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Double Bass Neck Joint Separation

P

pi_r_squared

Sep 3, 2008
123
0
#1
Is something REALLY BAD about to happen? :eek:

This bass belongs to a friend of mine who asked if I wanted to try playing one in their group. I've been playing it for about 9 months and just noticed the neck joint "issue" shown in the attached pic.

The back of the neck joint looks like the neck is starting to lift out of the joint (finish cracking, bare wood visible above the joint).

There's also a small displacement behind the neck. It's VERY small, but the finish has cracked as a result. The cracked finish makes the pics of this issue look much more dramatic that it looks in-person.

A little history:

She bought this bass used from a friend (may have been her friends' son's bass, or something), and I have a feeling that it hadn't been played in a LONG time. The tailpiece had been whacked hard enough that the tailwire had come out of the grooves, and the bridge and tailpiece were almost an inch off-center, who knows how long it had been like that.

I started playing it about 9 months ago, got an adjustable bridge for it, played for a month or 2, switched to nylon strings, continued practicing and doing a few benefit gigs up until now. Since I've had it, it has never been dropped or fallen over.

I do remember, about a month into playing it, after installing the adjustable bridge, I thought I was going crazy, but it seemed like after I set the bridge up to what felt right, over the next few weeks I kept having to lower the bridge to keep the action where it was. If that was when the neck joint started separating, it seems like it makes sense. Shortly thereafter I switched to weedwackers, just to try them. Didn't switch for any particular reason, other than to try them, but it seems now it may have been fortuitous.

I guess my questions are:

If I stay with nylon strings is this likely to stay the way it is? or likely to let go (in the middle of a gig, or course)?

Was thinking of going back to steel (or other higher tension) strings. Seems like a BAD idea until this is fixed?

Could prolonged lack of regular use, followed by several-hours-per-week type of use cause an issue like this to "just show up"?

If I stay with nylon strings, and do nothing, might it do more damage? (other than the obvious neck joint opening up).

Would cabinet/furniture carpentry experience equip me to fix this myself? I have torn-down and rebuilt large mortise joints (fret saw/shim/sand/glue work) in the past, but I'm not familiar with whats going on "under the surface" of this joint.

Is there any obvious way to fix this (or keep it from getting worse) without completely removing and re-setting the neck?

Thanks in advance.
 

Attachments

  • NeckJoint02.jpg
    NeckJoint02.jpg
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#6
The damage is done, as Salcott said, loosen the strings now, and see if you can slowly and gently work the neck apart from the body. It can cause more damage transporting it or moving it around if the loose neck torques in the joint and splits the block or cracks the top.

It might not be too much of a stretch for you to tackle the job if your woodworking experience is solid, you have skill with a chisel and can keep it razor sharp, and take the time to read up. The first challenge will be getting the remainder of the heel separated from the heel and out of the pocket. Then reattaching it to the heel, or adding new wood. Then decide if you want to add a dowel or metal hardware, then tackle the reset. Not simple, but it sounds like it's not a valuable intstrument, and if you're prepared to mess it up and go to a Luthier with your tail between your legs and pay them to fix your mistakes (and likely pay them more than if you brought it now), then go for it!
 
#7
tyb507 said:
The damage is done, as Salcott said, loosen the strings now, and see if you can slowly and gently work the neck apart from the body. It can cause more damage transporting it or moving it around if the loose neck torques in the joint and splits the block or cracks the top.

It might not be too much of a stretch for you to tackle the job if your woodworking experience is solid, you have skill with a chisel and can keep it razor sharp, and take the time to read up. The first challenge will be getting the remainder of the heel separated from the heel and out of the pocket. Then reattaching it to the heel, or adding new wood. Then decide if you want to add a dowel or metal hardware, then tackle the reset. Not simple, but it sounds like it's not a valuable intstrument, and if you're prepared to mess it up and go to a Luthier with your tail between your legs and pay them to fix your mistakes (and likely pay them more than if you brought it now), then go for it!
Click to expand...

But then he needs to set the proper neck angle, the proper tension on the tailpiece wire, position the bridge, and probably reset the soundpost.

pi r squared, you feeling confident with all that?
 
#8
lowEndRick said:
But then he needs to set the proper neck angle, the proper tension on the tailpiece wire, position the bridge, and probably reset the soundpost.
Click to expand...

The sound post has never moved when replacing the bridge, not sure why, but I guess I've gotten lucky. I've shaped and fit a bridge before, and it sounds like the tailwire can be tweaked "after the fact". That being said, the neck angle does sound quite intimidating :confused: It's the piece of the puzzle that I can't really "sneak up" on.

One thing that really has me wondering. Is the gap between the heel of the neck(? maybe the wrong word) and the block immediately behind it done intentionally? and if so, why?
 
#9
I didn't say it was easy, I said if he does his research and had skill with tools, why not try it. It's likely a <$1k bass, so there's not a lot at stake, and it presents the possibility to learn something. It can be done. All the things you mentioned are things that one can learn how to do, from books, videos, forums, contacting luthiers who are generous with their knowledge (of which there are a surprising number in my experience) etc. The information is out there, and if PiRsq is curious and driven, there is no reason he can't be successful.

Pi, If the "gap" you're wondering about is the one pictured, it's a crack. Not intentional, that's your problem!
 
#10
That's one of his problems.

Pi, depending on the type of glue that was used to set the neck this could be a weekend job or it could be a nightmare. If you decide to tackle the job yourself I see no reason not to replicate the original neck angle and overstand.

If the bass is a real cheapo, the heel may made from several pieces of wood glued together. That crack is suspiciously tidy and even.
 
#11
tyb507 said:
Pi, If the "gap" you're wondering about is the one pictured, it's a crack. Not intentional, that's your problem!
Click to expand...

The crack is along the horizontal seam in the picture, where the rear of the neck joint is elevated about 0.090" higher than the front of the joint. Very subtle angle.

The mismatch is also evident along the vertical "seam" at the rear of the neck (just in front of the "block" I was referring to), but that was NEVER a glued joint since I've seen this bass. It is a pair of smooth, cut surfaces, that look like they were never glued together, and have always (since I'd been playing it) had a separation of about 0.06". There is absolutely no cracking of the finish around that to suggest it was a crack, or was ever glued. Is that evidence of something someone screwed up in the past?

I'll attach another picture from a different angle, I think you will agree that the vertical line where the surfaces are mismatched is not a crack.

and thanks all so far for all of the input.
 
#12
It's evidence that major corners were cut when the bass was built.

The point of contact between the back edge of the neck heel and the button is critical, especially in a traditional European style neck mortise. Guitar-style mortises like those on Kay basses divide their mechanical strength differently, but on your bass the button is SUPPOSED to do most of the work of preventing the neck from levering forward under tension.

But because the neck heel is two pieces that aren't even touching, that mechanical strength isn't there. All you had holding the front part of the heel in place was the chemical strength of the glue, and that is failing. Your neck mortise is probably tapered slightly, like a pyramid, but not enough to add significant strength.

Remove string tension from the bass. Right now. When the joint fails it could be spectacular enough to injure you or badly damage the bass.

What I would do is coax both sections of the heel out of the mortise. If you're lucky and it was assembled with hide glue, hot water, a thin blade and steam will loosen the glue. White vinegar will plasticize wood glue. If there's epoxy in there, find another bass.

If you get the heel out and the mortise is in decent shape, I'd mate the sections of the heel with epoxy and reinforce with a countersunk lag bolt and washers and then reset the neck in the block with hot hide glue. Not a small job.
 
#14
A professional bass luthier can find out most of the problems and tell you how much money it might cost. He might evn give some hints if he thinks you can make the repair yourself given the rather low value of the bass.
But loosen the strings (just leave a little bit of tension to hold bridge and soundpost in position), avoid holding the basses weight at the neck and go to a luthier immediately or your bass might be damaged so much that a repair would become too expensive.
 

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