Humidity and neck bow

[Chrisk-K]

I used a search function but didn't find a definitive answer.

Does high humidity cause a neck to be flatter (i.e., lower action)?

[Meddle]

I'm not sure if I can help, but my personal story might help.

In the last few weeks we've been gunning the heating in our flat, and my bass developed some serious clank. I attacked the trussrod, but I followed the advice that you should slacken the rod first just to make sure it is not maxed. Having given it a tentative bit of a turn to the left I found the clank was gone....

Now was this because of radiators drying my room out or the laundry on my radiator humidifying the place? I put a glass on the radiator and it took about 5 days to evaporate.

[Chrisk-K]

After some extensive googling, I found out the answer.

High humidity --> back bow (lower action)
Low humidity --> forward bow (higher action)

[bucephylus]

Here's a practical way to think about it:

The absorption of the water into the wood in the neck causes the neck to try to be bigger (it swells). This means that the neck wants to be longer. However the truss rod restrains the neck from getting longer. This is effectively like tightening the truss rod. So, the neck will tend to flatten out, just as though you had tightened the truss rod.

Make sense?

[Meddle]

I thought wetter wood would be more likely to be shaped by the string pull, and drier wood would be more rigid and likely to straighten out?

[251]

Originally Posted by Chrisk-K

I used a search function but didn't find a definitive answer.

Does high humidity cause a neck to be flatter (i.e., lower action)?

Yes. + low humidity adds relief.

[ThrashMaster]

there is no set rule for this...just use your eyes to tell you if youve got too much relief or not enough, not what the weather did yesterday

[bucephylus]

Disagree strongly that there is no set rule. This is simple physics.

When the humidity goes up, your bass will go sharp and the neck will lose relief. When the humidity goes down, your bass will go flat, and the the neck will gain relief. This happens for the reasons that I explained in Post #4.

(BTW, I actually analyzed this essential problem in somewhat gory detail as part of my dissertation work. The analysis is published in J. Appl. Phys., 62, 4438 (1987), if you feel really inclined to investigate more than you would ever want to know about it.)

[srayb]

Originally Posted by Chrisk-K

After some extensive googling, I found out the answer.

High humidity --> back bow (lower action)
Low humidity --> forward bow (higher action)

I'm glad I found this thread. I was just about to tackle some trussrod adjustment this weekend. However I am sure now that it is the humidity (or lack thereof) causing the bowing I noticed this morning. (Same as another poster, apartment room with radiators.)

Short of purchasing a room humidifier, are there any other ways to try to maintain proper humidity? Has anyone used something like this?:
http://store.daddario.com/category/1...nt_Humidifiers

Thanks.

[251]

Originally Posted by srayb

I'm glad I found this thread. I was just about to tackle some trussrod adjustment this weekend. However I am sure now that it is the humidity (or lack thereof) causing the bowing I noticed this morning. (Same as another poster, apartment room with radiators.)

Short of purchasing a room humidifier, are there any other ways to try to maintain proper humidity? Has anyone used something like this?:
http://store.daddario.com/category/1...nt_Humidifiers

Thanks.

Proper humidity has to do with where you live. If you kept your basses in a humidity controlled room, you would never play out or go to a rehearsal. As soon as you left the controlled room, the bass would slowly adjust to ambient conditions. Learn to adjust the truss rod & expect to do so 3 or 4 times a year, adjusting string height to suit, in between. Then you can store your bass where it is convenient to play. 8-)

[srayb]

Originally Posted by 251

Proper humidity has to do with where you live. If you kept your basses in a humidity controlled room, you would never play out or go to a rehearsal. As soon as you left the controlled room, the bass would slowly adjust to ambient conditions. Learn to adjust the truss rod & expect to do so 3 or 4 times a year, adjusting string height to suit, in between. Then you can store your bass where it is convenient to play. 8-)

Is this a good thing to do?

If I understand you correctly... instead of trying to adjust the humidity for the bass, I will adjust the bass for the humidity?

I agree with your reasoning, though. In winter adjust for low humidity, and in summer adjust for high humidity (for where I live anyway).

Thanks.