Old Potato Bug Mandolin project

[Jerry Ryan]

I just accepted this project to restore an old potato bug mandolin. I plan to simply clean it up, retain original finish. Tuning machines are good, just need to replace one button that is missing, or all buttons, depending on what I can find. The separated section is all there, just needs to be glued back in place. Clamping will be the trick. Has anyone had a similar odd clamping project?

Jerry Ryan

Inland Nebraska

[Ned Knepp]

Jerry, I've been kicking this around all day and the only thing I can come up with besides gluing blocks to the outside on either side of the separations and using them as clamping points is to make a set of body forms that can be cut in two and used as to clamp the body into shape. I don't THINK you need  will need to support the inside too much,based on the little bit of experience I have with these but you should definitely ( as I'm sure you will) do a careful dry run to insure that things stay in alignment.

I think I would make a board to support the body, face down with a wedge to support the lower face so that I could concentrate in the back and not be concerned about distorting things too much. If you did this, maybe you could use some straps to pull the body joints tight. 

[Jerry Ryan]

Ned:

Thanks for the input!  Good points to consider and will post the outcome!\

Jerry

[Frank Ford]

Before you stress out working on a complex clamping arrangement, it would pay to spend some time with a roll of masking tape to see if  you can align and dry clamp it all back together.  By pulling the tape tight, you can often accomplish a seemingly impossible job in just a few minutes.  Those glue joints usually aren't under a lot of stress so gluing and "clamping" with tape can work quite well.

[Jerry Ryan]

Thanks Frank! good point. I have also had small miracles happen in applying pressure in odd places with rare earth magnets.

Jerry

[Eric Steven Johansen]

The bowl back shares several characteristics with wooden barrel construction so when moistened it creates its own clamping pressure. My process is to apply a liberal amount of hide glue to the joints, clamp with tape, and then apply boiling water with a brush through the soundhole to the inside of the joint. Let it sit for a day and then clean up the excess glue with hot water on a cloth. Haven't had one fail yet. 

[Jerry Ryan]

Thanks!  Will post the results!   Jerry

[Dave Yelverton]

Totally agree with Frank. I've just completed a job on a bowlback where about 30% of the joints were separated. HHG + Stewmac's binding tape did the job perfectly. Just one caveat: if the joints have been apart some time, it's usual for distortion to have occurred. It's a good idea to do careful dry runs before finally glueing.

Good luck!

[Jerry Ryan]

Thanks! With the advise from here...I have a plan.  Jerry

[Jerry Ryan]

Finished it!

[Eric Steven Johansen]

Very nicely done my friend. Looks sweet, I must say..........

[Kerry Krishna]

Jerry, what a terrific job you did! So how did you do it? Were there any pictures taken of the process?

[Jerry Ryan]

Only this one of using linen to reinforce the body after fitting the separated body sections back together...shd have taken some of using magnets (one inside and out, moving about 1/2 inch at a time on each seam) to pull the body back together. Using hide glue to hold each piece in place until the interior was reinforced, then removed the glue with a damp cloth before refinishing with a shellac french polish. Oh and the missing pieces of tortoise on the sound hole inlay were replaced by searching my pick collection until I found the color and thickness I needed to make the pieces.

Jerry