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PostPosted: Tue May 07, 2024 2:43 pm 
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Walnut
Walnut

Joined: Thu Sep 19, 2019 4:56 pm
Posts: 31
First name: Daniel
Last Name: Russin
City: TUCSON
State: AZ
Zip/Postal Code: 85743
Country: US
Focus: Repair
Status: Amateur
I ordered this tenor uke for my wife, and it arrived with a big dent in the box and this nice pair of soundboard cracks. The seller is sending a replacement and I get to keep this one. This will be my first crack repair - I've just done nuts and setups and electronics so far. A free instrument seems like as good a place as any to learn, and this one has fresh clean cracks with easy access to them.

Tentative game plan:
- Humidify, to see if the cracks close at all. They don't move with reasonable hand pressure right now.
- Crank the neck back so the soundhole crack lines up? Or perhaps this will line up if it closes w/ humidity.
- Reglue the popsicle brace that's got to be loose.
- Simple titebond glue-up and small cleats, similar to Frank Ford's instructions here: http://frets.com/FretsPages/Luthier/Tec ... crack.html

The cracks don't extend past the bridge, which is not loose.

Does that seem reasonable? What am I overlooking? If the cracks don't close, am I stuck trying a spline? Hoping to avoid that...


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PostPosted: Tue May 07, 2024 3:43 pm 
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Contributing Member
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Joined: Sun Mar 06, 2011 12:04 am
Posts: 5789
First name: Chris
Last Name: Pile
City: Wichita
State: Kansas
Country: Good old US of A
Focus: Repair
Status: Professional
First things first - humidify.

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PostPosted: Tue May 07, 2024 4:22 pm 
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Koa
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Joined: Mon Oct 17, 2011 4:10 pm
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First name: Bob
Last Name: Gramann
City: Fredericksburg
State: VA
Zip/Postal Code: 22408
Country: USA
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And, release the string tension.


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PostPosted: Tue May 07, 2024 4:34 pm 
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Walnut
Walnut

Joined: Thu Sep 19, 2019 4:56 pm
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First name: Daniel
Last Name: Russin
City: TUCSON
State: AZ
Zip/Postal Code: 85743
Country: US
Focus: Repair
Status: Amateur
Already done - they are still on the instrument but floppy as can be!


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PostPosted: Tue May 07, 2024 6:14 pm 
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Brazilian Rosewood
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Joined: Fri Aug 19, 2005 4:02 am
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Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
I don’t think rehumidifacation will help here but it certainly won’t hurt so you can do that first if you want.

I have repaired several guitars with this damage. When you get a crack along the side of the fretboard and the rosette becomes misaligned the neck become a loose hinge and has pivoted up, raising the action. Clamp the body to your workbench and then place a clamp on the end of the neck, pulling it down until the rosette parts line up. Now start gluing up the cracks. You can probably close up the soundboard crack with a couple of clamps across the body. See if you can get some glue under any loose braces, especially up around the neck block. I usually add a few small spruce braces wherever I can in this area to prevent future reoccurring breaks.


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PostPosted: Wed May 08, 2024 5:10 am 
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Old Growth Brazilian Rosewood
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Joined: Fri Nov 02, 2007 9:49 am
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Location: Ann Arbor, Michigan
First name: Hesh
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Was the dent in the back or front of the box this looks like it was crushed.

Some info on how we use humidity to close cracks. Sure we can force a lot of cracks closed but if they don't stay closed in normal RH after that we have a lot of stress on the repaired crack and are only encouraging a new crack to happen perhaps next door or on the other side.

So we will humidify at 75% for up to three days (bag with car wash sponge in the bottom and we have put hygrometers in there too so we know what the RH is). Then, and this is the part that I rarely hear of others doing. We remove from bag and let it acclimate for a couple days at 45% RH. Really bad cracks tend to open back up and that's when we might fill instead of force it closed.

This one looks like a candidate for filling but rehumidifying is certainly worth a try.

Filling of course can be wood but there was a technique that someone at Elderly pioneered that we have done now many times on inexpensive instruments (the repair is suitable for the inexpensive stuff) where we fill with a quality epoxy that is dyed to match the wood. Works great. I don't do these Dave does so I don't have the details to share or I would. I do know that for wide open, big cracks he uses strips of BJR (back joint reinforcement) inside the box to hold the epoxy in place.

But the real point of my post is if you have to force a crack closed you are only encouraging a new crack to happen somewhere else. So keep that in mind as you humidify and consider your approach.

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These users thanked the author Hesh for the post: Kbore (Mon Jun 24, 2024 5:47 pm)
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PostPosted: Wed May 08, 2024 9:22 am 
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Brazilian Rosewood
Brazilian Rosewood

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Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
Rehumidification will not close the crack alongside the fretboard. That will need a clamp across the upper bout.


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PostPosted: Wed May 08, 2024 3:52 pm 
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Walnut
Walnut

Joined: Thu Sep 19, 2019 4:56 pm
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First name: Daniel
Last Name: Russin
City: TUCSON
State: AZ
Zip/Postal Code: 85743
Country: US
Focus: Repair
Status: Amateur
Thanks all - just got back from a trip so will be bringing it home with me today. I will bag it up and re-humidify first and see where that gets me!


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PostPosted: Fri Jun 14, 2024 12:28 pm 
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Walnut
Walnut

Joined: Thu Sep 19, 2019 4:56 pm
Posts: 31
First name: Daniel
Last Name: Russin
City: TUCSON
State: AZ
Zip/Postal Code: 85743
Country: US
Focus: Repair
Status: Amateur
Reverb wanted me to send it back, seller is just a drop shipper so didn't care...took a while to finally get sorted so now I'm working on this.

After humidification, here's how it looks. The neck side crack has aligned perfectly, and the bridge side is completely invisible. I am unable to get any feeler gauge between any brace and the top, even pushing down a bit.

I tried to work some titebond into the cracks, and I'm about 75% sure I was not able to get any in there. Kind of the opposite problem I was expecting to have. Out of the humidity baggie now so we'll see what happens.


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These users thanked the author Melt in the Sun for the post (total 2): Kbore (Mon Jun 24, 2024 5:47 pm) • Chris Pile (Fri Jun 14, 2024 2:01 pm)
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