1. ## Koreans use flex shafts with high tensions

Just look at the Korean team for example. Their favourite racket (half the team uses it!) is BS12, which is quite flexible even for most badminton rackets. So in order to compensate for that, they string higher SBS.
This may make sense

As you may know we are working on a computer simulation so that we can understand more about the mechanics of badminton strokes and the way to tune a badminton racquet.
We learned that we can divide the badminton strokes in slow and fast movements.

FAST STROKE

The pictures shows the very fast movement like a smash.

The picture tells us the following:
- The shuttle is in contact with the stringbed between 0,0395 and 0,04075. Sec.
- The string bed deflects during the contact between shuttle and string bed.
- The shuttle leaves with a higher speed (angle) than the speed of the racquet head.
- The shaft is still bent backwards after the shuttle already left the string bed.
We could pull the following conclusions from this:
- The “spring back effect” of the string bed powers the shuttle.
- The frame recovers after the shuttle is left, so the shaft does not add any power to this stroke.
With the fast stroke the racquet head is moving at very high speed and the impact of the shuttle causes the string bed to deflect.
The shaft is only used to accelerate the racquet and does not have influence at the moment of impact.

SLOW STROKE

The mechanics of a slow stroke (like an overhead from the back of the field) can work according to the “2 spring principle”.
In this principle the spring with the lowest stiffness “does the work”. When the string bed hits the shuttle at a lower speed the shaft will bend but the string bed will not be depressed.

The spring back effect of the shaft will generate the power with a slow movement stroke.
The Koreans could use flexible racquets with high SBS string beds to have 2 advantages at the same time:
- To generate maximum power transfer with smashes.
- To move the shuttle far into the other court with minimum effort.

What do you think?

2. ## Amazing or not at all?

Hi guys,

We organize a symposium called “Testing = knowing = understanding = using” in October. On this symposium there will be a special lecture about badminton, including a brainstorm about the relation between the playability for different badminton strokes and racquet specs, like SBS, Swingweight and bending stiffness of the shaft.

A lot of stringers who use our test device now for about 6 months will participate in this event.

There is one thing that puzzles me about our “badminton project” and that is the lack of feed back and discussion about the SBS tests and also about the relation between specs and playability.

We asked a lot of players about the influence of stiff shafts and very high tension on the playability of the racquet , but we get very few answers.

For all the badminton stringers who have the Stringlab 2 it is completely new to test their SBS after stringing.

We get happy mails about the way the test device works but no questions at all about test results that stringers experience with their own string jobs.

On the tennis forums there are always questions about string bed results with certain strings and in relation to stringing tensions for certain racquets.

Why is it that badminton stringers seem to sit in their stringing-workshop, experience a completely new thing in stringing and do not want to share their experience with others.

We know that quite a number of the Stringlab users are quite active on the forums and participate in discussions about much less interesting details in stringing.

I would appreciate to hear any ideas that can explain this.

Thanks

3. Re your fast and slow stroke analysis, you should keep in mind that unlike tennis stroke, badminton stroke incorporates a "whipping" motion. So the shaft plays a very significant role in generating power.

In my experience with rackets of various stiffness within a model line (eg. Victor MX series), extra stiff rackets are very demanding, ie very hard to generate power. And this is regardless of various string tensions. On the other hand, if a racket is too flexy, paradoxically it can be hard to generate power too, due to the head lagging too much, thus power is dissipated.

My general understanding is that the choice of shaft stiffness and string tension is absolutely dependent on the swing speed, acceleration, and release into the strike. Very much like how it is in golf, as to how golf clubs are custom fitted to the player depending on his swing style.

4. ## fast and slow strokes

Thanks Visor this is very useful and also confirms with what we understand players and our simulation program:

We divide the strokes in 2:
1. Very fast strokes like smashes with a lot of wrist action and “whipping” motion.
With these strokes the speed of the racquet-head is very high and the shaft serves to accelerate the racquet head. The bending of the shaft does not have influence on the moment of impact, as you can see in the graph the shaft is still bent backwards while the shuttle has left the string bed.
The string bed is deflected because the force of the collision between the shuttle and the racquet-head is very high. The amount of power that is generated , is a combination of “spring back” effect from the strings plus “sweeping energy” stored in the racquet head.
It depends on the type of player, what he prefers:
A player who generates tremendous “sweeping power” could prefer a higher SBS, also because that offers better control.
A player with less power will prefer a softer string bed, which helps to generate more power with less effort.
2. Slow strokes from the back of the field which should land as deep as possible in the “enemy court”.

Because the whipping effect will be much lower the shaft will bend on impact, and will offer “spring back” power which helps to accelerate the shuttle. Because the string bed is so very much stiffer than the shaft ( about 20 times) the string bed will not deflect at all because the weak shaft will not allow that.

A player only feels a difference between string beds when it really deflects and the string actually stretches. Therefore I agree with your observation that the SBS does not have much influence on the strokes when the shaft generates the speed.

Because the SBS is actually the figure that should refer to playability of the string bed, we want to obtain an advising table for different types of players and for different strokes.

It seems that players have to chose racquets specs both for their preference with fast and slow strokes. Different players will prefer very different combinations of SBS and stiffness of the shaft independent of their level of play.

5. Choosing a racket spec is actually not that complicated.

There are really only 3 criteria to consider.

1. Power
The racket and stringbed stiffness must be high but not so high that you have difficulty clearing baseline to baseline. That is, you must be able to *comfortably* hit baseline to baseline clears using only about 80-90% of your max power. If you need 100% power, then it's too stiff.

2. Accuracy
Your shots must go in the direction that you had planned/intended when you hit most of the time. If you aim a drive at your opponent's racket shoulder or a smash at an opponent's racket hip that should be just an inch over the tape, then that should be the shot that happens most of the time. If it doesn't, then the racket and stringbed may not be stiff enough. Get this right and the racket will feel like it's an extension of your arm, where all you have to do is think/react and the bird is where you want it to be.

3. Feel/Touch
This one is quite subjective but is also important. You must be able to feel the shuttle work on the stringbed when playing touch shots around the net or push shots at the front court. It must give you the confidence that your net shot is not too high and will just make it over the net, and that your push shots will land on the midcourt sideline as intended. Generally higher tension and racket stiffness will feel crisper and better for you to judge power input for soft shots.

6. ## My experience with SL users

This is very useful info Visor, I have passed it on to my colleague who makes the simulation. I can also use this as a basis in our brainstorm on the symposium.

I would like to add a little explanation to the message about the feedback of the “project-stringers” with a SL2.

Perhaps it helps to open up this discussion because it is actually not a
stringing but more a human problem.

It would be nice when Stringlab using stringers share their experience with other stringers so that these stringers get a better understanding about the many things that have influence on the final stringing result.

Maybe I understand the reluctance of the SL users from the email discussions that I had with some. I had an email exchange of 46 emails with one very dedicated stringer.

I think it works like this:

The drawback of the Stringlab 2 is that it shows that stringers may not be so good as they thought they are. The SL2 shows that stringing results are by far not so consistent as stringers may have thought.

It may not be so easy for experienced badminton stringers to admit that their results differ so much?
Our own “badminton home stringer” was the first guy who experienced this.

This table shows his first test results strung at the same tensions and on the same machine.

As we can see from the resent lists that he sent his stringing results improved considerably since then.

It would be very useful for “non-testing-stringers” when SL users inform them about the influence of the string type, the speed, the type of machine and the way of stringing on the final SBS.

“Our”stringer improved his results considerably by switching back (on his electronic machine) to a much lower speed of pulling.

I do not think that SL users should see the differences in their SBS results as a bad judgement of their stringing qualities.

It should be a challenge to get the wanted results with their own way of stringing and the string they use.

If a stringer can do that he can serve the player in the best possible way, because the player feels the SBS and not the stringing tension on the machine.

7. One thing worth mentioning is that the device is not a one button one result device. So while there are many variables that can affect the resulting SBS of a string, the device itself induces a great deal of variation in the results. Let me explain.

This is the basic principle of the device: A threaded rod goes through the racket strings and you have to put a big ring through that rod. The ring has half the threads inside so that you can move it freely up and down the rod and turn it to lock it. A lever with 3 positions is used to lower the rod.

Step 1) Insert the ring through the rod and press it against the string bed and turn it to lock it there. This is where the most variations come from as that initial pressure on the string bed will be different every time (and there is no way to make it the same every time). At this step, you get a first small number corresponding to the pressure on the stringbed/the resistance of the stringbed.

Step 2) Pull down a small lever that lowers the ring's position. You get a second bigger number corresponding to the resistance of the stringbed

Step 3) Reset/Tare the device and pull down the lever another position (the final position). You get a third even bigger number corresponding to the resistance of the stringbed. This is the SBS number shown in the figures that Stringtechno is publishing.

As you can see, you get 3 different numbers everytime and all of them matter, while Stringtechno's results only include the last one.

It is possible to get different results doing the process multiple times with the exact same racket. So say you do the process twice and get a SBS of 28 and another one of 32, both represent the same thing for that racket, but if it were 2 different rackets with those results, there would be no way to know if both stringbeds have the same stiffness or not just looking at the numbers.

What we've done to solve this issue was have a ring made with the same shape, but with full threads inside so that it is always locked on the rod and I can adjust the position by turning the ring. This way, I ignore the first lever position, put it right at the second position and adjust the ring in a way that I get the same number for every single racket (0,8 in my case). Then, I reset the value to 0, and pull down the lever to the last position. Using this technique, I am able to get much more consistent numbers that can be compared between different rackets without problem.

8. ## 2 misunderstandings / many SBS values

I think there are some misunderstandings in this post:

* A string bed has many SBS values.
The SBS of a string bed is the force that is needed to deflect the string bed 1 cm. This force depends on a lot of things, like string density, string-type, length of the strings and also on the amount of deflection of the stringbed. The deeper the string bed is deflected the more the string has to stretch the higher the SBS.
This means that the SBS is different in every position of the string bed and also depends on the way you measure it.
When a vibration test like the ERT300 or Stringlab 1 is used the deflection of the stringbed is smaller than when a “force test” is done like with the Babolat RDC or the Stringlab 2.

So, a stringbed does not have one SBS value, it has many depending on the position and the way of testing.
The table shows the tests done by a stringer of the Dutch forum who has all the test systems. As you can see the SBS values differ much. The Babolat RDC measures in a different unit, the RA value.

* There are only 2 test values.

As you can see, you get 3 different numbers everytime and all of them matter, while Stringtechno's results only include the last one.
For standard tests the ring should be locked on the pull rod, without pressure. The pressure is developed after switching to the middle position. We call this the “zero pressure”.
After resetting the display to 0,00 after the first stroke and the measuring stroke is made the display shows the SBS.
When stringers want to know very accurate SBS values we advise them to note the zero pressure / SBS combination.

The stringer can get more info from the test by doing 2 tests with different zero pressure by locking the ring 1 ‘pitch’ lower on the pull rod.
The SBS with the higher deflection will always be higher and the difference between the 2 values tells something about the stiffness of the string. The bigger the difference the stiffer the string.

I think that you can say in general:

- The more accurate a measuring system is the more important it is that the stringer understands the differences between the test results.
- It is important that a stringer uses any test device in such a consistent way that he can compare his test results as good as possible.
- The more accurate the test system works the better the tool shows the differences in values in different situations The SL2 measures to 2 decimal places while the vibration tests do not show any decimals.

I hope this explains something.

9. My biggest gripe against this machine is that it is very hard to compare results between different rackets and strings. At best, you can compare your results for the model of racket between string jobs. I understand that you can obtain different SBS numbers for a racket, but this should happen exclusively with different devices (or if you do something weird to trick numbers).

Don't get me wrong I still like the device because it allows me to do things I couldn't do before. But I do think that such devices should be 1 button 1 result devices where if you test the same racket multiple times, it is impossible to get different results (by different I mean a big difference) unless you do something crazy.

I can't wait for other BC'ers that have this device to actually test it and give feedback. Maybe I'm totally in the wrong here, but I've yet to discuss with someone who has the device and hasn't made it.

10. Please have a look at this list.

It shows test results of 2 stringers, with different strings and different racquets and I think that they are very consistent. To be honest I am impressed by these results.

http://www.stringway-nl.com/pdf/STRI...tension-2 .pdf

I can't wait for other BC'ers that have this device to actually test it and give feedback. Maybe I'm totally in the wrong here, but I've yet to discuss with someone who has the device and hasn't made it.
I will send you the email addresses of all the project stringers who use the system, by mail, so that you can exchange thoughts.
None of them is active on this forum I think.

One more question:
Do you use a constant pull machine or a lock out? With a lock out it is impossible to get consistent results.

11. Originally Posted by stringtechno
Please have a look at this list.

It shows test results of 2 stringers, with different strings and different racquets and I think that they are very consistent. To be honest I am impressed by these results.

http://www.stringway-nl.com/pdf/STRI...tension-2 .pdf

I will send you the email addresses of all the project stringers who use the system, by mail, so that you can exchange thoughts.
None of them is active on this forum I think.

One more question:
Do you use a constant pull machine or a lock out? With a lock out it is impossible to get consistent results.
I'm using a constant pull machine.

And I'm getting very consistent results (usually exactly the same or +/- 0.2) using the threaded ring.

12. ## OK perfect

I'm using a constant pull machine.

And I'm getting very consistent results (usually exactly the same or +/- 0.2) using the threaded ring.

That is good to hear Yan.

And if you prefer to use the threaded ring it is perfectly ok of course.

You are the only one who has one but if others would prefer to have one it is very easy thing to make.

It is even a cheaper system but we find it a not so good because it takes longer to put it on.

13. ## The Stringlab 2 in use in several events.

The Stinglab is 2 is making quite a nice career, because it will be used in several events in the coming months:

- The Dutch stringing forum organizes a symposium “measuring = knowing = understanding = using” about tuning racquets for badminton and tennis individually for different types of players.
5 “Test-stations” with Stringlab 2 systems will be used to test the racquets of the participants.

- On the junior tennis tournaments, organized by the Dutch Tennis Association, the Stringlab 2 will be used to test the string bed of the players. This is important because too many juniors play with the wrong string at tensions which are much too high for them.

- This week the Stringlab 2 will be demonstrated on the Dutch Open badminton championships organized by Yonex.

- From the beginning of this year we ran a badminton project, with many badminton stringers. We did not receive any negative comments from the project-guys but we did receive many compliments.

- The symposium on 25/10 will be finished with a badminton brainstorm about the relation between stiffness of the shaft and SBS and the playability.
Yonex people will participate in this discussion and this simulation will also be used for the discussion.

- You can see the Stringlab in action in this video https://www.youtube.com/watch?v=mUQr...ature=youtu.be

14. ## PRE production offer for 2nd series

We are very happy with the respond from Stringlab 2 users. We hardly received comments and quite some compliments and therefore we are going to produce a new series.

There will only be 1 major change which will lower the price considerably;
We will replace the wiring by printed circuits.

A new PRE-production offer will be valid until November the 1st.

After some months for now,
Is there any hand held device for measuring sbs?

16. Originally Posted by Sunray7

After some months for now,
Is there any hand held device for measuring sbs?
Yes there are hand held sbs testers like the ERT300 and our Stringlab 1.

They generate the natural frequency in the stringbed, measure the frequency and calculate the stiffness out of this value.

These tools do not function for badminton racquets because the racquet also vibrates which makes the sbs test very inaccurate.

17. Had consistent results with the ERT 300 so far, even for badminton. More so than with the Stringlab 2.

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