Re-gluing loose brace

[whistler]

At a rehearsal a two days ago, I took out my mandolin, to find that the action had suddenly dropped, to sch an extent that there was a buzz on every note and some notes above the 7th fret did not sound at all. It did not take long to work out that a soundboard brace had come loose. I have traced this to what seemed at the time to be quite a small knock about a fortnight earlier (I had not played this mandolin during that time). The mandoling in questtion is nothing valuable - a laminate-topped, oval-holed 'A'-style, bearing the name 'Harmony', probably built in the early 70s - but it excelled in its playability and, with the addition of a piezo transducer, has served me very well as a gigging instrument over the years. So I think it is worth the trouble of repairing it.

I have repaired loose braces before on larger instruments (guitars and basses). The problem in this particular case is accessibilty - the soundhole is small and partly obscured by the fingerboard extension, so there is no chance of getting in with my hand. The brace that is loose (the only brace in the whole instrument, in fact) is of the transverse kind, under the bridge. Since there is a 10th fret neck-body join, this is a long way from the soundhole.

I have been trying to think of possible solutions, and the easiest would seem to be taking the back off. But I would like to avoid this if possible. Can anyone offer any tips on how to do this job through the soundhole?

[sunburst]

It can almost surely be glued working through the sound hole. You'll probably have to make a tool to use as a "prop" between the back and the brace to clamp the brace back to the top. One of the easiest things to do is cut out a piece of wood, sort of "L" shaped, so that you can insert the short end of the L through the hole and use the long end of the L to lever it into place between the back and the brace. It usually takes a little time, trial and error to get the angle and length's of the "arms" of you L right.
You'll also need a small inspection mirror, sort of like a dentists mirror, and a way to get some light inside the mandolin.
Once you have your clamping mechanism figured out and practice putting it in place until you can't go wrong with the process, then you put some glue under the loose brace (syringe with tubing, palette knife, whatever you can think of to get the glue back in there) and "cam" it into position.
For a laminate top and an inexpensive instrument, I'd probably decide to use epoxy to glue the brace.

First things first though. I assume you have already taken the strings off of the mandolin, but since you didn't say you did, I'll say... IF you haven't already done so, remove the strings.

[brunello97]

Just a few days back Frank Ford posted a step by step process of repairing a sunken top on a Gibson A. Some fo the methods would probably be helpful for your process. Have a look:

http://www.mandolincafe.net/cgi-bin....t=44483

Mick

[dave17120]

Hi Whistler, it's eminently possible, just fiddly........ and when you have those fretboard extensions partly covering a small sound hole as well, doubly so!!!

Having said that, I thought a photo of my 'interior tool kit' might help..... no high-tech stuff here I'm afraid! The only flash bit (other than the light that is!?!) is the little screw-thread 'wotchamacallit' from Stew Mac, which I have found the easiest way to keep pressure on the brace while the glue dries.

Hope that helps a bit, Dave

[BlueMountain]

Sunburst knows immensely more about this than I do, but I'd rather use Titebond than epoxy. If you to want to use epoxy, I'd suggest that before you try it on your mandolin, you mix up a batch (30 minutes or 1 hour epoxy, not 5 minute, please), let it sit 24 hours, and see if it sets hard and cures. I bought a pint of 30 minute epoxy from Tower Hobbies--usually a good source--mixed it carefully, and glued on two tone bars on a cheap laminate mandolin. Three days later the epoxy was still sticky. A week later, still tacky. I ended up peeling off the epoxy--easier than I expected--it was a lot like taffy--and reglued with Titebond. No problem. Held just fine.

I assume that I got a bad batch of epoxy, as I tried another repair with this epoxy, with the same result.

[Antlurz]

Yup. Epoxy might be the ticket, but as stated above, I'd check out a bit of it before hand to make sure it's not a Monday morning or Friday afternoon batch.

Many epoxies are still gummy after a long time. Don't buy the cheapest stuff.

Ron

[Frank Ford]

This is a standard job at our shop and we do 'em all the timeon old Gibsons. #Quick and easy once you get the hang, and the fingerboard extension generally is no problem. #This is the only special tool I use:





The Rest of the Story

Now, your Harmony is likely to be more problematic, but if you can get a clamp to reach all the way down there, you can certainly make a long gizmo to deliver the glue, maybe a long thin palette knife, or just a blade soldered onto a wire.

[whistler]

Thanks, everyone for all your advice so far (more is welcome!). I've been away from home for a few days, but I'll start putting some of your ideas into practice when I get back tomorrow.

John (Sunburst) - Why would you use epoxy for this particular job? I think I'd be more comfortable using Titebond, as it's what I'm used to - and I try and avoid epoxy where possible, anyway, as it causes a slight skin reaction.

I already have the dentist's mirror, and a little long gooseneck light. The problem would just seem to be getting everything - mirror, light, tools and glue - in through the soundhole at once, and still having the room to manoeuvre. But I'll keep trying until I succeed.

Thanks again.

[sunburst]

I was considering epoxy because of it's long open time, (the time you can work with it before it sets to much to be reliable) because it is likely to stick pretty well to whatever wood is in there, clean or dirty, or to any glue if there is any delamination of the top where the brace has pulled loose, and because it is a pretty good gap filler and is therefor forgiving of a poor fit (the possible cause of the joint failure).
Titebond will probably give you enough working time if you practice your clamping procedure and can work smoothly and efficiently. It will probably stick well enough too. Epoxy just takes the time pressure off of you.