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  1. #1
    Administrator kwun's Avatar
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    Default BG65 tension loss is higher than we think

    I recently received 2 AT900P to be strung. one of them BG65@30lbs. the other one BG65@26lbs.

    it just happens that i did the 30lbs one a day earlier than the 26lbs. both are strung with identical stringing pattern at these main/cross tensions:

    30lbs: 29/31
    26lbs: 25/26.5

    both string have never touched a shuttlecock. so all tension loss is internal.

    i didn't record the frequency of the 30lbs when it was done, but i did record the frequency of both right after the 26lbs one is done (and one day after the 30lbs one)

    30lbs: 1170Hz
    26lbs: 1163Hz

    what does that mean? that means BG65 strung @30lbs loses almost 4lbs just sitting there. untouched.

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    Oh my :0, I just got my z force strung at 26 lbs with 65 ///:,

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    I think the BG65 is indeed a stretchy string. Great for durability, not so for long term playability.

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    Regular Member Blitzzards's Avatar
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    There are two parts to this:

    1. Do you consider the string bed resonant pitch right after stringing the actual tension or the one after one day of tying the final knot? You are still correct that BG65 stretches quite a lot but the other strings do the same thing - BG80, NS30, NBG99, etc. from my experience.

    2. How much do you need to tension to get rid of the slack in BG65? One experience I have is stringing BG65 at 33lbs, played with the racquet for a week, and from then on until I cut the string after one month from the string job (i.e. week 2 onwards), the tension settled to roughly 30lbs.

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    Regular Member wguan126's Avatar
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    That's a lot. Just a wild hypothesis. Is it possible that the AT900P with 30 lbs happens to have some injuries in the frame? A microfracture may affect stability which in turn lowers the frequency. 4 lbs overnight is madness.

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    Administrator kwun's Avatar
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    no. i have inspected the frame beforehand, i wouldn't have strung it at 30lbs if there is any type of fracture. and it probably won't have survived anyway.

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    Regular Member wguan126's Avatar
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    Any fractures that are recognizable with unaided eyes are not microfractures. I'm sure you've seen ppl break rackets with a clear or smash. Those are the rackets with preexisting conditions. LOL!

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    Regular Member Blitzzards's Avatar
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    A related update:

    I strung a racquet with BG65 Power at 34lbs last week. The string bed resonant pitch has dropped to roughly 32lbs now over the weekend. I have not gotten the chance to play with the racquet yet.

    The thickness of the string really does affect the tension retention. One might consider regularly restringing with it after using it for two weeks, like how the professional players do

    But I agree a fresh BG65 or BG65 Power possess one of the best crispy and stiff stringbed feel.

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    Hi kwun
    Tension loss of bg65 is a very well known an old story.
    Did you pre stretched? that you ve told us might be expected if the string is from a 33ft set (coil memory), without pre stretching and using a crank machine pulling just once each time.

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    Regular Member wguan126's Avatar
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    Quote Originally Posted by silvestre351 View Post
    Hi kwun
    Tension loss of bg65 is a very well known an old story.
    Did you pre stretched? that you ve told us might be expected if the string is from a 33ft set (coil memory), without pre stretching and using a crank machine pulling just once each time.
    @silvestre351 , you miss the point. No matter with prestretch or not, given everything being equal, 4 lbs are a lot. Besides, I don't think manual prestretch or coil memory is a big deal for wise 2086. But it is not clear regarding the ECP prestretch setting he used.

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    Regular Member craigandy's Avatar
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    If you had recorded the frequency right after stringing the 30lb racket and it was consistent with others 30lb bg65 frequency then maybe you could say this drop happened, but you may have just made a mistake. If you are stringing yonex pattern 2 piece lots of room for discrepancy at tie offs etc.
    Would be nice to find out, but not much can be taken from the info you provided

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    Hi wguan126
    Of course 4 lbs is a huge loss in such a short time. I totally agree!
    It was never mentioned he used a wise 2086, I also have one, I apply prestretch 10 %, and I would be very surprised if it would result that tension loss, unless the ECP and prestretch are disabled.

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    Administrator kwun's Avatar
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    to clarify, it was done with Gamma 6004 6pt + WISE. prestretch was on.

    yes. tension loss for bg65 is a known factor for a long time. the point of this thread is not to point out the tension loss itself, but the magnitude of it. everybody says, yeah, i might lose a lb or 2 lbs. as we have experimented before, even bg80 would lose a pound overnight without hitting the shuttle once. the tension loss for bg65 was thought to be in the region of 2lbs or so. i just didn't expect the tension loss to be as high as 4lbs.

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    Administrator kwun's Avatar
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    Quote Originally Posted by craigandy View Post
    If you had recorded the frequency right after stringing the 30lb racket and it was consistent with others 30lb bg65 frequency then maybe you could say this drop happened, but you may have just made a mistake. If you are stringing yonex pattern 2 piece lots of room for discrepancy at tie offs etc.
    Would be nice to find out, but not much can be taken from the info you provided
    the comparison is quite sound. as it was done using the same stringer, machine, flow and pattern.

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    Administrator kwun's Avatar
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    Quote Originally Posted by wguan126 View Post
    Any fractures that are recognizable with unaided eyes are not microfractures. I'm sure you've seen ppl break rackets with a clear or smash. Those are the rackets with preexisting conditions. LOL!
    if there are any fractures in the racket that is substantial enough to structurally contribute to a few pounds of tension loss at 30lbs. i think the racket would've experienced a catastrophic failure already.

  17. #16
    Regular Member craigandy's Avatar
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    Quote Originally Posted by kwun View Post
    the comparison is quite sound. as it was done using the same stringer, machine, flow and pattern.
    Nobody is perfect everyday. Any fault that happened will less likely show up directly after stringing, more likely after the strings have settled, especially with tie offs etc(I am pretty sure you cannot recreate the same pull by hand on the knots every time and all that goes with it). I am not saying something untoward happened I am just saying it is a possibility and we (even you) don't know with the limited info you recorded.

    It would be interesting to find out though and also where the loss is. I started string 1 piece for bg65 and tension loss is much less. I strung, it tested frequency, then next day it had obviously dropped inc 1 session. Still sitting at that exact same frequency after another 6 hours play(10 days) though.

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  19. #17
    Regular Member wguan126's Avatar
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    Quote Originally Posted by kwun View Post
    if there are any fractures in the racket that is substantial enough to structurally contribute to a few pounds of tension loss at 30lbs. i think the racket would've experienced a catastrophic failure already.
    You misunderstood my argument, kwun. 1) microfractures will not contribute to tension loss. instead, it will affect the stability of the frame, which in turn affect string vibration (or string swinging) during testing due to the energy loss at the microfractures. This results in a lower frequency. In other words, the tension appears lower than what it actually is. Nevertheless, I give it to you that this is a wild hypothesis. 2) To your comment of a catastrophic failure, if the fractures are at 12 o'clock, it is likely that the racket will not manifest a failure during stringing. Replicate the experiment will give the final verdict. Nice finding!

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