The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Reply
 
Thread Tools
  #1  
Old 05-21-2017, 01:12 AM
jared1177 jared1177 is offline
Registered User
 
Join Date: May 2011
Location: Norway / Alabama
Posts: 340
Default Cocobolo split repair

I bought this Cocobolo set a few years back. Had it shipped from South America to here in Norway. With the humidity differences the back pieces began cupping and warping extremely.
I then noticed that where it was cupping was already what appeared to be cracks going through the wood, and the seller mentioned the cracks were just outside the perimeter where the cutoffs would be, but the crack indeed went from top all the way to bottom.

I soaked both in water and then set them under a heavy machine that flattened them back out. I let them sit there for a month or two. When I took them out they had flattened, but the one side slowly began to cup up again where the crack was. I slowly pried down on the crack to investigate it more and noticed it was barely hanging on together so I went ahead and cracked them apart.

What are some ideas of how I can salvage this set and still use it? I don't want to throw it away.
If it had the crack a bit closer in to where the middle seam joint would be then I could make it into a 3 piece back of some kind, but being with it located on the outside of the body it makes it a bit awkward.

I've thought about matching the other side with it and splitting it in the same place, and then put purfling pieces and make it into a 4 piece back.

Where the crack happened no wood was lost, but obviously putting it back together properly I would need to plane them and make a proper glueing surface. There is still slight cupping on the smallest piece that I could probably get to flatten back out, just haven't tried.

I have not sanded them down yet and are 5mm thick.

Would it help to make them thinner first before joining back together or doing anything? I think it could help make them more flexible.

What say you?








__________________
2013 Jared Booth OM - eurospruce/mahogany
2014 Jared Booth 00 - europspruce/rosewood
2015 Jared Booth 00 - sitka/mahogany
Reply With Quote
  #2  
Old 05-21-2017, 01:52 AM
dekutree64 dekutree64 is offline
Registered User
 
Join Date: Nov 2009
Location: Kansas City, Missouri
Posts: 1,263
Default

Make it into a 4 piece back. If one half split, the other will be prone to it as well, so go ahead and cut it in half now.

Then flip the pieces so the flatsawn area is at the center seam and the outer edges of the lower bout, and cut away as much of the center flatsawn wood as possible for the width of guitar you want to make. Could add a narrow center wedge (like 1") matching the binding wood to get rid of even more of it.

Or don't cut the other side in half, and make a harp ukulele. It would include a bit of the split prone wood, but I think it would be outside the waist at least, so it might be ok.
Reply With Quote
  #3  
Old 05-21-2017, 03:03 PM
John Arnold John Arnold is offline
Registered User
 
Join Date: Jan 2009
Posts: 4,082
Default

I would just joint the crack and glue it together with no purfling strip. With minimal material removal, the reglued crack should be invisible, or nearly so. I would not do the other half unless I determined there was a crack there, too.
If necessary, I reinforce the joint on the inside with a cross-grain strip. Make it from a dark colored wood so it is not visually distracting.
The crack probably occurred because the board had a surface check due to improper seasoning. After resawing, this crack was in the outer slice. This is a very common issue when resawing dense hardwoods. Ideally, the checked wood is planed or sawn off first........before sawing the 'keeper' slices.
BTW, the warping is often another symptom of improper seasoning of the board. After resawing, the outer slices tend to warp the most, due to the stresses from drying.
Reply With Quote
  #4  
Old 05-21-2017, 06:54 PM
redir redir is offline
Registered User
 
Join Date: Aug 2011
Location: Mountains of Virginia
Posts: 7,657
Default

I would try and rejoin it too. I've done that a few times that I can remember. When you thing about it, it's not really any different then joining a back any regular way and when done right it will be stronger now.

Having said that, that board seems to want to misbehave. Making a 4 piece back just might be the thing to have it settle down.

If you use cutoffs from the same board as a back strip for the repair it will be nearly invisible.
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Thread Tools





All times are GMT -6. The time now is 04:43 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright ©2000 - 2022, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=