Balance point & flex: Educate us

Balance
1.) The balance point is the point along the shaft at which a racket can be balanced (on your finger for example).
2.) The balance point is measured from the end of the handle (the point furthest from the racket head).
3.) Each manufacturer may have a slightly different definition of head-heavy / head-light. However, most also specify a standard balance point, measured in milimeters - the higher the number, the more head-heavy the racket.
4.) You can measure the balance point just by balancing a racket on your finger, and measuring the distance to the end of the handle. I have no idea if manufacturers test a strung/unstrung racket though.
5.) I think it's something like <285mm is head-light, >295 is head-heavy. Again, I'm not sure.
6.) The more head-heavy a racket, the less maneuverable and more powerful it will be. A head-heavy racket is also more stable on contact with the shuttle.
7.) Balance points may be altered...
8.) ...by adding weight (eg. lead tape) to the head or handle. Adding an overgrip also makes a racket feel more head-light.
9.) A head-light racket is better for defensive players (esp. net player in doubles) who need a very maneuvrable racket in order to react quickly.
A head-heavy racket is better for attacking players looking for extra power on their smashes and clears. It is also good for beginners who may struggle to clear from baseline to baseline.
10.) It's been suggested that a stiff, head-light racket may be a contributing factor in some shoulder injuries.


Flex
1.) During a powerful stroke, the shaft of a badminton racket will flex, effectively storing energy. With a well timed shot, the racket will recoil just as the head contacts the shuttle, releasing this energy, and increasing the power of the shot. The stiffer the racket, the less it flexes and the more quickly it recoils (depending on the materials used).
2.) There is no standard way to measure to flex. It would be quite easy to measure the amount the shaft bends under a given load, but this only tells half the story. Depending on the design and materials used, the actual elasticity could vary significantly. Still, you can get a fairly good idea just by flexing a racket by hand.
3.) Different manufacturers measure flex differently - some have a numerical scale, whilst others give only a fairly vague description such as "stiff", "medium" or "flexible".
4.) Flexibility/Stiffness determines how easily the racket flexes, and how quickly it recoils.
5.) The ideal stiffness is proportional to the racket speed you can generate. An overly soft flexing racket will not recoil fully before the shuttle is hit, meaning the energy in flexing the racket is essentially wasted. However, if the racket is too stiff for your swing speed, it will not be flexed enough, and thus won't contribute any extra power. An advanced player with excellent technique should use a stiff racket, whilst a beginner with a slower swing would be better off with a more flexible racket.
6.) I don't think there's any practical way to alter a racket's flex without affecting its balance aswell. Probably extra weight at the head would also cause a racket to flex more.
7.) see 5.
8.) Not that I can think of.
9/10.) I'm sure a lot of things affect a racket's flex. I'd guess that the materials used are probably the most important factor.
Shaft diameter must play some part in determining stiffness, but is not a reliable predictor of it - some rackets are designed with a narrow shaft to make them more aerodynamic, but are still made stiff by other means.
Shaft length can be related to flex too - the old Carlton Megaflex series had a longer shaft than other rackets, which meant a greater overall flex.


I feel like I'm back in school sitting a test
Not sure "recoil" is the word I'm looking for, but I can't think of a better one right now.
There's a pretty good chance I got some of that wrong, so if anyone would like to make corrections...

 

amazing, this is a 5 star thread, thanks Skanbuzz and Sketchy for starting such a useful thread, especially you guys doing this on X-MAS day!!!

I've recently experienced different "flex" rackets and how stiffness affect my own game. I had chance to try a Nanospeed 9000 X and I found myself struggle to handle it (26 lbs). Then I found a NS7700 (medium flex) is very easy to use but later I found I can generate most powerful smash with AT900 p and MP 99, both of these I believe are Stiff. so I concluded that Stiff suits me best.

 

To add on what Sketchy has already written on flex: I like to look at flex in a racket as its capacity to store potential energy from the players swing. The more flexible a racket is, the easier it is to store that energy. The stiffer the racket is, the harder it is to store it. However, the stiffer your racket is the more energy it can store and release on impact.
One could put it like this: you have to carry 1000kg up a hill using a wagon. You have a choice of 2 wagons; one can carry 100kg, the other 500kg. At a 100kg you can go up the hill with ease, but it will take you ten trips. If you take the 500kg it will be very hard, but you only have to do 2 trips. It depends on how capable you are.

# 6

A racket's flexability is inherent to its design and cannot be changed. You can however make it easier or increase the amount of flex it develops by either increasing the speed of your swing or by making your racket head heavy using lead tape.

This is my view on it, the rest I agree with sketchy.

 

I believe Chinese badminton racquets measure flex in terms of the shaft's flexibility. Insofar as I know from Yonex some 2 years ago, based on a series of communications with Yonex Research in Tokyo, their definition of flex was then based on the flexural modulus of the materials used in the frame and shaft.
I believe Yonex was right that time as it makes sense. It is possible to make a racquet with low flexural modulus in the frame but with a very stiff shaft. Such a racquet will have no power as the frame, not the shaft, will flex too much. It is better to use very high flexural modulus materials for the frame and a very stiff, or stiff, or flexible shaft from very high flexural material. The latter is much better but how do you differentiate them with the former type?
Ideally, manufacturers should specify flex (flexural modulus) for the frame and for the shaft separately. But no manufacturer does that. So one has to go by feel for the shaft and look out for the materials used on the frame, even the latter is buried in high sounding descriptions that mean nothing.

 

Measuring tennis racquet stiffness is actually very simple. It is exactly the same as measuring the shaft flexure/stiffness of badminton racquets. Whilst it may be a very useful measurement in tennis racquets, it is quite useless in badminton racquets if you want to find out the flexural modulus of the frame. The Babolat RDC for testing/measuring tennis racquets cannot measure a badminton racquet frame flexural modulus. The only "machine" that can test such a property is a device like a player's hand who can whip a shuttle at the fastest handspeed with wrist snap. Toss a shuttle up-to make sure it has no real incoming force colliding with the stringbed-and then use a powerful and very fast wrist snap to power the shuttle from end to end. Frames with very flexible materials will not go very far and they also lack that crispy feel of sheer speed.
Even revealing the materials used can be misleading. One manufacturer's hmg can be worse than another's hmg. Sometimes you even get an ultra hmg frame feeling less stiff than another manufacturer's lower grade hmg.

 

@skanbuzz
1. So if I purchase an even balance racket and add an opvc over grib, will that make the racket head light?

Depend on the grip, if you put thin overgrip the BP move slighty, not more than 5mm but if thick overgrip maybe it move about 10-15mm so it can be head light

2. How do we apply lead tape to correct the head light situation above?

You can do that but remember put a lead tape also increase the gross weight. If your racket is already in 2U range (90-95gram) you might have difficult to handle a racket more than 100 gram ( like a training racket )

3. On flex: If say the diameter of the shaft: outer and inner: 7.4/3.6 and 7.8/4.8. will the 2nd one be more stiff?


Depend on material use at that racket Let say 7,8/4,8 Carbon Graphite shaft will be more flex than High Modulus Graphite with Titanium Wire at the same spec.

errr add something.....BP usually taken with no overgrip and unstrung condition, fresh from the store

 

Forgot to ask before, but the other thing I've been wondering about, is how accurate are the specifications manufacturers give? ie. What tolerances do manufacturers work to?

I have a Prince Whisper TT 81. On the racket itself, it says "Balance Point 295mm". However, I've tested this myself and found the actual balance point to be about 284mm, which seems like quite a big difference to me.
The racket still has the original grip, and is strung, which should make it more head-heavy if anything.
I'm not complaining - I actually prefer head-light rackets anyway, but is this kind of variation normal?

 

^
YY same also Ti-10 is even balance racket but all my Ti-10 1,2,3 gen all head heavy with BP around 290-295 (empty)
Normally the range must not more than 5 mm +/- but in actually some could be far more than that maybe you just "unlucky" with that

 

Excellent thread! We should sticky this!

I'm using a Babolat Satelite Star and the balance point was advertised as 295mm (strung). I measured it myself and it was indeed the correct balance point - no issues there.
I did however have a slight issue with it later when i came to replacing my grip. The racquets original grip was suprisingly thin - not quite overgrip thin, but nevertheless very thin for an original grip. So when it came to replacing it with a new grip, i was struggling to find one that didn't alter the balancing point of 295mm. The replacement grips i bought - including babolats own replacement Syntec grip - (maybe i was using the wrong ones, cos they were tennis grips) were all either too thick or too thin. I even tried wrapping multiple layers of thin overgrip directly to the wood, but it just didn't offer the same vibration absorbtion. The balancing point fluctuated frombetween 305-310mm and 280-285mm. Which changed the racquet's play and feel completely!
I did find the perfect grip in the end - Karakal P U Super grip. Definately the best grip, as it wasn't overly thick or thin, and i just wrapped it once over the wood and that sorted everything out (295mm +/- 2mm).

P.S. can someone clarify the balance points that are considered head heavy/balanced/light? Always wanted to know that.
Would 295mm (strung) be considered even balanced?

 

295mm when strung is consider slightly head heavy only

 

Balance point simply refers to a point some where on the shaft which balances a blank racquet, the measurement being taken from the butt end to the point of balance. It very roughly tells you if a racquet is head-heavy, even-balanced, or head-light.
But there is another more important specification manufacturers don't specify. Unlike tennis racquets, badminton racquets have a rather long, narrow and slim shaft. This gives it shaft flexibilty. Some racquets have very stiff shafts, some medium stiff, and others more flexible. Do not confuse shaft flexibility with material stiffness. The same racquet with the same materials can be made to have a very stiff shaft or a very flexible shaft, simply by playing around with shaft lengths or/and shaft thickness. The often neglected specification is the flex point on the shaft. If the flex point is higher up towards the tip, it will have more power and will recover faster after a shot. If the flex point is lower down the shaft, power is less and recovery slower. But this is a more complex area in racquet design.

 

1.) Yes; of course it does. Thicker gauge strings are probably heavier than thinner ones due to their added thickness. This might not always be the case (strings are made with different materials and they have different densities). The added/lowered weight at the head of the racket due to heavier or lighter strings will affect where the BP is, as all changes in weight to the racket do.

2.) No; even at different tensions, the strings and the racket weigh the same so providing these factors are kept the same, tension won't make a difference to BP, just to the way the racket plays.

3.) I'm not quite sure. I'm getting a couple more Karakal MTec 70s soon so I'll measure their unstrung BP and strung BP (Nanogy 98 strings) and tell you the difference. Generally, I think the difference is fairly large but I haven't tested myself to check.

4.) There are too many technologies to list. As a general consensus, flexy rackets are better for weak players because they can make them bend. Hard hitters can still make an extra stiff racket bend so they get more power from them. Due to the slightly longer time the shuttle spends on a flexy racket's stringbed, flexible rackets tend to have better control (some may disagree)

5.) Put something small under the shaft of the racket and move it until the racket balances. Measure how far along the racket the thing was. For flex try bending the racket in your hands (gently) but the best way is to play with the racket. Or, you could take some high speed photos of a swing and watch the racket flex.

6.) See above.

 

1. Although thicker string like BG65 is slightly heavier than say BG66-it would weigh roughly 3.3g for BG65 and 3.0g for BG66 when strung-remember the stringbed is not all on the tip end of the frame but it covers the whole frame. the bottom line is that the b/p effect is very small. Many moons ago I wrote down a simple formula to calculate such a change on b/p.
2. Again the difference will be negligible.
3. Again, any difference is negligible.
4. Badminton racquets do not have specs on exact shaft diameter or the shaft's flex point.
5. Flex, what flex? There are now 3 types of flex-one for the shaft's flexure/stiffness, another one for the shaft's bent or flex point, and a third one for the flexural modulus of the materials used to make either just the frame, or just the shaft, or both? This is a very complicated area.
6. I don't think the shop will allow you to strip away the thin shrink wrap on the handle so that you can measure the b/p. You can have a feel of the shaft's flex but not its bent or flex point. Do you know that given a bent point that is fixed it is possible to improve a racquet's playability? Just as it is possible to improve, it is also possible to degrade its playability. To my knowledge, I am not aware that racquet manufacturers know about this.

 

I was just wondering...

In jump smashes, for example, a lot of energy is generated by the body which is transferred to the racquet and enhances the power of the shot.

1. How does shaft stiffness affect this energy transfer?
2. And how do the properties of the materials used in the shaft affect the same?

this thread should definitely be made a sticky!!

 

Here's my personal tuppence - it won't apply to manufacturers!


Balance

I interpret balance point as applying to strung and gripped rackets i.e as I would take them onto court. Balance is universally taken to be from the bottom of the grip end and, since almost all rackets are in the 675mm region nowadays, it is a pretty standardised quantifaction. The terms "head light" et al, however, are NOT, with different players having different interpretations: somebody who's used nothing but Armotecs for years might class an Arcsaber as "head light" while a Nanospeed user might go the other way. With regards to its effect on gameplay, if you do a lot of backcourt work and are usually assured of a big swing (singles players, men in mixed), a head heavy racket is usually prefered; level doubles players normally go even.

Balance points can be moved very easily - I myself have some lead under the grip of my Arc 10 to get it down to 290 - but it's more difficult IMO to go more head heavy, as there's a limit to how much lead tape you can get on the head (it also looks ghastly if done wrong); leading the handle-end is much easier and the tape is easily concealed.


Flex

This is far more mysterious and contentious, but IMO it need not be; there is a machine called the Babolat RDC that gives a numerical value of tennis (bah!) racket stiffness by holding the butt end in place while pulling down on the head. The units don't really matter, it's just a way of comparing different rackets (which is what ultimately matters). If some unit of stiffness is needed, car chassis stiffnesses are measured in Newton-meters per degree, and it would be easy to work out how much torque is needed to bend a racket tip, say, 10mm off the horizontal when the shaft is constrained at the cone.

I know of no way of changing flex; it's inherent to the materials and construction of the racket. If two rackets have the same flex but different balances, the head heavy one will probably bend more when making a shot, though.