clamping conundrum

[otterly2k]

Hi all -
I could use some help figuring this one out--

I am working on a flat bodied mando for a customer. It is probably 1920's era, and has a very shallow body cavity and small soundhole. It came to me with a cracked top and inspection revealed cracked top braces -- which are transverse. It was easy to fix the ones closest to the soundhole, but for the ones further back, I'm having a hard time figuring out how to clamp it.

Problem is, anything long enough to reach the braces is too long to fit in through the soundhole-- there's not enough depth to allow for "swing" room -- kind of like trying to move a long sofa in a small doorway and around a corner. I've tried all the usual clamps-- cam, c, guitar bridge clamps - even the nifty StewMac scissor jack is too big to fit inside this little mando.

Your thoughts and ideas are welcome. This is an instrument with not a lot of monetary value, but it does have sentimental value to the customer. I think he and I are in agreement that major surgery (e.g. taking off the top or back) would be overkill in terms of expense. His goal is to stabilize the instrument to where it could be played.

thanks in advance
KE

[Bluetickhound]

Maybe you could fabricate something that would work with a miniature turnbuckle like so:
http://www.savacable.com/pages/prod_02_05.html

[belbein]

Hi all -
I could use some help figuring this one out--

I am working on a flat bodied mando for a customer. It is probably 1920's era, and has a very shallow body cavity and small soundhole. It came to me with a cracked top and inspection revealed cracked top braces -- which are transverse. It was easy to fix the ones closest to the soundhole, but for the ones further back, I'm having a hard time figuring out how to clamp it.

Problem is, anything long enough to reach the braces is too long to fit in through the soundhole-- there's not enough depth to allow for "swing" room -- kind of like trying to move a long sofa in a small doorway and around a corner. I've tried all the usual clamps-- cam, c, guitar bridge clamps - even the nifty StewMac scissor jack is too big to fit inside this little mando.

Your thoughts and ideas are welcome. This is an instrument with not a lot of monetary value, but it does have sentimental value to the customer. I think he and I are in agreement that major surgery (e.g. taking off the top or back) would be overkill in terms of expense. His goal is to stabilize the instrument to where it could be played.

thanks in advance
KE

Magnets?

Seems like the StewMac "experts" thing had something about this.

[otterly2k]

yeah, I think magnets might be where I'm headed next -- still looking for a clamping option if one exists

[Dale Ludewig]

Yes, magnets. Rare earth magnets are wonderful for this sort of thing. But you may have to do the job a little at a time. I've found that trying to get them into place can lead to some blood blisters and cursing if I try to get too many in at a time. You may have to make a caul of some sort that you tape to the magnet.

[rockies]

I have used a product called "friendly plastic" for this. It is a plastic (little beads) that can be put in hot water and then molded to a shape, cooled and then shaped if necessary with files etc. It can be used over and over, I have made a faux brace and shaped the plastic around it, embedded the magnets in the plastic, (2 stacked and pairs spaced (pair near each end of caul), make sure same poles are up) Cool and removed the cooled plastic caul from the faux brace. Now the difficult part, cleaning joint if brace is loose from the top and then getting the glue in. Then get the plastic caul in place on the brace and after putting some paper on top to protect finish put the magnets on to pull the brace into place. I usually us 3/4" magnets in the caul and have used 1" on the top. Hope that is understandable. Put the magnets down very carefully on the top, they can jump and really dent the surface, also can pinch fingers and cause blood blisters, don't ask how I know.
Dave

[Marty Jacobson]

Check out Frank Ford's "take-apart" clamp...
http://www.frets.com/FretsPages/Luth...ntedclamp.html

[J Caldwell]

Depending on the amount of accessible space you have available, wood wedges may be an option for the cracked braces. Make 2 wedges of the appropriate size, anchor the first one w/double stick tape and push the second one in on top of the first until it makes contact with the cracked brace and closes up the crack.

[Bluetickhound]

Now that's one for me to file away for future use myself! Simple yet perfect...

[Jim Garber]

I think that is a great name for a band made up of luthiers: "Clamping Conundrum". Thanks, Karen! Also, glad to see you are doing that luthier job. I still have the box of parts -- I intend to put it together one day.

[MikeEdgerton]

For magnets: Find someone in the computer repair business and pick up a few bad hard drives. Take them apart and you'll have the strongest rare earth magnets you'll ever find.

I'm reluctant to even talk about the other thing I've done in this situation but here goes. I actually forced a portion of a bicycle inner tube inside a mandolin when I couldn't reach the spot and inflated it to push up a loose brace. The down side is that if you inflate too much you'll explode the mandolin.

I'd go with the magnets.

[Magnus Geijer]

Something along the lines of a violin soundpost, with a Y-shaped top would probably be my solution. Can't beat a stick for simplicity.

[sunburst]

I agree. "Setting a soundpost" then clamping the outside of the instrument over the "sound post" works pretty well. I also like the two wedges idea though. Either way, clamping the outside of the instrument helps close the gap at the brace without stressing the structure of the instrument as much as just forcing something inside between the top and back.

This gives me an idea for a devise for situations like this... I'll have to think about this one for a while...

[Jim Adwell]

Some kind of adjustable jack for the "soundpost" would probably work...

[John Arnold]

I agree. "Setting a soundpost" then clamping the outside of the instrument over the "sound post" works pretty well.

I have glued hundreds of braces using popsicle sticks cut to the proper length and wedged in place. My exterior 'clamp' is often nothing more than two slats with holes drilled in the ends, coupled with spool clamps.

[pops1]

I have glued braces using a lever approach. I apply pressure to the end of a wooden rod thru the sound hole and it rises like a lever in the depth of the instrument to glue the brace in hard to get area's.

[Michael Lewis]

You also have to figure out how to get the glue in the right places, with minimal mess.

Oh, for magnets I have used K&J. Take a look at their web site and learn a lot about magnets, then order what you think you will need. Can't have too many magnets.

[otterly2k]

This community ROCKS -- these are some excellent ideas and I really appreciate the help! I have friendly plastic and some magnets, but I think I might try the popsicle stick / sound post method first... and you are right - getting the glue in there is going to be challenging too.

Thanks so much!
KE