Bowlback mandolin, exploded

[mandocello8]

Some interest in bowlback mandolins recently. I might as well post the one I have, as I have not seen "inside" views quite like this, anywhere else. I hope you find them entertaining.

This is the only bowlback mandolin that I have ever played that (a) was structurally sound, (b) had correct geometry and (c) had usable tone. It was loud with good projection, worked in a loud Irish bar and was a conversation starter when busking. It suffered explosive self-disassembly (elephant stepped on it). I will likely put it back together.

in storage:


general layout:


details: (neck and headblock are separate parts, joined by mystery joint) (headstock is modified by competent luthier to take modern tuning machines)


details, top:


ribs and odds: (absent bridge and modern tuning machines are on a different bowlback mandolin)


some thoughts on reassembly. the top braces were rough and split (install new ones, very good looking braces were posted just the other day). business part of top is intact (keep it, no new top), all ribs are intact (just re-glue). joint of bowl and neck needs to be stronger, I am thinking metal or G10 inserts.

[brunello97]

Wow. The elephant had good aim.

Good luck with the rebuild.

Are you planning to post some "in progress" photos of the work?

When I was first playing bowlbacks, I bought a few corpses as projects to learn their anatomy and details and some repair strategeries.

The Italian / Euro made bowls with the integral neck block pose an additional complexification when reassembling...you've got to reassemble the staves while keeping the neck geometry just right.

Making a jig of some sort to keep things aligned might be a good idea. You can find photos of the old jigs the bowlback makers used here or online.
Some folks have made simpler versions that look like they work well.

Poco a poco....

Mick

[Richard500]

Since you liked it so much, any idea who made it? Maybe there are others.
If you go with a mechanical connection, you may be able to make alignment possible after assembly and avoid the problem Mick describes.
Best luck; it looks very possible.

[brunello97]

If you go with a mechanical connection, you may be able to make alignment possible after assembly......

Richard, do you have an idea in mind for this 'mechanical connection'?

Perhaps addition a thick 'half disk' inside the bowl just 'south' of where the neck bock would be.
Use this to align attach the broken staves.
Then adjust algin and bolt / pin / dowel the neck block to the added disk?
With the top broken away there maybe you could get access to such a joint.

If you can't get the Goddess Durga to help you, taking the time to make some alignment and positioning jigs will be crucial.

I've reset necks on a couple of Italian bowlbacks the hard way...and I wouldn't recommend it.

Dave Hyndes has a "neck-ectomy" process he uses, wherein he saws off the neck from the neck block and then re-mates the surfaces and pins them back together.

Sounds scary but doable. More radical but perhaps a bit simpler than my thought process above.

Certainly simpler than my whole bowl / whole neck resetting method.

He's described it to me, but I don't think I've seen in progress photos of the operation. He might have some on his website.

Mick

[Jim Garber]

It doesn't look particularly well-made to me. I am not sure about the decoration—if the flowers and blue dot painted border was done originally or not. Certainly would be a challenge to put back together but, unless the OP has a lot of free time or seriously wants to learn to re-fabricate cheaply-made mandolins, I would look elsewhere. I am guessing there are plenty of comparable mandolins that would suit his musical purpose.

Years ago I had a friend who mostly played in loud Irish bars and his mandolin was one of those Korean one that sold in the 1970s for about $49 new. It suited him and you could hear him quite well over a half-dozen fiddles.

[Tavy]

Oh my.

[Richard500]

Mick, the only one where I went bolted was a couple years ago on this interesting, but strange brace-less, mahogany top thing, where obviously making a serious mistake was inconsequential. I did detail it here, but not with process photos. Basically, the neck is sawn off, not out of necessity, but because I needed to raise the entire fretboard in order to get some good breakover angle at the bridge, the soundboard being completely flat.
Internally, I measured and made a fairly thick plywood bulkhead to completely cover the back of the neck block, which was cracked and probably too weak. Then, making a long alignment tool with drill inserted from the tail end, located a clearance hole for a bolt in the new wood and through to the still detached neck. A furniture-type brass threaded insert went into the neck as low as reasonable, with epoxy on the external thread. A slight angle correction is sanded on the end of the neck by inspection.An allen bolt and large washer went inside the bowl, and since there’s an oval hole, tightening and adjusting was easy. The fretboard extension, raised with a shim about 1/4” is then clamped in best alignment and glued. Note that the board itself didn’t have to be removed at all, none of the staves was disturbed and the top stayed on. Once adjusted, it was taken apart and the flared part of the neck glued in for added stability. A brace was added to the mahogany top. I wouldn’t call this a high-skill repair, just an experiment. Plenty strong at a guess, and no acoustic implications. It is a different sounding thing, but aren’t they all?
For a more ‘normal’ bowlback where visible surgery would be ugly, I’d definitely remove the fretboard first and analyze the neck connection, but still saw it off forward of the stave ends and bolt through from the inside. Wildwood even bolts from the outside and plugs the hole, which is easier, and very likely a coarse wood screw could be strong enough if the neck block was sturdy, but using a nut and bolt plus a bulkhead is both adjustable and stronger.

[Simon DS]

Probably a change in atmosphere, that’s what happened to my bowl-back when my ex-wife looked after it.

[mandocello8]

OP here. the way it self-disassembled, with all pieces intact, it is more of an "assemble me" bowlback mandolin kit than a wreck. with two good things - it takes modern tuning machines and it will likely sound good when completed.

history is unclear, it was given to me by somebody who moved to vancouver island. likely it was in their family before that. the flowers in the top look original, the blue-coloured decorations look added later. there was a flower painted on the headstock, style did not quite match the flowers on the top (did not survive conversion of the headstock to modern hole spacing, alas) (original tuning machines lost, ouch!)

workmanship looks crude compared to other bowlbacks posted here. except for the ribs. they are done very carefully, with nice little softwood strips between them.

reassembly is stalled for now. I am undecided whether reassemble the neck joint or the bowl first. Or I could take the top off and follow the conventional assembly sequence. Except that redoing the top will be more bite than I can chew...

also I will need to understand bowlback geometry. original geometry has fingerboard parallel to the top, yielding a low bridge. in theory I could add an angle between them and have a taller bridge (with bigger break angle). (I have a Portuguese made pancake mandolin like this). I am sure there is books to read on this topic...

meanwhile, the noisy irish bars remain closed (or do not do live music). this is slowly changing, when the time comes, my 1890-ies mandolinetto will likely work there just fine (also loud and cool looking).

[brunello97]

Mick, the only one where I went bolted was a couple years ago on this interesting, but strange brace-less, mahogany top thing, where obviously making a serious mistake was inconsequential. I did detail it here, but not with process photos. Basically, the neck is sawn off, not out of necessity, but because I needed to raise the entire fretboard in order to get some good breakover angle at the bridge, the soundboard being completely flat.
Internally, I measured and made a fairly thick plywood bulkhead to completely cover the back of the neck block, which was cracked and probably too weak. Then, making a long alignment tool with drill inserted from the tail end, located a clearance hole for a bolt in the new wood and through to the still detached neck. A furniture-type brass threaded insert went into the neck as low as reasonable, with epoxy on the external thread. A slight angle correction is sanded on the end of the neck by inspection.An allen bolt and large washer went inside the bowl, and since there’s an oval hole, tightening and adjusting was easy. The fretboard extension, raised with a shim about 1/4” is then clamped in best alignment and glued. Note that the board itself didn’t have to be removed at all, none of the staves was disturbed and the top stayed on. Once adjusted, it was taken apart and the flared part of the neck glued in for added stability. A brace was added to the mahogany top. I wouldn’t call this a high-skill repair, just an experiment. Plenty strong at a guess, and no acoustic implications. It is a different sounding thing, but aren’t they all?
For a more ‘normal’ bowlback where visible surgery would be ugly, I’d definitely remove the fretboard first and analyze the neck connection, but still saw it off forward of the stave ends and bolt through from the inside. Wildwood even bolts from the outside and plugs the hole, which is easier, and very likely a coarse wood screw could be strong enough if the neck block was sturdy, but using a nut and bolt plus a bulkhead is both adjustable and stronger.

Thanks, Richard.

What you are calling a bulkhead is what I had in mind with the 'neck-ectomy' approach. Bulkhead is a good term for this. If the OP can cut a bulkhead that can also serve to align his bowl staves that might be very useful. Or multiple bulkheads to reassemble the whole bowl before the top goes back on. They wouldn't need to be glued in place.

Fair play to you for doing this with the top on. The long drill bit with "alignment tool" sounds interesting. Did you drill in through a hole by the tailpiece? I'm not quite getting how this went.

I didn't realize Jake W had gone through a neck-ectomy on an Italian or integral neck / neckblock mandolin. Did you see that on his site?
If so, I'd enjoy checking it out.

I've had my eye out for an inexpensive MOR Italian bowl to work on. Maybe trying a neck-ectomy would be a fun wintertime project.

Mick

[Richard500]

Yes, enlarged a tailpiece screw hole. A small diameter drill that long can be made by brazing a bit on a rod, as bit extensions are too large, and aircraft bits too short. Once there’s a pilot hole for alignment, the holes are then expanded from outside to provide bolt clearance and for the threaded insert. The tailpiece here was way off center and had do be relocated anyway. Same idea is used to make long allen wrenches.
I’ll look for Jake’s page; I know it related to some bowlback discussed here recently, but might take some time.
For the OP project, I think preserving the top to bowl joint and not removing it might avoid potentially nasty fitting later as just using a form or mold for the staves might not agree with the original shape. This does make assembling the bowl tricky, but as long as everything meets up in the end, should be ok. The staves, being liberated likely have relaxed a bit. A form that knocks down toward the end, say, at the last couple of staves would be useful, or a negative, too.
Your idea of a removable bulkhead is the same thing.
To me, lacking enough experience, the one piece neck-neck block also seating all the stave ends can’t practically be restored, and that terminates these instruments, once it moves, so surgery is justified, at least on lower value ones to keep them playable.
By the way, the handsome American Conservatory recently in my paws, looks like deformation of the entire bowl over the last century, and not the neck, so more thinking is needed. Don’t want to damage this one.