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Fixing a waist “crack”
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=51828		 Page 1 of 1
Author:  SnowManSnow [ Thu Apr 18, 2019 12:12 pm ]
Post subject:  Fixing a waist “crack”
I’m not sure what to call this anomaly ... I guess it is more of a figure split.
The wood in question is highly figured sapelle. On the inside of the waist the wood has lifted along a figure. It isn’t all the way through or anything like that, but I’m not sure the best way to keep this from running (although I don’t think it would)
I don’t have an actual pic since I’m at the office, but here is a genuine hand drawn sketch of what I’m taking about.
What would you do to mitigate this damage?
Thanks
B
Image


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Author:  sjfoss [ Thu Apr 18, 2019 12:41 pm ]
Post subject:  Re: Fixing a waist “crack”
Snow,

Superglue and a caul (with wax paper). Hand hold it until it dries, then sand it back to invisibility. Make sure you tape off whatever you don't want to get glue on.

The presumption here is that the 'crack' has the wood fibers all still there, only needing some persuasion to go back into place. From the drawing it appears to be on inside of the bass sidewall; not too many people ever look there.

Steve
Author:  SnowManSnow [ Thu Apr 18, 2019 1:02 pm ]
Post subject:  Re: Fixing a waist “crack”
sjfoss wrote:
Snow,

Superglue and a caul (with wax paper). Hand hold it until it dries, then sand it back to invisibility. Make sure you tape off whatever you don't want to get glue on.

The presumption here is that the 'crack' has the wood fibers all still there, only needing some persuasion to go back into place. From the drawing it appears to be on inside of the bass sidewall; not too many people ever look there.

Steve

That is the location yes.


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Author:  Woodie G [ Thu Apr 18, 2019 1:27 pm ]
Post subject:  Re: Fixing a waist “crack”
Keep in mind that thin CA will tend to soak into mahogany, sapele, and other relatively porous woods, and that can result in some differences in how the repaired wood and the wood around the repair takes sealer and finish. You might take some of the scrap material from the side or back to allow assessment of whether your intended filler will show any sort of visual mismatch. Based on our experience with sapele, khaya, and genuine mahogany, epoxy wets out without showing evidence of previous CA repair, while tinted pastewood filler may or may not show the previous CA repair, depending on the degree of penetration of the CA.

Something to think about.

Other options are to work with hide or fish for the repair, using rare earth magnets to ensure sustained clamping pressure over the time period.
Author:  profchris [ Fri Apr 19, 2019 4:37 am ]
Post subject:  Re: Fixing a waist “crack”
That looks to me like runout, separating as part of the bending process. I've been there!

I'd be tempted to sand it smooth and then glue a thin laminate on the inside to make sure it doesn't open up further. Not CA, as others have mentioned, in case it runs through to the outside. If you use an offcut of the same wood and feather the ends, it should be practically invisible through the sound hole.
Author:  bluescreek [ Sat Apr 20, 2019 2:17 pm ]
Post subject:  Re: Fixing a waist “crack”
no ca here wax paper and wood glue will do fine. I use my spreader and mold to close them
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