Neck Resets

[gitnoob]

Originally Posted by charles Tauber

Ah, not so much. Strength is not the same as resistance to creep. Creep is the mechanism at work here, not failure due to lack of mechanical strength.

Wood creep or glue creep? It's been wood creep on all of the vintage guitars I've examined, and good structural support should reduce wood creep.

[arie]

Originally Posted by gitnoob

Wood creep or glue creep? It's been wood creep on all of the vintage guitars I've examined, and good structural support should reduce wood creep.

wood tends to shrink over time. to much "localized" constraint will result in cracks. the guitar needs to be build so that all it's members share in the work as equally as possible IMO. not easy to do though and still get tone -thus the challenge of luthiery. proper seasoning of the wood, stress free building methods, and on the user end, correct care and sensible string gauges all help.

[gitnoob]

Shrinkage shouldn't be the main issue, I'd think. As long as the wood was dry when built.

As Charles said, the issue is creep. So I want to ensure that we're agreeing on terms. The "creep" issue that should be the major concern here is that wood under deformational stress tends to stay deformed over time. That's what causes the neck angle to change.

So the goal should be to limit those deformations without limiting tone production. Since the upper bout is more about structure than tone, a robustly-built upper bout seems key.

The lower bout is trickier, but I think the bridge plate can help. I never understood why Martin, for example, uses a cross-wise grain orientation on their bridge plates.

[redir]

I did a neck reset on a classical once by lifting the neck and slipping the joint. I'd probably never do it again unless it was a very collectable piece and then I'd just have them take it to an expert. It's a major PIA. The alternative would be converting to bolt on.

[charles Tauber]

Originally Posted by gitnoob

The "creep" issue that should be the major concern here is that wood under deformational stress tends to stay deformed over time.

More or less. Perhaps a better description of creep is the slow deformation of a material under load. Creep of glue may also contribute - I don't' know for sure.

Since the upper bout is more about structure than tone, a robustly-built upper bout seems key.

I have pondered that for a while and don't think so anymore. If the upper bout is infinitely rigid, but the lower bout isn't, nor is the "connection" or transition to the lower bout, the guitar will still fold in the middle, just that the upper bout will fold as a rigid unit. It just transfers the problem elsewhere, rather than redistributes it. Basically what arie said.

My current thinking is stiff sides to take the load. Obviously, I'm not the first person to arrive at that. Others have come up with other solutions such as the framework in lattice-braced/double tops and the use of carbon fiber rods to transfer/distribute the load.

Some crude experiments/measurements I've done on the difference in stiffness/deflection offered by kerfed vs. solid linings has convinced me that I want to use solid linings. It adds considerably to the static strength of the assembly, its ability to resist bending. I'm assuming, without hard evidence, that this will translate into less creep over time.

[gitnoob]

You'd be interested in my 110-year-old Bohmann.

Laminated sides (in those days, lamination was a high-end feature).

Double-X, so one of the few 1900-ish guitars that could handle steel-string tension.

And three UTB's, so it handles the neck load pretty well.

The only weakness? Poor sound hole reinforcement a la Martin. Deformation on either side of the sound hole. And it could benefit from a neck reset.