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Repair of Alvarez Yairi DY57 Acoustic Guitar
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Author:  johnparchem [ Tue Apr 23, 2019 12:23 pm ]
Post subject:  Repair of Alvarez Yairi DY57 Acoustic Guitar
A friend of mine (a professional bass player) tripped over his knock around guitar and cracked the neck right off. I do not think these are worth a fortune but he did like the guitar. When I looked at it, I though I could quickly get it in playable condition but I thought I would run my plan by you guys to set me straight. He does know that the repair will be visible.

Although it looks bad, I have the pieces and can put them back together and keep the neck alignment in place. Looking at his saddle perhaps improve it.

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My thought is to clean up the old glue on the poor glue job on the neck block extension, I can tell only part of it was joined, and reglue it and the broken heal block with a structural epoxy. I would use fish glue or titebond hide glue to put the top back together. I thought of using hot hide glue but I really want the open time to get every into position as it is a 3D puzzle piece to fit in. Both the fish glue and the titebond hide glue are cleanable.

Once in and clamped (no glue yet) It looks like I can do a reasonable job of keeping things in alignment with the same neck angle.

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Author:  B. Howard [ Wed Apr 24, 2019 6:40 am ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
Lots of long grain to glue on the top, that's good. The head block and heel will be the trouble spot and as you can see 70% of the original glue did nothing in that area. I might opt for some small dowels in there to hold it together.
Author:  philosofriend [ Thu Apr 25, 2019 11:26 am ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
When it came time to glue it I would have my clamping cauls made so that I could put on the two outside strings and tighten them just enough to be straight. The cauls can poush down in the middle of the fretboard between the two strings. I don't want that glue to set up unless I am positive that the neck alignment is perfect: side to side and neck tilt both. Looking at how the two strings align on the neck and the action height would tell me if I needed to loosen the clamps a bit, shove the neck into better alignment and retighten the clamps.

After that first glueing dried I would glue in many light spruce splints with their grains going across the separations. Other spruce triangles could be glued in at the corners. If I make it a little stronger than when it was new, without adding much weight, it won't be coming back to me to fix again.
Author:  Barry Daniels [ Thu Apr 25, 2019 1:08 pm ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
Fish glue would give you the longest open time. The long grain of the breaks will certainly be to your advantage. But getting all the joints to close will be a challenge. Will be interesting to see how this one turns out.
Author:  Hesh [ Thu Apr 25, 2019 6:56 pm ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
I didn't read any of the posts but wanted to point out that there is no saddle left AND someone has already filed in string ramps. As such this thing has a poor neck angle (before it broke) and likely will have the same poor neck angle when pieced back together if a neck reset is not done.
Author:  dpetrzelka [ Thu Apr 25, 2019 7:47 pm ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
I would be tempted to separate the neck and heel from the body and top piece - this would allow for easier handling when gluing the body back together, and set you up for doing the neck reset that, as Hesh pointed out, likely needs to be done.

Separating the neck will also ensure you are not fighting the weight of the neck when glueing that top/body piece back on. You can really take care to align the grain and get a good clean glue-up.
Author:  Barry Daniels [ Thu Apr 25, 2019 8:22 pm ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
That is a good idea, Daniel.
Author:  johnparchem [ Fri Apr 26, 2019 1:09 am ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
Thanks all, for the suggestions. I decided against a few of the options because I just could not put the time in it. I found nice used versions of this guitar for about $500. I did decide that I was not going to give it back without a decent bit of saddle showing at a good action. I kept with my decision to use structural epoxy for the neck block and I used titebond hide glue for all of the non structural work. Both gave me a decent amount of working time to get things right. I mocked all of the clamps and played until I was able to have a straight edge from the first fret to the current short saddle with an action of about 1 mm. I use the first fret instead of the nut as it results in an action that is closer to the result when strung up. Anyway my reasoning was that going from 1 mm to 2.5 mm of action would add 3 mm to the saddle. Part of the damage when the neck broke off was a missing wedge of mahogany just at the transition to the heel. That missing piece was enough that even when all clamped up the weight of the head stock and tuners pulled the neck back a touch and gave me the exact neck angle I wanted. Here is the saddle with 2.5 mm action for the low e. The E string is 12.5 mm off the top. The action could be lowered to 2 mm if he wants.

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To illustrate, I actually switched to a straight edge when I checked it for the real glue up.

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Here is where the wood was missing I already filled it with a mahogany patch and have started finish repair

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I never promised an invisible repair, the guitar has plenty of scratches and pick gouges so it was not too hard to do a repair that sort of blended in. Well at least the guitar really plays well.

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Author:  SteveSmith [ Fri Apr 26, 2019 7:46 am ]
Post subject:  Re: Repair of Alvarez Yairi DY57 Acoustic Guitar
Nice work. Always feels good to take a broken instrument and turn it back into a player.
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