Humidity and Neck Angle

[Grumbum]

Would high humidity raise an acoustic's (dread) action? What is a good way to check to make sure the neck angle is correct on your guitar?

[BothHands]

Not sure about the affects of humidity on neck angle.

A basic check for correct neck angle is to rest the guitar on its back and lay an accurate 24" straight edge on the fret board. I use a simple piece of 3/4" aluminum angle iron (L-channel) resting atop the frets like a "V".

Slide the straightedge toward the saddle until it meets the front edge of the wooden bridge. The corner of your straight edge should be right at the corner where the top surface of the wood bridge meets the side/edge surface of the wood bridge.

If the corner of your straight edge is lower than the top surface of the bridge, your neck is leaning forward. If the straightedge corner is higher than the top surface of the bridge, your neck is leaning backward.

I'm sure there must be more accurate ways to measure, but this is a seat-of-the-pants method that can keep you from buying a problem, or help you understand where things stand when deciding your next move in terms of repair/restoration.

[John Arnold]

Humidity has little effect on the neck angle per se, but it can affect the belly of the top. As the top wood swells from gaining moisture, it will rise in the center because the braces are holding it on the inside. This will raise the action.
When the neck angle is correct, the strings should be approximately 1/2" off the top in front of the bridge with acceptable action.
If the strings are lower than 3/8" above the top with good action, it may be time for a neck reset.