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Jeff White

Can't close a center seam

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I can't close this seam separation, so I'm thinking (looked up old MN posts)of laying strips of cloth along each side of the opening to hydrate the wood and subsequently close the opening.  This was something Michael D. mentioned at some great length in a post.  Jeff H. (and others) mentioned on an old post about using pillars to pull it together in conjuction with the hydration.  Question I have is:

     How do I hydrate the area well enough to close it, without messing with the ability for the pillars to stay on (because of the hydration and subsequent failure of the pillar to back jt)?

 

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I have the exact same issue with a very nice violin. The back has been separated so long that the wood has reacted to moisture adjustments as TWO SEPERATE HALVES instead of one joined piece. Not sure what to do yet.... but building up pressure in them by forcing them back together sounds iffy. If they are overhydrated to a point that they "swell" back into proper alignment... and are glued that way.... when the over hydration evaps wont that cause ALOT of built up energy to pull on things...(that aren't supposed to be pulled on)???
Im simply stating a question because I don't' understand

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Jeff, it looks like that might pull together with pillars, without hydration. The danger of moistening with strips of cloth is that it can badly curl or distort the arching, which looks pretty good right now from the photo.

 

If you wanted to make the back a little more plastic to assist in getting things together, you could apply some pressure from the pillar clamps, and put it in a high humidity environment for a week or so, and see what happens. Sometimes multiple humidity cycles will allow further "creep", enough to take much of the stress off the joint.

 

Hullguitars, the first thing I notice is that the purfling seems to be holding the joint apart a little bit. That will probably need to be taken out of the way. This also might be a case where slight wood removal (chalk fitting) at the lower block portion of the joint will allow things to come together, without stressing the heck out of them.

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Jeff,

Is the back separated from the end block? If not, I'd consider the possibility of separating the endblock and a couple inches of rib from the back to give it a little more wiggle room to close. It looks like the separation goes all the way to the edge.

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I have an old English cello to do next year. The back has been open for years and both sides have curled in dreadfully. The wood is thick and very strong. I've never done one as bad and I'd appreciate any suggestions as to how to straighten it out.

Thanks. Conor

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Conor, I've never had one this hard to get together.

 

 Jerry, man, you don't miss a thing.  Yes, I removed wood in that area so as to be able to pull it together.  the 1/2" area at the edge was hitting way before the center and I couldn't get it together.  In order to rough it out, I carefully pulled sandpaper straight through there until it was parallel, figuring I would then chalk the final area for fit.  Problem was, I could barely get the area together, and when I do, the area further away from the edge won't budge.

 

David, I am also concerned about the curling because the two sides currently are pretty similar(can't completely tell as I can't bring them together). Humidity??? Really.....I live in California. :rolleyes: .  I was  going to try the pillar clamps (a bit more lengthy in the distance from the crack for strength), but noticed Jeffrey H's and  Michale D. talking about moisture in an old post.

 

Hull, yeah, I'm a little concerned about the pressure too.

 

Doug, It's been separated from the block, all the way almost to the CB's in order to help.

 

I can get the edge to touch with pressure, but that center won't completely close.  I'm going to try my original thought and just put on some pillars, have nothing to loose.  David, I like the idea of pressure over time.     jeff

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Would it be heretical to suggest slipping a carefully made and selected plane shaving into the joint to fill the gap, and just accepting a little visibility in the final result? That might allow the violin to be put back into service without building stress into the joint.

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Heretical, no, but I am not sure that isn't a last resort.  No matter the amount of touch up, it would be somewhat obvious on a maple back.  Much easier to get away with it on a spruce top, though usually less neccesary to do it to begin with.  I have considered that, but really don't want the scar as there is no way  "I" have the skillset to hide that on this varnish.  But, I'm not ruling it out in the end.   jeff

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It sounds like the geometry of the straight line join between the two plate halves has changed, or never was proper since it was made. It's possible that originally it was glued under stress, and over time stress won the fight over the glue bond.

 

It's not fun a fun job, but perhaps to get it right the back needs to be removed, the join cleaned up with a fine set plane on a shooting board, and re-glued. You'd be removing barely any wood, just enough to make the join dead-straight again.

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It sounds like the geometry of the straight line join between the two plate halves has changed, or never was proper since it was made. It's possible that originally it was glued under stress, and over time stress won the fight over the glue bond.

 

It's not fun a fun job, but perhaps to get it right the back needs to be removed, the join cleaned up with a fine set plane on a shooting board, and re-glued. You'd be removing barely any wood, just enough to make the join dead-straight again.

Yikes, this is a 60's Pfretzschner and there is no way I'm putting that much work into this. :blink:   Just economics on my end.  I would go with Mark and plane a shaving in there before I would do that.  I think I can get it pretty close with the "time, and pressure of the pillars" method......(maybe mixed with some....humidity).

We'll see.  jeff

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