Carbon Fiber Straight D tube?

[Stephen Cagle]

I'm gonna chime in here. I've played several mandolins over the years that had carbon fiber rods in them and one in particular that I see pop up on this site every now and again. I love the concept and I also love extremely lightweight mandolins (I remember having a conversation with Joe Booher and he stating that you really want a well built, lightweight mandolin) That really stuck with me and I believe he was playing a Dearstone at the time. Several years later I had a mandolin in my possession (no need for the name) and it had a CF rod in the neck. It needed some relief pretty badly. It almost was considered a bow in the neck. I had a bldr dig out the CF and install a regular TR so it could be adjusted. Messy work to say the least but digging one out of a neck is not an easy thing to do and the bldr had his work cut out for him for sure. This CF rod was sitting down in the neck fully covered in epoxy. Yeah pretty tough to say the least. It was done and worked out pretty well for the work that had to go in to it.

Now with all that said it sounds to me that if you know what your doing (and honestly a lot of what I'm hearing in this thread is going right over my head) that you can certainly use CF rods correctly and possibly would never have an issue. I wished I'd had a better experience with it.

[peter.coombe]

There are failure rates for everything, and from what I have seen from over 25 years of instrument making the failure rate of truss rods is higher than carbon fibre. From over 200 mandolins and mandolas, my failure rate is zero. Two had a bow that was corrected by a refret, so minor problem rate is 1%. One of those the owner had been using heavy strings and it needed a refret anyway. It has come back another 2 times for a refret and the neck has remained straight. It is now 23 years old. The other one is doing just fine as far as I know. So if a carbon fibre rod is big enough and installed correctly the failure rate is very low.

This comes up again and again, and always someone comes up with an example of a carbon rod failure. Usually the reason it failed is the rod is not big enough. There are plenty of truss rod failures, but for some reason we never hear about that.

[Marty Jacobson]

Another way necks can fail is due to the individual grain or stresses in the neck wood. A metal truss rod does very little to help stabilize the neck wood, and in fact increases some local stresses. While a carbon fiber stiffener stabilizes and supports the neck wood and does not add any localized stresses. Big difference, potentially, especially if using wood with lots of runout (i.e. Curly maple).

I also extend the CF rod or rods way up into the headstock until they feather out to nothing due to the angle of the headstock, potentially aiding in reduced headstock damage in the event of impact.

[amowry]

To add to what Marty and Peter said, a lot of the neck issues I see occur at either end of the neck, where the trussrod slot weakens the neck and the trussrod does nothing to strengthen it or provide adjustability. In addition to headstock breaks, I sometimes see an issue at the other end of the neck where an instrument has been over-humidified and the end grain of the heel has absorbed moisture, forcing the entire neck backward. Trussrods have no effect in that area and the slot probably weakens the neck there. Carbon fiber strengthens it because it can run all the way to the end of the neck, or even into the fretboard extender.

[j. condino]

"There are plenty of truss rod failures, but for some reason we never hear about that." +1000


When someone like Andrew or Marty or Peter, who have a combined century of building world class instruments easily in any configuration you can imagine, say they'd rather have carbon fiber in the neck than a traditional adjustable steel truss rod, it amazes me that folks around here still want to argue with them....