# Thread: String tensions for optimal power

1. If you look at it in physics' point of view, the statement that lower tensions produce more power is true. Lower tensions, in my opinion, are universally at a range of 0-19 lbs. Why? Racquets cannot handle an infinite amount of tension; therefore, there are limits. The limits thus create partitions within the range of tension a racquet can be strung ta. Low would be 0-19 lbs, medium would be at 20-26, and high would be 27-30 (most racquets us amateurs use usually can't handle anything higher than that). Now, the low tension issue is resolved.

At these tensions, more power is generated than any other range of tensions. But what about the optimal point of strings? Well, power and control have a reciprocal relationship, kind of like sin and cos values of angles. A 45 degree angle is usually the "optimum" since its sin and cos values are equal. A careful look at 45.2 degrees shows a slight increase in sin and slight decrease in cos. When the angle is increased to 70 there is a huge increase in sin and huge decrease in cos when compared to 45 degrees. When the angle is decreased to 44.8 and 20 degrees, a similar trend is observed, except this time sin is the one that decreases and cos increases. This trend can also be applied to strings and tensions. Once you veer off the optimum, you get more of one and less of the other. There will always be more power if the tension is under the optimal tension.

But why? Because of the trampoline effect that was mentioned earlier. A trampoline effect is basically mimicing a bounce. When a ball bounces, it changes its momentum. The change in momentum is not just the original momentum, it is twice the original momentum. Why? Because the bird's original momentum was going towards the racqet but the end result is hte bird going away of the racquet. Two of the original momentum are needed, one to cancel to movement towards the racquet, and one to propel it away from the racquet. Add the force of the swing to the bird, and the increase in power occurs.

2. To prevent the same issues being repeated, please refer to this thread.

Higher tension for more power?

the link can also be found in the equipment FAQ's (other links as well)

There must be a lower limit to the optimum power transfer as well. Don't see many people playing with tensions of 0lbs....

3. I have also merged various threads on the same subject into one thread. That's why the same question gets repeated within this thread

moderator

4. Cheung is right

The word here is OPTIMAL,

Balance...

if your string is strung at a high tension you LOOSE the optimal trampoline effect thus less power.

If your string is strung low you also loose the optimal trampoline effect coz all of your strength will be absorbed by the low tension string.

5. I still remeber the days when my stringer did not have any proper machines to string rackets. It was totally hand-strung then. He has 3 ratings: low, medium or high......and uses the sound of the strings like when you strum the guitar to gauge the tension! He watched my progress and and readjust the tension to suit me. Good man but lost his life to a robber 2 years ago.

Okay, I have decided that the suitable tension for me is rather variable. I don't have very powerful arms now that I am not playing regularly. Besides, I am not like I was in my 20s when I was extremely active in sports! I stop playing for many years and for the last couple of years have only played on/off. Now that my son has taken an interest, I'll probably play a bit more often. So, there it goes....what tension is optimum for control or power is likely to vary with my indulgence in the game! For me....and I mean for me only....I'll just stick to 23-25 for the moment and enjoy! I'll made adjustment from time to time to suit myself and only myself. My son complains that his AT700 SP strung @ 24lbs is rather stiff. I tried it and it's fine for me! Guess I might get another and string it at 22lbs instead....\$\$\$.

6. I had my racquet strung at 24lbs at the stringer's recommendation saying, "Can't let it (BG85) go lower than that, else the string will move about".

My experience with it is exactly like what frictionman had. At first it felt as if the racquet was having power problems, ultra-hard and dfficult to really hit the shuttle far without putting more strength to the shot. There's almost no 'boom' sound to any smashes that I did but a low metalic *pheck* sound.

Now, three months later, the string should've loosened up a bit by 1 - 2 lbs and as of last Friday's game against a husband-wife team, combined with corrected body rotation and posturing, the smashes went *boom* and *bang*. Similarly, my touches for the net this time worked better with higher ratio of the shuttle going over.

One question : Would you string it high and let it loosen to achieve later 'peak' condition or string it at the 'peak' and 'rush' to use it before the string goes below your preferred tension?

My personal answer to this should be the first option as I can't afford stringing continuously without burning a whole in my wallet!

7. well i string some of my racket at 20 lbs and some at 22lbs the ones strung at 22 lbs i can generate more power than the others at 20 lbs and i can produce greater control too at 22 lbs i did this as a little but iw ould never go abouve 22 lbs. in my own experience i can generate more power and control at 22 LBs.

8. cricket wasnt really using a physics point of view o.0

it looked more mathematic to me...

Heres your Physics point of view ^^;

for some reason i doubt the reliability of the "trampoline effect" its not a regular term in physics, the only remote thing like it is the rule where when you increase the force by shortening the time, (impulse; ft = mv, where momentum is conserved), which is the main idea behind the wrist flick (to shorten the contact time).

The longer two things stick together the more kinetic energy it will lose (ask a physics teacher, inelastic collision = KE is not conserved)
and we all know kinetic energy directly relates to its velocity.. (sorry if i lost some people x.x)

by increasing tension, you will decrease contact time, and because impulse = momentum (conserved), your force is higher when time is lower. (basically more power transfer)

Here's my guess as to why some people think lower tension = more power:
Usually lower tension is recommended to beginners, and beginners usually lack power AS WELL AS ability to hit the sweet spot!
meaning, because higher tensions have smaller sweet spots, and beginners tend to miss smaller sweet spots, they find the lower tension (larger sweet spot) rackets to give more power, but in fact its because they can hit the sweet spot on those.

Trampoline effect.. o.0 in physics terms, its something that purely removes kinetic energy through heat from the fibers stretching more...

on a trampoline (the racket string bed), KE is converted into spring energy + heat, and then converted back to KE (with the heat portion transfered to the environment), no matter how you look at it in terms of physics.. its a losing situation o.0

Hope it made some sense... im using basic physics concepts that mightve gotten rusty... since ive taken calculus based awhile ago too... x.X

9. Originally posted by kwun
control is the one that i haven't completely figured out.

originally i thought the higher the tension the better the control, as control are usually done at lower force shots, at lower tension, there will be more bounce and thus difficult to control. however, i also read that some ppl prefer it because they think the birdie is in contact with the string longer so it is easier to control that way.

i haven't seen an argument saying that extremely high tension is bad for control though.
Well I think in a sense both of them are right, but I would say that these are two different types of controls.

High Tension = less bounce, so this is designated at the control of the hight. The shuttle may not go exactly where you want it to go, but it certainly wont bounce as high as the low tension string beds
Low Tension = more contact time, so this is desingated at the movement of the shuttle. The shuttle will probably bounce higher than the low tension stringbed, but it will prolly go closer to the precise destination than the higher tension racket

this is jus a guess tho... nothing to support this ^^"

10. Ok I will try to make the argument more black and white.

After playing some badminton yesterday, I found that swing speed is THE factor to consider when finding your optimum tension.

Having left my racket in a relatively warm place for a week, the tension dropped quite considerably. I found that I wasn't hitting as hard as I used to. In fact, I found that slower swing speeds produced the same if not more power compared to higher swing speeds. In some cases I felt the shuttle being dragged back into the string bed. I wasn't very satisfied, so the following week I left my racket in my car boot. Tension increased and I found that higher swing speeds produced more power.

In conclusion, I feel it's right to say that, since most of us here have high'ish swing speeds, we ought to use higher tensions for more power.

Any feedback appreciated.

11. All this talk about tension! What about thickness? Given the same tension (say 22-23lbs) and the same racquet, what difference does thickness have? Let's not get scientific or anything. Just let me know what you've tried and what difference you feel.

12. Originally posted by norby
All this talk about tension! What about thickness? Given the same tension (say 22-23lbs) and the same racquet, what difference does thickness have? Let's not get scientific or anything. Just let me know what you've tried and what difference you feel.
I have 2 rackets: A at 21 lbs (0.68 mm) and B at 23 lbs (0.70 mm). I get more power out of A than B, but the feel of B is much better. In this case, tension plays a greater important role in play than thickness. But I somehow feel that with thinner gauge strings not all of the energy of the racket is transferred to the shuttle.

13. Originally posted by kwun
a graph to illustrate the tension vs power transfer characteristics.
Hmm... i 'm not happy with that graph because power should not be 0 as tension appraoches infinfity.

The optimal energy transfer is when the string vibrates in sync with the shuttle bounce speed. At infinite tension, there is no string vibration and hence it is a perfectly elastic collision with an energy transfer of is exactly half that of the optimal tension, which is half of all energy. At 0 tension, the strings absorb all the energy since it doesn't push back, and hence has negative energy transfer.

energy transfer:

14. the shuttle energy upon leaving the racket would be energy transfer + current energy

15. Kwun's graph is clearly wrong because if energy transfer was 0 at very low tension, then a bird hitting a 0.00001 lb tension racquet would bounce back as fast as it hit it.

If my above graph is correct (and i feel it is) then a user can see quick gains in power by increasing tension but slow losses in power as the tension moves higher than optimal. No idea about what that optimal tension is... no idea.

16. Originally posted by Kurodo
for some reason i doubt the reliability of the "trampoline effect" its not a regular term in physics,
Kordo, i think you miss understand the trampoline effect. The bird is in contact with the strings for a definite amount of time. If the strings are too loose, then as the shuttle compresses the strings inward, the stroke would have already ended and the shuttle wasted energy in compressing the strings without getting any of it back. If the tension is too high, then the shuttle would have compressed the strings, lossened the strings, and but on the cycle back to compressing the strings when the bird leaves. The energy transfer v tension is actually two actiosn in progress:

as tension increase, total energy exchange decreases.
as tension approach optimal, the percent of energy gotten back from the energy exchange approaches 100%. The two equations are not independent (energy return can only ever reach 100% when tension is infinity) but are approximately independent at lower tensions.

So it is approximately a linear equation plus a quadratic equation. The approximate quatradic equation is what kwun posted. The approximate linear equation goes from -1 at 0 to +1 at infinity.

17. Originally posted by Kurodo
Trampoline effect.. o.0 in physics terms
they are not using physics terms.
In your own post, you jump between lay meanings and physics meanings as well. I.e. "power"

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