carbon fiber neck reinforcement

[Dan of SC]

Any of you guys ever use carbon fiber to reinforce a neck? I see LMI sells sticks of it in various sizes, and I've seen I've seen necks with channels routed for it on either side of the truss rod. Seems like it would have to be very tightly fitted, maybe even glued in to do any good. I'm starting a second guitar using wood from a huge door made of Honduran mahogany in the 1980's. The first one has a little too much relief in the neck and I've tightened the truss rod as tight as I dare. I'm thinking maybe because it's not quartersawn, and the carbon fiber might help but I have no idea how to use it. Any help? Thanks, Danny Gray

[redir]

Quarter sawn necks are ideal for stability but it's not necessarily stiffer than a flat one. The issue of carbon fiber in the neck is a very complicated one. You definitely want to glue them in. This is the way I understand it and some one can correct me if I am wrong:

The idea is best thought of as the concept of an I-Beam. If you have an I-Beam as a column with a statue on it then anyone of the fibers in that beam are under equal compression load. Now take that same beam and try to bend it with the caps on top and bottom. What you have now is one cap on the top in compression and the bottom cap under tension. The in between is a web that is in shear.

At rest a guitar neck is just a beam or a staff. There is what is called a neutral axis and at rest that would be dead center in say a perfect square stock beam. The U-Shape of a guitar neck places the axis closer to the top fretboard side. When you add string tension the neutral axis will move closer to the top. This axis is the transition between compression on top to tension toward the bottom within that shear zone.

So the problem with adding a carbon fiber rod into a neck is that you are adding it to this area known as the neutral axis where essentially nothing is done. You want to add it as far away from this axis as possible IOW the cap of the I-Beam. That would mean either routing a channel out under the fretboard or very deeply into the neck.

So just dropping a CF rod into the neck like you would an adjustable one probably doesn't give us the advantage that we think. I'm sure you will have a little stiffness above the neutral axis but probably not enough to really make it worth it.

I still use a CF rod in my classical guitars just because

[michaelht1]

Finished a guitar in April and used carbon fiber flats on either side of the truss rod, yes they are glued into the cut grooves with Titebond wood glue.