Bandolim neck join

[sounder]

First off, I want to thank all the contributors that produce such an incredible forum.

I am building a copy of a Regis Bonilha bandolim, modified for ten strings, truss rod, adjustable bridge and a fan fretboard. My question relates to the neck join. There is only 7/8 inch of blocking, forward of the seam at the neck heel and body. It's 5/8 at the bottom of the blocking because it is vertical inside the mando body. The blocking, or cover veneer has horizontal grain. The neck heel seems to small to take a bolt, but maybe I'm wrong about that. Pegged mortise? Does anybody know how neck joins are typically done on bandolims? A magnet has no attraction at the heel cap or inside the blocking.

[Dusepo]

A 'Spanish heel' joint seems likely to me. Otherwise a dovetail. That side port should enable you to get a good look.

(Side issue but I wouldn't recommend putting a strap button on the heel.)

[PT66]

[QUOTE=Dusepo;1915303]A 'Spanish heel' joint seems likely to me. Otherwise a dovetail. That side port should enable you to get a good look.
I would think if it were a “Spanish heel” (neck extension into the body) you would easily see the two different wood colors inside unless it is covered.

[sounder]

Thanks Dusepo, There is no seam on the block inside, so you are likely right that it is not a Spanish heel. however the block seems too small for a mortise. When magnified, the neck/body seam shows black at some of the seam. Now, I'm thinking this may be a black epoxy butt joint. Any opinions or comments are welcome.

[Richard500]

No actual knowledge, but two ideas surface: One, the wineglass rib shape allows for using the ribs for considerable strength compared with more usual construction. Two, if you are trying to make an accurate replica, rather than re-engineering it, it would be good to get the area x-rayed if you can. Where the truss rod is anchored may also be relevant, if the original has one.

[sounder]

No actual knowledge, but two ideas surface: One, the wineglass rib shape allows for using the ribs for considerable strength compared with more usual construction. Two, if you are trying to make an accurate replica, rather than re-engineering it, it would be good to get the area x-rayed if you can. Where the truss rod is anchored may also be relevant, if the original has one.

I like the X-ray idea. No luck yet on finding access to a machine. I'm trying to make an accurate replica, with changes for a North America market, (more humidity and temp changes.) by adding truss rod, adjustable bridge, fan frets and ten strings.

The wineglass rib shape looks sharp and seems intrinsically strong There seems to not be much room for a mortise and I question its ability to add strength over a epoxied butt join. And thanks PT66.

[ProfChris]

I made a couple of ukuleles with a similar appearance at the heel/body join. Rather than a separate neck block, I just continued the neck inside the body and cut a rebate in the sides of the heel which I glued the sides to. So, conceptually like a Spanish heel but without slots to fit the sides into.

The neck extended about 3/4 inch into the body to form the neck block element.

Of course, I only had about 30lb of string tension to worry about, but there's a lot of glueing surface so I suspect it would hold up to steel strings OK. I think the challenge would be bracing the top so it didn't sink under tension at the upper bout/part (I guess it has no bouts!).

[Dusepo]

I made a couple of ukuleles with a similar appearance at the heel/body join. Rather than a separate neck block, I just continued the neck inside the body and cut a rebate in the sides of the heel which I glued the sides to. So, conceptually like a Spanish heel but without slots to fit the sides into.

The neck extended about 3/4 inch into the body to form the neck block element.

Of course, I only had about 30lb of string tension to worry about, but there's a lot of glueing surface so I suspect it would hold up to steel strings OK. I think the challenge would be bracing the top so it didn't sink under tension at the upper bout/part (I guess it has no bouts!).

This is what I meant by Spanish heel, not like a guitar construction. This is how I built a bandolim I recently completed. Plenty strong enough for mandolin string tension.

[sounder]

This is what I meant by Spanish heel, not like a guitar construction. This is how I built a bandolim I recently completed. Plenty strong enough for mandolin string tension.

Thanks Dusepo and ProfCris, yes, why have a join at the heel when there is no call for it.

Spanish heel it is then.