Carbon Fiber Rods - what size, and why?

[Dennis Leahy]

I see a group buy about to happen on CF rods, and note that everyone is buying 1/8" x 3/8" x 18" rods. That got me thinking...

In my extremely limited experience of seeing CF installed in guitar necks, 1/4" (6mm) wide rods were used. Is 1/8" thick the more typical size that luthiers are using?

Has anyone considered using the round tubes that Harry Fleishman uses: Pultruded Carbon Rods at LMI, that cost $3.75 for 1/4" x 18" or $4.75 for 3/8" x 18"?

For those that plan to put these in adjustable necks, what is your plan above the body/neck joint?

Anyone gonna try Rick Turner's method of inletting the CF into both the underside of the fingerboard as well as into the neck?

Thanks in advance for your thoughts. I have been thinking about using CF in necks, but really don't know what size, or why.

Dennis

[jeffhigh]

This is something I am thinking through at the moment.
It seem like a lot of the typical CF installations have the rods pretty well right on the neutral axis of the crossection.
Seems it could be improved with a rod located near the back of the neck as well as just under the fingerboard.
With reinforcing anything in bending the key is quantity of the reinforcing material and position.
Jeff

[Dave Higham]

LMI don't give the wall thickness (or inside diameter) of their CG tubes. If the wall thickness is 1/16" they would be about 1 1/2 times as stiff (or resistant to bending) as a 3/8" x 1/8" rod used 'upright'. In their photo they look to be less than 1/16" thick, so the stiffness is probably about the same. After that, it's a matter of which is easiest to incorporate. For me, it's the rectangular section. I've used them in the necks of 3 (different) electric basses.

[Craig]

Dennis,
I've installed the 1/8 " X 3/8 " rectangular section c.f. on my last project . 4 mm. either side of the two way truss rod. 3/8 " is about as deep as you can inlet into the neck . I have heard stories of some guys "coming through " whilst carving the neck , so you have to be careful. I installed them mainly because it was a twelve string neck and wanted to be sure it could cop the additional strain.

Some builders report a sound improvement when using them , but I really don't know if this is correct or not . They make the neck a little heavier , and understandably limit the truss rod's available movement . although the c.f. does have some 'give '. Are they absolutley necessary ? NO , but they do strengthen the volute area of the neck when installed their full length through the scarf joint etc.

I'm including them on my current project , because it has an adjustable tilt neck and the c.f. serves to stiffen the fretboard extension

Jeff , these 1/8 " X 3/8 " rods do in fact extend to near the back of the neck.

[jeffhigh]

Yes Craig if you have them offset like that it will be getting close to the back of the neck. I guess what I was wondering is why not put a strip centrally at the bottom of the truss rod channel.

[Bob Connor]

I've used 1/8 x 3/8 on a couple of twelve strings in a similar fashion to Craig.

I'm very impressed with how they keep the neck straight and I feel that they even out the response of individual notes up the neck.

I'll be using them on all instruments from here on.

Bob

[Arnt]

I do it the same way as Bob and Craig, and I have noticed the same thing; the neck feels more solid as you move up and you get less ‘dead spots’ in the higher positions. I probably can’t give you the right technical terms for this but it seems that a more solid foundation for the fretted notes makes them clearer and there is more sustain as less energy gets cancelled out by potentially weird vibrations going on in some positions in a less stable neck. There is also the benefit of a more solid neck / headstock transition if you extend the bars all the way to the headstock veneer, and this makes me sleep a little better as I don’t make scarf of v-jointed headstocks so there is a lot of short grain in the headstock. My next mandolin will have only a carbon fiber rod as neck reinforcement, with all those tuning machines they are neck heavy enough as it is and there is usually not the same need for tweaking of relief as on guitars.

[Dennis Leahy]

OK, thanks to all who replied. Sounds like the 1/8" x 3/8" should work out fine then.

Dennis

[Dave Anderson]

Dennis, I have used CF in my last three guitars- 1/8 x 3/8. I like the added strength and they
are very simple to install. I rout two slots close to the truss rod on my router table and epoxy
them in. I run them into the headstock for more strength at the volute. I like em!