There's nothing left to do tonight but go crazy on you
Back in the 1970's a lot of guitarists went crazy over the Ovation bowl-back guitars. Using a Lyrachord body, Charles H. Kaman, an aeronautical engineer known for his pioneering work in helicopter and aerospace design, revolutionized the guitar building industry. Product endorsements ensued, and through many years of experimentation, Ovation still stands out as a pioneer in using alternative materials to produce beautiful and quality stringed instruments. This Jay Turser of mine is an obvious copycat, using some lower-quality parts, but it is just as capable of being a very playable instrument and producing some very tasty sounds.
To stabilize the neck joint, I put in a set of machine bolts with brass inserts. First up was enlarging the existing screw holes to accept the new brass inserts.
The inserts went in with ease, and I moved on to the visible part of this addition at the bowl side of her body. Due to the length of the machine bolts and grommets I chose, it was necessary to partially countersink the grommets through the Lyrachord body and into the neck block
With the new body grommets and brass neck inserts in place, I restrung This Old Guitar again to confirm that the neck centerline was still true, and it was fine. However, the clamping force of the four machine bolts was much more than with the four wood screws, and I quickly realized it was necessary to shim up the joint, one more time. After gluing up a partial length oak shim, I started the process of filing, chiseling and sanding it down to a good fit.
After restringing and tuning, I checked her action and was pleased to finally be close enough to finish her action adjustment with some minor reshaping of her bridge saddle to get to 0.08 inch 12-th fret action at her high and low E strings.
As expected, the new neck set angle and saddle height adjustment took care of the playability and intonation issues. However, there is one remaining structural issue.
The new neck set angle produced a slight amount of separation between the body and fretboard. This separation, combined with her nice, low action, is just enough to produce some upper fret buzzing when being played near the body. As I want to keep her neck removable by simply pulling four bolts, gluing the fingerboard to the body is not an option. In order to fix this, I'll be inducing some back bow into the upper end of her fretboard by means of some carbon fiber strips, the next time I get to work on This Old Guitar.