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OT - Isn't someone here a luthier?
 

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 4795
Location: Nashua, NH

8/28/21 8:08 PM

OT - Isn't someone here a luthier?

A friend brought me an ukulele with a cracked back (shipping damage) that she would like fixed. The crack follows the grain and I was able to push it back flush, so the only visible indication of the damage is the cracked finish. What's the recommended method of repair for this? My initial thought is to try to flow some thin cyanoacrylate wood glue into the damaged area from the outside, but I don't want to do anything until I get some expert advice.

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Sparky
Joined: 08 Dec 2003
Posts: 18166
Location: PDX

8/28/21 8:16 PM

CA glue is one way, what is the finish? And does it need to look as close to not repaired as possible?

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Nick Payne
Joined: 10 Jan 2004
Posts: 2529
Location: Canberra, Australia

8/29/21 2:46 AM

Have a look at https://www.youtube.com/watch?v=Q6782J_zJLs from a good luthier who has quite a lot of such videos.

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Andy M-S
Joined: 11 Jan 2004
Posts: 3266
Location: Hamden (greater New Haven) CT

8/29/21 5:04 AM

I'm no luthier, but I have done some work on my own acoustic guitar. My attempt to install a magnetic pickup in a too-small soundhole (small guitar, OO-size) broke a piece off inside the rosette, and I used Titebond hide glue for the repair, which is now invisible.

For the back, I might consider reinforcing things by gluing a thin strip of wood (like a coffee stirrer) over the inside of the crack. That will bind the edges of the grain, and applying the strip should force a little glue into the grain (be prepared for cleanup on the outside, if necessary).

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 4795
Location: Nashua, NH

8/29/21 6:40 AM

More details

I'm not sure what the finish is, but it's high gloss and pretty thick. I'll try to find an unobtrusive spot where I can test it with alcohol to see if it's shellac and lacquer thinner to determine if it's lacquer or a catalyzed finish that's impervious to solvents.

That video link was exactly what I was thinking of doing. Since it's just the back and should not be under any major stress, I don't think it will be necessary to reinforce it from the inside. Although the crack is very tight now, I wouldn't want it to buzz if the back shrinks at all.

The situation is that this uke was ordered through Amazon and shipped from China, but it's a $574 instrument, not junk (https://www.amazon.com/Snail-Ukulele-Vintage-Ukelele-Starter/dp/B07PQ848W7/ref=sr_1_1?crid=V1U02Y8X3QBJ&dchild=1&keywords=snail+ukulele+tenor&qid=1630240261&sprefix=snail++ukulele%2Caps%2C183&sr=8-1).

It wasn't properly packaged and arrived damaged. The seller replaced it, but doesn't want the damaged instrument back, so we'd like to make it functional, if not as pretty as new.

My plan is to stabilize the crack with CA, which should hide the finish damage as well. I'll probably try to buff it out somewhat, but I'm not going to get into refinishing it unless she asks for that, which seems unlikely.

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Sparky
Joined: 08 Dec 2003
Posts: 18166
Location: PDX

8/29/21 11:24 AM

"high gloss and pretty thick"

Polyester in good probability and should be cat finish as such most likely.

Sure is pretty!

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 4795
Location: Nashua, NH

8/31/21 4:49 AM

Thanks Sparky. I've got thin CA on order. I'll carefully scrape the glue level to minimize or eliminate the need to sand, but what would you recommend for buffing the finish? I've got 2000 & 3000 grit sandpaper, rubbing compound, polishing compound and various products for use on cars and boats.

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Sparky
Joined: 08 Dec 2003
Posts: 18166
Location: PDX

8/31/21 9:50 AM

Sounds like you know pretty much everything can be wet sanded and polished.

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