Yesterday Rick Turner was the guest speaker at our guitar club meeting. He brought several instruments and spent the evening answering questions from instrument making to sound amplification to the business of guitarmaking.

One of the things that Rick talked about that really made sense was stiffening the fretboard with a couple of 1/8" x 1/8" graphite "rods".

This comes from a Kenny Hill observation that the first line drawn in basic guitar design is that of the string(s). All other lines are drawn 'down' from that. Next would be the top of the frets - the relationship between the bottom of the strings and the top of the frets being crucial. According to Rick's thinking, stabilizing, i.e. reinforcing, the fretboard would be more effective than reinforcing the next level down, the neck.

Interestingly, there was an upright bass maker at the meeting, who said that fingerboard (no frets on an upright bass) reinforcement was used to good effect in upright bass making! (Some pretty serious fingerboards there!) In the case of 21st century ebony fingerboards over Chinese maple necks; the maple moves, but the reinforced ebony doesn't. 

Rick used 2 graphite 'rods' on the guitar that he sent to Antarctia (minus 60 degrees and single digit humidity). It was a guitar with an adjustable neck with the fretboard floating above the upper bout. Apparently it worked like a champ.

Hard to argue with empirical evidence.

Another place Rick uses graphite is on top of the back reinforcing centerstrip. It stiffens the back, and, he reasons, improves the reflective properties of the box, which is good for projection. This is in contrast to the 'flexible back' school of thought, where the back moves in concert with the to to amplify the sound. His point being (and that of Ervin Somogyi at last summer's GAL convention Listening Test seminar) that when most people play steel string guitars, they hold the guitar against their body, thereby dampening away the harmonic amplification effect. The eye-opener for me was that if the customer wants a guitar that projects, we build it with a stiff back; if he/she wants a sound that envelops the player, we can do different things, like add a soundport.

It was a very interesting evening.

Larry

The guitarmaking club is the String Instrument Makers of Southern California (simscal.com) We're in Orange County (CA) and the Los Angeles South Bay - Torrance, Redondo Beach, etc.

We have about 25 members of mostly amateur steel string and classic guitarmakers. Many of us are graduates of the Orange Coast College (OCC) guitarmaking program. This year, we will have a couple members showing at Healdsberg. – Jim Ellsberry and Monica Esparza. Last year, Jim, one of our officers showed his arch tops at the Newport Guitar Festival; two members - Monica and Chris - attended Jose Romanillos’ guitarmaking seminar in Sequenza, Spain; and several other members attended the Guild of American Luthiers convention in Tacoma. Some of the membership are really into guitarmaking.

We also teach guitarmaking, both steel string (Bob Mattingly method) and classic (Jose Romanillos method) guitarmaking with about a half-dozen students in each group. The steel string class is taught by Eric Nichols, who taught guitarmaking at OCC for 10 years. Monica, who, in addition to being an OCC guitarmaking graduate, has taken Jose Ramanillos’ guitarmaking seminar for the past 3 summers, teaches the classic guitarmaking group.

In addition to this, we have quarterly meetings, which have included some excellent “hands-on” demonstrations”, such as, a French polishing demo in 2005, featuring Ron Fernandez, where everyone in attendance French polished a piece of spruce or cedar. In 2006, we had an inlay demonstration, featuring Jimmi Wengert (Kathy’s daughter) and R. C. Allen, and also a hands-on intermediate rosette-making demo, where attendees routed the rosette channel and glued-up a few rosette-sticks into a simple pattern. Et cetera. Equally important, these meetings are social get-togethers, an opportunity to “show-and-tell” our latest projects, share our latest “discoveries”, and generally hang out with other guitarmakers.

Mike,

'Rods' was a poor choice of words for lengths of graphite reinforcement stock that are 1/8" x 1/8" square.

Rick used 2 and they were laminated into 1/8" x 1/8" channels cut in the fretboard. That puts them about half the thickness of the fretboard, with the top of the channel pretty near the bottom the the fret slot.

Don said, Certainly 1/8"x3/8" CF rods in the neck are going to provide more stiffness than the 1/8"sq CF rods in the fretboard wood. Once it's all glued together, they work together, not as seperates.

One reason that putting a stiffener in the fb is more effecient is that the vast majority of the stiffness of a beam comes from the outer surfaces, in this case, the fingerboard and the back of the neck.  I'm not an engineer and don't know the math but the area where most people put those 1/8" x 3/8" bars in the neck is pretty much right on the "nuetral axis" of the neck, an area that contibutes relatively less to the stiffness of the neck.  In fact, I've been wanting to test the idea of cutting slots in that location and leaving them open as a way to reduce weight.  My guess is that the neck would lose very little stiffness in the process.

The fb is stressed in compression and the back of the neck is in tension.  The bulk of those forces are felt at the outer surfaces and decrease essentially to zero where the forces switch from compression to tension.  In a symetrical beam, that would be the mid point.  In a neck, the shape of the neck and the extra stiffness of the fb mean that the nuetral axis would move toward the back of the fingerboard.

From a structural standpoint, I'm curious why a super stiff neck is needed when you have a truss rod.

From a sound standpoint, I'm really curious.  When I put carbon reinforcement in my necks, it seemed to add power and maybe sustain but at the expense of warmth and color.  I've never swapped out necks on the same body to really verify the effect though.  It was just just an educated guess.

I'm convinced that mass and stiffness of the neck have an effect on sound but there are so many variables that I can't imagine the effects are universal.  For instance, it may be that relationships between the box frequency and the neck frequency are the main thing.  Stiffness would be related to that but that doesn't mean that stiffening a neck would have the same effect on tone for all guitars.  As Don said, things work as a system and I think it's often misleading to generalize too much about the parts.