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I recently bought one of my guitars to the tropics and have noticed the action getting higher.
I notice no neck distortion or top deflection in the usual planes. (ie fretboard or saddle depression) It does seem that the top has become more convex across the lower bout top to bottom raising the saddle in the middle almost as if there was a radiused brace under there.
Is this the humidity..? Is it a problem ? anyone experienced this before? should I put a bag of rice in there?

Humidity - the curse of the guitar whether to high or too low and dry. Same thing happened to my brother when he went to Costa Rica - he only took a cheap guitar for that very reason. When not playing keep it in its case and leave it there when you notice major changes in humidity and temp and let the whole this acclimatize. If its not too bad you may find that when you return and if done slowly it may return to normal... but teh key is to try an dlet teh thig adjust as slowly as possible.

Not sure about the rice?

Wood expands much more across the grain than with the grain. The sides are holding the edges of the soundboard in place (more or less) and the expansion caused by the increased humidity then causes the center of the top to rise as you have described. If you stay in that climate for very long, you may want to lower the action at the saddle if there is enough of it above the bridge. When you return home, a new saddle would probably be in order. You also may be able to reduce the relief in the neck by adjusting the truss rod, but going too flat will cause fret buzzing. I'd let it acclimate in the case for at least a few days before making any adjustments, though. The bag of rice is an interesting idea that I've not heard before. I know that they put rice in salt shakers in restaurants to keep the salt dry...

Chuck

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"To live a creative life, we must lose our fear of being wrong"
- Joseph Chilton Pearce

The cross-grain width of an unmounted, unbraced spruce top can change by 3/8" during wide swings in humidity, though older seasoned spruce moves less. As your top absorbed moisture from the humid island air, it expanded in width and had nowhere to go but up. It's a normal reaction. The bag of rice will help for awhile, but probably will soon get saturated. Try it and see what happens to the action. Can't hurt. You might need to change the rice often, or dry it in a microwave. I wouldn't mess with the truss rod to change the action.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Yep humidity will indeed make your guitar look pregnant if it is exposed to enough humidity.

Some builders like Mario will include two saddles with their guitars, a summer and winter saddle in an effort to provide extra value and ensure that the owner can have pretty consistent action regardless of the time of year.

What you are experiencing will correct itself when the guitar is returned to a humidity environment closer to what it was built in which is probably 42 - 48%ish.

Welcome to tropic life. Indeed it's caused by humidity. I build at between 42 - 45 % RH and I used a standard bolt on neck, I found that I'd get the neck set just right, but then once the instrument was finished and had to live a life in high humidity, the action was so high as to be almost unplayable, necessitating a neck reset before the guitar had even been played .

Now I build with and adjustable neck and problem solved.

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Allen R. McFarlen
Barron River Guitars & Ukuleles
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