Franks side bulge jigs question

[onewent]

Greetings ... a while back, after seeing the idea on Franks .com site, I made a number of similar aluminum jigs to push bulged sides back in line with the top for regluing.  This approach has mostly worked.  However, a stubborn guitar with a birch body got over cranked and the force split the side, causing unnecessary damage (my guitar).  I'm currently working to reglue about a 10" section of another birch bodied guitar and have it jigged up.  I've cranked to the point where the bolts are harder to turn and I'm hearing stress noises from the body and am now worried about another cracked side.  (See photo)  The bulge extends the side only about a sixteenth, but I just can't seem to get it to line up..I hardly move it a thirty-second with the jig force.  The guitar is supported by a series of the same jigs on the opposite side.  Any ideas re the jig set-up, and other suggestions to close the gap?  ..thanks, Tom

[Thomas James]

I am wondering if the top has shrunk?

[Eric Steven Johansen]

Flat sawn birch, it probably has shrunk. Happens a lot when the side is loose for a while. I'd try rehumidifying for a while and concentrate on the inside top upper bout (warm moist shop towels are my choice). Keep the joint lightly clamped to avoid warpage.

[onewent]

Top shrunk, makes sense.  So humidify that top bout area of the top?  ..but keep the joint clamped shut?  ..thanks, Tom

[Eric Steven Johansen]

I lay the dampened towel against the inside area of the top that's shrunken, over the course of several days, changing the towel now and then, to rehydrate that section, and when it's as close as it'll go I glue her down. The clamping I am referring to amounts to binding tape. Just enough pressure to keep things from distorting.

[harrison phipps]

I think you will get the shrunken top to move easier and further if you loosen the inside brace located just above the soundhole.

[George Roberts]

Wood tends to shrink much faster across the grain than in the same direction as the grain.  An antique table or desk top that has a "breadboard" cleat across the end, will show as much as a 1/4 " or more difference in shrinkage from "across the grain" as compared to "with the grain."  This difference is much more pronounced with new wood, or wood that has not had adequate aging or drying.  In terms of guitars, mandolins, ukeleles, etc. the tops tend to shrink laterally more than the sides do in length.  The result is that the sides are then too long to fit the top.  Trying to force them together is usually frustrating and unsuccessful.  Unfortunately, the solution is to shorten the sides, or widen the top, neither of which is a desirable option. 

By the way, I love your jigs and clamp set up.  I worry that it is like Cinderella's sisters trying to make the slipper fit.

George

[nathan clark]

Looks like you have plenty gluing surface between the top and lining. Have you considered adding binding to solve the problem?

[William F.Eden]

I think if it were my Guitar I would do what Nathan has sugested .That is what I do all the time and if just bindings are not enouf I would add some purflings as well, alwas works for me.Bill...........

[George Roberts]

I think Nathan's solution is brilliant.

George

[onewent]

I've not done anything to this guitar as yet, still thinking through options.  I see the theory involved in the humidify solution, but I've done this with other birch boxes and all kinds of weird distortions happened to the body.

Binding is out of the question.  Although a perfectly practical solution to the problem, it raises another significant issue, the originality of the guitar.  Although it's a cheap Harmony from the 30s, this color scheme (Green Duco) is extremely rare (at this point to my knowledge, the only one), thereby adding 'value' beyond its humble place as a cheap guitar where alterations bear no consequences.

Appreciate the insights and ideas .. am leaning toward the humidity idea, and releasing half of the upper brace, since this brace was loose anyway, giving credence to the idea that the top shrank rather than the side bulging.  I already reglued the brace, but can undo it if needed.  Tom

[Eric Steven Johansen]

As a dealer in vintage instruments I'm with you on the no binding idea. Loosening that upper brace would definitely help and, as I've pointed out earlier, securing the edge of the top to the sides will keep the top from becoming distorted. Add moisture slowly and be patient. I once repaired a Gibson L4, where the back had an open crack that was 1/8" wide at the widest point, using the rehydration method. It took two weeks for the crack to close, but once glued and cleated, it's still closed to this day.