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Saddle Pulling Up, How Urgent?

Discussion in 'Setup & Repair [DB]' started by jlmorgan84, Jul 11, 2017.


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  1. jlmorgan84

    jlmorgan84 Supporting Member

    Feb 16, 2014
    Seneca, SC
    So I picked up my bass from my repair guy a few days ago, he glued a small seem separation down for me, and while playing it today I noticed that the saddle is pulling up, not completely, but it's definitely tilted.

    I've got a few shows coming up the next few weeks. I know this is an easy fix and probably wouldn't take long, but it's a bit of a drive to the shop and I'd like to have the bass in hand. I've sworn off doing repairs myself.

    How urgent is it to get the saddle glued back down? Is it going to damage anything to leave it this way for a few weeks? It's a plywood bass so it's not like the top is going to crack. What are your thoughts?
     
  2. I had that on my bass for 30 years until I corrected it myself a few weeks ago. No damage, and my one has a carved top.
     
    jlmorgan84 likes this.
  3. jlmorgan84

    jlmorgan84 Supporting Member

    Feb 16, 2014
    Seneca, SC
    You've just told me what I wanted to hear, thanks!
     
  4. Ortsom

    Ortsom Banned

    Mar 23, 2016
    As DM says. But keep an eye on it to see that it's not going anywhere.

    Might be caused by the tail gut stretching a bit, during tuning-up the strings. Don't forget to look at your bridge & push the crest down as required (TP side square to the top, good contact of the feet/soles w/ top), to prevent bridge warping.
     
  5. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    if all your luthier did was glue up a seam, it is highly unlikely the that the tailgut will stretch any more image.
    However the tailgut, particularly if it is steel cable, can imprint rough grooves in the ebony, and when you tune up the strings the tailgut can catch on those grooves and pulls the saddle over. Filing the grooves gently and lube with graphite helps avoid this.

    FWIW I would never knowingly let a bass out if my shop with a lifting saddle. I think there is a possibility it could pop out during use - which would be embarrassing on a gig to say the least ...
     
    Last edited: Jul 12, 2017
    RSBBass likes this.
  6. Ortsom

    Ortsom Banned

    Mar 23, 2016
    Solid materials respond to a variation of load by deformation. How much they deform depends on how hard they are, but even the hardest diamond deforms. That deformation can be elastic, plastic, or a combination thereof. As a consequence the tail gut will (elastically) stretch a bit each time the instrument is tuned-up, regardless of the work done, or anything else. And when the tension is released, it shrinks again, by the same amount, that's what's called 'elastic'. This is basic physics, and even a luthier should know this, at least if he has any interest in understanding the world around him. Of course that stretch during tuning up will come in addition to movement caused by settling in of the gut during the tensioning up, and the net result is an upward force on the saddle. At some stage the glue gives.
     
  7. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    Thanks for the physics lesson. However, we know that the amount of elastic stretch on 8" of 3mm stainless cable under typical string load is so tiny as to be insignificant compared with the sliding movement over the bridge, or the initial bedding-in stretch when the cable is first tensioned :)
     
  8. It it were a carved top, regardless of how stable it may appear to be, it would make me nervous. A loose saddle being pulled against the top like a lever seems like it could induce cracking in the top grain. The saddle is a problematic area, even under normal conditions—dissimilar woods adjoining in a high-tension area that's basically a fulcrum. I can't even begin to count the number of old basses I've seen with those signature vertical streaks extending northward from the corners of the saddle where cracks have been cleated up.

    A ply bass wouldn't cause me such heartburn, however. Note: I'm not a luthier, nor do I play one on TV.
     
    Last edited: Jul 13, 2017
  9. Ortsom

    Ortsom Banned

    Mar 23, 2016
    Where have we learned that this TG is 3mm steel cable?

    Please explain: in what way is the initial bedding-in movement any different from from what's happening in subsequent tensioning-ups, to which I referred to as "settling in of the gut during the tensioning up"? IMO the same process happens over & over again, each time you tension up. If you don't agree, please explain why not.

    And what on earth do you mean by "the sliding movement over the bridge", which is allegedly so much bigger & more significant than the elastic stretch in the TG? Or is that once again just BS?

    IMO the tuning up process results in an lifting force on the saddle, which, depending on geometry & strength of the glue joint, may cause the joint to fail, at some stage. I think we very much agree on that. And that is what I implied in my #4, and once again I have no clue why you, Matthew Tucker, have to make such a point out of that. What is the red flag? Your statement that "it is highly unlikely the that the tailgut will stretch any more" is total rubbish, it stretches each time you tune up, and comes back each time you take the tension off. Nothing better to do over there?
     
  10. I would be very happy if you would write your opinion on the matter here, and leave the personal stuff out.
     
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  11. the_Ryan

    the_Ryan

    Jul 10, 2015
    Ithaca/Seattle
    Indeed.

    Discussing different opinions and explaining thoughts and (not) coming to a consensus are all good, but personal attacks make both sides look bad.
     
  12. RSBBass

    RSBBass

    Jun 11, 2011
    NYC
    Strictly on the physics I would disagree with the idea that the cable stretches when under tennsion and returns to its original length when the tension is released. This would only be the case if the material is 100% elastic. Some materials are more elastic than others but few are 100% elastic. Also over time the elastic properties of a material can change to being less elastic. So if a tailgut has been tuned and released several times, I find it unlikely that it would return to its original length, particularly if it was a metal cable.
     
  13. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    Most good tailwires are multifilament, whether stranded stainless, kevlar, dyneema or whatever. Typically, they are overengineered for the job; that is, the actual breaking strain of the cable used is way in excess of that expected to be encountered on a bass. The materials used are chosen for their low stretch properties.

    What is actually happening on a tailwire is this: When first strung up, as the cable is pulled tight, there is a degree of stretch as the filaments "bed" and knit together tightly, and as any knot used (in the case of synthetic) tightens on itself. Luthiers know to allow for this initial stretch, depending on the material used. But, after that initial stretch, to all intents and purposes, that's it! It doesn't spring back to initial length. (Sure, there is a tiny amount of inherent elasticity, but practically speaking, it is so tiny as to be irrelevant. Even IF the elasticity of an 8 inch cable was a huge 1/4" (unlikely), this elasticity would of course be distributed evenly along the whole length of the cable, so the stretch in the bit passing over the 3/4" saddle would be about 0.5mm in the old money, which is nothing!)
     
    Last edited: Jul 14, 2017
    RSBBass likes this.
  14. Now I am confused, because I thought multifilament meant "made by combination of different materials", but I suppose I am corrected.
     
    Matthew Tucker likes this.
  15. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    Sorry Povl, if I indulged in excessive technospeak.
     
  16. Ortsom

    Ortsom Banned

    Mar 23, 2016
    Povl & the_Ryan, to you I apologise for indeed letting my self go a bit, it's just that I'm getting totally sick & tired of Mr. Tucker picking on whatever I say, even when it is totally sensible.

    I gave my opinion on the matter in #4, which seems harmless enough: helpful and not in any way confrontational. I acknowledge that saying "Might be caused by the tail gut stretching a bit, during tuning-up the strings." is a quite broad-brush description of what's happening (and incomplete, it ignores the direction of the effective force of the TG on the saddle, as it bends over it, which is there in addition to friction forces). But there I thought that was enough. Makes sense?

    But once again me saying anything makes the red flags go up in Sydney, and it appears to be absolutely necessary to correct me. We hear that "it is highly unlikely the that the tailgut will stretch any more". Of course that is right up there with statements like "It is rarely possible to place the bridge foot exactly centred on the bar". In the BS category, that is. And the prime driver for making statements like that, appears to be to just negate what I say, rather than contribute to what the OP asked, or share valid relevant deeper truths, or insights.

    OK, so on second thoughts, we now actually seem to all agree that a TG does actually stretch a bit, when going from un-tensioned to fully tensioned. Yes, the first time more than later times (depending on the material), and yes, the ratio plastic/elastic also depends on the material. But that's all not so important. If the movement of the TG is less than the elastic movement of the saddle, the saddle will just elastically 'spring' (or strain) with the TG movement, and assuming all the forces are below their breaking strengths (the strain in the glue stays below it's breaking strain), nothing more will happen. If, on the other hand, the TG movement is more than the elastic movement of the saddle, 1 of 2 things can happen:
    • either the TG slides (indeed, a tiny bit) over the saddle, towards the pegbox. Prior to doing so, the saddle first experiences the static friction force, and when the TG starts to slide over it, that friction force is reduced to the level of the dynamic friction force, and movement stops. Due to weather & re-tuning you may build-up new friction force over time, but as long as the force is below the strength of the glue joint, nothing happens. So yes, make slick & lubricate, as that reduces friction forces. (Teflon shrink wrap?)
    • When building-up stress while straining, the saddle joint breaks before the TG starts to slide, and the saddle comes up a bit. Initially that will be a tiny bit (these movements are very small indeed), so small it is not noticed by the luthier, but over time it may tilt a bit more & become visible. How much it tilts after the glue joint broke depends a.o. on the shape of the saddle & the other dimensions, but the saddle position can be stable (like in DM's case). But it need not be, and a loose saddle is a hassle whenever you want to do anything, and easily fixed.
    Mr. Tucker has been so kind as to quote a number for the TG movement: "the stretch in the bit passing over the 3/4" saddle would be about 0.5mm", so the question to ask is not if one feels this is this is big, small or tiny, but how it compares to the elastic movement in the saddle's glue joint, before that joint breaks.

    Let's see, we're talking here of a well fitting HHG joint, wherein the thickness of the glue layer is typically 0.1mm. Can we see this 0.1mm thin layer of hard HHG grow to a thickness of 0.6mm at the edge, and do so without failing? I think it will either fail, or the TG will slide.

    Now you may say 'a set HHG layer is always thicker than 0.1mm', and that may be true, so say we have a more sloppy luthier and he made a 1mm thick glue layer. And you may say 'Mr. Tucker's 0.5mm estimate of the TG stretch is way too high' (as I think it is for a steel cable, but once again, we don't know what kind of TG we are dealing with here; it might be nylon that stretches even more), so say it stretches only 0.05mm. So then the question is: Can we see this 1mm thick layer of hard HHG grow to a thickness of 1.05mm at the edge, and do so without failing? 5% expansion without failing? And that year after year? I don't think so. I think even with these conservative numbers, either the TG will slide, or the glue joint will fail at some stage.

    (Now there's a lot more to be said, and we can go & take stress-strain curves into account for the different materials (TG, glue, woods), and the shape & height of the saddle, and the other dimensions, but we don't have the details.)

    After many more words, I cannot do anything else than conclude that TG stretch can definitely play a role in such a saddle joint failure, and that my initial "Might be caused by the tail gut stretching a bit, during tuning-up the strings." digests a lot easier, and does not at all need to be rebuked by a "it is highly unlikely the that the tailgut will stretch any more". Furthermore, the fact that Mr. Tucker himself suggests to lubricate & smooth the TG path implies that he too recognises there is movement, so why on earth negate what I said? Well, he just had to, apparently. And that's what this is all about.

    I would be very happy if you would not accuse me of turning the matter towards the personal, instead see that it is Mr. Tucker who starts being personal, for the umpteenth time.
     
  17. turf3

    turf3

    Sep 26, 2011
    Ah yes, just like academic controversies, where the fighting is so fierce because the stakes are so small.

    Sometime I'll tell you some stories of how apparently rational people can nearly come to blows over the format of part numbers.
     
  18. From a practical point of view there might friction kick in before the tailgut is completely straight. Together with the catching of the rope in the unwanted saddle grooves that might lift the saddle substantially more than pure material elasticity.
     
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  19. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    Yes, that is exactly what happens, and what I tried to describe in my first post.
     
  20. jlmorgan84

    jlmorgan84 Supporting Member

    Feb 16, 2014
    Seneca, SC
    So I'll just get it glued back down then? ;)
     
    RSBBass likes this.