The Solera

With tools en route it was time to work up a solera. A solera is a guitar-shaped work board upon which the vast majority of construction takes place. The word is Spanish in origin, literally translating in English to something like crossbeam or stone base. Using a solera, as opposed to a more modern technique employing a solid form, is a bit more challenging. With this approach the burgeoning instrument is not held fixed within the confines of a mold. Instead, the bits of the guitar are assembled free-form, thus requiring more precision on the part of the luthier.

In spite of the added difficulty, a clear benefit of the solera is that it affords a more acute awareness of the quality of the construction at any stage. A mis-bent set of sides, for example, will be quite obvious as it will not sit nicely within the template lines drafted to the solera surface. Conversely, a set of sides clamped within a rigid mold may betray no such signs of an ill fit. Instead, errors are masked and will remain invisible, living within the final instrument as trapped stress that ultimately manifest as cracks, dimples, and tonal limitations.

I built my solera more or less according to the specs in Cumpiano with a couple of modifications. First, I substituted a sheet of ½” MDF for one of the three sheets of ½” ply to be glued together. Second, I chose to hand carve the domed contour of the guitar into the solera itself rather than utilizing a cork shim. Most of you are probably not aware of the fact that luthiers intentionally dome the tops and backs of their instruments. The reason for this is that a domed plate is structurally more resilient than a flat one, which, among other things, allows the luthier to build lighter, more responsive instruments without compromising on strength. Use of a shim (a narrow spacer placed around the periphery of the plate during gluing) or a dished out solera are simply two ways of achieving this domed profile. However, only with the latter method is the plate supported over its entire surface during gluing. Because of this, there is added stability during assembly. What is more, there is no danger of imparting a plateau to the finished plate, an effect that is possible using a shim.

Below is the basic process from start to finish:

Gluing up the ply and MDF sandwich, using bricks from my garage as clamping weights.  Cinder blocks would work just as well.  Note: don’t forget the wax paper. There is quite a bit of squeeze-out during this procedure. Used white PVA glue here.

Template from the Cumpiano book; based on an Antonio Torres design. Torres is the father of the modern classical guitar. Many of the design features of today's guitars are a direct result of Torres' work in the late 1800s.

After working up a sturdy template in Masonite (upper left), the pattern is then transferred to the would-be solera prior to being cut out with a coping saw.

With the rough shape cut out, we further approach the template lines with coarse rasps and files.

The finished solera ready for detailed markup and “dishing”.

Scale plans of the final instrument are drafted on a large sheet of butcher paper. Measurements are often pulled from this sheet so I keep it hung up on the wall near the bench.

After transfer of the complete pattern to the solera, the lower bout is carved to a 25’ radius using a small convex-soled hand plane.  The dish is deepest (1/8") at the bridge and gradually returns to the top surface depth at the template outline and to a line tangent to the top of the sound hole.

The finished solera is shown here with a straightedge to highlight the contour of the dished solera. In retrospect it may have been easier to carve the ply-side of the solera as the plywood, being a polylaminate, has built in depth indication (i.e. the tiny laminated sheets of the ply help you to carve uniformly by eye). In the future, I may carve the other side to the 15' radius needed for gluing up the back.

Some additional modifications were made to the solera a bit later on. Firstly, two 1/2" bolt holes were drilled in the neck segment to allow for direct bolting of the solera to the workbench.  This is necessary for some of the later stages of construction. Secondly, a small hole was also drilled at the center of the sound hole for the clamping shoe, which will be needed to secure the soundboard during the side gluing procedure.

Looking back…
No doubt, building the solera was an important first milestone. Though, knowing this I can’t help shaking my head at the amount of effort poured into something so simple. But I cut myself some slack here. It was the first step of many and I was going to be damned if it wasn’t done right. I was building a house and this solera was the foundation upon which everything (figuratively and literally) would be built. There was no way I could have managed to begin the guitar without a proper solera.

This perfectionist compulsion is something that will surface again and again… and again, so take heed. I see it nowadays for what it is: an inextricable property of me with roots that run too deep to pull up. It is something I recognize as being an alternating source of strength and woe; a trait that is at once an asset and a handicap — more often, thankfully, the former — which is derived from the rather effective pairing of a fierce stubbornness and an indomitable fear of failure.