Day 2: Jigs and Go-bars

• How many luthiers does it take to change a light bulb?
  
• Just one, however, he has to build a jig first.
  

Building a guitar is an interesting balance of precision and feel. One of the advantages of working with Chuck is that he has the knowledge and equipment needed to ensure precision at crucial stages in the process. Feel is still required however. Wood has a character of its own and there are unique aspects of grain, shape and thickness which will contribute to the strength and tone of the guitar. Subtle adjustments are ultimately made based upon feel.

Today's work consisted of adding strength to the three main components in the sound box. The sides are strengthened by gluing kerfed strips of cedar along the top and bottom edges. The kerfs, or saw cuts which go most of the way through the lining, allow it to conform to the shape of the body. Thin vertical strips of mahogany are added to provide additional strength and rigidity. The result is a very light but strong perimeter for the soundbox.

The front and back of the guitar will be braced to add strength. A precise curvature is introduced at this stage; with a 25' radius in the case of the soundboard and a tighter 12' radius for the back. This is where the jigs and go-bars come into play. The strips of wood which will be used as braces and tone bars are shaped to conform to the appropriate radius. Chuck has build a few jigs and templates which when used with the table router, impart the desired curvature. The gluing is performed on a go-bar deck which consists of a piece of medium fiber board with a shallow dish-shaped recess which will hold the parts to the desired shape as they are glued.

Each of the rods in the go-bar deck exerts a force of approximately three pounds so in the photograph showing the rosewood bridge plate being glued into place, the twenty rods are exerting some 60 pounds of force on this small vital component. After passing through holes in the bridge, the strings are anchored to this bridge plate by the tapered bridge pins. Strength and good acoustic coupling are essential hence the use of a thin piece of dense rosewood.

By the end of the day the three main components of the sound box have been reinforced and the desired gentle curvature built in to enhance strength and sound projection. The next stage will involve carefully shaping the braces to remove as much weight as possible without compromising strength unduly. This process will require a delicate touch and feel.