Questions on repair - reattaching partially-detached back

[mreidsma]

Last week I picked up a late ‘70s Ibanez 518, a nice little solid wood A-style, from Goodwill for under $100 with the original (and nearly mint) hard case. In the photos from the listing, I could see that the top of the back had come loose, but for what I paid for the mandolin, that wasn’t too worrisome. Of course, caveat emptor when buying from Goodwill: they neglected to mention that the rest of the back had been sloppily glued back on by what appears to be Elmer’s glue. I couldn’t see that in the photos, and the description mentioned a reglue but I assumed they were talking about the loose area. Ah well, it’s a beautiful mandolin!


Here’s the bottom with the mystery glue. It might be hard to distinguish from the wood, but that’s because everything there is white glue. There were no close ups of this seam in the listing. Sigh.

It was clear that the back had come mostly loose sometime in the past, prompting the mystery glue job. The trouble was, the back was glued on after the sides had come out of shape, so the sides stick out at several points around the mandolin.

I set about to remove the old glue, so I could get the sides back into shape and get the back to fit again. the treble side of the mandolin is still glued up, and I am trying to keep it that way. I figure it will be easier to get the sides back in shape if I have at least one side already attached properly. If I gently put pressure at the tailpiece, I can move the bass side in and the back lines up all the way around. This leads me to believe that I can make a jig that will hole the sides in place while I glue the mandolin up. I picture something like a jig for building a mandolin and holding the sides in place while you glue the back on, shaped like the back so that the sides will line up. I’d use hooks attached around the jig to do the string clamping trick to hold the back down. But I’m getting ahead of myself!

I’m slowly removing all the glue. I suspect it’s Elmer’s - it is very white, and it softens in vinegar. I don’t really want to use vinegar to remove it because (as I’ve read here) now instead of glue in the wood I have an acid. So it seems like another problem to deal with. Gentle heat from a heat gun and scraping with a small bookbinding palette seems to be the best method of removing all the glue. I’m going slow and trying to avoid heating the polyurethane finish. After a few days or working here and there, I’m about half way around the opening.


Here’s a shot of the inside where you can see the glue removal.

The mandolin came from central Florida, so high humidity and hot. Maybe that contributed to the glue failure? It’s now in Michigan, so high humidity in the summer and warm, and freezing and what feels like negative humidity in the winter.

So I’m trying to figure out a few things, and have a few questions. A few things to start with:

First, I have built several instruments, so I’m comfortable working on this myself and seeing it as a learning experience. I only say that because the first post to any question is always “take it to a professional.” If this were a nicer mandolin, I would do that in a second. But I have less than $100 invested in this non-historically significant instrument, and I’m okay if it becomes a repair lesson!

1. I can scrape the glue off down to wood, but won’t there still be glue in the pores? Does that affect the glue I choose to use for the repair? Can I get it out?
2. Should I glue this up with HHG? My wife is a book binder and we have a HHG pot in the bindery, about 15 feet from where I’m working on this mandolin. I also have original Titebond, but I am not looking forward to scraping white glue off in this comes loose again.
3. Is there a better/different way to realign the back and sides when this happens? I couldn’t find a lot on the forum on what to do when the sides don’t line up. Just a lot of warnings not to let it happen.

Thanks again for the great advice and tips that have been put here over the years. Really helpful to get me started.

[rcc56]

You can make a temporary mold out of lots of things. On a recent back replacement, I used piece of rigid insulation board. The fit doesn't have to be too precise-- you can insert a shim in a loose spot if necessary.

Elmer's is a polyvinyl glue and it's a pain in the neck to remove. You might be able to glue some sandpaper to a thin piece of wood or metal, and use it as a sanding block inside the joint if there is enough room. The more of it you can get out of there, the better, because the glue wicks into the pores so much. I am reluctant to use any solvents when removing polyvinyl-- sometimes the solvent just drives the stuff deeper into the pores.

Hide glue sticks well to a freshly scraped wood surface if the pores are not sealed. It also sticks to itself fairly well. It does not hold on contaminated surfaces. I doubt it will work here unless you get down to really clean wood.

I've used vinegar, but only a couple times. In both cases, the old glue was hide glue, and I got a good joint with new hide glue. I do not know whether it will do you any good here.

Titebond Original is an aliphatic resin, not a polyvinyl glue. It will stick to surfaces that are not perfectly clean. Cured Titebond is soluble in both water and alcohol.

If this was my job, I would probably use Titebond, even though I am inclined to use hide glue more often than a lot of other people. Whatever you use, get the joint as clean as you can. If all else fails, you may have to loosen the back further so you can clean the joint up really well.

[mreidsma]

Thank you, great advice! I love the tip about about the rigid insulation board, I never would have thought of that. But of course it makes sense it would be strong enough. I’m on another forum where folks built campers out of that rigid insulation and not much else.

I’ll keep cleaning and plan on Titebond for the glue joint once I get things clean and a jig made. Thanks again for the help!

[sunburst]

It might make things easier to just go ahead and remove the back completely. Cleaning the glue would be easier and thus probably more thorough, and it will have to be realigned to be re-glued anyway.
Lots of people have designed and made jigs to align rims with plates. Frank Ford has a good system on his website Frets.com.
Here's a jig a quickly threw together many years ago to align a rim. I figured I'd make a better one eventually but this one works so well that I've just kept using it.


The screws used for forcing alignment are ground flat on their ends and I use scraps from mandolin sides for pads between them and the rim. I can drill new screw holes wherever I need them.

[mreidsma]

John, thanks for those photos - that’s sort of what I had been thinking (my idea was significantly more crude) but your ground off screws solve the problem I was stuck with, which was how to put specific pressure in certain areas. And thanks for the tip on Frets.com - it was my first stop but I didn’t catch the title the first time through. For anyone else looking, Frank’s side compression test page has his very slick set up.

I went ahead and took your advice and removed the back completely. The sides didn’t change, and it will be so much easier to remove the glue. I seem to remember a thread where someone asked if anyone had removed the back on a PacRim mandolin, so I’ll put some photos up later.

I grew up next door to a luthier in Holland, MI, and I continue to be amazed by the creativity of ever luthier I have met. And generosity! Thank you all for sharing your ideas and experience.

Thank you again!

[mreidsma]

Okay, so I got the back off. It was only held on by about 4 inches, so it wasn’t hard. I was able to clean up the rest of the glue much more quickly than when I was trying to work through a narrow crack. Here’s some photos of the inside of the mandolin. While the marketing materials say “hand carved” top and sides, the grain leads me to believe they were pressed into shape, with some carving around the f-holes.





And here’s the back, now free of rubbery white glue. This was kbviously pressed and not carved:



Personally I think the flaming looks better on the inside.

I started building a jig that will let me gently push the sides back into shape so I can reglue the back. I have a lot of the pieces cut and ready to assemble, but I’ve glued up leather scraps or felt on the areas that touch the mandolin. Hopefully it’ll rain as predicted this weekend and I’ll not be able to do that yard work and wil instead have to stay in the shop and work on this jig.

[rcc56]

Make sure you observe the neck angle when you reassemble-- taking the back off can cause changes in geometry which might not be noticed until it's too late if you don't look for them.

[multidon]

Hah! That kind of tells you how much stock to put into the claims of “hand carved top” !

[mreidsma]

Here’s the catalog page: http://www.ibanez.com/anniversary/ex...t_id=361&now=4

Note it says “hand carved” top (where no doubt someone used a machine to thin around the f-holes) and just “carved” for the back. So maybe Ibanez says “carved” when they mean “pressed.” Or maybe they called the press that shaped the plates “Carver.” If you put something through Carver then it’s been carved!

I did have trouble at first identifying whether this was a 517 or a 518, and saw similar confusion in previous forum posts. In case someone else has the same question in the future: the 518 has the violin-style purfling on the body and on the headstock. The 517 has black binding on the body only. (The 517 also has laminate sides and back, but this is an easier way to tell.) Here’s the catalog page with the 517.

[bennyb]

If you've got a thickness gauge, you could check the thickness at various locations. I would expect a pressed top to be relatively uniform thickness; however, I don't have reference for that - just seems logical.

[j. condino]

The ribs pop so often on old vintage Gibson A mandolins that I have a deicated jig just for alignment.

j.
www.condino.com
facebook at condino string instruments

[mreidsma]

The top and bottom are uniform thickness, with the exception of the areas around the f-holes, which are slightly thinner thanks to the “carving.”

I’ve got the mandolin in the jig, and have done a dry run getting the back to fit and using the string “clamps.” I need to make a few modifications to the jig to get a perfect fit, and then I’ll be ready to glue the back up. Right now it’s in the jig after I glued up a loose end on the bass-side brace.

Mine was missing the paper label. Anyone have a photo of a mid-70s Ibanez label? I feel like this is my chance to make a replacement label. If not, it can go back together without it, but I figured I should try.

One last question: any problem leaving this in the jig with the strings holding the back down for several days? Heading out of town and I thought I’d glue it up before we left so I’m not tempted to tinker with it while it dries!

[mreidsma]

I just looked at several photos of other similar era Ibanez mandolins and am convinced that there never was a label. You can see most clearly here in fd’s Ibanez: https://www.mandolincafe.com/forum/a...9&d=1495234111

I also found a thread that mentioned a 517 by the original owner and he said it had no markings except the headstock, which I assume excluded the label.

[mreidsma]

We’ll, it’s in the jig all glued up. Now I wait! I don’t think that the back is lined up perfectly 100%, because there is a 1” spot where I think it overlaps by a half a millimeter, but I’m going to call that close enough. Thank you everyone for all the advice! While I wait I’ll service the tuners and clean and buff everything else. Once I’m back from vacation I’ll clean and level/dress the frets, fit the bridge, and string it up! I have a few sets of strings on the way, including some monels that I am excited to try.

[mreidsma]

Well, I glued the mandolin up earlier this week and after 24 hours pulled it out of the jig. I cleaned and lubricated the tuners, which had 40 years of fuzz and dirt accumulated in the gears, and then polished all the gold plated pieces. After reassembling, I leveled the frets and took off just enough to take care of some divots on the treble side in first position. The. I dressed the frets and polished everything up with some 600 grit sandpaper and 0000 steel wool. Then I cleaned everything and put some lemon oil on the fretboard and broke out a new set of J74s.


Here’s the back joint after glueing.

I had planned on waiting until after we returned from a short trip to string it up, but I couldn’t wait. I set the intonation, and from the darker finish left from where the bridge had been for the past 40 years, it must have been hard to play. The bridge was about 3/8” closer to the fretboard than it should have been. The action on this mandolin is super low, and it has a sweet, rich tone that surprised me for a Pacrim mandolin. It is all solid wood, though. I’ve played it for a few hours and I don’t want to stop. MAS is fun, but playing a mandolin you worked hard to repair and bring back to life is an even better high than just getting a new mandolin.


Here’s the finished mandolin, with a strap made by my Dad.

Thank you again to everyone for the advice and encouragement! This is such a great community.

[Jeff Mando]

Good job! Enjoy it!

[William Smith]

Its always fun to fix an ugly so called duck or even modify one!, I've done a few mods on 30's Gibson A models with F-holes, let Randy wood do a few on some 30's F-7's as that was out of my league so to speak. I had one of those Marlboro guitars from some years back that between my parents and others was able to get 2 guitars and only cost 50 bucks each with all the miles, not bad. I gave them both away, one to Dad-he sold it for some quick cash, and the other to my cuz.. anyway I enlarged the sound hole "Clarence" style as we are both nuts about his playing, I scalloped the braces and put a real nice old tortoise style guard on it, a little set up and not bad sounding at all when done. FUN!