Glueing a center joint crack with gap

[GeronimoM]

Hello!

I have a 5cm crack in the center joint by the saddle. Before glueing, there was a gap of about .2mm (2 sheets of paper). The gap does not want to close easily. Using the pillar and wedge method, and thick hide glue, I've managed to close it maybe half way. The gap is just about closed when seen from the underside, but still visible from the top. This suggests that the force created from the pillar method was creating a bit of an arch where the seam was tending to buckle upwards. 

This is a personal violin and I'm not concerned about appearance on this one. I just want to know if anybody has any opinion of strength and longevity of this compared to no gap. And any other suggestions on how to fix. I'm inclined to just glue on some cleats and close the body. Thank you

[Brad Dorsey]

I don't know of any good solution for this.  If you could somehow pull the crack closed and glue it, the top would tend to be distorted such that the widest part of the lower bout would contact the ribs before the block area of the top would contact the block.  Then pushing the top to the block would stress the top, possibly re-opening the present crack or starting new ones.

So, to avoid stressing the top, I think it's better to not try to close the full length of the crack tightly.  Possibly glue as much of the crack closed that will close easily, possibly fill the remainder of the crack (I don't know with what.), cleat the crack, and take solace that whatever you did would be covered by the tailpiece.

[Blank face]

Such gaps are usually resulting from a distortion in the lower belly wings. These can be corrected by damping the inside at this areas, maybe using layers of wetted paper towels for a certain time span, and the gap might close on it's own so that it's possible to glue and cleat it before it can reopen.

[David Burgess]

13 hours ago, GeronimoM said:

This suggests that the force created from the pillar method was creating a bit of an arch where the seam was tending to buckle upwards. 

This suggests that your wedging was inadequate. How many "dry runs" did you do to make sure everything was right before trying to glue it? In some procedures, painstaking prep and practice is key.

And as Blank face mentioned, various areas can be moistened or dehydrated to expand or contract as needed to bring parts together. Once solidly glued, they will tend to remain in that state.

[HoGo]

I use small wedge between the ends of pillars to align the crack so both inside and outside will close at the same time. BUt re-humidifying the plate is good idea before handling the crack.

[The Violin Beautiful]

Adding water to the surrounding area can shrink gaps considerably. Clamping with pillars can do quite a lot given time and careful setup. If after all that you still have a gap, I’d wonder if wood was just missing and consider filling it in with a thin strip. Again, only after exhausting other options. 

[GeronimoM]

Thank you for the suggestions! I'll try hydrating the lower belly with paper towels, see if I can close the gap, otherwise maybe a thin strip of spruce is the best route to go.

Edited June 15 by GeronimoM