Experiment: How do you want to deform your racket?

Discussion in 'Badminton Stringing Techniques & Tools' started by thyrif, Jun 1, 2021.

  1. thyrif

    thyrif Regular Member

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    Science Report

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    @thyrif / @Dekkert
    2020-2021​

    Introduction
    As stringers, we all want to know how to do the best job. Some top stringers have made some comments on Youtube about how they are instructed to string by Yonex. Not all of them seem to do the same, still, so this sparked some discussion. We decided to “science the sh*t out of it” and give it a go.

    Question
    The question we all wish to answer is: how to best string a badminton racket?

    This has many factors and can be open to interpretation, as it depends on what people think is (most) important: Maintaining shape of racket head, keeping tension, the feel and characteristics of the stringbed, preventing racket breakage, player performance, etc. And there are many different ways to string a racket.

    When researching we found that the most important factor is retaining the original shape of the racket head. As we already decided we’d string bottom up (see why in the discussion), we wanted to test the different main/cross ratios and their results on the racket head shape. The following different ratios are often used:
    • Square: M=C. E.g. Main = 28 lbs, Cross = 28 lbs
    • + 2 lbs: E.g. Main = 28, Cross = 30 lbs
    • + 10%: E.g. Main = 28, Cross = 30.8 lbs. (the last 5 crosses at +0%). This is the official Yonex recommended method according to Tim Willis.
    Assumption made for this experiment is: The closer a strung racket’s shape is and stays to the original shape, the better the feel and performance of the racket stays.

    The main factor we will be checking out today is Main/Cross Tensioning method: Which Main/Cross Tensioning method gives the best result in racket shape and shape retention?

    Method
    Stringing methods
    In our test we will string rackets with following specific Main/Cross tension methods:
    • Square (without 6 o’clock adjustment)
    • Square with 6 o’clock adjustment
      • On many machines the 6 o’clock support gets a little bit loose after pulling the first main. Here we re-adjust the 6 o’clock support to support the throat of the racket at this time. This is a much practised adjustment amongst stringers online and we would like to know what the adjustment does, therefore we isolated it in this experiment
    • Yonex method
      • +10% on crosse
      • Last 5 crosses +0%
    The Yonex method is close to +2lbs method in our testrange, we decided not to include it in this experiment.

    All rackets will be strung:
    • Two piece
    • Bottom-up
    • Yonex loop double pull mains 10/11
    • All supports finger tight, no visible deformation
    • +10% on all knots
    • Dekkert: double pull first/last two crosses

    Measuring
    We measure the racket shape in different timeframes:
    • Before stringing (unstrung)
    • Immediately after stringing
    • 48 hours after stringing
    • After playing 1-2 hours
    The racket is measured in four locations, on the inside of the frame, on top of grommet:
    • Length (inside of middle grommets)
    • Lower width B11
    • Middle cross width
    • Top width A15
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    Rackets

    3x Yonex Astrox 99 and 3x Victor Super Wave 35. A racket for each method.

    Tools
    • A 300mm vernier caliper with 0.02mm accuracy
    • Thyrif: Superstringer T20 dropweight 6 point stringing machine with Chudek supports
    • Dekkert: Pro’s Pro Challenger 1 dropweight 6 point stringing machine
    • Thyrif and Dekkert have been stringing for years and string on average at least a couple of rackets every week
    Results

    The averages of the deformations are shown. Beneath you can find the individual results per racket. Also, there are some test results of some other rackets as a bonus. The extra rackets are all strung with the square + 6 o’clock adjustment only.

    Overall
    All rackets have some sort of deformation, in a specific egg-like pattern:
    • Length starts out shorter, then elongates a bit (0.5mm)
    • Width low starts out wider, gets smaller on most rackets (0.5mm)
    • Width center starts out close to original, gets smaller
    • Width top starts out smaller, gets even smaller
    Deformation around 0.5mm was considered good, around 1mm decent, and around 1.5mm poor.

    We looked at the timeframe After Playing most, as that is the time the racket is used the most. But you can see the racket settles between stringing and playing up to about 0.5mm in most measure points.

    Square (without 6 o’clock adjustment)
    The length settles in close to original, but the width is very egg shaped, with the bottom expanding by 1mm and the middle and top getting 1mm and 1.8mm smaller respectively.

    Square with 6 o’clock adjustment
    Length and middle width are similar to square, but the low and top are a lot better at 0.5mm and 1.3mm respectively. We are missing a datapoint for After playing for the AX99 here and used the 48 measurement for average instead.

    Yonex method (+10% on crosses, last 5 crosses +0%)
    Great scores on length and lower width deformation, but the middle and top are getting very small at 1.5mm (worst middle score) and 1.8mm respectively.


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    upload_2021-7-25_16-34-40.png
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    upload_2021-7-25_16-34-13.png
    Conclusions
    Our main focus was to test which main/cross ratio keeps the racket head shape closest to the original. The test was limited to three different stringing methods on two different racket models and tracked the deformation up until after an hour of playing, when the racket should be settled. In the Discussion we will list some other ratios and factors to be discussed and possibly researched further.

    Findings
    The data suggest the square with 6 o’clock adjustment method scores better in retaining the overall shape of the racket, with the least deformation of tested methods. While the Yonex 10% method had great length and bottom scores, it had the biggest shape deformation at the middle and top. So it is quite interesting why Yonex recommends the +10% on the crosses. The square had a very THICC bottom and thin top.

    The results seem to confirm what many of us already think. Which is, that there is no specific need for extra pounds on the crosses. In the discussion we will give our thoughts of why that might be.

    Side note: As seen on the extra results, it seems the compact frame rackets (Duora ZS and Nanoflare 800) react kinda strange on square + 6 o’clock adjustment. They become quite a bit shorter and the bottom part expands more than other rackets, especially on the Nanoflare 800.

    Data

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    Well, that was a long post. What do you guys think of our findings?
     
    #1 thyrif, Jun 1, 2021
    Last edited: Jul 25, 2021
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  2. thyrif

    thyrif Regular Member

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    Post was too long.. Continued

    Discussion

    Factors that play a role
    The different methods and rackets have shown different results. As stated often on this forum, the factors that play a role in keeping the original shape are: machine, stringer’s experience and racket model. With that said, it is assumed that all rackets are more or less the same and that this factor plays a negligible role.

    • Machine: This might indeed play a bigger role. Our machines are one of the cheaper to midrange ones at 300-500 euros. Our 6 o’clock support becomes a little bit loose when pulling the first main, this is an issue we hear from a lot of stringers online. The side supports might not be as sturdy as other machines. The expensive machines possibly have less issues, and therefore might have different results on the different stringing methods.

    • Experience/racket: It is said that the racket plays a negligible role. However, the extra results have shown that different models can react more extreme on a certain method (* only one M/C method is tested on the extra models. Other methods would need to be tested also). So the experience of the stringer comes with every racket model he/she strings, and after every stringjob the deformation should be measured. One ratio is not necessarily the best ratio for all rackets. But to know this, it would need a lot of experimenting by the stringers.
      Point made: rackets also play a factor and are related to experience with the racket.

    • Do they design the racket for the shape it has unstrung, or engineer it for the shape it has after stringing to their specifications?
    Other methods
    We only tested three different methods. Actually two different ratios and one where we readjusted the 6 o’clock support. Of course there are many more ratios to explore.
    • As a result of the Yonex 10% being good at the bottom but thin on top Thyrif also strung one racket with +10% on the bottom half of the crosses and the top half +0%. The results were quite good. Similar to square + 6 o’clock adjustment.
    • Maybe we can try doing only bottom third at +10% and middle +0% and top third -10%?
    • Or you can try to do +1 lbs on the crosses.
    • One piece?
    Like we said in the conclusion, it seems that there is no need for extra pounds on the crosses. Many of our fellow stringers also concluded that. But we don’t all understand why that is. Why is Yonex advising +10% on all their rackets, while our results show the biggest deformation when doing so. Many people said that the mains compress the frame, and the crosses should restore that. But, because of the friction caused by the mains or the racket compressing from just the mains, we should add 10% on the crosses.

    My feeling says different (mind you that I’m no physicist by any means):
    With modern machines with 6-point support there is less deformation than with older 2-point machines.
    Furthermore, I think that the egg-shaped frame makes sure that no extra pounds on the crosses is needed (mostly). Because of the egg shape the frame can withstand more pressure inwards from the top/bottom than from the sides. Therefore, no equal force is needed on the crosses. But what about the tension loss caused by the friction? I think that because the crosses are shorter than the mains, they don’t need to be pulled as tight as the mains. So, the friction and length equal that out. Maybe in some ways similar to thinner strings that don’t need as much tension compared to thicker strings?

    Feeling of the stringbed
    As often said, it can also all be up to the player’s preference. Even the top players have different requests and don’t simply follow the manufacturer’s recommendation.

    An important question that pops up is: How much of a deformation is acceptable or too much? We have measured deviations of 0.1 mm to 2.33 mm. When can we say it is too much? Is it more than 1 mm, more than 2 mm, or above 3 mm? The +10% seems to deform too much. But is it harmful to the frame? If not and a player likes that feeling, then why not?

    Dekkert:
    I personally find that the +10% feels tighter than square. The shuttle leaves the stringbed quicker too. More repulsion. It seems to hold tension and crisp feeling better though.
    The square + 6 o’clock adjustment feels good to me. Somehow it feels as if it is more even spread, if that makes sense.
    The square without 6 o’clock adjustment really feels dead from the beginning. I don’t know why that is.
     
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  3. stradrider

    stradrider Regular Member

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    Interesting experiment!!!

    I was lately happy with another method that in my view solves the egg shape problem (suggested by Kwun first I think?). It is the square method with added some (2-3mm?) squeeze to the lower side supports (with adjusting the 12'c after the squeeze).

    I feel it helps to keep the shape best way, and also don't need to adjust the tension midway which is also one less thing to think about...

    Did anybody try it?
     
  4. thyrif

    thyrif Regular Member

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    Ah, interesting that the same shape was observed by others as well. This seems to try the same thing as the 6 o clock adjustment in our experiment. My gut feeling wouldn't like squeezing it "by feel", but rather adjust the 6 o clock to touch the racket again when tensioning the first main.
     
  5. stradrider

    stradrider Regular Member

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    Yes, but with the effect of correcting the bottom up deformation since queezing the lower supports keep the upper part a little wider?...
     
  6. thyrif

    thyrif Regular Member

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    Probably also make it longer (you also mentioned 12oc adjustment after)
     
  7. stradrider

    stradrider Regular Member

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    Exactly, that way we avoid the rounding of the frame when using square method so there is no need to add tension on crosses. Probably works only on good machine, since it might not be enough if side supports are weak or especially for people with 2 support machines that might even need to add 4 lbs on crosses?
     
  8. stradrider

    stradrider Regular Member

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    It came out a bit wrong, since you cannot squeeze side supports on 2 point machine... However if we are doing these kind of tests, it might be good to also compare different effects on machines with good side supports, bad side supports and without? If someone have the possibility...
     
  9. s_mair

    s_mair Regular Member

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    All thumbs up for investing the time and effort into this. And some very interesting results as well. Of course, the machine used is a huge factor in all of this, so it's still up to the individual stringer to make some experiments and get to know his or her own machine best possible. And I think the physics are very different if you are using a 6-point or a 2-point machine too.

    The re-tightening of the 6 o'clock in a way compensates the slight deformation and movement in the supports and load spreader once the first forces are applied. So basically, you are mostly restoring the original distance between the two main supports.
    But somehow nice to see that my personal impressions are pretty much matching the data you've gathered there. Every time I tried +2 lbs. or +10% in the past, the racket has always felt kind of "stressed out", even if the total length was still on par.

    When I filmed my mounting process a while ago, I noticed that I'm going into that direction as well. I normally do two rounds. The first one only to get all supports slightly in touch with the racket and letting it find the centered position. The second round I kind of go bottom-up. I give the racket quite a tight "hug" at the lower side supports, causing it to slightly compress and being squeezed upwards. But I think it's less than the mentionend 2-3 mm. I finish at the 12 o'clock support and normally, it needs a little re-tightening as well at that point. I'd say thats maybe 1 mm there at this point.

    Here's the (unlisted) video for reference:


    Eversince I'm doing it that way, I have never had any issues with visibly deformed heads, no matter if I'm doing 1- or 2-piece or even hybrid setups. But going back to my initial point: This is only valid for this machine and I'm not saying this is the perfect way to do it on any other machine as well.
     
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  10. HomeStringer_JP

    HomeStringer_JP Regular Member

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    I did the exact same measurements.
    With my 6-point support machine, the results were the same: thicker bottom, even center, and thinner top.
    The results were better when I set the main support a little larger and the bottom side support a little tighter.


    Sent from my iPhone using Tapatalk
     
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  11. Mark A

    Mark A Regular Member

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    Three thumbs up - nothing better than nerding out over an open question on stringing. RIP Yonex machine users, though - no 6 o'clock adjustment for u :p

    Any chance you could try a 50/50? I'm wondering how starting the crosses from the middle would affect the head/throat deformation...
     
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  12. thyrif

    thyrif Regular Member

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    Yes! Hopefully we can inspire some more nerdfoolery all around!

    I haven't done a 50/50, and not sure I'd like to, feels a bit fishy to me, more stress on the corners?
    I did do one with just the bottom half at +10%, top half 0%, without any adjustments in the supports. That one racket was super close to the more tested method of 6 o'clock adjustment.
     
  13. Kaelhdris

    Kaelhdris Regular Member

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    Should you try with a paizhuan pattern, then ? :)
     
  14. Petrichor

    Petrichor New Member

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    This is extremely useful to me! I just asked my stringer to string my Astrox 100zz with +10% last 5 cross 0%. Compare this newly strung racket to the same model racket from my friend who strung 2 pieces square with a much lower tension, I can see with a naked eye that mine is much more slim (center width cones in). The question is do you think this would this affect longevity of my racket?
     
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  15. thyrif

    thyrif Regular Member

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    It will probably be fine, it may play just a little better when it's closer to the original shape. We did not test this, that was our assumption. It is also possible that your friends racket was strung on a different machine with different supports, and came out wider. Please compare to unstrung shape instead.
     

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