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Length and its relation to tension

Discussion in 'Strings [BG]' started by Gregory Bruce Campbell, Mar 12, 2003.

  1. Gregory Bruce Campbell

    Gregory Bruce Campbell

    Apr 14, 2002
    Helena, MT U.S.A 59602
    BEE basses, Morley pedals
    I am curious about a topic regarding length of strings...

    I believe that the physical length of a string changes tension over the vibrating (or scale) length of the string regarding tension...

    The information I can find is only debates based purely on speculation...

    I would like to maybe buy a tensiometer... a tool often used in the aircraft industry...

    Does anyone have any true insight or know of experiments tried regarding string tension?

    Is there information available about builders actually PROVING this debate one way or another?

    Again all I can find is information on theories, no proof yet...

    Please enlighten me with your thoughts! :)
  2. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA
    I think if you simply did a search for "tension" at this site, you'd run accross more reading than you'd care to deal with. Much of it very detailed and substantiated.

  3. Gregory Bruce Campbell

    Gregory Bruce Campbell

    Apr 14, 2002
    Helena, MT U.S.A 59602
    BEE basses, Morley pedals
    Thank you very much! I'll try it.
  4. rickbass

    rickbass Supporting Member

  5. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    You'll find a few threads in the Luthier's Forum. They include not mere opinions, but the equations. The tension is proportional to the unit weight (weight per length) of the string, and proportional the square of the scale length and to the square of the frequency. This information is obtained both from college physics books and from the D'Addario website. Furthermore, I have used the equation in working with wire cable, and with belts, and have confirmed results both with deflection-type tensiometers and with inline (tension-loaded) load cells.

    This is not magic, it's science. Logical and repeatable.
  6. Gregory Bruce Campbell

    Gregory Bruce Campbell

    Apr 14, 2002
    Helena, MT U.S.A 59602
    BEE basses, Morley pedals
    Thanks guys!
  7. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001

    Now that I think of it, I also did it in Physics lab in college. The equations and relations held true then, and I don't thinks the laws of physics in this universe have changed in the last few years.
  8. pilotjones,
    I was wondering if a MUCH stiffer wire core-maybe ALMOST inflexible-like solid rod rigging on a sailboat would allow for a short scale (30" or less) low B string to be stiff enough to sound as well as a 34-36".

    Seeing as how short strings are floppy, would it be possible to make something with almost no flop to begin with that could still sound a B? In other words, something almost OTHER than a string-as we think of them?
    You seemed (from your posts/job experience,etc.) to be the guy to ask. I am longing for such an invention but have no metalurgical/machining skills to experiment myself!:meh:

    Thanks, Jim:meh:
  9. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    Unfortunately, both theory on string vibration, and actual practice rely on several assumptions that are mostly the opposite of what you are suggesting.

    1. The string is flexible. Little energy is required to deflect it away from rest position. (Deflection is the side-to-side movement of vibration.)
    1a. Little energy is required to bend it away from its rest 0 degree angle at the ends.
    2. Its cross-sectional width is small compared to the length.
    3. Its amount of deflection is small compared to the length.
    3a. The angle of deflection at the ends is small.

    In theory, when these conditions are met, the string can be treated basically as a one-dimensional object with mass. The forces of resistance to bending can be neglected. In practice, meeting these conditions makes it move and sound "like a string" instead of "like a solid bar."

    Lets say you started with a plain wire string, like an unwound electric guitar g-string, and strung it on a 34" scale bass, at a moderate bass tension. For this example, I'll use the following: a .017 guage string, which when strung as a guitar g on a 25.5" scale guitar would have 16.6 lbs tension; and the tension of a .100 bass E-string, which is 36.5 lbs. Surprisingly, it will sound a note a nearly two semitones above a guitar g. This is because, despite the increase in scale length, we bassists use over twice as much tension! But you now want change the sting somehow to make it produce a bass low E.

    In order to lower the pitch of a string, while maintaining the same scale length and tension, one must manipulate the remaining variable- the unit weight, or mass per unit length. However, if we did this by simply making a single strand of wire thicker, it starts violating the assumptions above (it becomes stiff), and it starts sounding like a solid bar instead of like a string. This is why wrap-around-core consruction is used- it increases mass per length, while (mostly) maintaining the flexibility.

    This D'Addario file is a good reference for string tensions.
  10. Gregory Bruce Campbell

    Gregory Bruce Campbell

    Apr 14, 2002
    Helena, MT U.S.A 59602
    BEE basses, Morley pedals
    Here is the reason why I originally posted...

    But, before I begin, I'm not looking for flames JUST FACTS... I will take great offense if the subject changes to focus on what people DON'T LIKE about how many strings I use...

    I currently play two Warrior 9 string basses... I left Warrior on good terms as an artist THIS WEEK to pursue building a signature bass with BEE basses...

    My friends at Conklin turned me on to the fanned fret concept and I am now way into fanned frets!

    The reason I initially wanted fanned frets was to shorten the treble side to allow me to use a wound A# string instead of a .018 plain ... and I was able to figure this out accurately...

    Now I need to determine the scale length of the bass side of the neck...

    Being that the recommendation is unanimously a longer string for a lower note etc.

    Now the thing for me to solve... I would like the shortest span of the difference between scale lengths that I can possibly get away with to have it still be worth doing the fanned frets...

    Lately I have been having some wrist pain in my left hand, even with the usual 34" scale basses I play...

    I experience the pain on my 4, 6, and 9 string basses equally...

    I was HOPING to have my new 9 string built at 855mm (33.66135 inches) for the bass side scale length and 801mm (31.53537 inches) for the treble side scale length...

    I planned on compensating for the short string by making them physically longer past the nut to the tuner by making a reverse headstock 9 keys on one side...

    The debate is will the physical string length compensate? Most experts say that it is only the vibrating length of the string that affects the tone of what people often refer to as a tight "B" and I have an F# lower than that!

    I have see where companies extend the string length past the vibrating length such Warrior and Ritter...

    I am so confused!

    So the goal in summary, I want the treble side shorter so I can use a thicker string...

    I want the shortest fan span possible while still making it valid to even have done...

    (it has been recommended not to exceed a 2.5" difference, an i would like to keep it as close to 2" or under as possible)

    BUT, I want my "B" and "F#" strings to sound great!

    What specifically would you suggest?

    In the mean time, I'm going to read the link that RickBASS suggests as many times as I can find the time to do today!
  11. Gregory Bruce Campbell

    Gregory Bruce Campbell

    Apr 14, 2002
    Helena, MT U.S.A 59602
    BEE basses, Morley pedals
    One of the reasons I felt comfortable trying to get away with the shorter scale length, is that...

    I recently put SIT rock brights on my Warrior and the core was so much thicker and higher tension than my usual Dean Markley blue steels that I had to give my truss rod 2 cranks to accommodate the strings! They sound the best by far for the 3 brands I've tried for the low F# string.

    There is much more high frequency clarity in these strings! I assume it is greatly due to the tension!

    But I don't know for sure...
  12. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    String length in the nonspeaking portion does not affect tension.

    Core thickness does not either. If your new strings tuned up to a higher tension, then they must be heavier strings.
  13. The first point, agreed.

    The second point, I'm not so sure about. If it were true, then every roundwound .045, say, would have exactly the same tension, and both personal experience and the numbers I've seen on string sites like D'Addario and T-I suggest that's not true. Are you perhaps leaving out the mass factor, as pointed out in the Novax article? Since cores are solid and may be either round or hexagonal, it seems logical that strings with different size cores, and thus different proportions of core to wrap for a given overall diameter, could have different masses, and thus potentially different tensions at the same length and pitch.
  14. dhuffguitars

    dhuffguitars Luthier/Bass Wanker depending on your opinion

    Sep 18, 2001
    And can't the tension of the strings winding produce a different string tension at the same string guage?

    Dr strings show on their package that there is like .108 of metal on their .105 strings, but the tension of the strings winding it compresses it to a .105. So there is more mass on their .105 than another companies .105????

    I love this topic!!!!!!!

    Also, I know this is a TENSION topic, but shouldn't we add in the bolt on/set/neck through factor. And the neck stiffness also plays a factor in TONE, which is what we are after at the given scale length/string tension..........

    And the bridge mass/anchor point of the string, if it is anchored with balsa versus a 1" block of steel, the string anchor will give/flex a minute amount when the string is vibrated correct? Wouldn't that gives us the false assumtion that is had to do with string tension?

    I look forward to hearing from others!
  15. I dont understand why there is this concern with tension. I have a 5 string Yamaha bass with 34" scale, among others. My TI Jazz Flats, which are very low tension, sound wonderful, even the B. So do D'Addario XLs, which are medium tension. On the other hand, GHS Boomers, which are high tension, have a crappy B, even after trying many replacement Bs. This leads me to believe that string tension is not necessarily a factor in the performance of a B string.
  16. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001

    I agree, but only slightly. Yes, the string cross-section can be divided into the "core area" and the "winding area." The core is 100% metal, and the winding area is it least 79% metal and at most 21% air (there are a few assumptions being made here, that I won't go into unless anyone is interested). So increasing the core size while maintaining the same OD will increase the weight of the string - but only slightly.

    I just ran a spreadsheet of an approximation. On a string of .100 OD, going from a .017 core to a .020 core, an 18% increase in core size, yields only a .3% increase in mass.

    One of the approximations used was that of only one wrap onto a round core. Hex cores will increase the mass. Also, the greater the number of layers, the greater the mass, since the fill % goes up. Also nickel is more dense than steel, so a nickel-wound (not nickel-plated) string will be heavier than a steel -wound one of the same construction.

    One point that I had not considered before, and that I do think is significant, could be what 9string is feeling. A string with a larger core will be harder to pluck, or "stiffer." This is to say, it requires more force to pull it sideways the same distance, or put another way, it moves less given the same plucking force. This is because the string is less elastic. This difference would be felt most down by the bridge, where it takes more force to move the string to begin with.

    It's a fine point, but what this means is that a string with a smaller core will feel less stiff, and easier to pluck. People might describe this as lower in tension, but what it really is, is more difficult to increase the tension (during plucking). If the string were actually lower in tension, the note would go down in pitch, unless you increased the string size. And, given the same amount of energy put into during plucking, it would vibrate in a wider path, requiring raising the action in order not to buzz against the fretboard.
  17. Geoff St. Germaine

    Geoff St. Germaine Commercial User

    Yes, it is the mass difference between the strings that can make a difference, as well as stiffness. Good old waves and vibes.

    I am playing a Dingwall 6 string. The fan is 3.75" across the strings. The difference is 3/4" per string. One a nine, that would be 6", which is pretty huge. It makes a difference how exactly the bridge is laid out as well, it can alter the fanning significantly.

    I don't see why there would be a problem exceeding 2.5". Maybe it would be uncomfortable on a 9 string to fan them that much. I don't even know what the difference would be if the difference between the top and bottom were only 2" on a 9 string. That is only 1/4" difference per string. Maybe that is the difference you are looking for, just something to think about.

  18. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
  19. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    One of the things to consider is not just the amount of staggering, but also the angle. In other words, let's say you decided on 3/4" difference in length between sucessive strings. You could do a fanned fret instrument with a straight-across (conventional) nut, and all the staggering at the bridge end. You could do one where the bridge is not at all staggered (except for intonation), but the strings were staggered 3/4" at the nut - producing a very extreme angle! Or, you could do what Dingwall does (and Geoff correct me if this is not accurate): the 7th fret (1/3 of the way up the string from the nut) is straight, so the nut is staggered at .25 per string, and the bridge (before intonation) at .50 per string. This .25" in length at the nut, combined with an approximately .375 distance string-to-string, produces a 34º angled nut (compared to normal nut), a straight 7th fret, a 22º 19th fret, etc., all of which Dingwall felt made a comfortable instrument.
  20. john turner

    john turner You don't want to do that. Trust me. Staff Member

    Mar 14, 2000
    atlanta ga
    9 string?!?! what the hell do you need _THAT_ for? ;)

    seriously, as was stated earlier, there are a few truths that need to be stated.

    1. the string outside the vibrating area of the string will have no effect on the tension of the vibrating area of the string. the only effect that what goes on at the headstock or the bridge can have is how tightly the string will be seated in the nut or bridge saddle. this may affect how the string feels when you pluck it, but it's not going to effect the tension.

    2. if you want a string with higher tension at a certain scale length tuned to a certain note than what you are getting, you're going to have to use a heavier string. the difference between different manufacturers strings of the same scale length and string diameter using different string architectures, such as hex core, compression wound, etc, is really going to be negligible compared to change the string gauge.

    the new sit strings you are using that you like so much are a heavier gauge than the dean markleys. you should try getting a heavier gauge from dean markley as well and see how they compare.