about 10, but will probably build another batch of them since they are so essential in this process. The more clamps there are, the more things can be glued in parallel...
All the bracings in the fan are carved to an elliptical contour, and feathered at the ends (shaved down flush to the soundboard). Different heights are prescribed for each brace, with the highest being in the center and then a gradual degradation to the outer fans.
This is the lower tranverse brace, which is slightly convex. It gives the soundboard a very small arch (about 1/16 inch at the belly) which improves the structural integrity of the soundboard. Just imagine bending a piece of paper when it is flat, and when it is slightly rolled (perpendicular to the direction the bend). The paper is much stiffer when it is slightly rolled.
The finished soundboard with bracing.