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Thread: Ko'olau Alohi Strings

  1. #11
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    Quote Originally Posted by rappsy View Post
    So, is there a string of this type that you have changed to? I do like this nylon type string.
    No, I don't have Alohi or Titanium strings on any of my ukes any more. I prefer the more stable fluorocarbon strings in general.

    You know that I'm a fan of Oasis strings.

    Quote Originally Posted by stevepetergal View Post
    I tried Alohis a couple of times. My experience was negative. Like yours, mine took forever to start holding a tune. Then, once they did, I didn't like the way they sounded. I don't believe the warm strings/cool strings thing. Moving up or down in pitch a but, due to temperature change? Mm...maybe, but strings re-tuning themselves? Quote the Cowardly Lion, "Imposserous"!
    They don't change by themselves, it's a thermal expansion/contraction effect of the material. Steve, you'll find several thread references to the temperature sensitivity of the Alohi / Titanium strings if you look. Here's a couple.

    http://forum.ukuleleunderground.com/...hi+temperature
    http://forum.ukuleleunderground.com/...hi+temperature
    http://forum.ukuleleunderground.com/...hi+temperature

    Also found a great technical explanation of why nylon strings go sharp from a polymer engineering professor on the AGF.
    http://www.classicalguitardelcamp.co...art=15#p593985

    "Re: strings going sharp during play
    Quote
    Post by grwagner Thursday 25 November 2010, 10:43 am

    As luck would have it I teach polymer engineering at a local university...

    Nylon (polyamide) is a highly crystalline thermoplastic. In the melt phase (liquid) it's amorphous with the molecules going in all directions and not in contact with each other. As it cools and solidifies, it crystallizes. The universe being what it is, the molecules try to minimize the amount of energy contained in the crystal structure. They do this by packing as closely together as possible. With Nylon 66 you get long parallel chains of molecules linked by Van der Waals (VdW) bonds. The crystallization process is affected by temperature, and the rate of crystallization drops as the temperature goes down. What this means is, the exact conditions of drawing the string are very critical for the final properties of the polymer. If the strings are cooled rapidly after drawing they will be less crystalline, but if they are warmed up the process will continue at a slow but measurable rate. In short, the manufacturing process has a big impact. The thicker strings will tend to cool more slowly during processing and thus be more crystalline in the core than on the surface. This results in a heterogeneous structure that can change slowly over time (hence some of the troubles we have with "defective" G strings). Factor in that the transition from amorphous to crystalline results in 4-7% shrinkage and you get the idea that the bulk of the tension variation comes from the relation between the continuing tendency to crystallinity fighting with the amorphous "regions" left in the finished product.

    There is also a work-hardening effect, where vibration results in chain dislocations and re-forming of VdW bonds, which might account for a fair amount of the sharpening of the note. This effect is reversible because of the tendency of polymers to creep when left under tension.

    On top of this you have the thermal expansion of nylon. As it warms up it expands (0.004% per Kelvin degree) - but here you've got to be careful to think in 3D. Does it expand radially (increasing tension along the length) or linearly (decreasing tension along the length)? Most strings are produced by drawing, so the alignment of the molecules is along the length of the strong, known as "machine direction orientation". Most of the VdW bonds will then be radially aligned, since they are between parallel molecules. Since the VdW bonds between molecules are much weaker than the covalent bonds within the molecules, they'll loosen first when warmed or put under mechanical tension. What you get here is - with new strings - a "caterpillar crawl" along the chain where the molecules dislocate. That makes the strings go flat. Then - with old strings that have acquired a degree of temper wherein the VdW bonds don't move so much any more - it's the radial bonds that elongate and make the string swell a bit. That tends to pull the chains, so to speak, and can result in sharpening of the note.

    There's also a tiny bit of change in the elastic modulus with temperature - it goes down - but for a highly crystalline structure the effect is not great. And then there's humidity, which tends to swell Nylon. And the neck itself, which can expand or contract since it's made of wood. All of this probably explains why some guitars are less affected than others.

    Hope that clears things up rather than confusing it more..." Post by grwagner on the AGF Thursday 25 November 2010, 10:43 am
    Last edited by Doc_J; 07-29-2017 at 09:01 PM.
    -Hodge
    Humble strummer of fine ukes.

  2. #12
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    All that is well and good. But, the formula quoted proves there is an extremely small amount of change as the temperature of the string rises (0.004% per degree Celsius). That may be significant when going from 0 to 30 degrees, but that's not what we're talking about. It might be interesting if we could test this theory on ukulele or classical guitar strings. No one has established what temperature changes these strings experience, if any. It is possible, as the player's fingers contact them the warmth of the fingers and the friction between the fingers and strings raise the temperature. But, this would be extremely slight, and only in the very small areas where the fingers contact the strings. All other factors being equal, my guess is the temperature change across the length of a string could not be even that one degree, possibly not anywhere near one degree. That's not taking into consideration the movement of the string as it vibrates. This interaction with the air likely would have some cooling effect, and this would take place across the entire vibrating portion of the string. Again, so slight you would never notice, but the strings might actually be cooling as we play. We may have a formula and a theory or two, but we don't have the science.

    The thing I said was preposterous is the notion that strings will re-tune themselves. The general tuning may go up or down on its own, under certain circumstances. But as it does, it goes out of tune. When reversal of these circumstances causes the tuning to go in the other direction (down or up) it also goes out of tune. The relationships between the strings are always changing, and the factors that change these relationships are incapable of making the calculations necessary to tune the instrument. A monkey couldn't tune you ukulele. It's ridiculous to suggest that a change in humidity (or temperature) can.
    Last edited by stevepetergal; 08-11-2017 at 02:09 AM.
    If everybody wanted peace instead of another TV, then there would be peace.
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  3. #13
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    This is an interesting thread. My question is what type of tuners do you have? I've had issues with friction tuners slipping and keep a screwdriver handy so I can tighten them up the right amount when necessary, so just another possiblity worth considering depending on what type of tuners you have. If they are geared then that's less likely the cause but still a possiblity.

  4. #14

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    I experienced the same thing as Hodge : the strings would be Cold and sound flat when I first picked up my uke. So, I'd retune right away. They warmed up and got sharp. So, I would have to retune down.

    I have Gotoh tuners on the ukulele. Guess it's time to change to fluorocarbon strings.

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