MIMF

Hi fellows,

I back with a big thing. a big mama.
I have a Chinese double bass with massive top which I repaired the broken top last month and now it's time for the twisted neck.
I already fixed that kind of problem on guitars and bass but on a Double bass it looks big.
what do you think about the following process:

I first remove the ebony finger board. (could it come from it?)
I then heat the neck with a smoothing iron and wet cloths until it is hot.
at the same time I heat a 5cm large/4cm thick/60cm long iron rod
once both are hot, I put the rod on the neck and start to press it slowly until I achieve a straight neck.
Let the clamping in place for the night
and put on the (same?) fingerboard.

Does it looks crazy to try to straighen such a twisted neck?

Looks like a neck reset is in order.

If it were me. I would.

1 remove neck
2 remove fingerboard
3 straighten fingerboard with heat, steam, and clamping.
4 flatten neck, plane and sand till dead flat.
5 replace fingerboard
6 reset neck to proper angle
7 check fingerboard and plane flat if needed.

The neck looks bent forward (too much relief), not twisted. You need some relief but certainly not as much as in the photo.
First check the fingerboard for any loose areas. The fingerboard is a significant part of the structure of the neck, and must be well glued to the neck or the neck can easily bend like this one.
If the fingerboard is well glued then it should be removed, both glue surfaces cleaned, and reinstalled on the neck. Careful clamping with a beam will help flatten the curve in the neck. Hot hide glue is the usual glue for this application as it will not 'creep' if it gets overly warm like carpenters wood glue can.

There may be no fix without reinforcement. As Michael said, the fingerboard acts as reinforcement, but cannot make up for a "soft" neck. I went through several fingerboards before having a new neck made for my bass. This was before Carbon Fiber reinforcement became common.

Also (maybe this is obvious) the relief is planed into the fingerboard (the fingerboard is never flat), rather than the whole neck and fingerboard being bent.

It might be prudent to reinforce the neck while you have the fingerboard off. If well done, it won't do any harm. The repair can only be as effective as the quality of the materials. I've been told that the Chinese basses vary greatly in quality and that the better ones have wood that is much better than they deserve. But the less expensive ones might have questionable wood.

The fingerboard seems poorly jointed to the neck. on all the sides jonctions between fingerboard and the neck the glue joint seems cracked and you can easilly put a samll needle in the crac at some (lots) places.
The glue they use (I saw it when removing the top) looks like a past more than a thin layer of glue.

do you really think the fingerboard & the neck (separatly) can come back flat with lots of heat and press?

Can I do it without removing the neck? the neck block is in non identified wood of loose quality..... and I really don't want to remove the top once more to change it due to neck removing damages.
Thanks, guys

Cédric.

So much bulk of glue tells me it was a poorly glued joint. There should be only a trace of glue in the joint if properly glued and clamped.

Joshua's idea of reinforcing the neck before reinstalling the fingerboard is valid. The fingerboard to neck joint MUST be properly and well glued for it to provide the stiffness it is designed for.

I don't think you need heat to reshape these parts. As much heat as would be required you would be putting your neck and fingerboard in danger of over drying and causing cracks. I think it needs to be clamped flat while the glue sets and dries.

This can all be done with the neck remaining attached to the body, but be careful to avoid causing damage (glue drips, clamp marks, etc.) to the body in the process.

Hi fellow,

I am back and the repair has been done.
I removed the fingerboard with a spatula, a metal rod, a domestic iron, an old tshirt and some water. heating the finger board with the iron with the precious help of a damp(wet) Tshirt. after 1/2 an hour of labor, the fingerboard jump off. as you can see on photos, the gluing job was poor and the glue (was it trully glue???) looks more like shewing gum than glue. I used a plane blade as a scrapper to remove this strange material on the neck. an hour off job.... and another hour to clean the fingerboard.
I used a straight 1" thick 5" large 2feet long plain metal heated with the iron to flaten the neck, then the finger board.
next a good gluing job with titebound.
and finally a big setup: fingerboard curve refining, new bridge.......
Finally it works fine in about 6hours job.

thanks alot for your help

Cédric.

Cedric, you are going to glue the fingerboard with hot hide glue, are you not? It is the only glue I trust to resist creep under stress.

Huuu ! the repair is now completed and I used Lmii white glue (note titebond as I said) in which I give all my confidence.




C.