I haven't posted any projects for a while and had this one come in a few weeks ago for back cracks, I thought would be season relevant. The instrument had not been humidified and dried out rather badly. There are 4 cracks in all with one that is stem to stern, ouch!
The obvious one, a crack in the upper bout where it looks like it also took a hit, center seam lower bout and at the lower bout at the bottom of the image that is a bit hard to see. I put a couple of large size Dampits in it, put it in a plastic bag and stuck it all back in the case. I let it sit for a week and a couple of days, everything closed up nicely.
I hadn't looked at anything else yet and had a few surprised inside when I got some mirrors in it to get ready for the crack repairs, hence the Trojan Horse topic title The back braces where all almost entirely loose from the back, which actually made the crack repair somewhat easier. I also discovered a nasty crack in the X brace. I called the guy, told him the bad news and discussed what might be possible, short of back removal and X brace ectomy.
The bandaid plan was to jack the brace closed and saturate it with CA, which I chose for it's great capillary wicking ability. Of course I had no idea if it would hold, given the vertical nature of the break but had nothing to loose tying. I used a turn buckle and a squeeze clamp.
You cannot rush this! CA is not instant and wood connections must be left alone for it to fully cure. I left this clamped up for a couple of days, hitting it with more CA each day, so I was quite sure all the CA that could get in there, did.
Using the Infra Red lamps to keep things warmed up, I first work in the water thin stuff and then follow up with thicker glue. I know it's gotten into the crack when I see it wetting the inside in my mirrors. Magnets, plastic cauls and LIGHT clamping pressure to keep things aligned.
I made a batch of Mahogany cleats for the back and installed 33 of them on this project.
As mentioned earlier, all of the back braces where loose and mostly off. That came after crack repair and cleating. I use magnets a lot for brace repair but you have to be extremely careful! I managed to get this all done with out any blood blister accidents..this time. I do one side of one brace at a time, I don't like pushing my luck.
At some point, someone thought it a good idea to slot the bridge pin holes but stopped after just cutting some very narrow slots. I could barely get some of the strings out without breaking them, they where wedged so badly in the tiny slots. One of them had a busted off one still stuck in there under a string. I cleaned the slots up as best I could and made them so you could turn the flute of the bridge pins away and correctly seat the ball end of the string on the bridge plate. I was at the mercy of what had already been done though and some of the spaces between the string pairs was not ideal but a least a person could change their strings without a battle every time. I did not spend the time I would normally making things look pretty if it was on a priority hit list, the owner's budget was wearing thin.
The White wrappings on the octave G string came stock out of the package of new, old stock GHS strings I had. I broke the .008" D'Addario tuning up and down to correct the action change from the X brace repair. It only lasted 3 tune ups but broke de-tuning it the 3rd time (Insert expletive here).
The work is all done ... front and back of this cool old Guild 12 string.
If at all possible I try to get the strings above or below the holes in the middle of the tuner post, not across the holes. The edges of the holes is the place where the string usually breaks. Not a bad idea to make sure that the edges are smooth with some steel wool or fine sandpaper before putting the strings on. Will take some time on a 12-string though! Tuners on a slotted headstock are safer, it's easy to make sure that the strings are resting on solid surfaces.
You must be responding about the .008" octave G string that broke during the final set-up. I always put many wraps of string on the post when I wind up plain steel strings or small diameter wound. It was well under the post hole and actually did not break there but somewhere between the nut and post. This is always a problem when doing set up work. The strings will be brought to pitch and loosened up several or many times before an action is dialed in. More often than not, as in this case, they break when you de-tune. I try when possible, to do the bulk of a set up using an old set to avoid breaking new strings, especially if it is an expensive set like Thomastic mandolin strings which are around the $40 mark. I didn't have that luxury on this project and I also didn't have a spare 8 lying around, so I put a 9 on it and of course pointed that out to the client.
I do it the same way, lots of tuning up and down! For me the string breaks at the string post most of the time :-)
Way to take down the Trojan horse Paul.