Loose tone bar

[mandobassman]

I have a cheap Johnson MA-120 that I bought to hang on the wall for when I want to play something quickly and don't want to pull out the Breedlove from behind the couch. It didn't have a bridge on it when I bought it (for $40). I picked up a bridge from Elderly and after fitting it, I was amazed at the sound from this cheapie. The bass tone from this mandolin is nothing short of stunning (no exaggeration). I soon discovered the top was sinking on the bass side and looked inside with a dental mirror and, yes, the bass tone bar is coming off at both ends. I have two questions.

First, I have the proper clamps to put inside the F holes but I would like to know what glue to use and what is the best way to apply it.

Second, since I've never seen this situation before, I am wondering if the low end is so responsive because the tone bar is loose, and will it change the bass response when I glue it? I would hate to lose that tone. I have been playing it for a couple of months now and it is holding tune, so I don't think it is getting any worse.

Any advise is surely appreciated.

[multidon]

It will be interesting to see what is said when our resident experts chime in. As for me, I think that a top that has been properly carved should not sink, period. The tone bars are not really for support, but for sound. The support for the string tension actually comes from the proper arch of the top. Now X bracing is a different story, I believe that helps support, but not tone bars. This is evidenced by the mandolins out there that have tops with no tone bars or bracing. They are good mandolins and they were made that way for a certain sound. You can try glueing the tone bar back but I don't think that will solve the basic problem which is, your top has sunk and changed its shape , most likely permanently, because it was carved too thin.

[mandobassman]

I recently read a newsletter from Roger Siminoff about that very subject. He also says that tone bars are nor for support (hence the name "tone bars"), that they are inappropriately called "bracing". But in some cases they tend to be supportive as well. In any case, I have read about sunken tops being fixed by clamping and re-gluing the bars. If nothing else, I'm hoping that by re-gluing, I can prevent it from collapsing altogether. I am most interested in what effect it will have on the tone, because right now the tone is better than any cheap mandolin has a right to sound.

[Big Joe]

A good wood glue like titebond is sufficient. Clean the area as best you can, then apply the adhesive and clamp it. Leave the clamps on overnight. That should take care of it.

[multidon]

If you do decide to try glueing the tone bar back I would think it would only enhance the tone, not detract from it. The tone bar making better contact with the top would mean better distribution of vibrations throughout the top, hence more volume and tone. In fact, if you let it go, it will probably get worse and maybe develop a buzz, which I'm surprised you don't already have. I did not mean to sound discouraging in my previous post. If it were mine, I would try re-glueing it for sure. On an inexpensive instrument, there is nothing to lose so might as well try it. I totally agree with Big Joe about using Titebond. The luthier's best friend! So much easier to work with than HHG. Make sure you use some type of caul on the outside to protect the top from damage. I would use a palette knife (available from any art supply store) to carefully scrape out the old glue as much as possible, then apply a thin layer of Titebond to the same knife and use that to work the glue into the gaps. Clamp overnight as Big Joe says. Good luck! Let us know if it is successful.

[mandobassman]

Multidon, I did not take your comments as discouraging at all. I appreciate constructive comments, positive or negative. I am an experienced player and know what's involved here. This is a cheap mandolin and while most would wonder if it's even worth it to bother with repairs, I must say this mandolin is most definitely worth it. The response from this thing, especially the low end, is stunning. My biggest question was about the best way to apply the glue, working through the F hole. I'm certainly not even thinking of taking the back off. I read a recent thread about a similar situation on MandoHangout. One of the resident luthiers there suggested he un-string it and clamp it (without gluing) for a couple of days because sometimes the top will come back up on it's own. If it does, then glue it re-clamp overnight and it should be good. Does this first step seem necessary? Also, is there a way to pump glue through a tube or something like that. Would that be easier than a palette knife? Thanks for everyone's help.

[Lee Callicutt]

http://www.frets.com/FRETSPages/Luth...andobrace.html

[multidon]

Thank you very much for that FRETS link Lee! I had not seen it before but I was extremely happy to find out that the procedure I gave is substantially the same! I'm doing my victory dance right now...

[mandobassman]

Well, I did the repair. I seems to have worked pretty well. There is still a very small bit of the end of the bass tone bar nearest the tailpiece that is still up slightly, But I got the majority of it and it looks like it is holding. The top did come up a little bit, so it is not sunken as much as it was before. It was hard to tell but when I put the strings back on I didn't have to have the bridge raised as much as before and is much more even now. Before the repair, the bridge on the bass side was nearly twice as high as the treble side to keep it level with the fingerboard. I applied the glue with a very skinny syringe from one of my son's old medications. Worked nicely. I wasn't able to get the clamp as close to the end of the tone bar as I would have liked, which is probably why it didn't glue all the way down on that end. Overall, I am happy with the result. I was mainly interested in making sure it didn't get any worse. Thanks for all of the help!