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View Full Version : Rehydration of an old uke



Timbuck
06-16-2014, 01:04 AM
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 ?

tobinsuke
06-16-2014, 02:55 AM
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.

BlackBearUkes
06-16-2014, 03:49 AM
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.

kkimura
06-16-2014, 03:51 AM
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.

Michael Smith
06-16-2014, 05:53 AM
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.

Timbuck
06-16-2014, 07:41 AM
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:)

kkimura
06-16-2014, 08:25 AM
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.

Teek
06-16-2014, 08:31 AM
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.

stevepetergal
06-16-2014, 12:23 PM
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".

ukuleleCraig
06-16-2014, 01:23 PM
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

Michael Smith
06-16-2014, 02:18 PM
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.
.

BlackBearUkes
06-16-2014, 02:18 PM
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.

Timbuck
06-17-2014, 12:17 AM
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.

Telperion
06-17-2014, 03:39 AM
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

BlackBearUkes
06-17-2014, 03:46 AM
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.

Telperion
06-17-2014, 05:18 AM
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

BlackBearUkes
06-17-2014, 08:59 AM
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.

Telperion
06-17-2014, 03:51 PM
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-Precision-Soldering-Knife/dp/B000BRBZUG/ref=sr_sp-atf_title_1_2?ie=UTF8&qid=1403055669&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-Chisel-17-Lightweight/dp/B00085EOI6/ref=sr_sp-atf_title_1_5?s=hi&ie=UTF8&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

resoman
06-18-2014, 04:34 AM
I was kind of wondering if one of these might work
http://www.amazon.com/Top-Flite-TOPR2100-Sealing-Iron/dp/B000X4RXR6/ref=sr_1_1?ie=UTF8&qid=1403101993&sr=8-1&keywords=monokote+heat+iron
I used them in my old airplane hobby days. They have a built in rheostat.

aaronckeim
06-18-2014, 04:57 AM
Rehydration won't do enough to fix that. I have had this problem many times with restoration of old Hawaiian ukes. Duane is right as usual. Take it apart and re-build it.

Timbuck
06-21-2014, 08:55 AM
I got the go ahead nod from the owner, and today I made a start.....the back came away easier than I expected with very little damage.
And the art of the builder from 90 years ago was revealed to me.....I noticed on the upper bout a loose bracing had been fixed on one occasion.
But how about those linings ???? I don't know what to do about them.
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1203_zps2ffb7d22.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1203_zps2ffb7d22.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1194_zpsb5951733.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1194_zpsb5951733.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1195_zpse7750a2f.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1195_zpse7750a2f.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1198_zps2ce2f1a9.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1198_zps2ce2f1a9.jpg.html)

BlackBearUkes
06-21-2014, 10:40 AM
This is very common construction for the time period. Why bend the linings when you can simply bend and break as you go. Looks like the repair to the upper brace was done by the pour it from the bottle technique. Why use a llttle when more will do the trick. I would simply make any repairs (remove broken braces, repair cracks, etc.) and clean it up as best you can. Fun stuff!

Timbuck
06-22-2014, 02:02 AM
Today I removed the braces and cleaned and tidied the innerds......And just to find out how it is that this uke is so loud for it's size, I got the Micrometer out and did some measuring...For those not familier with imperial Micrometer, the thickness reading is....
TOP = .058" (1.47mm) SIDES = .050" (1.27mm) BACK = .111" (2.81mm) The back thickness suprised me
Here are more pics
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1214_zpsaa60c9eb.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1214_zpsaa60c9eb.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1207_zps6c6db828.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1207_zps6c6db828.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1208_zps443c047b.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1208_zps443c047b.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1210_zps710b0c05.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1210_zps710b0c05.jpg.html)

Timbuck
06-22-2014, 11:37 PM
I have now shortened the braces and fitted them back into place with "Hide glue" of course..and I am now getting ready to replace the back...I can see all sorts of problems here co's after a trial fit I see it is going to be difficult to get it to line up exactly all round :(...Due to inbuilt stresses I suppose ...I'll have to give this part of the job a lot thought..Maybe even design a jig to hold every in place when gluing as I want to avoid sanding level afterwards as much as possible co's the sides are only 50 thou thick (thinner still in places)... Another problem is the Hide glue going off too quickly to allow time for minor adjustments :confused:
All advice is welcome at this stage :anyone:
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1221_zpscf0612d3.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1221_zpscf0612d3.jpg.html)

ProfChris
06-22-2014, 11:48 PM
Ken, I work with hide glue mostly, and find my "luthier's" (ie, not my ever-loving wife's) hair dryer invaluable. For glueing on backs, for example, I heat the wood, glue and clamp, and then heat again to allow fine adjustment and clamp tightening. The heat ungels the glue (unless you heat so much that you dry it out). Hand warm is enough to keep the glue liquid.

Timbuck
06-23-2014, 03:17 AM
Thanks Chris..That sounds as if it would work....I now realise that I don't have enough suitable clamps to finish off this job , so I've ordered some more....I could have made up a few spool clamps but I don't have enough parts, threaded rod/ inserts and all that stuff..and modern plastic ratchet clamps are cheap and plentyfull.:D and work just as well for this job.

PereBourik
06-23-2014, 04:31 AM
Just for the record. I'm not a builder and probably never will be, but I LOVE this thread.

orangeena
06-23-2014, 05:45 AM
That looks like a fascinating project Ken, great to see how they used to make these things, it kind of makes my shoddy workmanship look a bit better.
Max

Michael Smith
06-23-2014, 05:55 AM
You could use fish glue to put the back on. Also you could make some pieces of wood about the size of popsicle sticks and tape them around the sides of the uke with about 1;4" standing proud to line top in place

Timbuck
06-23-2014, 07:04 AM
You could use fish glue to put the back on. Also you could make some pieces of wood about the size of popsicle sticks and tape them around the sides of the uke with about 1;4" standing proud to line top in place Another good idea to consider...Reminds me of days in the Shipyards, when they used Dogs and wedges to hold the steel plates in position for welding:)

Pete Howlett
06-23-2014, 08:00 AM
Use string...

Timbuck
06-23-2014, 08:19 AM
Use string...
Already tried that Pete on a dry run...I wasn't happy with it :( the sides are so thin at just a gnats cock over 1mm they distort all over the place.

Pete Howlett
06-23-2014, 11:26 AM
Masking tape? Make a 'form' that fits inside the uke from cardboard that you can cut apart and pull out through the soundhole - it's have Stewmmac guitar kits were once done (probably still are- I haven't checked).

aaronckeim
06-23-2014, 04:52 PM
I also recommend masking tape or binding tape to reglue the back. Every piece you use, you can control the fit carefully and make sure things line up. The only warning I would give is to make sure that the top stays flat to the neck and that you don't change the neck angle by messing with the geometry of the sides too much. I have used a flat caul or workboard taped in place for this.

ukantor
06-23-2014, 09:37 PM
68158Hi Ken,

I had a similar challenge, rebuilding an old uke, and made a flat workboard, as suggested by Aaron. It had to be grooved to accept each fret, and hollowed out to fit over the bridge. It was crude but effective. Here's a photo.

Timbuck
06-23-2014, 10:57 PM
Thanks for that John and Aaron, Pete, and others .....All these methods and suggestions are being noted...Keep them coming ;)

Allen
06-24-2014, 10:42 AM
If you size both sides of the joint with HHG and let it dry up a bit, then position the back to the sides and hold in place with binding tape. You can then wick in some more thin glue. Will reactivate what is all ready there and you'll have all the time in the world to position everything as you like.

Timbuck
06-26-2014, 09:29 AM
Clamps arrived today.....Got the the glue pot cooking...Scientifically lined everything up with indexing marks..sized both parts clamped them together and wicked in thin glue ..all went well in the begining :)...Then I found some areas were not coming together as neat as I desired :(and the area at the end block was oozing out a black substance from the end grain of the pinewood block activated by the moisture in the glue :wallbash:...So i've taken the back off again...and I'll have another attempt tomorrow.

Next Day Update I now have the back in place and half glued...Fingers crossed hoping it will be ok this time:shaka:

Timbuck
06-27-2014, 08:22 AM
Success!...The back is on again, Having first made a splint to hold the neck angle in place...I used the method recomended by "Allen" with the help of the Hairdrier as per "Prof Chris" working around the uke a section at a time ....Putting a new back on would have been easier but I wanted to keep the original lable in place ;)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1238_zps343f9c52.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1238_zps343f9c52.jpg.html)

Timbuck
07-02-2014, 05:33 AM
Thats it Job done !.. All I had to do was unglue the back ...removed and shortened all internal bracing, tidy'ed up nasty linings..removed glue stains from previous repair...Refit and glue the back on... Fit bushes in headstock due to enlarged tuner holes...level the frets...and apply a bit of FP here and there. and now it's a "Happy old Uke" again :)...It's very loud and plays great, the thin neck at the nut end takes a bit of getting used to tho'

It's a good job i'm doing it for free co's the hours would have outstripped the value....I learned a lot doing it but I don't fancy doing another for a while.
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1259_zps86ffbe72.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1259_zps86ffbe72.jpg.html)
http://i219.photobucket.com/albums/cc143/shiregreenbod/IMG_1269_zpsa02b9755.jpg (http://s219.photobucket.com/user/shiregreenbod/media/IMG_1269_zpsa02b9755.jpg.html)

orangeena
07-02-2014, 06:06 AM
Almost as lovely as one of yours.

resoman
07-02-2014, 06:23 AM
Ken, Looks like you did a really nice job! Congratulations

Pukulele Pete
07-02-2014, 07:46 AM
Looks like you did a top notch job on that uke. I really enjoy posts like this , Thank You !

DazW
07-02-2014, 11:54 AM
Wow! Looks gorgeous. Really enjoyed following this thread, great to see it restored to its former glory

ericchico
07-02-2014, 12:03 PM
Nice work. Its funny I have completed one Ukulele and im almost done with my 2nd and I have a few people coming to me asking if I could fix theirs. A post like this keeps me in check and helps me say NO, can I just make you a new one I need the practice ;)

Matt Clara
07-02-2014, 12:11 PM
Somebody may have already mentioned this, but Bob Taylor has some very good videos on rehydrating a badly dried out instrument:

Part 1: http://youtu.be/tB8tELj43RE

http://youtu.be/tB8tELj43RE

Matt Clara
07-02-2014, 12:12 PM
Part 2: http://youtu.be/bWcGdWFiv4M

http://youtu.be/bWcGdWFiv4M