Old uke repair

[old_picker]

Not exactly sure which is the best way to tackle fixing the split in this lovely old uke. Dates back to the 1920's as far as the owner can tell from her family history. It is beautifully built and weighs next to nothing. Seen a couple of these listed for sale at around the US$950 mark so well worth the repair apart from its history in the owners family.

There's a split in the top where it has lifted away from the edge which is pretty straight forward. The split in the back is quite wide and goes from the brace just behind the the sound hole right up to the leading edge of the front bout. Initially my idea was to glue a strip of blackwood veneer [cross grain] along the crack and attempt to clamp it through the soundhole using a flat brace above and below. I use tefflon to separate clamping cauls from glue seep. Once stabilised my idea was to fill the void with blackwood dust and glue then scrape and sand it flat. Possible refin on the back. I assume it is finished in shellac but it may be nitro. Any ideas?

I am hoping to effect the repair without removing the back but if I have to so be it.

Would be interested to hear any comments on my methodology.

Here are some pics firstly a couple showing the headstock logo and a shot of the inlay work on the fingerboard and then the damage. Looks like I may have to replace the bridge as well.

[blackalex1952]

Well I'll put my two bob's worth in. Bear in mind that I'm not the most experienced repairer here. Firstly, it's Koa wood, so you may get a match with blackwood. Someone here who uses koa might offer you a slither of scrap which you might put in with the wedge technique if you end up deciding to go down that path. I would not fill the gap with sawdust. There are many good videos of wedge repairing soundboards and backs on youtube.
The first step for me would be to rehydrate the instrument, which is very feasible as a uke will fit in a 20gallon bucket with a lid or a similar container. Even a plastic bag will do, and a little steam. If the gap closes up enough then try gently clamping the sides to see if the gap closes completely. If this turns out to be the case, some hot hide glue. If not, effect a crack repair with the wedge and the back in place. Double sided tape and a straight edge for wedging out the crack with a vee shaped scraper or knife. If you can completely close the gap with the clamping method after rehydrating, there will be minimum cosmetic work to do.
Then, to avoid taking the back off and/or for clamping in a centre seam, I would use pyramid cleats with the grain going at right angles to the grain of the back. Pyramid cleats have the following characteristics. They are light and strong. They can be positioned with a pointed piece of wire pushed into the apex of the pyramid, glue applied, then after positioning the wire can be quickly flicked out of the cleat, the vacuum formed by the glue holding the cleat in place. Hide glue helps even more if you hold a difficult cleat in place until the glue gells. (you can practice using a table cloth and a table fully loaded with fine china )
The worst case scenario is to remove the back and rejoin with a piece of koa wood in the crack and a centre strip or cleats on the inside. I am assuming that like all those early ukes it has no back bracing and is slightly arched? If the back does have to come off, and is arched, you may have to support the arch on some kind of dished arrangement in order to do the wedge neatly.
The bridge probably doesn't need to come off, as it looks in your photo to only be damaged where the first string attaches. So a little neat inlay of koa on the damaged bit or even a new piece the length of the bridge will deal with that. I would avoid adding too much mass to either the bridge or the back. Spruce, koa or blackwood cleats inside the back will be fine.
To test for a nitro finish use the cotton bud in nitrocellulose lacquer thinners test. It is most likely a varnish or french polish and a bit of shellac would be my method. For most finishes it sticks like the proverbial baby **** to a blanket. -Ross

[old_picker]

Thanks for the considered response. The back is slightly arched but there is one transverse brace just below the rear of the sound hole. The crack begins in front of the brace. The issue with this crack is that the back has warped around the crack and in elevation looks thus:



I'll try rehydration as a first step as suggested and see if I can pull things into a straight line from there.

[kiwigeo]

Is there a back seam reinforcing strip?

Cancel that...just noticed the crack is not along the join....

[old_picker]

Had a look for half an hour re wedge repairs and could not find anything specific. I have an idea of how it goes and seen info on it somewhere but where? Any one got a link?

I don't work on acoustic instruments often [pretty obviuosly] but its just wood only thinner bits.

[simso]

Well I'll put my two bob's worth in. Bear in mind that I'm not the most experienced repairer here. Firstly, it's Koa wood, so you may get a match with blackwood. Someone here who uses koa might offer you a slither of scrap which you might put in with the wedge technique if you end up deciding to go down that path. I would not fill the gap with sawdust.

I hope I have interpreted what someone has meant by wedge repair, I call mine splint repairs, the insert is wedge shaped, so I hope I am not mis-leading you by referring to it as a splint repair.

Had a look for half an hour re wedge repairs and could not find anything specific. I have an idea of how it goes and seen info on it somewhere but where? Any one got a link?

Link to a splint repair

http://www.mirwa.com.au/HTS_Splint_repair.html

steve

[blackalex1952]

Sorry Steve...splint repair is a more common terminology! My experience of warped backs is to do the repair in situ somehow and don't try to re curve old wood that has settled into that shape. I had a back on a high end guitar that had been left in the sun in a hot case (the usual reason) and as well as drying out, the foam liner in the case had bulged inward because there was an air bubble trapped. This meant that the guitar was sitting for a long time under pressure. No amount of re humidifying and clamping in a dished board would restore the back curve, so
I just re shaped the back braces to suit the new inwardly curved section and repaired. The guitar still sounded good. The end result was a shape similar to the shape in your picture. The client didn't want me to take the back off and put a new back on. A little heat from a heat lamp will soften the glue on the back brace, along with a thin spatula or a feeler guage to crack the join. The brace can then be re glued after the seam is repaired. Be prepared to make a new back if things don't work out. Scott Wise in Margaret River WA might give you a piece of Koa if you approach him. He make beautiful sounding ukes. There may be some forum users who will help with a splint at least. Also, don't use superglue because if the glue join fails you will have to buy some superglue remover in order to continue. That's why I like the traditional HHG. Another trick to mention, and I haven't watched simso's vid yet, is to use neodymium magnet discs inside and outside the cracked back seam to align the crack evenly. -Ross

[old_picker]

thanks for the tip off on the Koa. No binding on the back so it should come off reasonably easily with a bit of heat and a sharp knife if it goes that far. If no koa is available I have plenty of well dried blackwood.

I like the idea of neo magnets to pull up the cleats.

I wont be using superglue any where in this job - easy to get it on but if it goes wrong it is a cow do anything with.

[blackalex1952]

Just make sure you try repairing it in situ first. That figured and aged Koa looks great, I wouldn't be risking that authenticity on an old instrument. Every well made uke with Koa I have heard has an edge, to my ear, over all the well made Blackwood ones I have heard. So a new Blackwood back would be my last choice. Besides, if you can put in a wedge and cleats then re glue the braces it will be far less work. -Ross

[jeffhigh]

Without the instrument in hand, it is hard to say. Might be able to fix it without back removal, but it is not a big deal if needed. Try a clamp across the upper bout, does that close the crack?
I would NOT however be Hydrating it before repair. If you do succeed in swelling it up by super hydrating it and then gluing, you are setting it up for failure in the future after repair when it gets down to ambient humidity.

[blackalex1952]

I would NOT however be Hydrating it before repair

Jeff is probably correct. He is more experienced than I am. I suggested re humidifying after a maker I really respect had suggested that to me for another job. So far the "other job" has held up, but that is not to say it will stay that way.
I will stand corrected! All my past crack repairs I have done have been after taking the repairs down to 45%RH. That's one thing I like about this forum, some VERY experienced luthiers here, and they are kind enough to share. Good luck with that precious old uke! -Ross

[simso]

Whilst I understand peoples mind sets above on repairs, I personally never commence a repair without the instrument being hydrated correctly to start with

Steve

[blackalex1952]

I try not to be caught by mindsets, and assume people, including myself, actually know what they are talking about...I am fascinated by wood movement relative to building and repairs, a healthy discussion on this forum, probably a new topic, would be most valuable to us all. I have some information in the form of the wood databases which include the radial and tangential shrinkage data and also the book "Understanding Wood" by Hoadley. Experience in repairing is what many of us lack. I recently had to repair a guitar re build where the soundboard and neck were the only parts left after a serious accident. So I had to make new back and sides. The problem that occurred was that the guitar had lived a rough life humidity wise, and this was exacerbated by a fault in my dehumidifiers sensor which caused the sound board to sit in storage in the dehumidifier at a very low RH. This caused the braced top to curve radically upwards, along with some glue creep as the braces had curved as well. The soundboard was also of course, sealed because of the lacquer on one side only. I have a chronic health issue which necessitated the long storage time as I had to take a break for a while. I should have clamped the soundboard into a radius dish for the process anyway, which I later did in order to effect the repair and will now do in cases like this in the future. I actually posted questions regarding this on this forum and received some good answers.
So I thought about it a lot and did the following.
I took a radius dish and placed some stickers across it, which allowed for the bridge which was still attached to clear the dish. Of course this changed the radius slightly so I chose a suitable dish to allow for the correct radius on the soundboard face. I then placed the over dry soundboard in a plastic bag and introduced a little steam, sealing it up. While that process was going on I wrapped my go bar deck in plastic with a plastic sheet as a "door". Inside the deck I mounted 2 heat lamps. I could also introduce steam if necessary to raise the wood moisture content. Cycling the soundboard through a humidity regime was an option. Then when the soundboard had absorbed some moisture overnight, I placed it on my modified radius dish with the go bars very gently sprung on the braces but nor stressing the soundboard with a full bend. I then carefully monitored the RH and temperature within the deck with the heat lamp on and slowly brought the RH back down and the surface temperature up so that the glue had a bit of a chance to "creep" between the braces and the plate. I did this very carefully and increased the go bar tension gradually until I had the whole thing conforming to the radius dish. Then I turned everything off and left it all in the dish to re humidify to ambient humidity in my workshop, leaving it for a couple of weeks while I did other jobs including the back and sides construction. Before I removed the dish and soundboard I took the RH back down with one lamp. I then checked the soundboard and had made a lot of progress, to my great relief! I ran a feeler guage around each brace, checking the integrity of the glue joins. I was very careful during the process to keep the surface temperature conservatively low, hoping to get the glue to move without failing. Not sure if this affected the clue, the creep being one of speculation only, but I did get a result. So the soundboard was then clamped into the dish for storage and placed in the recently repaired and re calibrated underbench humidity controlled storage at 45%RH for another week. The process worked and the guitar is now stable and rebuilt, sounding better than new, according to the happy owner. I re used the old back braces with the new timbers and then tuned them using the Gore/Gillet methodology and Visual Analyser to get the body back and soundboard resonances into a good working relationship. I guess luck had a lot to do with this repair! Repairs are the most scary aspect of luthierie that I know of!HA HA!
I recently made a silly mistake, and told a fellow more experienced luthier. He said "You won't make that mistake again". I answered, "NO! I'll make a completely new one and learn from that!" -Ross

[jeffhigh]

Whilst I understand peoples mind sets above on repairs, I personally never commence a repair without the instrument being hydrated correctly to start with

Steve

Hydrated correctly, yes
If it has been in a very dry situation
But at the moment RH along the east coast is pretty high and chances of it now being in a dry state in Old-picker's workshop would be pretty remote.
Superhydrating it deliberately would just leave it vulnerable to future shrinkage and cracking.
If the crack won't close with low clamping force a splint will be needed

[old_picker]

I have no idea in what conditions it has been stored - probably warm and dry - _ i added some steam to a plastic bag and bagged the uke for 48 hours - it has hung in the neck cupboard in the workshop since debagging it. My workshop holds between 50- 60% humidity most of the year round. Should be ok for repairs next week.

[old_picker]

Epilogue
I thought I should post back the results of the job.. The only photos of the finished job were on my phone and they do leave a little to be desired. I apologise for that.

The main objective here was to turn it into an accessible instrument for a beginner [the grand daughter of the original owner]. The value as a collectible instrument was not a high priority dictated by its intended use and the budget available. The original tuning pegs were long lost. The tuner holes were out of round and very close to the edges of the < 6mm thick headstock. To work they needed to be reamed to fit a set of pegs. For a learner I guessed that a set of friction fit tuners would be very difficult to manage. There was a distinct danger of splitting the very thin head stock due to the paucity of material around the holes. If the collectible status was a high priority I would have referred it on to a colleague who is well versed in repairing old instruments.

The crack repairs were glued with Titebond original. The main crack was done with a strap of blackwood veneer built of four strips of alternating grain making a strap of approx 2.5mm, It was carefully clamped with a shaped caul through the sound hole. A real monkey puzzle getting it lined up right with my primitive guitar sized clamps.

The damaged bridge was notched out leaving a 2mm strip of the original wood at the front incluiding the original saddle and the bottom. A notched piece of Blackwood was glued to the original wood. Colour matching was not real great but mechanically it worked very well. This was the trickiest part of the job.

I decided to use a set of Grover heads which I aged a little to match the uke and attached using a method many of you will view as a bit of a travesty. Long story short I could tell young Kate was very happy with the job by the smiles as she heard a few clumsy chords ring out around the workshop.

It has a bright and cutting tone that would be heard from a good way off. Exactly the ticket when standing on the beach with a dozen players greeting friendly visitors coming ashore. Unfriendly visitors would be hearing a different sound which would have nothing to do with ukuleles.

[kiwigeo]

Nice work Ray....

[routout]

Gota love the rope binding age related.

[Mark McLean]

That worked out a treat. There is not mush point having it "authentic" if it is not playable. This looks like a great outcome.