Question?

[Billy Apple]

If you move a bass from a dry atmosphere into one with more damp (but a similar temperature) in the air would the neck?

i) Forward bow
ii) Back bow

And why?

Edited July 1, 2016 by Billy Apple

[hubrad]

Possibly i) and possibly ii). Also possibly neither.
It all depends on expansion and contraction of bits of wood.

[BassBus]

..and that is why a lot of manufacturers use multi-laminate necks. Each bit of wood expands and contracts at different rates.

[BassBus]

The same piece of wood might also have different densities through its length. Depends how the tree it came from has grown.

[PlungerModerno]

In general - wood expands when it gets wetter and shrinks when it gets drier.

In practice is depends on grain, glue joints, and finish - each piece of wood moves differently, in 3D (Length, Breadth, and Thickness). No two glue joints are the same (minute inconsistancies in the jointed surfaces, imperfections in the glue mix, etc. All finishes are porus sooner or later - apart from inch thick lead or depleted uranium - that will keep the moisture in / out forever! Obviously unfinished wood is asking for instability - certainly when compared to the same stock covered in oil, wax, or laquer.

Multi-Laminate Necks are using the same logic as plywood: many grain directions + strong glue joints = Massively improved average strength and stability.
Such is my understanding at least. I've been wrong before. It was a Thursday.

[Billy Apple]

[quote name='PlungerModerno' timestamp='1467411664' post='3083596']
In general - wood expands when it gets wetter and shrinks when it gets drier.
[/quote]

So lets keep things simple. It the strings are pulling one way and the truss rod is counter acting that, what would the result be with a change in moisture? Plus if damp wood expands, would it make the wood spongier and less rigid?

[PlungerModerno]

It'll depend on the specifics of the wood in question. For a bass neck that's not flood damaged the change in stiffness and density will be minute - what may be important is the size. Even a fraction of a milimetre in the wrong place can make a big difference.

I'd recommend reading up on it:
[url="http://www.wood-database.com/wood-articles/wood-and-moisture/"]http://www.wood-database.com/wood-articles/wood-and-moisture/[/url]
[url="https://en.wikipedia.org/wiki/Wood_drying"]https://en.wikipedia.org/wiki/Wood_drying[/url]
[url="http://woodgears.ca/lumber/moisture.html"]http://woodgears.ca/lumber/moisture.html[/url]
[url="http://woodgears.ca/wood_grain/shrinkage.html"]http://woodgears.ca/wood_grain/shrinkage.html[/url]

[Grangur]

[quote name='Billy Apple' timestamp='1467412571' post='3083602']


So lets keep things simple. It the strings are pulling one way and the truss rod is counter acting that, what would the result be with a change in moisture? Plus if damp wood expands, would it make the wood spongier and less rigid?
[/quote]
It would make it more prone to movement.
Movement can include warping can include more irregular change in shape than you describe. It can also include splitting in the woods or separation in the pieces of wood.

Over all its not recommended as a way to fix any kind of problem if that's what you are thinking.

Why the question?

[Phil Starr]

You aren't going to get a straight answer to this because the straight answer is; it depends.

Wood expands and softens when wet. Ultimately this is down to changes in the inter molecular forces which 'stick' the wood fibres together. How much depends upon so many factors it would be hard to predict which piece of wood would expand the most. It varies between species and also between different trees and different parts of the same tree. My guess would be that some bits of rosewood would change more than some bits of maple and some less for example.

Strings and truss rods are going to be more or less unaffected by moisture but both expand when heated so a change in temperature is going to have a separate effect to the humidity changes, and that will take effect a lot more quickly than a humidity change. It takes weeks for timber to become seasoned when you use it in a different room and I store timber for months before I use it in critical situations. I suspect most of what makes your bass go out of tune when moving from room to room is down to temperature rather than humidity.Wood changes a lot but slowly.

The best thing practically of course is to keep any instrument away from damp and store them in the best cool dry space you can find.

[HowieBass]

Of five basses that moved from a damp house to a dry house the only one that suffered any significant change was my Squier VM Precision (strung with flats) and that developed a significant forward bow over the period of a few weeks - once I'd adjusted the truss rod it's remained stable. I reckon that bass has the thickest neck too. If the bass were to move back to a damper environment I'd therefore expect it to develop a back bow.