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crack across the grain


vlnclo
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Cracks across the grain are unusual, and serious. End grain does not glue well, so internal reinforcement will usually be needed.

That said, you have not posted a pic of the damage, so my reply can only be taken as general advice, and not necessarily specific to your problem.

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My guess is that Sheldon doesn't mean a break across the end grain, which would, indeed, be unusual and serious.  I think is he means a crack that runs perpendicular to the visible grain lines of the top.  The most common type of top crack is in a plane perpendicular to the plane of the ribs.  But he probably has a crack whose plane runs parallel to the plane of the ribs.  Because of the arching, this type of crack runs across the visible grain lines.   A picture would clarify.

If I'm right about the type of crack that he has, top removal is almost certainly required, because the clamping force to close the crack has to be exerted through the thickness of the top, rather than across its width.  Or maybe it could be clamped with magnets without removing the top.

Edit:  Sheldon, I wrote the above before I saw your pictures.  Now that I've seen them, I think I'm right.  But can you get a better-focused close-up picture of the crack?

Try pushing down gently on each side of the crack while looking closely at it.  Can you the see the crack open and close when you do this.  If you can't, the crack may have already been glued.

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6 hours ago, Sheldon Weiner said:

The crack lies under the tailpiece and about an inch from the bottom. The picture on the right is the best I could do and shows most of the crack. It's about a little over an inch long.

P1010217.JPG

P1010219.JPG

The pic is so blurry, it’s hard to tell what is going on, but from your description, it looks like the top has sheared across the endblock.

If that is in fact the case, this would be very bad news, at an area such as this which carries a huge load from the string tension.
You need to have this examined in person, by someone who knows what they are doing, as soon as possible.

 

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That area on the arching, on both ends, crosses a lot of grain on the curve, and can split with the grain. It would take a pretty good impact to crack it straight down, but not so much to split the grain.

If it's a split, a good luthier might be able to free up the top from the lower ribs, and glue and clamp the area. If it's an actual cross break, probably not, due to reinforcement needed.

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I'm afraid that I can't get a better picture of the crack. If I press down on both sides I don't see an opening. Nor can I see any distortion of the arch. However, if  touch the crack while bowing a string (a really awkward thing to do) it feels as as both sides are vibrating independently. 

I appreciate all your suggestions, but I guess the only safe thing to do is to have a luthier evaluate it.

 

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10 minutes ago, Sheldon Weiner said:

it feels as as both sides are vibrating independently. 

Not exactly sure what this means, but regardless, that is not a very good test for a crack. One would expect the part of the table glued to the block to feel different than the part not glued to it without a crack.

 

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Can’t see much from the picture but as noted this crack is most likely parallel to the length of the ribset. Did this just appear out of nowhere? Normally this kind of thing occurs from improper top removal of a top with grain run out. If that is the case there is a lot of glue surface. This should help with repair and if from top removal may already have been glued.

If it is a new crack that came out of nowhere then I haven’t got a clue.

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I just took it to a local repair shop where they assured me that it is just a scratch and doesn't go all the way through. That's a relief. I  really do appreciate the responses I got from all of you. This is a great source of of intelligent suggestions and information.

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42 minutes ago, Sheldon Weiner said:

I just took it to a local repair shop where they assured me that it is just a scratch and doesn't go all the way through.

Good.

Note: The ends of your tailgut under the tailpiece should be trimmed back because they can cause scratches.

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