When is a Crack not a Crack?

Had a customer return an uke the other day. She was concerned about what appeared to be a crack in the lower top plates between the bridge and the endblock. She says she noticed it several years ago and it has not widened and appears stable. She is not particularly concerned.

The uke was built about 5 years ago. The top is reclaimed old koa. Upon examination, it appears there is some separation of the top plates in that area. There is a slight ridge that can be felt.



There does not appear to be "cracking" but separation. Glue is still visible between the plates. It appears to have been like this for awhile.

Overall, the "crack" is not readily apparent from a distance and the uke looks and plays fine.



My reaction is to not mess with it since it looks stable. However, I'm not liking it. I could further stabilize the thing with a little CA but I'm not sure it would do anything since there is no where for it to flow. The owner wants to keep the uke and does not want her money back.

As you say, it isn't a crack. If it were mine, and had been like that for some years, not becoming worse, I'd be inclined to leave well alone.

I'm guessing there is no reinforcing strip on the back of the butt joint. The position of the separation would make fitting of a substantial internal cleat difficult, but that would be the best solution IMHO.

John Colter

ukantor said:

I'm guessing there is no reinforcing strip on the back of the butt joint. The position of the separation would make fitting of a substantial internal cleat difficult, but that would be the best solution IMHO.

John Colter

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No, there is no reinforcing strip on the inside. However there is a central fan brace that goes right underneath there which would make putting a cleat in there challenging to say the least. I'm inclined to let well enough alone. It is what it is!

Yup - I'd agree with that.

John C.

A crack like that is almost always user error. That is usually caused by leaving the ukulele in a hot car or in direct sunlight. They won't remember doing it but they at one point did.

Hi Sequioa, that is a beautiful ukulele! I'm not at all qualified to comment from a builders perspective, but I think your problem is due to wood selection rather than your building technique. I've cut and dried thousands and thousands of koa ukulele and guitar sets, and some wood will not stabilize no matter how carefully it is dried. By the look of it, it seems like there was something going on in the tree right above where the lower bout was cut from. Maybe a branch grew out, or the tree twisted sharply- that's what generated that beautiful bit of curl and caused the grain to flatten out towards the center of the ukulele. In my experience, koa that has this kind of grain switch is never stable, it's always fighting itself.

I would define a crack and seam separation as effectively the same thing, although they technically are not the same.

I'd rather fix a crack then a seam separation as a crack doesn't have existing glue to remove before gluing (unless your center seam was glued with hide glue then it's easier with just hot water.

I've not done a test to see how well titebond sticks to an already dry layer of itself- another youtube video for me to do!

JJohansen said:

In my experience, koa that has this kind of grain switch is never stable, it's always fighting itself.

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Yes I totally agree. This was a strange piece of koa from the get-go and there was some discussion about it here on this very list years ago. The wood itself was extremely dry and hard like something you would expect from a reclaimed specimen. Very difficult to work with as I remember. I think the seam separation probably happened within a few weeks or months after construction when it was settling in but of course it was long gone and I never saw it again. Once it settled in it became stable. Anyway, anytime you are using wild grain like that you are taking chances.

I would define a crack and seam separation as effectively the same thing, although they technically are not the same

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To an owner of such an instrument they are exactly the same thing, even after you've tried to point out what the differences might be.
Miguel