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    Default Playability and shaft- and stringbed- stiffness?

    Hi guys,

    Part of our project is to find out more about playability and the specs of the racquet.

    To inform the Dutch market we are making a series of articles for the Dutch Badminton ass and the coaches.

    But after talking to some coaches and players we do not get much direction, concerning the preference of players for a certain stiffness of the shaft and of the combination of shaft and string bed.

    Perhaps you can help us a little further:
    - For what type of play, or strokes does a player prefer a stiffer or more flexible shaft?
    - What is the advantage of a higher or lower string bed stiffness?

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    Regular Member visor's Avatar
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    Shaft stiffness:

    Depends on the player's swing and play style.

    If his swing is fast, compact and uses mostly wrist, then stiff shaft is preferred.
    If his swing is slower, longer and uses mostly shoulder/upper arm, then flexy shaft is preferred.

    If his play style is control and accuracy, then stiff shaft preferred.
    If his play style is power, then flexy shaft preferred.


    Stringbed stiffness:


    It's easy to get caught up and confused with the high tension equals more accuracy and low tension equals more power debate. But most importantly and irrefutably is that higher tension will give a smaller sweetspot that is more potent... only if the player has a fast enough racket head speed and can consistently hit the sweetspot. In other words, technique.

    Another reason a player may prefer higher tension is the faster and more controlled contact and rebound of the stiffer stringbed, which is important for fast exchanges like drives and defending smashes.
    Last edited by visor; 11-23-2013 at 03:37 AM.

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    Default Playability vs racquet specs

    Thanks Visor, this is already tells more than we heard up till now.

    The purpose of the project is of course to bring the understanding of playability and racquet specs in line, so that we can design an “Advisor”. The ideas is that we can monitor that much better when we can measure the actual SBS and shaft stiffness at the moment that the player plays.

    Therefore we are working on a computer model that shows the deflection of the string bed and bending of the shaft with different speeds of racquet head.

    Purely from the mechanical side we see it like this, please correct us where needed:
    - When the racquet head moves slowly and hits the shuttle, the shaft will bend much more than the string bed will deflect, because the shaft is the much weaker spring. We see this as the 2 spring model.



    - When the racquet head moves very fast and hits the shuttle, the stiffness of the shaft has much less influence. It is actually a collision between the mass of the racquet head and the mass of the shuttle. The stringbed will deflect more depending the lower the sbs of it.

    Our questions are:
    - Is it true that a softer stringbed generates more speed on these fast strokes?

    -Is it true that a stiffer shaft offers better accuracy in these fast strokes?

    -Is it true that a flexible shaft offers more power on slower (longer) strokes?

    - Is it true that a softer string bed does not generate more power on slow strokes? (because the shaft bends away and does not allow the stringbed to deflect).


    Any input is appreciated.
    Last edited by stringtechno; 11-24-2013 at 03:56 AM.

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    Our questions are:
    - Is it true that a softer stringbed generates more speed on these fast strokes?

    -Is it true that a stiffer shaft offers better accuracy in these fast strokes?

    -Is it true that a flexible shaft offers more power on slower (longer) strokes?

    - Is it true that a softer string bed does not generate more power on slow strokes? (because the shaft bends away and does not allow the stringbed to deflect).
    I would say:
    - Yes
    - Yes
    - Yes
    - Not sure

    However, nothing is ever black or white. There are different ways to generate more speed in badminton. Power and Repulsion are two different things, however both kinda contribute to the speed of the shuttle.

    The general knowledge is that stiff rackets and stiff stringbeds offer more control and soft rackets and soft stringbeds offer more power. Then, someone will choose accordingly depending on their strength (string/racket) and swing (racket).

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    Thanks Yan.v,
    It is good to exchange thoughts while we are waiting for the parts of the Stringlab 2 to come in.
    And if we agree on 3 of these 4 that is not too bad.
    It is the intention of the computer simulation to help us understand more and to confirm our thoughts.
    We are testing the simulation at the moment and this is how it looks, more explanation soon.

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    Regular Member visor's Avatar
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    I would say... it depends...

    In my few yrs of browsing the forum and experimenting with many different rackets of various specs and many different strings at various tensions, I've come to the conclusion that the mechanics of a badminton racket is quite easy to understand, as it's very much like a golf club.

    For pure accuracy, this is easy: the stiffer the shaft and stringbed system, the better the accuracy, period. There's absolutely no confusion or argument there.

    For pure power, this is also easy: the flexier the shaft and stringbed, the better the power. To an extent. Some bending and unbending of the system needs to occur for power and this is where it gets slightly complicated.
    ***The optimal energy transfer depends on perfectly matching the timing of the bending and unbending of the shaft and stringbed with shuttle strike.***


    Reread that last sentence again if necessary. It's very critical to understanding power.

    If your stroke is inherently powerful, explosive, with fast racket speed, then the unbending of the flexy shaft and stringbed occurs too late, way after shuttle strike. Energy transfer will not be optimal as the energy stored in the shaft is not fully unloaded onto the shuttle.

    At the other extreme, if your stroke is weak and slow, no or not enough bending and unbending occurs, so no extra energy is stored into the system, and no extra energy is available to be released onto the shuttle.


    To repeat :
    ***The optimal energy transfer depends on perfectly matching the timing of the bending and unbending of the shaft and stringbed with shuttle strike.***


    Again, understand this and you'll understand how to choose the right racket specs and tension for your swing style.
    Last edited by visor; 11-26-2013 at 04:51 PM.

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    Thanks Visor, I think that we will get together nicely as long as we enter all our thoughts into the discussion.
    Let’s compare your text with the graph:

    Vertical axis shows the displacement and the horizontal the time.

    The graph shows the displacement of the shuttle (red), the racquet head (black), and the stringbed (orange)
    This graph shows a high speed stroke with a speed of the racquet of 80 mph resulting in a shuttle speed of about 160 mph. The shuttle has no horizontal speed.

    If the graph shows a horizontal line there is no displacement, the bigger the angle with the horizontal axes the higher the speed.

    The shuttle hits the stringbed at the crossing of the black/orange and the red line.
    After that point the shuttle is in contact with the string bed and starts to move.
    The racquet head moves away from the stringbed, which means that the stringbed is deflected.
    The racket head (black) moves away from the blue line which means that the racquet bends.

    At the next crossing the shuttle leaves the stringbed, the racquet is still bent backwards.

    CONCLUSION;
    It is obvious that the stringbed transfers energy to the shuttle.

    QUESTION:
    The question is if the shaft is offering any energy to the stroke because that “bending energy” is still in the shaft being bent backwards.

    I think that the shaft is much to weak to add speed compared to the stiffness of the stringbed.
    Of course we can learn more about this when we compare graphs at different racquet speeds.

    What do you think?

    We got the figures from this site
    http://hypertextbook.com/facts/2006/ShuMeiDeng.shtml

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    Quote Originally Posted by visor View Post
    I would say... it depends...

    In my few yrs of browsing the forum and experimenting with many different rackets of various specs and many different strings at various tensions, I've come to the conclusion that the mechanics of a badminton racket is quite easy to understand, as it's very much like a golf club.

    For pure accuracy, this is easy: the stiffer the shaft and stringbed system, the better the accuracy, period. There's absolutely no confusion or argument there.

    For pure power, this is also easy: the flexier the shaft and stringbed, the better the power. To an extent. Some bending and unbending of the system needs to occur for power and this is where it gets slightly complicated.
    ***The optimal energy transfer depends on perfectly matching the timing of the bending and unbending of the shaft and stringbed with shuttle strike.***


    Reread that last sentence again if necessary. It's very critical to understanding power.

    If your stroke is inherently powerful, explosive, with fast racket speed, then the unbending of the flexy shaft and stringbed occurs too late, way after shuttle strike. Energy transfer will not be optimal as the energy stored in the shaft is not fully unloaded onto the shuttle.

    At the other extreme, if your stroke is weak and slow, no or not enough bending and unbending occurs, so no extra energy is stored into the system, and no extra energy is available to be released onto the shuttle.


    To repeat :
    ***The optimal energy transfer depends on perfectly matching the timing of the bending and unbending of the shaft and stringbed with shuttle strike.***


    Again, understand this and you'll understand how to choose the right racket specs and tension for your swing style.
    very well summarized and spot on.

    for those who do not understand or agree, they have to start realizing that the world is not a monotonically increasing or decreasing relationship. there are non-linearities everywhere.

    another way to look at it would be, a wooden plank nor a fish net will give you much power when hitting the shuttlecock. the optimal stiffness/tension is going to fall somewhere in the middle.

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    Hi kwun,
    I hope our project will not consist of agreeing or disagreeing!

    It should be the intention to understand more about so many complicated matters like the mechanics of the badminton stroke.

    When we combine a lot of opinions we hope to become wiser together.
    With the new testing tool and the simulation we can try to fill in those “question marks” that still remain.

    2 things are certain for me in the meantime:
    - There is still a lot to learn.
    - How complicated the badminton stroke technique in combination with racquet specs may be, it will follow the mechanical “rules”.

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    Quote Originally Posted by stringtechno View Post
    Hi guys,

    Part of our project is to find out more about playability and the specs of the racquet.

    To inform the Dutch market we are making a series of articles for the Dutch Badminton ass and the coaches.

    But after talking to some coaches and players we do not get much direction, concerning the preference of players for a certain stiffness of the shaft and of the combination of shaft and string bed.

    Perhaps you can help us a little further:
    - For what type of play, or strokes does a player prefer a stiffer or more flexible shaft?
    - What is the advantage of a higher or lower string bed stiffness?
    there is another issue that almost no one talks about. its the frame stiffness, rigidity and its "elasticity".

    imagine a big rectangular wooden frame with a tight net, if you crash into it the wooden frame will flex, so will the net. if you crash into a metal frame with the same net, the impact will be different as the frame flexes differently.

    ultimately this is one factor that differentiates racquets from each other, you can grab a bunch of racquet models with the same shaft stiffness, same balance point, same weight, and they play differently.

    the swinging aerodynamics too...

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    We fully agree, therefore the frame stiffness is a major item in our project also because our new tool can also measure the stiffness of the shafts.

    The stringbed is much stiffer than the shaft (15 to 30 kg/cm against 1 tot 2 kg/cm) which makes it a little difficult to understand their “cooperation”.

    The influence of the shaft is huge, because it is the weaker spring in the system, and will deflect much more than the string bed.



    In our opinion you have to divide the mechanics in 2:
    - Very fast strokes (from the wrist) in which the “hammereffect” of the racquet head does the work, like in the graph.
    This can be seen as a collision of the head and the shuttle and the shaft was only used to accelerate the racquet head.
    The stringbed deflects because the forces at this head speed are very high.
    It is difficult to understand that the bending energy in the shaft adds extra speed to the shuttle (because the shuttle leaves the stringbed before the shaft bends back).

    - Slower strokes were the force on the shuttle is also applied by the shaft coming from the hand of the player.
    In this case the shaft will bend much more than the string bed will deflect, and the bending energy of this bending can generate speed in the shuttle.

    Apart for the shaft stiffness the Swingweight of the racquet also has big influence because it genereates the shuttle speed with fast strokes.

  12. #12
    Regular Member visor's Avatar
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    Quote Originally Posted by vajrasattva View Post
    there is another issue that almost no one talks about. its the frame stiffness, rigidity and its "elasticity".

    imagine a big rectangular wooden frame with a tight net, if you crash into it the wooden frame will flex, so will the net. if you crash into a metal frame with the same net, the impact will be different as the frame flexes differently.

    ultimately this is one factor that differentiates racquets from each other, you can grab a bunch of racquet models with the same shaft stiffness, same balance point, same weight, and they play differently.

    the swinging aerodynamics too...
    Good point.

    Frame stiffness is also a significant contributing factor, in addition to shaft and stringbed stiffness.

    That's why certain rackets with soft frames like AT700 are so powerful and feel so nice, but have more problems with strings sinking into the frame over time. And that's why certain overly strong frames with fully woven carbon fibre are strong but feel numb and are difficult to generate power easily.

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    Regular Member visor's Avatar
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    Quote Originally Posted by stringtechno View Post
    Thanks Visor, I think that we will get together nicely as long as we enter all our thoughts into the discussion.
    Let’s compare your text with the graph:

    Vertical axis shows the displacement and the horizontal the time.

    The graph shows the displacement of the shuttle (red), the racquet head (black), and the stringbed (orange)
    This graph shows a high speed stroke with a speed of the racquet of 80 mph resulting in a shuttle speed of about 160 mph. The shuttle has no horizontal speed.

    If the graph shows a horizontal line there is no displacement, the bigger the angle with the horizontal axes the higher the speed.

    The shuttle hits the stringbed at the crossing of the black/orange and the red line.
    After that point the shuttle is in contact with the string bed and starts to move.
    The racquet head moves away from the stringbed, which means that the stringbed is deflected.
    The racket head (black) moves away from the blue line which means that the racquet bends.

    At the next crossing the shuttle leaves the stringbed, the racquet is still bent backwards.

    CONCLUSION;
    It is obvious that the stringbed transfers energy to the shuttle.

    QUESTION:
    The question is if the shaft is offering any energy to the stroke because that “bending energy” is still in the shaft being bent backwards.

    I think that the shaft is much to weak to add speed compared to the stiffness of the stringbed.
    Of course we can learn more about this when we compare graphs at different racquet speeds.

    What do you think?

    We got the figures from this site
    http://hypertextbook.com/facts/2006/ShuMeiDeng.shtml
    For that graph, the coloured lines are not very distinctly different from each other on my monitor. Can you please add some arrows to label them which is shuttle, stringbed, shaft, etc ? Tks.

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    Of course I will try that later today.

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    I hope this is better, I can not change the graphs itself, because that comes directly from the calculation program, have to ask my collegue. if any questions come up just let me know.


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    Regular Member visor's Avatar
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    Interesting. Do you know what string and tension they used? Racket is steel or graphite? Feather bird?

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    To do calculations we enter specs:
    - Stiffness of the shaft.
    - SBS of the stringbed.
    - Swingweight of the racquet.
    - Mass of the shuttle. (here one with feather)

    This is possible because we have measured these values with our testmachine.

    It is also the basic principle of the project:

    By thinking more in specs it is easier to find a “set up” that suites the player best.
    Iow, if the player goes to the stringer he gives his racquet to the stringer and says “this is what I like”.
    The stringer measures 25 kg/cm and knows that he has to aim at that result.

    If the player goes to the shop for a new racquet he can look for one with the same stiffness as the one that he has.

    BTW
    The stiffness and the SBS can both be measured in a very simple way without our tool.
    If you are interested I can make a sketch.

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