I glued and cleated the cracks and glued the loose brace using hide glue - the hot kind that you mix up from flakes the day before. It is more trouble to use than yellow glue, epoxy, or super glue, but has the advantage of being totally reversible with heat and moisture, so that if I screw up it can easily be removed, or if the repair fails it can be re-glued with the existing glue just by heating with a moist cloth warmed on an iron and then letting it cool.
The next day I strung up the guitar as a 6 string tuned to concert pitch and within a few minutes the brace that had been loose broke in half (I guess it had a weak spot). It was about 10 pm so I just went to bed and glued it the next day, also sandwiching the joint between two new strips of wood the depth of the brace and about 3/32 inch thick (cut from a scrap from a guitar top left over). I let the glue cure overnight and this time strung it up with all 12 strings, tuned down 1 whole step to D. It lasted a few more minutes this time and then the fret board and the section of the top right below it shifted about 1/8th inch toward the bridge. I hadn't noticed, but I suppose in the break the previous day the 2 cross braces under the fret board had come loose at that location (under the fret board); at any rate they were loose now. I pulled the 18th fret and drilled 2 holes through the fret board and the wide cross brace beneath, shaped 2 ebony pegs, added hide glue and tapped the pegs in, then put the fret back and re-glued the cross braces to the top (at least around the edges) where I could get hide glue in.
After curing overnight, this repair failed just as before, with the fret board and the section right below it shifting toward the bridge (the piece of the top directly under the fretboard has cracked on both sides and can move independently from the rest of the top).
I was stumped so I went and asked a local luthier for advice. After bringing the guitar up to tension he immediately concluded that the heel block had become separated from the guitar body, and suggested removing the neck and rebuilding the block. I had not expected to have to do such a drastic repair, but figured it would be a good learning experience since I had read about the procedure but hadn't done a neck reset before. However, I kept wondering how the center section of the top was moving (while the outer part of the top wasn't) when it was now solidly attached to the wide cross brace that spanned the width of the whole top. I didn't see how the problem with the heel block could explain this.
I looked at the braces more closely and noticed that the wide cross brace had come loose from the outer section of the top on one side; I further noticed that only this side of the center section was moving, i.e. the center section was pivoting, held in place on the other side but moving on the side where the wide cross brace was detached. Aha! I thought. I wedged a small piece of wood under the loose part of the brace to hold it away from the top, and put as much hide glue into the opening as I could, then heated the area with a hot moist towel to make the glue runny again and let it cool while holding the joint in place.
The next day when I strung up the guitar to partial tension it still moved, but not as much. Even though it was not tuned up fully to D, I thought I was on the right track, and figured maybe I just didn't get enough glue in the joint. So I drilled a small hole in the top over the brace and put hide glue in the hole. And I glued a 3/32 inch piece behind the wide brace, butting the other side against the brace by the front of the sound hole, to act as a stop to keep the wide brace from moving. But the "sistered" pieces I had glued on to fix the broken sound hole brace protruded so I stopped the piece where these started, which happened to be just at the edge of the crack in the top (it would have been better to fit a piece and span the crack, to double the effect of the wide brace). So just in case, I glued a similar piece between the wide brace and sound hole brace, under the fretboard, hoping that it spanned to the other side of the crack enough to serve this function.
After the glue cured and I tuned up, the center of the top only moved about 1/16th of an inch and held for 6 hours, before I detuned the guitar. In this condition the guitar was quite playable, and sounded good. But I could still see that the center section was moving, changing the neck angle slightly for the worse, and buckling the far side of the sound hole some. I figured the luthier was right, the heel block was detached from the sides of the guitar. When I checked I found that this was true. Also I saw that even the far side was moving, but the heel block was not detached on that side so the effect was different. I'm thinking that this may be caused by the loose side and may go away if that side is fixed.
But I'm still hoping to avoid removing the neck (since the guitar does not need a neck reset, the neck angle is good if the joint holds). So I pulled back the binding at the top and heel joint and put hide glue in the small opening, then heated and let cool. I don't know if I got enough glue in the joint to do the job; maybe I will end up having to pull the neck to really fix it.
That's a lot of work! Pretty interesting! Is that pick guard part of the repairs or did that guitar come factory like that? Looks nice, and of course how it sounds is the most important!
ReplyDeleteIt's a replacement, but it's the factory shape (I could tell by the glue residue). Doesn't quite fit the outline, but it's only a millimeter or so on the side by the bridge where you can see the glue from the old one showing. Some of the factory ones were single ply (this is 3-ply with a nice black/white stripe on the bevel), but some must have been thicker because I've seen pictures where they where attached with screws.
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