Effectiveness of CF stiffening rods?

Ask your wood and other materials questions here. Please DO NOT post pictures and ask us to identify your wood, we have found that accurate ID is nearly impossible, and such discussions will be deleted. Thanks.
Post Reply
Brian Evans
Posts: 873
Joined: Sat Aug 30, 2014 8:26 am
Location: Tatamagouche, Nova Scotia

Effectiveness of CF stiffening rods?

Post by Brian Evans »

How much effect do they (the typical 1/8" by 3/8" rods, not a tube or a wrap) actually have? Some people treat them as almost infinite stiffness, put two in and the neck won't move for decades regardless of temp and humidity, but I also read (probably here) that they actually only increase stiffness on the order of 15%, and with the whole cube root of beam dimension thing going on, that is about the same effect as adding a couple of millimeters of depth to a normal wood neck. Has anyone done the math? How about twist?

Brian

User avatar
Barry Daniels
Posts: 2486
Joined: Thu Jan 05, 2012 10:58 am
Location: The Woodlands, Texas

Re: Effectiveness of CF stiffening rods?

Post by Barry Daniels »

I have not done the math, but I believe you don't want excessive stiffness or your truss rod will not work. I put too much CF into a 6-string bass neck once and had difficulty setting the relief. Won't do that again.
MIMF Staff

Brian Evans
Posts: 873
Joined: Sat Aug 30, 2014 8:26 am
Location: Tatamagouche, Nova Scotia

Re: Effectiveness of CF stiffening rods?

Post by Brian Evans »

Barry, I did a similar thing when I carved a traditional three piece maple neck with a vintage deep vee. I used a single "Gibson" style rod and it can barely move the neck. I am going to re-carve that neck to lighten it up a bit, that might help the truss rod out. This is part of why I wonder if multiple CF rods are needed, truly optional, or a bit of a fad, in the context of a normal 14 fret guitar neck.

Mario Proulx
Posts: 821
Joined: Fri Jan 06, 2012 12:08 pm

Re: Effectiveness of CF stiffening rods?

Post by Mario Proulx »

If you still need the truss rod, you haven't used enough reinforcement...

Choice of adhesive is --paramount-- if any reinforcement is to be effective over the course of time.

Alan Carruth
Posts: 947
Joined: Sun Jan 15, 2012 1:11 pm

Re: Effectiveness of CF stiffening rods?

Post by Alan Carruth »

Even if a CF rod doesn't add a lot of stiffness, it may help limit how far the neck moves. Wood cold creeps, and can take on quite a set over a long period of time. That's why we use truss rods; not so much to make the neck stiffer as to counter the bending stress that drives the creep. CF is not as subject to creep, if I understand it correctly. Even if it is, if the rod is on the tension side of the bend it will take up a lot of the stress with a small displacement, and may eventually carry enough to stop the neck from moving well short of what would have happened without the reinforcement.

Post Reply