Changes in Neck Relief

[Jon Hall]

A technician adjusted the truss rod in my KM956 three weeks ago because there was too much relief resulting in a high action. It has played fine and has had great intonation since then but it when I played it today the action was a little higher and I can see a little more neck relief but not as much as it was before the truss rod was adjusted. I keep a humidifier in the case and only leave it out when I'm playing it. Does anyone know if the changes are due to the dry air or the humidity when it's in the case?

[Gary Leonard]

Short answer: Yes
Long answer: Check this out:

https://www.montanalutherie.com/pain...ust-truss-rod/

[mandroid]

Yea one advantage to a Carbon Mix, is its not acting like a hygrometer

with changes to the temperature and relative humidity causing wood to swell and contract.

as it takes on the RH around it..

Museum display cases monitor the RH of their collections that are vulnerable to such changes..


...

[GTison]

I’ve read articles in the last few years about Over Humidification in the last tree years. Google that. You appear to live in east Texas. Somewhat similar to here in NW Florida. So I would think humidification would mostly unnessary. Maybe in the winter when the heater stays on.

Necks and tops do move w humidity. I’ve had my neck truss rod set in Nashville and some time (weeks months)later discover the need for adjustment. This has happened at least twice. The luthiers involved had mixed reactions to this. The gulf coast is usually a wetter and warmer place to live.

Maybe get an accurate hydrometer and skip the humidifier for a week or two. See if the action or relief changes. (Unless of course you are running a heater that drys everything out.)

[GTison]

That could have used some editing.

[Br1ck]

I cringe when I hear the word action and neck relief in the same sentence. Too many confuse the two. Action is set at the nut and bridge. These two points control string height. The truss rod only effects the bow in the neck. Yes, this could be lumped into the word action, but it is best to separate the two issues.

A mandolin needs very little relief. Too much resultes in buzzing up the neck. I've found getting the neck very flat, then leveling the frets flat and recrowning them is the starting point to very good action. Fail to do this and you are going to get buzz at the neck joint, most likely, as there is usually a hump there. Some can live with this, but when you pick up a high dollar instrument and it plays clean and seemingly effortlessly up the neck, a leveled fretboard is the reason. You can get a Rogue to play like this.

Usually I've found that string tension provides enough relief, and even a bit too much. A truss rod does not raise or lower action except in the middle frets.

[Hudmister]

A mandolin needs very little relief. Too much resultes in buzzing up the neck. I've found getting the neck very flat, then leveling the frets flat and recrowning them is the starting point to very good action. Fail to do this and you are going to get buzz at the neck joint, most likely, as there is usually a hump there. Some can live with this, but when you pick up a high dollar instrument and it plays clean and seemingly effortlessly up the neck, a leveled fretboard is the reason. You can get a Rogue to play like this.

I am curious why even with more expensive quality instruments there is often a hump at the neck joint. I know the truss rod does not extend through the neck joint but it seem builders would find a solution to this common problem short of the fret leveling and crowning you describe.

[Br1ck]

It is the nature of wood. Things change over time. Ship a mandolin across the continent, things might happen, or might not.
But learning to do a fret level and crown will put you way ahead of the game as far as playability goes. In my neck of the woods, everything costs more and a fret level and setup is going to run $150. I have around a dozen stringed instruments.

I bought an inexpensive closeout mandolin to learn this on. It started horrible and ended up slick. I did the Meldrum setup first. Went from horrible to tolerable. I'll bet most Eastmans and Kentuckys are decent, but could still use that something extra. Tools are an expense though, but you get a lifetime use once you have them. I am interested in lutherie though, and can see someone not wanting to do this.