Double Bass Repair questions for BSO

[INTP]

I was given a CCB as a repair project and would like to solicit suggestions.

First off, I have low expectations, as this is clearly a low quality item (There are no markings of origin anywhere). But I do consider myself to be pretty handy and welcome the learning experience. FWIW, I used to play DB in high school but haven't had one of my own, so this could be a transition to something nicer.

This bass suffered a broken neck joint and the original owner gave up on it. A friend grabbed it and glued the neck but never reassembled it. I saw it sitting in the garage where it had been for a year and got the bass, bridge, tailpiece, and strings separately. There is a tailpiece in place, fwiw.

I did a dry fit and found a few significant issues (the strings are not under full tension at the moment). Other than the neck joint 'repair', the endpin plug does not seat in the hole in the bottom. The hole is about 1/8" larger in diameter, and someone tried unsuccessfully to shim it with rolled up sandpaper. (The sandpaper has chinese writing, so I wonder if it shipped that way.) The result is that the end pin shifts forward when string tension is applied and makes a horrible creaking noise. This seems to me to be the most urgent issue and I'd like to fix this first. I'm not sure the best way of approaching this, but I thought it might make sense to glue a plug into the hole with hardwood and re-drill the hole to the proper dimensions.

Also the bridge was never fit to the front of the bass. Kind of close, but not a proper fit. I think I can tackle this, although if the bass turns out to be playable, a proper adjustable bridge would be a better solution.

The neck joint appeared to have separated cleanly, and I see minimal wood damage due to that happening. However, it was glued with gorilla glue, and wasn't set fully. I actually think the gap will work in my favor because it will allow me to reach in and work some glue out and hopefully remove the neck in one piece. I don't look forward to doing it, but I think it will be possible to disassemble the joint and use chisels to get the glue out, then set it properly with hide glue.

I got a mirror and looked inside and while the quality is low, the seams all seem to be holding and there isn't any major cracking of the plywood. The soundpost is about 5/8" diameter and looks like it was carved with a pocket knife. The ends are adjusted to the curve of the body, however.

There's a bit of finish damage between the neck and fingerboard on one side, but the fingerboard doesn't appear to have separated from the neck at that point. The nut looks like it was cut with a screwdriver or other dull instrument. I haven't measured the fingerboard, but it looks fairly straight and doesn't have any obvious damage.

The tailpiece is metal. I am certain that I could fabricate a replacement in my workshop, depending on everything else.

Thanks for your input. My main hope is to get experience that I can carry forward. I don't think that I'll turn this into a great instrument, but if I can get it playable and learn something, I'll be happy.

 

[KUNGfuSHERIFF]

Oh, my. The way the neck is set with that glop you are unlikely to ever get it out of the block without major damage, never mind chiseling the glue off of the wood and doing a proper reset with hide glue.

 

[bassmastan]

Well if its a polyurethane glue like gorilla glue (it sort of looks like that) you could try using denatured alcohol carefully, the only thing is the alcohold can strip the finish. It can make it a little easier to chisel out.

I wish you the best of luck, this is a tough one to take on, it's doable but its going to take a lot of time, could prove really fun (I know I would enjoy doing it!) or really frustrating!

 

[INTP]

Thanks for the replies

I went ahead and removed the foamed gorilla glue that you see in the above photos to see the condition of the joint a bit better. Between the neck and the back piece there is a tiny gap (was filled with foam) that is about the width of a razor blade. I was able to bottom out a single edge razor blade fairly easily, going side-to-side to remove the glue in tiny flakes. I think that gives me a chance of getting in there to remove or at least sever the glue enough in that area and hopefully not damage the back when/if the neck joint comes off. I'll have to switch to a different blade to get any deeper, but I think it will work.

The light colored gap you see on the sides is unfinished wood from the joint not being seated properly. gives an idea of the gap underneath.



On the underside if the neck, there's a 1/8" or more gap, although it is certainly tapered and the gap gets smaller toward the back. It won't be easy to get in there, but I think I can access a fair amount of it. (I could also get a small pry bar in there to help apply pressure from underneath, when the time comes, and if needed). On the sides, the joint is snug except that the grain wasn't cleaned up so there is an irregular surface. I can kind of get a razor blade inserted in some places, but not all the way around.

My experience with polyurethane glue is that it will fail much more easily than other glues, but will leave a messy residue. I never use it myself, but am hoping that cleaning out the gaps will help it fail in a way that preserves most of the wood.

I'm not too worried about the finish at this point, so a solvent isn't out of the question. But from what they say on the gorilla glue site, once it's cured solvents don't do much.

 

[INTP]

I measured the endpin plug and it is 1.1" tapering to 1.0" over about 1.9"". The hole in the bass is about 1.2" though it is not really round. Would it be better to plug the bass and re-drill or try to get an endpin plug to match the bass. I think the plug I have is close to a standard size, so I'm inclined to modify the bass to allow future options, if needed.

Can anyone comment on what the 'right' way to do this would be?

 

[JoeyNaeger]

You should be able to free the sides of the mortise with a putty knife or something similar. The floor of the mortise may be a problem however. The safest option would be to remove the fingerboard and loosen the joint with a long separating knife. I bet that varnish won't dissolve with alcohol, but you should of course test that in a discreet spot.

 

[INTP]

You should be able to free the sides of the mortise with a putty knife or something similar.

I used a 1" putty knife to go around both sides and also the back. There was a distinctive foam crackling noise while I totally separated those spots. I used some dental picks to get part way under the bottom side of the joint. Then I applied a little pressure to see what would happen. More crackling, then POP, it came apart. I worked slowly but still only took about 30 minutes.

FWIW, the missing chips on the front were lost during the original joint separation. Otherwise, I'm happy that nothing else broke during this extraction.



I really think the loose fit plus the use of foaming glue saved me. Gorilla glue is weak when used without a tight fit.

I now get to sharpen my chisels for scraping the glue off and cleaning up the surfaces. Once I remove all the "glue", I can add some wood to get a tight joint. This was never a good fit, and was destined to fail.

 

[KUNGfuSHERIFF]

Wow, very lucky! I've had the unfortunate experience of working on several basses that had been Gorilla Glued and, well, there was no joy in Mudville.

 

[INTP]

Wow, very lucky! I've had the unfortunate experience of working on several basses that had been Gorilla Glued and, well, there was no joy in Mudville.

I think I got lucky that there were gaps:

 

[JoeyNaeger]

Hah! I was actually going to post that same video. That is my favorite youtube woodworking channel.

 

[robobass]

You look like you're on your way. Too late now, but I think pickling vinegar is way better than alcohol to loosen glue joints, although I don't know that anything is effective for urethane glues. On the socket, yes, plugging the hole and drilling and reaming a new one is the right way to do things. The reamer is expensive, so you might want to take the the bass to a shop for this once you've plugged and drilled. Otoh, you sort of need a lathe to make the plug anyway, so consider just making a new socket that fits. That sandpaper is like measles. It never completely goes away. That bridge is totally not fitted. With your apparent skills, if you buy the right knives and such, I bet you could do a decent job of it. Ever consider throwing your hat into pro bass repair? With some training, I bet you'd be an ace!