Double Bass Plywood delam on upper bout

E

Ed S

Nov 14, 2019
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#1
I'm experiencing what I believe is delamination on the G-side upper bout of my ply (2010-ish Engle). If you look closely at the image below, you will see 3 spots - 2 appear as chips, and between them there is a line, where I assume a 3d chip is beginning.

The first one appeared a year or more ago. I just assumed it was a chip in the finish. This is my "beater" bass, which gets played outside in all weather, laid down (with bumpers) in parking lots, etc. I don't TRY to beat it up, but I'm not worried about keeping it pristine. So I didn't think about it. My main concern was not picking at it or anything to make it worse.

When I noticed the second one, I asked my wife, who is a luthier, to take a look on it. My wife makes and works on violins. The only basses, and the only ply, she works on are mine. Her assessment is that this is a delamination, rather than just the finish. Looking closely, she sees a seam where the ply was distorted when bent. Her plan is to inject some hide glue, clamp it, and then brush a thin layer of varnish over it.

I just wondered if any of you who work on plys more regularly have ever encountered something like this, and if you have any thoughts on how to address it (if you feel it NEEDS to be addressed.)



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#2
Been years, but delam on Knilling/Glaesel/Englehardt/Kay plywoods usually, but not always, started at an edge and moved inward. Seldom was there a visible sign of it, unless at an edge. Aging and drying were the reason most of the time. Tapping or dragging a fingernail over a separation sounds different that nonseparated, hollow, and can feel soft under finger pressure. Can also rattle when played. Glue and clamp would be the way to stick it back. If you don't mind a tiny hole(s), cleats and a cleat jack would apply pressure to both sides that you otherwise couldn't get with the top on. Basses that have started delaminating keep on delaminating, something to keep up with.
 
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#4
Cool. Do you often see chips occurring in a straight line like that?

And if you encountered them, would you just ignore them, or try to keep them from worsening.

To the extent I was concerned at all, it was due to the fact that they seem to have been multiplying.
 
#5
Ed S said:
Cool. Do you often see chips occurring in a straight line like that? And if you encountered them, would you just ignore them, or try to keep them from worsening?
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If you mean the chips along the front of the neck joint: The finish is broken all along the joint, which indicates some minor neck flexing side-to-side. This could mean some weakness in the joint, or simple thermal or humidity expansion, or it could mean the bass went down on or took a hit from its bass side that shook the neck. It's not something to worry about now, but if it progresses substantially you'll want to have a pro take a look at it.
 
#9
Ed S said:
(Let's hope my bassplaying skills exceed my photography chops!)
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I'm sure they do... :D

To me looking at them through a digital microscope (!!), those two items appear to be little divots like there was some tiny collision with something hard, sort of gouging into the finish. The little scratch in between them looks like a similar occurrence in its infancy.

If this were my bass, I'd guess it was from my Bass Buggy, as the straps convene with the bungee cords very near that place. Do you use a Bass Buggy too?

I couldn't discern any de-lamination just looking at the picture.

I am not a luthier but if there really is a de-lamination forming there and injecting HHG was a possible solution, I'd be concerned about how hard it will be to clamp that location. Short of opening that seam which might cause other trouble, it probably would require creating some cauls for the ribs on both sides of the neck block area and using a really big clamp. My understanding is that HHG doesn't fill well, so I'm not sure what adhesive would be best there.

I'm afraid if it were my double bass and it was definite de-lamination there in that location, I'd probably proceed full speed ahead with some benign neglect and maybe just watch it for a long while.

Whatever it is, I'm sure that double bass sounds great, and your gut strings look wonderful!!!

-- Don
 
#10
Don Hergert said:
To me looking at them through a digital microscope (!!), those two items appear to be little divots like there was some tiny collision with something hard, sort of gouging into the finish. The little scratch in between them looks like a similar occurrence in its infancy.
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That was my first thought. Although I'm not as careful w/ this bass as I am w/ my other, I couldn't figure out how I banged that particular spot. Another thought was, during the summer I regularly play outside in the sun - tho not generally in the hottest part of the day. So I wondered if that was an effect of heat/sun.

I know I've seen some old plys with wear on that spot. I wondered if I was seeing the beginning of that. What got my attention, however, was when the 2d (and infant 3d) divots occurred in a perfectly straight line. If I'm careless enough to be banging my bass there, how could I simultaneously be precise enough to bang it repeatedly at the exact same spot? ;)

Pretty sure the perfect alignment and the thickness of the chips contributed to my wife's thought that they involved more than the finish.
Don Hergert said:
If this were my bass, I'd guess it was from my Bass Buggy,
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Now THAT'S a great idea. I do have a BB, and have been using it more often the past year or 2 as my hip has worsened. But I ALWAYS use it with the bass in the bag. And I'm not sure I'm careful to always put it on the same side. No marks on the other bout. Tomorrow I'll check if the bungies meet at that exact spot.
Don Hergert said:
I am not a luthier but if there really is a de-lamination forming there and injecting HHG was a possible solution, I'd be concerned about how hard it will be to clamp that location.
Click to expand...

Yeah - she spoke w/ a good friend (who is a master luthier) and he made a suggestion involving seam clamps or something. Again, these folk are not use to working with ply. I think my wife's initial idea was for ME to press the chips down with my fingers for however long it takes to set! :D

Don Hergert said:
I'd probably proceed full speed ahead with some benign neglect
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We think alike, my friend! I've got ZERO problem with aesthetic damage. Just want to avoid/delay anything structural. My biggest concern was that some day I'd absentmindedly pick at it like a scab...
Don Hergert said:
I'm sure that double bass sounds great, and your gut strings look wonderful!!!
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Well, it IS an Engle. So we all know it sounds like crap, isn't worth more than its weight as firewood, and is permanently damaging my left hand and wrist! ;)
 
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#12
KUNGfuSHERIFF said:
Don, lightly modified plastic clothespins can be used to clamp delaminating edge overhang on ply basses.
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Thank you for that info KFS, clothes pins would be very handy, although it doesn't seem like the area Ed is describing is the edge overhang... I think he's looking at the rib center just below the neck block -- but I may have that wrong...

@Ed S, did I get that wrong, were you talking about the edge overhang?
 
#15
Ed S said:
Yeah - she spoke w/ a good friend (who is a master luthier) and he made a suggestion involving seam clamps or something. Again, these folk are not use to working with ply. I think my wife's initial idea was for ME to press the chips down with my fingers for however long it takes to set!
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From above. When/if she decides to glue it, I'm confident she'll be able to get it done.
 
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#16
I don't think there's anything there TO glue. I just see a couple little dings or peck marks. If I had to guess, I'd bet that this is where you park the zipper on your bass bag and then it gets bumped and makes that little peck mark. I've got little marks like that all over my bass.
 
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#17
Don Hergert said:
Ok, thank you Ed for clarifying...

@KUNGfuSHERIFF, I would trust your judgement much more than mine, what would be the best approach for a ply de-lamination in that area if it existed?
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If it existed? Take the top partway off, slit the delaminated area with a razor blade, knife in some hide glue and clamp with magnets. Luckily this ain’t that.
 
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#18
I took a close look at my bass and I found multiple location with little peck marks just like the photo. I can guarantee there's no delamination on the ribs of my bass! (It's fully carved.)
 
#19
Thanks for checking. Were they all in a row on the upper bout like mine? I likely would not have even noticed these if they weren't staring me right in the face while I play!

I am in no way committed to the idea that this is delam. So please don't get hung up on that term. My wife looked inside, and there certainly is no damage to be seen. She has made and finished several instruments, and in her opinion, these are "thicker" than the finish. But that is just one part-time non-bass luthier's opinion.

My sole concerns are:
1. how/why is it happening; and
2. as it seems to be increasong(albeit slowly/miinmally), how do I dufus the process (or do I even try?)

Checked the zipper and bass buggy ideas suggested upthread, and don't see how those could be the cause. I really don't care if these little chips chip off leaving little white divots. But my wife is going to see if she can "stabilize" that portion of the lam/finish.
 
#20
The peck marks I saw on mine were in various locations. Mostly, I think, on the lower bouts, because that's typically where I park the zipper for my bag.

If you're worried that the finish might flake off, put a dab of Bullseye Amber shellac on each one.
 
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