In the days when I was learning how to build, things were simpler. I was so privileged to learn building from the Guitar Research and Design Center (GRD) in Vermont. We learned a tried and true method of construction very similar to Spanish classical guitar building methods. I have built many guitars using the notes from this school experience. Every one of these guitars are very much alive and kicking today, which speaks to the incredible wisdom and practicality of the GRD method adapted and taught by Charles Fox. These guitars have a modified Martin scalloped “X” brace pattern, with an integral “Spanish heel/foot” neck design. Although many solid attributes accompany this way of doing things, there are some disadvantages. I will give a brief summary of what we have adopted for our new designs.
We have discovered that in time, say 20 years or so, A guitar will “settle” into a condition that causes many well made guitars to require a neck re-set. The top which has been braced in a flat geometry will in time “belly” or heave upwards behind the bridge. This in real terms, creates an arched effect on the top, which is very desirable by the way. As the top arches due to the string tension, torque of twist over the bridge, the neck also has a tendency to move upwards from the same pull of the strings. In time, to maintain a good playing string action, the saddle and bridge must be made thinner and thinner. Yamaha steel strings have this awesome sound for being as they were an economical buy back in the 70′s.
These guitars have shown up in repair shops everywhere with this very settling issue. Most of the time, the prescribed cure is to plane down the bridge. This allows for the action to be corrected for a period of time. At some point, the bridge becomes too thin to function properly. The saddle needs some depth to be stable, and the bridge pins also require some mass to hold the strings in tune. When you have a more valuable guitar like a Martin or Gibson showing these symptoms, a more invasive treatment is justifiable. A neck re-set requires that the neck must be carefully separated from the body. This is usually done using heat and steam to loosen the glue holding the heel and fingerboard tail in place. Once the neck is removed, a careful re-alignment must be measured and executed on the heel’s dovetail joint. The neck is then re-glued to the body, and the strings set up for a new lease on life.
The modern philosophies of guitar building have included what we call…. “pre-arching” the top. Not everyone agrees about this, but, not everyone agrees about anything any more do they? Anyway, we have decided to pre arch our tops at Moriah Guitarworks. The prevailing sense about this is that pre-arching introduces counteractive stress on the top, which resists the stress applied by string tension. This allows the top to assume the geometry in which a flat top would assume in time. As the arching creates stability by being forced into its new shape, it also allows for lighter construction to maintain playability. So, pre-arching, in design allows for less upward movement of the top, and tensile strength, which allows for less mass and lighter structural requirements. The lighter the construction, the more dynamic is the sonic response to string vibration. It’s what we call “mean and lean” at Moriah.
When you arch the top, (and Back) you are creating a geometric challenge in setting the neck in initial construction. Every guitar will come out different, as woods and humidity while building vary from one guitar to the next. Our tops work out to be around 30′ radius or so when the neck is finally ready to attach. The ideal is to have the fingerboard running over the top to be in line with the rest of the neck, while providing a good thickness for the bridge on the body. As you can see, there are so many issues created by this pre-arching dynamic. However, the end result is simply indescribable. When we finally put Scott’s together, it was apparent that this method of building is totally worth the trouble of figuring it out.