View Full Version : Soundboard and moisture problem

12-26-2015, 09:00 AM
Hi All,

I am posting this issue i have here in the Luthier's section to get some pro's advice on how to correct my issue with my ukuklele's soundboards possibly being damaged by high humidity.

I live in Taiwan, a sub-tropical island just east of Mainland China. Weather here is quite humid year round, 55% ~ 95%. I have 2 of my prized ukes sitting in a humidity controlled box, usually. I went away for almost a year and come back to find that somehow someone unplugged the unit and the ukes basically were at the mercy of the humid air. I now find that the section of the soundboard below the bridge is bowed outwards slightly on both of my ukes. One is Koa and the other is Spruce. I'd like to know if there is a way to fix this? I thought of taking two 2" wide strips of wood on the front and back of the uke, covering over the bowed section, and use 3-4 C clamps spaced evenly across the width of the lower bout, clamping down with light pressure while I put the ukes back into the humidity controlled box and see if the soundboard can be straightened while it shrinks as humidity is lowered. I usually leave the setting at 50% RH before.

Any suggestions would be greatly appreciated.

Pete Howlett
12-26-2015, 09:32 AM
Stabilise and see what happens before doing anything drastic! Getting back to 50% should restore to the original condition...

12-26-2015, 09:36 AM
High humidity isn't the worst thing that will happen to your uke. It's the very dry that does the most damage. What happens when you have high humidity is that the timber will expand across the grain the most. Only the very slightest along the grain. When the humidity is higher than when the instrument was built, the top and back will expand across the grain and those parts will raise up. Get a dome in them. If on the other hand it gets very dry, those parts will sink down making a dish. If very severe the timber will split along the grain.

If you are saying that the sound board behind the bridge towards the tail block is slightly bowed up, then this is normal and in fact desirable. It's caused by string tension rolling the bridge towards the sound hole, and pulling the soundboard up behind the bridge. It will also be very slightly sinking the soundboard in front of the bridge. If the timber is at a high RH then it may be difficult to see.

I would just put them back in the RH controlled box and let them dry out a bit.

Beau Hannam Ukuleles
12-26-2015, 12:03 PM
I would just put them back in the RH controlled box and let them dry out a bit.

Yep .

12-26-2015, 01:55 PM
If you haven't already, you might want to release the string tension while it dehumidifies.