One or two truss rods in a 12-string neck?

[viento]

I´m intending to build a 12-string neck with open peghead of "normal" size.
Should I insert two truss rods like some 12-string guitars have or
would one do the job?
The neck will meet the body at the 14th fret.

[mb propsom]

I've found a single truss rod to be sufficient.

[mirwa]

Twin truss rods allow a person to not only combat relief, but also twisted necks.

My favorite modification for 12 string necks, is retaining the single truss rod, but then fit two carbon fibre stiffeners, one on each side of the truss rod, have done this on a multitude of older 12 strings and on a couple of brand new off the shelf guitars as well

Steve

[viento]

Thanks for your help!

[JDaniel]

Originally Posted by mirwa

Twin truss rods allow a person to not only combat relief, but also twisted necks.

My favorite modification for 12 string necks, is retaining the single truss rod, but then fit two carbon fibre stiffeners, one on each side of the truss rod, have done this on a multitude of older 12 strings and on a couple of brand new off the shelf guitars as well

Steve

Do the carbon fiber rods make it more difficult to get a correction out of the adjustable rod?

[mirwa]

Nope

Steve

[Shuksan]

Originally Posted by mirwa

Nope

Steve

But pastor, how can this be? Shouldn't a stiffer neck require more force from the truss rod to move the neck a given amount? I've wondered about this for some time so I'm curious to know.

[mirwa]

Originally Posted by Shuksan

But pastor, how can this be? Shouldn't a stiffer neck require more force from the truss rod to move the neck a given amount? I've wondered about this for some time so I'm curious to know.

Simple, a straight solid neck, needs very little amount of truss rod adjustment, a poor neck needs lots of truss rod adjustment. A neck fitted with carbon fibre stiffeners needs a minuscule turn of the truss rod to give a super low relief

Steve

[mb propsom]

Viento, my experience is that carbon fiber isn't necessary in a 12 string neck. In fact, I've used carbon fiber in only one of my 12's and it made the neck so stiff, that loosening the truss rod nut resulted in no added relief.

[Shuksan]

Originally Posted by mirwa

Simple, a straight solid neck, needs very little amount of truss rod adjustment, a poor neck needs lots of truss rod adjustment. A neck fitted with carbon fibre stiffeners needs a minuscule turn of the truss rod to give a super low relief

Steve

Maybe I'm simple, but that doesn't make sense to me. Take two dead straight/flat necks, one stiffer than the other. Turn each truss rod nut 1/4 turn to tighten the truss rod. The truss rod in the stiffer neck should take more force to turn that 1/4 turn, no? The greater stiffness of the stiffer neck means greater resistance to the action of the truss rod bending it, no?

[mirwa]

Originally Posted by Shuksan

Maybe I'm simple, but that doesn't make sense to me.?

I sense passive aggressive, so final reply, clearly lets start with you have never fitted them so you are working in a theoretical world and not real life practicable world.

The neck with the single truss rod no stiffeners, needs some times 4-5 turns of the truss rod to make it straight, so the load on the nut is extremely high, the neck with the stiffeners is already resisting string tension, it may need 1/4 of a single turn to get it with perfect relief. A 1/4 turned nut is not being subjected to the same tension as a nut thats been wound on easily 4 turns to try and pull the neck straight.

Scenario one, the truss rod nut is on its won trying to pull the neck to straight, scenario two, the carbon fibre rods and the nut are pulling the neck straight. The load on the nut in the second equation is way less.

Its not about 1/4 turn static comparisons, its about neck relief comparisons in real world scenario.

Steve

[Shuksan]

Originally Posted by mirwa

I sense passive aggressive, so final reply, clearly lets start with you have never fitted them so you are working in a theoretical world and not real life practicable world.

The neck with the single truss rod no stiffeners, needs some times 4-5 turns of the truss rod to make it straight, so the load on the nut is extremely high, the neck with the stiffeners is already resisting string tension, it may need 1/4 of a single turn to get it with perfect relief. A 1/4 turned nut is not being subjected to the same tension as a nut thats been wound on easily 4 turns to try and pull the neck straight.

Scenario one, the truss rod nut is on its won trying to pull the neck to straight, scenario two, the carbon fibre rods and the nut are pulling the neck straight. The load on the nut in the second equation is way less.

Its not about 1/4 turn static comparisons, its about neck relief comparisons in real world scenario.

Steve

Nothing passive aggressive at all. I simply don't get your explanation. Your assumption is incorrect, I install truss rods in guitars I build so not hypothetical at all. Not once has a truss rod in my guitars needed anything remotely like like 4-5 turns to make the neck straight. When I string up my guitars, there is barely any need to adjust the truss rod at all. Ever. If I had to turn the truss rod 4-5 turns to get the neck straight something would be horribly wrong. So, I must be missing something here.