Best course of action for a bulge/sink top

Hi all,

The top of my concert uke is feeling the strain of the wild humidity variations in Tokyo, and it's developed a slight bulge between the bridge and the tailblock (I'd say 1-2 mm), and a very slight sinkage between the bridge the the soundhole. I'll upload a photo, but it doesn't show very well.

I released the string tension about 6 weeks ago, and let it sit, and it did improve somewhat, but action is still too high, and putting strings under tension again seems to have a negative impact.

I will take it in for repair eventually, but I would be interested to hear what you think could be down to fix this. The main reason I am asking is because my limited Japanese skills might not be good enough to help me understand what in the repair guy will say. If I can understand the problem, and potential repairs beforehand, it will help me greatly to communicate with the luthier.

Cheers!

Here' s a side shot:

This looks like the bridge is rotating under string tension, and not a humidity issue.

A bit is good. Too much may cause problems.

I just had a Koahloha in this week for some repairs to a top / side seperation that had far more bridge rotation than that. I was quite surprised at how much the sound board had sunk, with a corresponding bulge behind. Still sounded good and played well. The saddle had very little room to adjust and the client didn't mind the action the way it was. Not that there would have been much opportunity to adjust it, as the bridge would have needed to be replaced in that case.

Your solution as far as action will be to lower the saddle if there is room to do so. That can be as simple as removing some material from the bottom of the saddle. If there isn't enough room before the strings hit the bridge, then you are getting into another can of worms.

The bridge rotation is another matter, that may cost more than what the ukulele is worth if you want to go down that path. And be aware that anything done to rectify that is certainly going to change the tone, volume and response of the instrument.

I'm a layman, but perhaps changing the strings to a lower tension set could help with this issue?

How high is the saddle???

The higher the action, the more this will happen.

It should already have one, but if not you could glue a brace where the top is dipping.

PS- a belly behind the bridge is nice to see, but a dip in front of the bridge is not nice to see.

IMO that's just within acceptable range of deformation. As Allen mentioned, some deformation is expected and even desired but the amount you have is probably due to improper bracing. You can build an uke where the top remains straight as a cutting board but it'll sound like one too. Lowering the saddle will help you get the action back that you want while decreasing the levering effect that is torquing your sound board. If you don't have enough height on you saddle then it was made too low without regard to future adjustment. If needed, a skilled repairman can reduce the height of the bridge, exposing more of the saddle with a router and a jig. If it were me I would lower the saddle to an acceptable lever if possible and put the ruler away. BTW, this is one advantage to a radius top as it will minimize deformation in a properly built uke.

How old is the ukulele? That much deformation would be ok on a 50yr old instrument...but if its new then there's a problem inside

Thanks a lot for all the sound advice and suggestions. Glad to hear it's not humidity-related as the weather is the one thing I can't change here

The uke is just over a year old, which is why I worry a little about the deformation. It still plays well, and the action is certainly within acceptable levels. I will ask for the saddle to be lowered, for a start. It actually has an under-saddle pickup installed, so that's the first layer that can go as I won't get a chance to use it plugged in in the near future.

As the top changed shape and the action got higher, the sound became a little too loud to my taste. When I want to make some noise, I use the tenor How feasible would it be to somehow reinforce the brace between the bridge and the tailblock, without opening the uke? Doable? Impossible? Am I crazy?

Thanks again for all the advice.

Germain

I am no expert, but have been through a lot of ukes. The lighter built, lightly braced ukes [Koaloha is an example] seem most responsive, but in my experience seem to be more prone to the bridge tilt/bottom bulge/ soundhole sink. {Hawaiian belly] Heavier built ukes can be bullet proof but can sound dull. I am no builder but I think it is a balancing act. I myself would rather have the belly and the great sound. Of course , if it gets too bad then some action needs to be taken, but a little seems to be common, even in expensive ukes, and if I am happy with the sound and playability, I just live with it. I have never had a uke that was too loud, I just play them softer, I have had some that were too quiet, I sold those, even though they were high quality ukes. Your mileage may vary.

that's actual normal. no need fixing unless your getting bad intonation or buzzing.

If you have any trouble you can message me. My Japanese is decent. Also, just go to Shimakura Music in Ochanomizu. Out the Ochanomizubashi exit and go left down the street with all the music shops. It is maybe 3 minutes from the station...they speak English