Rehydration of an old uke

Timbuck

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A handsome Lad called by the other day with an old Mossman soprano
he had purchased...It is about 90 years old plays great and sounds great..but it has problems...the body appears to have shrunk and the ends of the braces are pushing hard against the sides causing the seems to come apart in those areas..Question if I go through a rehydration process like i've seen done at Taylor Guitars will the body expand back to where it was :)...or will it need the back removing and the braces shortened..I don't fancy the latter method :( or shall I leave as is :confused:
Has anybody done a repair like this ?
 
I am interested to see where this thread goes.... I have an old soprano whose friction pegs no longer hold. I suspect the headstock has dried out and shrunk a bit (enlarging the holes). Not looking to hijack this thread, but I will be interested to read the replies to Ken's post.
 
A handsome Lad called by the other day with an old Mossman soprano
he had purchased...It is about 90 years old plays great and sounds great..but it has problems...the body appears to have shrunk and the ends of the braces are pushing hard against the sides causing the seems to come apart in those areas..Question if I go through a rehydration process like i've seen done at Taylor Guitars will the body expand back to where it was :)...or will it need the back removing and the braces shortened..I don't fancy the latter method :( or shall I leave as is :confused:
Has anybody done a repair like this ?


I have done this kind of repair many times. It is best to remove the back and rebuild the uke to make things fit properly. It is almost impossible to rehydrate the wood, time has taken its toll. You should be able to retain the original look without much trouble.
 
I recently bought a used Ohana TK-38 that had the same problem with the lower back brace pushing the sides out. Elderly did the repair in less than a week turnaround time so I'm guessing there's a way to repair it without removing the back.
 
I recently bought a used Ohana TK-38 that had the same problem with the lower back brace pushing the sides out. Elderly did the repair in less than a week turnaround time so I'm guessing there's a way to repair it without removing the back.

They may use a camera and some kind of specialty saw. You could make a saw attached to a multitool like the Fein Multitool to get right in there and cut the brace ends.
 
Possible on a tenor I suppose...Can't see how I can get into this soprano like that:)

The seams on my TK-38 were open about a 1/16 inch. Maybe enough room to trim the brace from the outside. That said, I really have no business posting here beyond that as I have zero experience.
 
I hydrated a 1930s mahogany soprano enough just by buying it off eBay and letting it sit in my general 80% humidity coastal house to where it self sealed a gaping 5" back crack.... but that took awhile.
 
I've never restored a small instrument. But having rebuilt pianos for most of my life I've studied quite a bit about this subject. Much of it comes down to simple logic. Cut to size when fresh, the wood holds its size and shape pretty well under normal humidity. Once much of that moisture is dissipated by age, and the wood has shrunk, it is a new size under those same "normal" conditions. The inter-cellular moisture (the moisture the wood gets from the tree) has evaporated out. You can replace that moisture with water, using over-humidification. But, that moisture will simply evaporate out after returning it to its normal environment. Adding extra-cellular moisture can swell the wood, but it's temporary. Over-humidifying just adds water around the cells of the wood. An exaggerated example of this would be dunking wood in water. It will expand considerably whether it is new or old. But, when returned to 45% humidity, it will shrink back to basically the size it was before you dunked it. (in fact adding water might actually crowd out more of the natural moisture and cause further shrinkage) How quickly it shrinks back depends on several conditions, but it will happen.

An extreme case (which I thought was interesting):
We once received a piano from Florida (tropical by mainland U.S. standards) that had one crack in the soundboard. It looked like a rather straightforward rebuild. After simply sitting in our shop in Chicago, untouched for two or three weeks, it had developed dozens of cracks. By the time we began disassembly, not only was it riddled with cracks (100 or so), the one it had upon arrival was wider than 1/4".
 
They may use a camera and some kind of specialty saw. You could make a saw attached to a multitool like the Fein Multitool to get right in there and cut the brace ends.

Im sure I remember seeing a YouTube clip that Dan Erlewine from Stewmac did using a saw you mention. He did do it on a Guitar though - so access is obviously better. I can't find the clip, but this clip is well worth looking at. Dan always tries to do the repairs without opening up the body.
Maybe in Kens case though, there may be no option.

http://youtu.be/cjfQHsngzOQ
 
My Idea was to take a 6 piece of 1/4" aluminum rod hammer the ends flat on an anvil. Drill a hole in one end to fit in a multi tool. Epoxy a piece of multi tool saw blade to the other end. Then bend the rod as needed to reach the brace at the right angle.. Then use low speed to make the cut. I haven't tried it but it should work. Those multitools are amazing.

I just did a small repair for a gal who purchased a custom Koa tenor while she was in Hawaii. What a mess, the frets were beginning to stick out past the fretboard. She keeps a wet sponge in a plastic bag in her case with a few pin holes in it to try to keep it from coming apart. I suspect that will be a losing battle in the end. It was clear not all builders in the Aloha State are as careful as Chuck when it comes to controlling humidity in the build area. You have to be careful when you bring an instrument built in the tropics back to a place like California or the Southwest where RH is often in the 20s and 30s that your instrument wasn't built in 70% RH. I suspect many older instruments where built in relatively high humidity.
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It is my experienced opinion that the back should remove for this kind of repair. Even if you could saw off the struts and make them shorter, you still have to deal with the deformed sides. The inside struts are probably coming loose in several areas and also could be cracked along the grain lines. One thing I have noticed on ukes of this vintage is that the wood used for the struts themselves was usually junk that was left over from something else or cut wrong or both. There is no reason to try a salvage inferior wood or construction.

Plus, you will proably find a few more surpises and things that need fixing that were not visible now that the back is off.
 
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Hi Duane...If I do have to take the back off..What method do you suggest seeing as it's probably hide glue holding it together.. I have taken off the the the backs and tops before, but only on my own ukes, held together with Titebond...and I want to do as little damage as possible.
 
I've removed vintage hide-glued backs before using a hot putty knife. The putty knife should be thin and sharp. A heat source like a heat gun, small flame burner, or the like can be used to re-heat the blade as needed. It's a slow process, heating the knife blade, working the knife into the joint, re-heating the knife, working the joint, re-heating the knife, and so on..... but patience is the key. I've had trouble at the neck block getting clean separation, doing some damage to the back, but it was entirely because I wasn't patient. Maybe Duane has some good advice for working around the neck block.

-Steve
 
Hi Duane...If I do have to take the back off..What method do you suggest seeing as it's probably hide glue holding it together.. I have taken off the the the backs and tops before, but only on my own ukes, held together with Titebond...and I want to do as little damage as possible.

Do as Steve suggested with the sharp putty knife and heat. Patience is the key. Hide glue usually lets go easily. Try to watch for the knife edge on the inside of the uke as you work it around the edge. The biggest problems are the neck block and tail block if it has them. Just work the knife under the blocks slowly, trying not to crack the back.
 
Duane, what is your preferred heat source for this technique? I've had some success using a heat gun (that you might use to strip paint), but was wondering what the experts prefer.

-Steve
 
Duane, what is your preferred heat source for this technique? I've had some success using a heat gun (that you might use to strip paint), but was wondering what the experts prefer.

-Steve

I use a heat gun, it heats quick and clean.
 
Yeah, a heat gun seems best. I have, however, wondered about using a modified soldering iron. I had a thought of taking one of these X-acto irons with the 'hot knife' attachment:

http://www.amazon.com/Xacto-X73780-...9&sr=8-2-spell&keywords=wood+burning+hotblade

You could then fit it with a chisel style #17 blade:

http://www.amazon.com/X-Acto-Blade-...qid=1403055738&sr=1-5&keywords=xacto+blade+18

I'd then wire in a dimmer switch to control the voltage and see if I can achieve a constant blade temperature that would melt hide glue, but not scorch wood. Has anyone else had success with this kind of approach?

-Steve
 
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