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Racket head bent out of shape after stringing

Discussion in 'Badminton Stringing Techniques & Tools' started by ssj100, May 15, 2011.

  1. ssj100

    ssj100 Regular Member

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    Got my apacs Lethal 70 re-strung at 27 pounds. It has an isometric head. Unfortunately, it was strung at "27x27". The racket head was clearly bent out of proportion - it became significantly fatter and shorter.

    I'm getting it re-done at "25x27". That is, 25 pounds on the mains and 27 pounds on the crosses. Does this sound correct? I think it sounds right, as this would mean there is more tension pulling the racket head with "side-to-side" force.

    Another question I had was whether the "27x27" tension would harm the racket?
     
  2. ssj100

    ssj100 Regular Member

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    By the way, according to the apacs Canada/USA web-site, stringing should actually be done 3 pounds lower on the mains (for tensions between 23-31 pounds).
     
  3. GaryC

    GaryC Regular Member

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    I hope you can salvage your Lethal 70. How are YY's normally strung compared to Apacs? I am worried that when I need to restring my Apacs rackets that they might not do it like 23/26.
     
  4. ssj100

    ssj100 Regular Member

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    Just tell your stringer to string it at 23/26. I'm hoping 24/27 will do the trick for me.

    As far as I can tell, the Lethal 70 frame was still fine after we cut the strings again. It's a very robust racket. Regardless, I bought it as a back-up "copy" of my Lethal 60. If it breaks, I'll have more excuse to try other rackets - either one of SW35, VT80, MX80. However, I am really tempted to try the Lethal 90 and Lethal 100 too.
     
  5. GaryC

    GaryC Regular Member

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    Haha trying everything is always good. I just bought an edge saber 10 white and a nano 900 power because I want to try them when I can start playing badminton again. I just had surgery so I cannot play for 1 month :( so I buy things instead haha.
     
  6. kenzo

    kenzo Regular Member

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    Depends how much racket distortion there was, but if you haven't played with it there's very little chance it would have damaged the racket. The risk comes when you mishit on the part of the frame with the most stress, and on string breakage if a cross string breaks first. As for how much extra tension you need on the cross, 2 should be sufficient in most cases but 3 doesn't hurt.
     
  7. GaryC

    GaryC Regular Member

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    kenzo, is this normally how they string every racket? or is this specific to Apacs? I'm a newbie so I don't know anything.
     
  8. kenzo

    kenzo Regular Member

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    Well all stringers put extra tension on the cross to preserve racket shape and to provide equal tension on the mains and crosses. How much really depends on the stringer, some follow +2lbs, some +8.5%, some +10%, and looking at apacs, some +3lbs. The extra tension on the crosses is needed because once the main strings are tensioned, applying tension on the crosses will increase the tension on the mains due to the racket reshaping. So applying 27x27 on the mains x cross, you might end up with 28x27 and a distorted racket.
     
  9. kwun

    kwun Administrator

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    i always string main=cross and never have a distorted racket. i have done this up to 29.5lbs which is the highest i go regularly. i know AlanK who is the official stringer for Yonex USA also string main=cross. he has strung for all the top players in the world in various international and national events.

    whether the racket get distorted has a lot to do with the stringer's technique and skills as well as the stringing machine used.

    at the end of the days, whether it is main=cross or not doesn't really matter. what matter is how the racket plays.
     
  10. kenzo

    kenzo Regular Member

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    Technique and skill have nothing to do with whether the racket comes out distorted or not. If you tighten the side supports sufficiently (assuming you have side supports) then you won't have distortion, but it doesn't guarantee that you'll have equal tension on the mains and the crosses after stringing, that really depends on the flexibility of the frame. Not good practice and I don't recommend it, rackets I've tested that were strung with the same tension on the mains and crosses feel dead.
     
    #10 kenzo, May 31, 2011
    Last edited: May 31, 2011
  11. Blitzzards

    Blitzzards Regular Member

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    This is scientific nonsense. It is analogous to a stringer telling you that the tensions he gets out of his machine will feel "2lbs higher than the other stringers'". The only possible way for that to happen is if that stringer has his tension reader mis-calibrated and indeed puts 2lbs more than what it reads. How would you like it if you have two persons measure a simple line with their own rulers and then one of them telling you that even though his ruler reads X cm but then the actual length is X-2 cm?

    Doing the same tension for the main and cross strings will not by any possibility make the main strings have more tension than what you do the cross string at. The overall string bed may feel tighter but the reason is because if you do for example X-2lbs on the main and Xlbs on the cross the main strings are not as tight and even though the effective tension is Xlbs overall, the tension on the main strings is still not Xlbs and thus on shuttle impacts when there is displacement of the strings the main strings will suddenly feel not as tight as the cross strings.

    Stringing technique is a lot more important than you imply:

    When you string with a two point support machine, the factor that determines if the racquet frames come out distorted is if you balance out the tension pull of the main and cross strings. A shorter piece of string will have to be stretched to a higher tension to give the same amount of flexibility as a longer piece of string stretched to a lower tension. This is scientific fact. The +2lbs or 10% recommendation is an estimate for balancing the tension to flexibility ratio of the main and cross strings. Since you string badminton racquets starting with the longer main strings, to balance the flexibility and overall pull of the strings from both ends, you will have to string the cross strings at a higher tension or the frame will remain wider and shorter due to the pull from the higher compressive forces of the longer main strings.

    On a six point support machine however, because you have the four additional support arms to counteract the widening forces of the main strings even before you put the cross strings on, the overall effect of the compressive forces of the main strings are not as significant any more when you finish the string job. The tensions from both the main and cross strings will also balance each other out with the external help from the support arms. This is why it is possible to do the same tension for the main and cross strings and not end up with the X+1lbs on the main strings as you implied.
     
  12. kwun

    kwun Administrator

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    i recently string for one of my client his ARC10PG with BG80@27lbs. i used main=cross=27lbs with 6 pt mounting. and i got to compare it to my own virgin ARC10PG which has never been strung. here are the results. will provide more commentary later:

    IMG_0439.jpg

    IMG_0442.jpg

    IMG_0441.jpg

    IMG_0444.jpg

    IMG_0443.jpg
     
  13. kwun

    kwun Administrator

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    there are a few points i'd like to make. in general, i agree with some of what Blitzzards and kenzo says, but also at the same time, disagree with others. let's see if we can make this a educated discussion as there are still many unknowns.

    firstly, about kenzo's claim of higher tension in the mains. here is the theory.

    let's say we are tensioning the mains as 25lbs and cross at 25lbs (the actual tension doesn't really matter that much). after we finish tension the mains (before we start the cross). all the main strings are at 25lbs. and they are all perfectly straight if you look at them from the side. now, we weave and tension the cross. what happens to the main? they gets stretched by the cross strings so now they are zigzag and not a straight line anymore. what happens then is the main's tension must have increased because it was stretched. by how much? no one has ever measured it. but 1-2 lbs is a good guesstimate. that's what kenzo meant by the tension increase in main. i was one of the first people who pointed it out here in BC and i think it makes total sense.

    now, the next part. different technique/skills, different outcome. imho, there are many different variables that will affect the outcome of the stringing. a simple example, on a ECP machine, do you weave, tension, weave tension or do you weave a few and tension a few? the former will end up with higher tension as as the ECP has more time to stretch the string. or even further, do you leave the ECP running while you weave? or do you disengage it? that also affect tension. on a crank, do you wind the string fast? or slowly? or do you wind twice? 3 times? all those affect the final outcome. do you straighten your cross string after tensioning? that affect the tension too.

    these are just a few variables in stringer technique that affect the outcome of the string job. i was talking to AK a few months ago about stringing. he told me that in the big open (i think SAP or US Open) he was stringing with a few other pro stringers. even though the few of them are stringing with the same machine and using the same "tension", one of them always ends up with a tighter string job. these are all pros with honed techniques. and even then there are differences between them.

    anyway, back to the other point, main vs. cross tension and playability.

    kenzo was advocating that we need to have the final main tension to equal cross tension. therefore we need to compensate for the main zigzagging by adding more tension to the cross. while it appears to be a sound argument, i beg to differ. and i want to raise a question: why do we need final tension of main and cross to be the same in the first place?

    it certain sounds great, they are equal, but why do they need to symmetric? afterall, the racket head is a oval/iso shape and not a circle, the string density of the mains/cross after different. after all these variables, do we really think main tension needs to equal cross tension?

    perhaps they do need to be close, but with so many variables in play, i doubt the "optimal" (whatever that means) will be exactly main=cross (as dial into the tensioner)

    and therefore i don't think it is absolutely necessary to have to string cross 1-2 lbs higher than main to compensate.

    so what is the right tension?

    there is no one right way.

    there are many variables in technique and string machine / tensioner types, the optimal depends on the stringer him/herself. experiment with different tension ratios and see what give the best feel.

    kenzo found that main=cross for him and his machine to be dead. however, i found that main=cross gives the best feel. the different is that we string differently and we are using different machines. we may in fact, both be correct.

    another point about the racket shape, this is one factor that i think is important. afterall, when Yonex/Victor/whoever design these rackets, they have done their modeling and simulation and have found that that particular racket shape give the best result. we should strive to not deform the racket shape otherwise we will not get the same results as intended by the designer.

    and this also brings up the same point, it depends on the stringer. i find that if i use 2lbs more on the cross, the racket will come out too skinny, even with 6pt support. while if i use main=cross, i always get perfect racket shape as shown above. kenzo you might still be right but you will have to verify it on your machine because for you, you may get a perfect shape with +2lbs.
     
  14. kwun

    kwun Administrator

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    so the cliff note version of what i am trying to say is:

    there is no one correct way, cross=main, cross=main+1 or +2. it varies a lot and depends on your machine and technique.

    what is most important is to experiment with different combination, find out what give you the best performance/feel. that's the right answer for yourself. and note that the right answer for you may not be the right another for another stringer with different machine.

    and finally, i advocate that the final head shape should be maintained and there should be no distortion. this is easier to do with 6pt machine, and will require more work on a 2pt machine.

    there are too many variables.
     
  15. kenzo

    kenzo Regular Member

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    Wrong. Learn about constant pull vs lock out tensioning. Lock out at 26lbs will feel lower than constant pull at 26lbs due to string stretching. In the case of tensioning, once the mains have 27lbs, applying any sort of force horizontally will cause the racket to expand upwards, putting more tension on the mains. Any reasoning otherwise is just ignorance.

    Your reasoning is absolute rubbish as flexibility and length of string has nothing to do with tension. A flexible string can provide the same amount of force as a stiff string and the same with the length of the string, whether it holds the tension is another matter, but that's where constant pull comes in.

    You are contradicting your reasoning completely, not sure why I'm still replying to your points.

    Wrong. The supports are there to keep the shape as you apply the main strings yes, however when you pull tension on the crosses the racket still exerts an upwards expanding force. They are not as significant but they are still there.

    As for kwun's photos:
    The racket is shorter from your pictures. And you aren't even measuring the width of the unstrung racket horizontally. It is clearly fatter as well.
     
  16. kwun

    kwun Administrator

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    i measured both the strung and unstrung, both horizontally and vertically. and my ruler says they came out identically in both height and width.

    the photos above shows all the above measurements. there should be 5 photos. one showing both rackets side-by-side. and then 2 each showing unstrung/strung and vertical/horizontal. i don't see how you come to the conclusion that the racket is shorter. it will means that you eyes is more accurate than my ruler. ;)
     
  17. kenzo

    kenzo Regular Member

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    Because otherwise it will be purely the mains providing most of the power in your shots. Which one plays better is another thing, as you said it's personal preference.

    Yes keeping racket shape is very important, however I always find it's better to be 1mm less than 1 mm over. My strung rackets are always within 1mm under the original head shape, but I find in order to do this I need to compress the frame further using the side supports. As I said in my previous post your racket shape isn't perfect.
     
  18. kenzo

    kenzo Regular Member

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    Look at the photo, you are clearly manipulating perspective, taking that into account my observation is clear.
     
  19. kwun

    kwun Administrator

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    i don't see how you can come up with that conclusion. mains are longer and will stretch more than the cross. so if anything, the cross will tighten faster than the main.

    i think you need to look the 5 photos with my measurements again. or explain to me why you can tell the width/height better than my ruler. ;)
     
  20. Pete LSD

    Pete LSD Regular Member

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    I hate to sound like a repeater but what Kwun said is correct. Whether you pull the cross the same as main or greater than main, as long as the frame shape is about the same as an unstrung one you are on the right track.
     

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