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PostPosted: Wed Dec 06, 2017 10:09 am 
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Cocobolo
Cocobolo

Joined: Wed Feb 17, 2016 8:54 am
Posts: 166
State: Texas
Country: United States
Focus: Repair
I found a little uke that needed saving. A 1972 Kamaka soprano. These ukes are some of the more reputable and they have alot of history with the company. If you don't know the history you should check it out, one of the more interesting things about the company is that alot of their workers who assemble the components and cut/carve the tops and braces are either completely deaf or extremely hard of hearing, they do it all by feel. That's pretty neat in my opinion.

Onto the patient, most of the issues are failed glue joints and poorly done crack "repairs" that involved just shoving glue into the gap with no clamping or cleats. Lots of cracks in the top, oddly enough no cracks in the one piece back. The top bookmatch is also coming unglued. The bridge is in good shape.
The finish has this weird light discoloration to it, I think it's french polished but I'll find out later (if someone knows for sure what they used on these feel free to chime in). I plan on either refinishing it anyway as the discoloration looks nasty and hides all that beautiful koa.

Neck likely will need to be reset but the body is in such poor shape that removing it right now would probably destroy it. I'll have to fix/reinforce all the issues here before I can move onto the neck. This uke barely weighs a pound, extremely light build and VERY thin wood.

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My plan of attack is pretty simple.
1. Remove the back (easy because it's already mostly come loose from glue joint failure)
2. Attempt to remove wood glue from largest crack to level top and allow me to add cleats (the largest crack is not level and this will affect the top negatively).
3. Cleat all cracks
4. Repair any other cracks/failures
5. Re-assemble body
6. Reset neck (if needed)
7. Refinish (french polish)
8. Setup

We'll see how it goes. Kind of excited for this one, these old Kamakas usually have a pretty good sound, and plus koa just looks great so I'm excited to see how this wood will look when it's all said and done.



These users thanked the author DanKirkland for the post: pat macaluso (Wed Dec 06, 2017 12:53 pm)
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PostPosted: Wed Dec 06, 2017 1:51 pm 
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Cocobolo
Cocobolo

Joined: Thu Feb 09, 2012 4:10 pm
Posts: 145
First name: Chris
Last Name: Reed
City: Stowmarket
State: Suffolk
Zip/Postal Code: IP14 2EX
Country: UK
Focus: Build
Status: Amateur
Here's a picture of a Kamaka neck joint (date unknown) from frets.com. I've read that for a period dowels were used, but I believe the spline is most common.

Image

If the joint feels sound I'd be tempted to set the neck angle when glueing the back on again (and those loose seams might well explain why the action is low, as they'd allow the neck to pull forward). In any event make a jig to hold the neck and top in alignment when refitting the back- once it is off you will find the body can flex quite a bit!

Players seem to like 2 to 3mm action at the 12th fret (2mm is distinctly low, 3mm a touch high but good for heavy strummers). Lower than 2mm is likely to buzz. On my own, light, builds the bridge tends to pull up about 0.5mm, so I aim at 3mm action before string tension and adjust down to 2.5mm at the saddle.



These users thanked the author profchris for the post: DanKirkland (Wed Dec 06, 2017 8:46 pm)
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PostPosted: Wed Dec 06, 2017 8:50 pm 
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Cocobolo
Cocobolo

Joined: Wed Feb 17, 2016 8:54 am
Posts: 166
State: Texas
Country: United States
Focus: Repair
Thanks for the picture chris. I plan to remove the back tomorrow and see what the damages are.

The neck is projecting very low so a reset is now for certain. At this point I think that having the body back together, stringing it to pitch and then seeing where the action sits will help me get a better idea of what is needed for correction.

I called Kamaka and they informed me that the finish on these is lacquer. I would like to do a nice french polish on it since there's quite a few bald spots. Any recommendations on removing the lacquer safely? I do not plan on sanding anything off of this little guy.


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PostPosted: Thu Dec 07, 2017 5:07 am 
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Cocobolo
Cocobolo

Joined: Thu Feb 09, 2012 4:10 pm
Posts: 145
First name: Chris
Last Name: Reed
City: Stowmarket
State: Suffolk
Zip/Postal Code: IP14 2EX
Country: UK
Focus: Build
Status: Amateur
On ukes the neck is usually built very nearly in line with the plane of the top, i.e. almost no neck angle at all. If the fretboard + frets is 4mm thick, and you want 2.5mm action at the 12th, this gives you a saddle top height of 9mm with no neck angle. Uke saddles usually peak10-12mm above the top.

If I were restoring this one I'd take a piece of 2 x 2 timber and plane one surface flat to lie against the fretboard (masking tape will hold it in place). I'd like my saddle peak 2.5mm above the bridge, and 6mm above the fretboard plane (to allow for the bridge pulling up 0.5mm), so I'd rebate the bridge end 3mm. Then I'd line up the back with the bridge pressed against my piece of timber and see how good a fit I got. You might find that it fits pretty well - if the back is slightly longer than the body, glue it in place and trim off the excess, and you've fixed the action problem.

It's rare for a uke to need a neck reset because the string tension is so low, so I'd expect the main cause to be that the body has moved as the back seam gave way. If I build a uke face down, i.e. attaching the top to the sides first, I can move the neck back and forwards a huge amount. It's the back which locks the geometry in place.

Looking at your pictures I'd guess the cracks were caused by humidity swings, so some of the top bracing may be loose. Correcting that will change things of course, so fix that first before considering the geometry of neck and top.



These users thanked the author profchris for the post: DanKirkland (Thu Dec 07, 2017 7:02 am)
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PostPosted: Thu Dec 07, 2017 7:49 am 
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Cocobolo
Cocobolo

Joined: Wed Feb 17, 2016 8:54 am
Posts: 166
State: Texas
Country: United States
Focus: Repair
profchris wrote:
On ukes the neck is usually built very nearly in line with the plane of the top, i.e. almost no neck angle at all. If the fretboard + frets is 4mm thick, and you want 2.5mm action at the 12th, this gives you a saddle top height of 9mm with no neck angle. Uke saddles usually peak10-12mm above the top.

If I were restoring this one I'd take a piece of 2 x 2 timber and plane one surface flat to lie against the fretboard (masking tape will hold it in place). I'd like my saddle peak 2.5mm above the bridge, and 6mm above the fretboard plane (to allow for the bridge pulling up 0.5mm), so I'd rebate the bridge end 3mm. Then I'd line up the back with the bridge pressed against my piece of timber and see how good a fit I got. You might find that it fits pretty well - if the back is slightly longer than the body, glue it in place and trim off the excess, and you've fixed the action problem.

It's rare for a uke to need a neck reset because the string tension is so low, so I'd expect the main cause to be that the body has moved as the back seam gave way. If I build a uke face down, i.e. attaching the top to the sides first, I can move the neck back and forwards a huge amount. It's the back which locks the geometry in place.

Looking at your pictures I'd guess the cracks were caused by humidity swings, so some of the top bracing may be loose. Correcting that will change things of course, so fix that first before considering the geometry of neck and top.


Thanks chris! Like I said in the OP I'm not going to pull the neck until everything else is fixed. That makes sense about the back seam, I think I'm stuck on thinking this through like a guitar rather than a uke. Thanks for the tips and advice. Regarding a jig to hold the neck and the back I'll come up with one once the cracks are taken care of.

I did get around to pulling the back late yesterday. Wasn't too hard since it was mostly off already. I used my soldering iron with a wet cloth as a spot steamer to loosen the glue joint

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The back brace literally fell off as I removed it, not alot of glue area on it to hold it in place. Did get a look at some of the previous efforts to fix the cracks. Not too happy, bigger the gob the better the job I suppose....

Also there's a few cracks near the neck block I didn't get pics of.

Image

For cleats I'm thinking that I'm going to want to keep them as small and light as possible. I'll be taking a violin approach with this one, level the cracks and glue in the cleats. Then thin them down and feather to my liking. The center seam has light showing through it so I'll need to address that as well.

Both of the top braces are in good shape, there's no looseness to either of them. The bridge plate is also in good shape if a little rough, but that's to be expected.


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PostPosted: Thu Dec 07, 2017 11:50 am 
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Joined: Sat Jan 31, 2009 8:50 pm
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Location: Seattle WA
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I wouldn't be able to resist carving those top braces!


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PostPosted: Thu Dec 07, 2017 12:29 pm 
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Cocobolo
Cocobolo

Joined: Thu Feb 09, 2012 4:10 pm
Posts: 145
First name: Chris
Last Name: Reed
City: Stowmarket
State: Suffolk
Zip/Postal Code: IP14 2EX
Country: UK
Focus: Build
Status: Amateur
Good luck. It should sound and play nicely once you're done.


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PostPosted: Thu Dec 07, 2017 7:57 pm 
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Cocobolo
Cocobolo

Joined: Wed Feb 17, 2016 8:54 am
Posts: 166
State: Texas
Country: United States
Focus: Repair
Thanks Chris! Let's just hope it comes together well. Still a learner with all of this.

Today was cleating day. Took a while to level the cracks, I ran an 8 gauge string through the biggest crack to clear away the titebond so I could actually level it out. The previous owner obviously just shoved glue in there and left it as is. I also had clamped the body to glue the center seam

The cleats went in well, I tried to keep them extremely thin and light on the center seam as well as the other 2 cracks. I left them thicker near the neck since that area seemed to need some help. I used hide glue on the cleats to save myself from waiting for an overly long time.

Image

I didn't get pictures of it but I also put together a little jig sort of deal to hold the neck in the proper place like you (chris) had suggested. It's more of a weighted rope thingy that pulls the neck *slightly* back and then I am free to clamp the back on with some cams and spool clamps. We'll see how it fared in the morning, it was annoying to try to line up the sides with the back without a mold. Any suggestions on an easier way to do that Chris? I ended up just taping them when they were flat and gradually working my way around the whole thing to try to keep it in line with the sides/kerfing.


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PostPosted: Fri Dec 08, 2017 6:47 am 
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Cocobolo
Cocobolo

Joined: Thu Feb 09, 2012 4:10 pm
Posts: 145
First name: Chris
Last Name: Reed
City: Stowmarket
State: Suffolk
Zip/Postal Code: IP14 2EX
Country: UK
Focus: Build
Status: Amateur
I don't know an easy way I'm afraid. You could nail some blocks to a board and then use wedges to push the sides in. But I'd probably use hide glue to gradually work round, using finger pressure and tape.


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PostPosted: Fri Dec 08, 2017 8:10 pm 
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Cocobolo
Cocobolo

Joined: Wed Feb 17, 2016 8:54 am
Posts: 166
State: Texas
Country: United States
Focus: Repair
The back went on succesfully, there's one spot where it didn't perfectly line up with the sides, I'm not overly concerned with it but I might correct it in the future. I ended up using fish glue to attach it since the extra open time made it easier to tape the back in the proper position.

I realized when I was gluing it up that I should've drilled some tiny holes in the back and used pins to mark where it was when it was attached, that would've made life alot easier instead fidgeting around with the back while taping it down.

I also decided not to strip the lacquer finish entirely since it contains all the patina. I thinned it down a bit with raw alcohol and then added some shellac on top of it (about 30 coats of a light cut, a little under a 1/2lb cut). It really brought the color back to the wood, the top has a decent amount of figure to it, not a bad thing at all.

I had contemplated filling the big crack with something like a burn in stick, but then I decided against it and simply decided to push a slight bit of fish glue in there. If I had filled it probably would've been more obvious than just leaving it be.

Strung up, it has a suprising amount of tone for such a TINY little body. I was worried that the cleats might muffle it a bit and cause it to sound tinny. When single notes are plucked there's a nice bloom of overtones. And from further than 2 feet away the big crack is barely noticeable, you'd have to look at it very closely.

Some pics of the final product. Thanks to Chris for the advice on this one.

Image

Image


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PostPosted: Sat Dec 09, 2017 9:02 am 
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Cocobolo
Cocobolo

Joined: Thu Feb 09, 2012 4:10 pm
Posts: 145
First name: Chris
Last Name: Reed
City: Stowmarket
State: Suffolk
Zip/Postal Code: IP14 2EX
Country: UK
Focus: Build
Status: Amateur
Nice job!


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