Double Bass What to do about the tear-out?

[GretschWretch]

I believe I posted some time back about a mishap my Wilhelm Eberle experienced which resulted in the neck being knocked free of the body and the button being sheared off. I have looked at the button and believe separating it from the neck and re-attaching it to the back will be less of a challenge than I initially thought. And I know I will have to attach a reinforcement behind on the back. Does the reinforcement have to be ebony, or will other woods suffice?

On more closely examining the heel tenon I discovered some tear-out -- wood that should be on the cheeks of the mortise but got pulled along when the neck went and is
now attached to the tenon. How to remedy this I do not know. I figure my options are

1) Do nothing and hope that the tear-outs align in their proper places on the mortise cheeks when I reset the neck.

2) Using steam and a razor blade, very carefully coax the torn-off bits off the tenon and glue them in their proper places on the mortise.

3) Coax the torn-off bits from the tenon and shim the mortise cheeks without re-attaching the tear-out. This might result in a tighter, more stable fit, but it also would create gaps between the mortise cheeks and the shims.

There may be other approaches, but I'm blest if I can think of them. I'm appealing to the collective wisdom here.

 

[neilG]

A real button repair is a fairly complex operation. The button is an integral part of keeping the neck in place, and needs to be very completely and solidly part of the back. Go here to see what a graft looks like:
Repairs to a French Double Bass

 

[ctrlzjones]

The other (guerilla) option is to glue a second layer botton on top of the broken one. I’ve seen it. I have also seen luthiers who refuse to do it as it is considered to be a junky repair that could work or not.

 

[1st Bass]

Proper button graft is done from the inside… and is a pretty involved process. I remove the back…

 

[GretschWretch]

Thanks for the advice re the button, but IMO that is the easier problem to solve in that the course of action is more clear. What I really wanted advice on was what to do regarding the tear-out from the sides of the top block that adhered to the side of the heel. How should that be addressed?

 

[neilG]

How significant is the wood loss?

 

[GretschWretch]

How significant is the wood loss?

The wood loss is almost inconsequential; wood migration is the issue. Parts of what should be the inside cheek on the mortise (neck block) now are attached to the sides of the tenon (neck heel). Some of this I probably can coax off the tenon and re-glue to the mortise. Other bits, however, would be destroyed if I tried to get them loose. But these bits are so little as to be non-essential.

 

[1st Bass]

Then those particular splinters are just that: non-essential, and inconsequential.

If this were an irreplaceable original Amati bass, or something similar, I might strike a slightly more “pious” pose, considering every splinter to be sacred. But it isn’t, and “I don’t polish hammers.”

On the other hand, if I break a hammer handle, I don’t wrap it in duct tape and call it repaired.

A broken button, to me, requires removing the back, precisely grafting the old button back in place, using new wood secured from the inside with hot hide glue, in a patch that nearly supplants the button itself as well as at least that much wood inside the back plate.

Isn’t that a lot of work? Yep. Lutherie can get that way.

 

[KUNGfuSHERIFF]

Solid or ply back?

 

[neilG]

Best practice is to plane the cheeks smooth, add wood and re-cut the mortise. You have to decide if that's necessary. Just don't rely too much on glue for filling gaps.
Many years ago, I had an extremely well-known bass shop re-set a neck. They used epoxy to fill gaps, and the neck literally fell of the bass a few years later. A proper repair should last nearly forever. I'm still angry about that.

 

[GretschWretch]

Solid or ply back?

Ply top and back. It's an Eberle. And as a general FYI, it has a thin neck like a Kay, but not the dovetail joint.

 

[KUNGfuSHERIFF]

Overlay patch. It’s not worth the effort of inlaying a patch on that grade of instrument.

 

[GretschWretch]

Best practice is to plane the cheeks smooth, add wood and re-cut the mortise. You have to decide if that's necessary. Just don't rely too much on glue for filling gaps.

I know better (now) than to try to fill gaps with glue or wood filler; it has to be wood. Fortunately, I have some veneer that can be pressed into service. This weekend I plan to separate the button from the heel and the see what I can do regarding the cheeks. If planing looks too dicey (considering who will be moving the plane), I may try a combination of sanding and scraping to even the cheeks.

Many years ago, I had an extremely well-known bass shop re-set a neck. They used epoxy to fill gaps, and the neck literally fell of the bass a few years later. A proper repair should last nearly forever. I'm still angry about that.

This is where, for me, the mischief sets in. I have already searched online for DB luthiers in my area. There seem to be none. Most of what I found seem to be music stores that deal in bowed strings and have repairmen on staff, but no indication that any are fluent with DB repair. I will try widening my search.

And as the immovable object set against the irresistible force of "Get thee to a luthier" we have the immovable object of "Don't spend more money on repairs than what you can sell the bass for." A back removal and replacement is going to cost big bucks, not to mention the button work. On an Eberle.

I'm confident I can get the back off. Getting it back on, I dunno. I was hoping I could do the button reinforcement externally. I have seen pictures of the the reinforcing piece on the outside back of the instrument but I can find none now, and all the tutorials I have seen regarding button grafting say open the back and reinforce from the inside.

 

[neilG]

A former student of mine has a Gemunder shop bass with an external button replacement/reinforcement. It looks like a decorative medallion. I'm not sure if the button is part of the external piece or not. Maybe this is an option for a bass of the quality of an Eberle.