3/26/22 8:07 AM

A friend of Linda's dropped her U-bass on a concrete floor and it split. I've been asked to see if I can repair it. I'm assuming that the crack continues well past what's visible below. I'll check for any internal bracing that may be damaged and/or detached.

https://link.shutterfly.com/TzylnFjrIob

My initial thought from seeing the pic (I haven't seen the instrument yet) is to:
1 - Remove the black piece (pickup?) on the right.
2 - Clamp the crack closed.
3 - Mask both sides of the crack.
4 - Flow thin CA glue into the crack.

Does this sound like a good approach or is there a better way?

Last edited by Brian Nystrom on 3/26/22 10:27 AM; edited 1 time in total

3/26/22 9:53 AM

Link does not work for me. Dont know if it translates, but in pianos we use a slow drying glue, say on a splitting bridge, then clamp, then wipe excess, however, there is no underside to mask on a piano bridge.

3/26/22 10:28 AM

Thanks for the feedback. I changed the link to Shutterfly, so hopefully that will work. I have a variety of wood glues, but figured that CA would be the easiest and quickest. I've used it on smaller cracks that weren't really structural, but perhaps it's not the best idea for this situation.

3/26/22 11:46 AM

That is not a CA glue job IMO.

I'd remove hardware, use tightbond, clamp. I'd probable glue on an interior rib if I could get it in, Directly over length of the split. A slice of something flat sawn.

3/26/22 2:45 PM

I'm mostly with Sparky on this one. Take out the battery holder (pretty sure that's what the plastic bit is) then apply glue along the crack, clamp, and wipe off the excess with a damp rag.

My one concerns--and it may just be distortion in the photo--is that normally I'd expect the top-side and bottom-side joins to be holding the sides in proper position, but it doesn't look like it here (unless the crack goes way farther than it looks). It almost looks like the top and bottom slices are off (see the shadows at the edge of the battery box).

If the sides *are* in proper position, then it should be a matter of using Titebond or hide glue to put the sides back together. Titebond is a little slower to set, IME, so probably the right stuff here. Because that's not normally a highly stressed part, I wouldn't worry about reinforcing it--assuming that you have no problem getting the parts to line up easily along the break.

If everything lines up, the break/repair will likely be invisible.

I have a U-Bass that I was given in the closet here, and the sides on mine are plywood. That one looks a little nicer, though, so I suppose it could be solid wood. I don't know whether that would make a difference in repairs.

3/26/22 5:30 PM

Could be a Luan, in which case the interior bolstering along split will be necessary. As luan are 3 layer, and middle may not bond well. [speeling fixed]

Last edited by Sparky on 3/27/22 11:08 AM; edited 1 time in total

3/27/22 8:38 AM

Thanks guys!

I watched a few repair videos after I posted here and realized that CA is not the way to go here, since it's a structural rather than a cosmetic crack. Fortunately, the crack stops at the cutout for the battery box. The sides are solid mahogany and after taking the tension off the strings, the edges of the crack do not align perfectly if I just pull it closed. I assume that this is due to residual stress from the bending process. If I work from left to right, I can gradually align and pull everything together, so the new plan is:

1 - Make 6 - 8 spool clamps

2 - I'm thinking of using hide glue to get extra open time, but I'm going to check the open time on the various Titebond options to see which is the longest and decide what will give me the most working time. I definitely don't want to feel rushed. I plan to do a dry run before actually gluing it, so I have the process nailed down.

3 - On the left end, where the crack disappears, pump glue into it using a small suction cup. Working to the right, I'll add glue to a few inches at a time, aligning and clamping the crack as I go. I may get some magnets to help hold the alignment. The finish is intact, so if I do this right, the repair should be invisible.

4 - Once the crack is closed and the glue has set, I'll add some interior cleats to reinforce the crack. Actually, Linda will add them, as there's no way I can get my paws through the sound hole.

Here's a listing for the same instrument that describes it in detail:
https://reverb.com/item/39144678-kala-smhg-fs-fretted-all-solid-mahogany-u-bass-w-semi-rigid-case-satin-natural

The owner has apparently looked into local repairers and been unimpressed. Hopefully, I can do her instrument justice.

3/27/22 11:26 AM

If you decide to fix the finish as well, lacquer will stick on anything. Acrylic could work. Is is satin finish, pic make it loos so.

But just re-clearing the entire top side is an ok approach. Or drop fill the crack with a lacquer, and steel wool the shine off the drop fill. Letting the wound [verb] in plain site that is the earned provenance of battle scars is my preference ;) In use it will earn lots, with hope, less severe going forward.

Or clear over a decal/image of as many bars of pachelbel's canon score it takes to cover the wound [verb] ;)


I have a 1984 Les Paul [The Paul] with the face of the control area cracked from being dropped on the jack. Glued and drop filled finish over the actual cracks. Been like this for 15 year, stable, and earned provenance proudly worn. It is VG sounding LP, regardless of the non perfect cosmetics.

A large portion of gigged Les Pauls are used with glued headstock repairs, not all with refinish either. At least my 84 lacks this provenance... ;)

3/27/22 7:52 PM

BTW, relieve the string tension before your gluing/cure of the glue.

3/28/22 8:11 AM

The finish is actually in really good shape, so I don't anticipate having to do anything with it. It's satin and it does not fill the grain, so if I get everything aligned and glued, there should be no evidence of of the crack in the finish. Worst case, I have some clear satin lacquer that I can use to touch it up. I've already disconnected the two lowest strings from their tuners and detensioned the other two.

I'm off to make spool clamps!

4/1/22 12:07 PM

Here's a follow-up for anyone who's interested:

I made 8 spool clamps and used seven for the repair, plus a couple of small C-clamps to hold a reinforcement strip at the battery case cutout. I used Titebond Liquid Hide Glue for strength, open time and reversibility, should that ever be necessary.

https://link.shutterfly.com/4TY2zH3ySob

I couldn't quite get the two sides perfectly aligned, but they're within .005" or less. The joint is slightly visible and you can just feel it (it looks worse in the pics than in person). It's structurally sound and I added a small internal cleat at the end of the split and another in the middle for reinforcement.

https://link.shutterfly.com/t622xn1ySob
https://link.shutterfly.com/kwW5PsZySob

I tested some clear lacquer in one area and the result is lighter than the original finish. All Kala could tell me is that this discontinued model was made in Asia and finished with some form of satin polyurethane varnish. I suspect that it probably has an amber hue to it.

I'm going to have her look at it and decide whether she wants it sanded and refinished. Frankly, I hope that she decides to treat this as a battle scar and use it as-is. Matching an unknown finish could be a real pain and I'll probably have to do the entire side in order to get a consistent finish. I definitely don't want to make it look worse.

If nothing else, this has been an interesting learning experience.

Last edited by Brian Nystrom on 4/1/22 12:52 PM; edited 2 times in total

4/1/22 12:45 PM

With no shuterfly accnt, can't see the pics.

If you like, email them [little envelope there] to me and I will host/post them in the thread.

quote:

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Matching an unknown finish could be a real pain

---

4/1/22 12:52 PM

My fault, I didn't post shared links. They should work for you now.

4/1/22 1:01 PM

Car or Telecaster?

Nice work Brian, something I would have neither the skill nor patience for.....

4/1/22 1:04 PM

Got it.

In a way, if a right handed bow and upright instrument, it won't be in your face like a scratch on your drivers door. ;) Or top bout of an guitar you'll see a lot more. ;)

But seal it for sure, and I'd paint some finish along the crack line inside as well if practicable.

Some silica packets [Desiccant Dehumidifiers] in the case during sleepy time not bad idea either. In case, literally.


BTW, also arting up the instrument can cover up stuff too.

4/1/22 3:41 PM

Agreed, she's not going to see it while she's playing it and neither will anyone else. The glue has sealed the edges, but I can lay down a thin line of lacquer on the outside, just in case. On the inside, there's a thin like of squeeze out, so I think it's OK. I can only reach about half of the crack and some of it isn't even visible through the sound hole.

With ukes, they actually recommend a humidifier for the case, to keep the wood from drying out and shrinking.

I do have a few rolls of pinstriping tape...

4/1/22 3:44 PM

Dan, I'm a compulsive repairer and I simply can't help myself. I actually like challenges like this, as long as I think I can handle them appropriately.

Hmmm, I guess CRS actually stands for "Compulsive Repairman Syndrome". And all along I though it was "Can't Remember S**t". Actually, both apply in my case.

4/1/22 4:09 PM

Just show her Trigger

https://www.youtube.com/watch?v=b6IB0trJoJU

4/1/22 4:09 PM

It’s not perfect but it’s plenty good. Instruments that get played do not remain pristine. I got one guitar about 42 years ago and it’s kinda beat up. And I love every ding and scratch.

4/2/22 7:32 AM

Sparky, I took your advice about sealing the crack on the outside. I ran some lacquer along the edges, sanded it lightly with 1500 grit and blended it with 4/0 steel wool. It definitely softened the feel of the edges and reduced the visibility of the crack a bit. I think she'll probably be happy with it as-is. I'll find out tonight.

We'll also be cracking open the first batch of porter that Linda and I brewed, so it should be an interesting evening.

4/2/22 10:54 AM

Someone is lucky to have a friend with skills for the task. And the willingness to help friends. ;)

4/4/22 8:38 AM

The owner picked up her U-Bass yesterday and was very happy with the repair. However, I got a bit nervous when she asked if I was interested in getting into the luthier business. Apparently her preferred luthier has aged out of the business with severe arthritis. I had to explain that I took on this job because I was confident that I could fix it, but anything more complex would probably be beyond my ability. My major concern is that I would never want to make a bad situation worse. That said, I wouldn't be surprised if more more of these relatively simple repairs come my way.

In the afternoon, I worked on one of Linda's bikes and two for a friend, so I was back in my comfort zone.

BTW, the porter we brewed turned out great!

4/4/22 3:48 PM

Glad you didn’t get into the porter enough to drop the bass again!

4/4/22 7:08 PM

A friend of mine just took delivery of one of these bad boys:

https://www.ibanez.com/usa/products/detail/rg5120m_00_01.html

4/4/22 8:18 PM

Ahh... a shredder with a wizard neck. ;)

Dive bombs away.