Double Bass Pegbox cracked - how to repair

[notabene]

It is a bit hard for me to see the "fit", but please use only hide glue, mixed by yourself, not from a bottle. You might also use one or two thin maple dowels drilled, also hide glued in place joining the two parts.

This seems (to me)to be repairable with reliable sucess.

 

[Bassix76]

Hello,

I closed the larger cracks with hide glue. No problem.
The very thin cracks could only be filled using superglue.

I then tried to remove the nut with no success.
Then I heated with a hairdrier and it came off. It smelled and had insoluble residues, I suspect epoxy...
(also epoxy is thermoplastic...)

Then I cleaned everything from glue residues and put it together with the epoxy
UHU Plus Endfest 300.
The parts fitted together very good.
Now I am waiting...
Looks better than I expected.

 

[eh_train]

Dear Paul ...
Can you explain why you would prefer the rod from front to back?

If you think about which way the string tension is pulling, this is the most direct "antidote" to that. Especially if you drill downwards from where you start the hole (think of the right way to put in a tent peg). Coming at it from the sides will also work, but only if there are two rods. One rod alone, from the side, will only act as a pivot. And that will allow for plenty of tension on the pegbox.

How thick would you choose the rod?
I could imagine that a thicker rod gives a better stabilization due to its lower curvature?

CF comes in all shapes and sizes. A 1/8" rod should work nicely. And, as you showed in your example, two rods, one on either side of centre, will work even better.

 

[Bassix76]

If you think about which way the string tension is pulling, this is the most direct "antidote" to that. Especially if you drill downwards from where you start the hole (think of the right way to put in a tent peg). Coming at it from the sides will also work, but only if there are two rods. One rod alone, from the side, will only act as a pivot. And that will allow for plenty of tension on the pegbox.




CF comes in all shapes and sizes. A 1/8" rod should work nicely. And, as you showed in your example, two rods, one on either side of centre, will work even better.

Yes, I was thinking about drilling a centered hole slighty downwards and putting a CF rod there.
But there is not much place at all and I do not want to destabilize anything.
I will have to measure again after declamping in some hours.
Do you really think a 1/8" CF rod would be thick enough? That is only 3mm. I would have chosen something between 1/6 to 1/4".
And from the side: 2 rods from each side with a length of about 1" or better 2 rods passing from the left to the right?

Thanks, Alex

 

[eh_train]

Two 1/8” rods, spaced 1” apart, would be my choice. These are just reinforcing, not replacing the wood.

You don’t have much room for error on the bass side (in terms of getting the depth spot on). Measure 3x, mark on the drill bit the correct depth, and drill once. Also, don't have the 2 rods running perfectly parallel to each other. That way any future stresses will run along the rods in slightly different directions, and diffuse each other.

If you do go from the side, just two rods.

 

[Bassix76]

Yes, I was thinking about drilling a centered hole slighty downwards and putting a CF rod there.
But there is not much place at all and I do not want to destabilize anything.
I will have to measure again after declamping in some hours.
Do you really think a 1/8" CF rod would be thick enough? That is only 3mm. I would have chosen something between 1/6 to 1/4".
And from the side: 2 rods from each side with a length of about 1" or better 2 rods passing from the left to the right?

Thanks, Alex

Yes thats exactly what I thought. I will put 2

Two 1/8” rods, spaced 1” apart, would be my choice. These are just reinforcing, not replacing the wood.

You don’t have much room for error on the bass side (in terms of getting the depth spot on). Measure 3x, mark on the drill bit the correct depth, and drill once. Also, don't have the 2 rods running perfectly parallel to each other. That way any future stresses will run along the rods in slightly different directions, and diffuse each other.

If you do go from the side, just two rods.

Yes, that is exactly what I thought after measuring. I will have to find a drill long enough and then order 1/8" or 1/6" CF rod. I will put 2 pieces pointing slightly downwards.
But how does the air come out while glueing the rods in? Is this a problem?

 

[eh_train]

If you want to get much glue in you'll need to have the hole slightly oversize. Maybe a 5/32" drill for the 1/8".

 

[Bassix76]

Thanks for your valuable input.
I just ordered a long 4mm drill and a 3.5mm rod and will see how this turns out.

Have a nice week,

Alex

 

[DoubleMIDI]

I would rather drill a very thin hole at the edge of the larger one (when the dowel is inside dry), then remove the dowel and open the small hole to the larger hole (at least) at the bottom. That way air and too much glue can evaporate through the thin hole and the dowel sits in much better and less wobbly than with a larger main hole.

 

[Greg Clinkingbeard]

I’m old school and use wood dowels. I drill the hole the size of the dowel and cut grooves in the dowel. That preserves a tight fit and allows the excess glue to come to the top. The end of the dowel is always shaped with a point to mimic the drill bit. That way it goes to the bottom of the hole and forces the glue up.

 

[DoubleMIDI]

With a wooden dowel I either take some with grooves (or cut them) or would drill a thin hole completely through the dowel in the middle.

 

[Bassix76]

Hello All,

mission accomplished.

I drilled 2 4mm holes with different angles, filled with epoxy and introduced 2 3.5mm CF-rods.

After cleaning up I glued back the nut and installed strings and bridge.
Seems to be stable so far and I am glad to be able to play again !

So far I only noticed a slight buzz at the open D-string right at the nut.

I also built a wall mount to prevent my bass from skipping again in the future:

Dear posters, thank you very much for supporting me and for your time.

I have learned a lot, TALKBASS = number 1 !

All the best,

Alex

 

[Greg Clinkingbeard]

Good job! You might need to shim the nut.

 

[Bassix76]

Good job! You might need to shim the nut.

Thanks!
Yes, I thought about a shim but all other strings have a perfect small gap. Seems like the notch of the D-string was too low as indicated by a groove in the fingerboard. So shimming would also change all other strings...

 

[SAlcott]

I'd just shim the nut 1-1.5mm and refile the notches with a needle file-not a big job of you go slowly. The other option is a piece of something like plastic drumhead or even business card in the D slot. I've had that on one of my basses for 20+years.

 

[DoubleMIDI]

A piece in the nut groove can be helpful and works often well … until you need to take the string down and loose the piece. Not nice if you have that string break during a performance.

Since you already have the nut off, I would use a shim and file down the other grooves to fit.