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Ashley D 02-18-2013 01:23 AM

How can flexible racquets be powerful?
I'm a bit interested in the BLX Blade Team or the Donnay Pro One Oversize Extended. Both of these racquets are much more powerful than my current stick, the Rebel 95 (2009). However, the BLX has a flex in the mid to low 50s. How is it that a soft racquet can be that powerful? I understand swingweight and headsize make a difference, but the swingweight of the blx is pretty low too. Is it just the bigger head? Is it beam width?

klementine 02-18-2013 04:33 AM

It's all those attributes. The larger head means longer mains. Inherit power can also come from thicker beams, stiffness, balance, swing weight, static weight, etc. Either a combination of certain aspects or all of them combined.

For my money, nothing beats a healthy static weight. Even if the swing weight is low, the beam is thin, the head is smaller and the flex, low; if the static weight is up there, likely chances are I'll be happy.

Bartelby 02-18-2013 05:05 AM

I don't think flex has much to do with power from what I've read of the science involved. It feels more powerful as the ball leaves the string bed ever so slightly quicker.

ollinger 02-18-2013 06:03 AM

There's also the overlooked issue of resonant frequencies. If the shaft of a racquet and the stringbed deflect and then recoil at exactly the same frequency, a racquet will be particularly powerful.

DonDiego 02-18-2013 06:41 AM

We should first define what «power» is.

From my own experience (science aside), flexy racquets have a more «trampoline effect» than stiffer racquets. But stiffer racquets throw a «heavier ball». I prefer the latter because I feel I have better control.

luvforty 02-18-2013 06:51 AM


Originally Posted by ollinger (Post 7222044)
There's also the overlooked issue of resonant frequencies. If the shaft of a racquet and the stringbed deflect and then recoil at exactly the same frequency, a racquet will be particularly powerful.

excellent excellent point, and one that is almost always neglected, due to the lack of knowledge.

the resonance is important for both power and control..... if the shaft and the stringbed go out of wack, you can have hot/cold periods in the impact zone, giving unexpected results.

matchmaker 02-18-2013 09:21 AM

Swingweight is far more important for power than flex. The most powerful racquet I have is also the most flexible, but it has a huge swingweight.

Rogael Naderer 02-18-2013 09:46 AM

Yes, and SW is 'comfortable power' IMO. There's less trade off for comfort as there is with low flex.

Ashley D 02-18-2013 01:15 PM

Thanks guys. Appreciate the responses. I guess in the case of the BLX blade team it must be the 104 headsize and the beam width.

anubis 02-18-2013 01:40 PM

Flexible racquets absorb the centrifugal force, as opposed to transferring this force. Therefore less force is transferred to the ball with flexy frames, than with stiffer frames.

If you take two racquets with the same:
static weight
swing weight
head size
string pattern

Yet one has a stiffness of 57 (flexible) and the other has a stiffness of 70 (stiff). Swing them at the exact same speed and trajectory at a tennis ball, and you'll find that stiffer of the two racquets will generate a higher velocity ball. This is because more of the force is transferred to the ball.

So whenever you buy flexible racquets, just know that you have to work harder to generate pace. You can combat that by increasing the swing weight. I don't know what the formula is, if you were to take the above experiment and increase the swing weight of the flexible racquet in order to generate the same amount of pace as the stiffer frame. But I'm sure that formula exists somewhere.

perhaps someone around here knows?

Bartelby 02-18-2013 02:27 PM

So-called flexible racquets around 60 are still stiff and the difference between 60 and 70 is not that significant, except in terms of feel.

ChicagoJack 02-18-2013 04:17 PM

Hi Ashley

Flight Path and Depth Vs Power: We don't often take radar guns to our matches, so it's important to note first... that as players we have got some fairly wacky ways to estimate racquet power. Mostly we have no freaking idea about ball velocity, (MPH) and we are inferring about racquet power from depth, or height over the net. Those are things we do notice very well and pretty accurately. But both of these things are highly sensitive to string tension, string pattern, and string type. Open patterns, or slippery co-poly string will create a higher arc over the net given the same stroke. If the player compensates for this, by closing the racquet face, the result will be more spin. If the player does not compensate for this, the ball will land deeper in the court, not because it is traveling faster, but simply because it has a higher arc. Conversely, a tighter pattern, or sticky string will create a lower trajectory over the net. A player could easily perceive this as low power, because it is landing shorter in the court, or simply not clearing the net. Your rebel 95 has a fairly dense pattern in a fairly small head. Pair that with your sticky nylon string like X One Bi phase, which has the highest COF (string on string friction) of any string tested, and you have got the makings of a very low flight path compared to just about any other racquet. The more open patterns of the Blade team, (18x19, 104sq) and Donnay Pro One (16x19,105sq), is probably what creating a higher arc over the net... this is probably what you are interpreting as more power.

Having said all of that....A few important concepts:

1. Racquet stiffness has little or no effect on power when you hit the sweet spot ( Sweetspot = Center Of Percussion plus the Vibration Node) or just below (Best Bounce).

2. Stiff racquets offer more power for impacts in the top 10-15% of the hoop. Every racquet ever made has a dead spot, right near the tip of the frame. There is a spot, generally located right around the 1st, 2nd, 3rd cross strings down, where the ball just does not want to bounce at all. Complete dudsville. Stiffer frames flex less, so they offer incrementally more power at the very top of the hoop.

3. While stiff frames flex less, and offer fractionally more power in the dead zone right at the tip, you should put this into the context of a real tennis swing. In a volley motion, the tip of the racquet is moving pretty slowly, and nearly as fast as the handle. However, in a serving motion the tip of the frame is moving quite a bit faster than the center of the strings. For a med SW racquet with an ACOR of 1.40, the center of the strings is moving at about 72 MPH, and the tip is moving about 100 mph, on a 100 mph serve. What this means is that dead spot deficiency on a serve gets a big fat boost of juice from the racquet tip speed. That's why you can mishit near the tip on a serve and still get a pretty good result. However, if you mishit near the tip on a volley, or blocking back a 100 mph serve, the result is often that the ball hits the bottom of the net. What this also means is that the speed of the serve is almost directly related to the speed of the tip of the frame. If you want to hit your serve 1 mph faster, the best way to do that is to swing the racquet 1 mph faster.

4. The speed of the tip of the frame, plus the high sw of wood frames helps explain the following event. In 1997, in a comparative test done by Tennis magazine, [1] Mark Philippoussis, the six-foot-five, 217-pound Australian renowned for his powerful serve, averaged 124 mph when serving with his own composite racket. With a classic wooden racket, (where the stiffness ratings average in the low 30's, and a 72 sq inch head) he averaged 122 mph. Racquet power is a mostly a matter of swing speed and swingweight. Scud is able to hit nearly his top speed with a flexy racquet in the 30s, and a 72 inch head, because the swingweights of most of the woodies is north of 360, and he can stil swing it pretty fast. The other factors matter slightly, but only in terms of fractions of MPHs.

Link [1] Mark Philippoussis Serve Test, Wood Vs Graphite,00.html


ChicagoJack 02-18-2013 04:31 PM

Just to help illustrate my earlier points about stiff frames and inherent power:

1. The HEAD Radical Pro has 1% less power at the very tip, compared to the Aeropro, because it is more flexible. But it's basically a wash everywhere else.

2. The Donnay Pro One actually has more power at the tip, pretty even if not a bit higher everywhere else, even though it is more flexible, lower swingweight, and has a smaller head. It has no business pulling these numbers, but it does. It should show less rebound power near the tip, and slight less overall but it has more somehow. Perhaps it's the solid core construction.

3. And the massive 377 SW Boris Becker 11 Special Edition is listed there just in case anybody had any doubts about SW making the largest contribution to racquet power.

4. Bit of history here. Before we started firing real balls at real racquets, the brightest minds in all of tennis physics came up with a formula to estimate racquet power. They assigned a value to stiffness, swing weight, flex, and length, assigned a power number, then these digits were published at the United States Racquet Stringers Association database. From looking at that list, you'd conclude that stiffness is a very big deal. For a very long time, that educated guess was the best we had. In the link below you can see how (in 2005) I answered questions about racquet power using some of those estimates.

5. However, when we started firing real balls at real racquets and measuring rebound velocity, the results were shocking, and the old estimate formulas were thrown out the window pretty quickly. Here is a quote from Rod Cross speaking directly of that moment of astonishment I'm describing: Quote: " Figure 2 shows RP (Rebound Power) vs. swingweight for all racquets. The result is simply amazing. Instead of having the 268 dots scattered all over the place, the dots line up perfectly along four different curved lines. The four curves correspond to different racquet lengths. All racquets of the same length lie on the same curve, with short racquets having a bigger RP than long racquets. The result in Figure 2 shows that any two racquets of the same length and the same swingweight will have exactly the same RP, regardless of their weights and regardless of their balance points. The inbuilt power of a racquet in the middle of the strings therefore depends only on the length and swingweight of the racquet, and on nothing else." -- Rod Cross, Raw Racquet Power, Link [2]

Translation : What Mr. Cross is saying there, is that if stiffness played a huge factor in racquet power, what you would see is a gradual rise in power as SW increases, but that the gradual rise would look more like a stock market chart, with peaks and valleys punctuating the power levels btwn stiff frames, and flexible frames. But the results don't look anything like that. The results show a nearly perfect relationship, a perfectly smooth arc because nothing else really matters near the center of the frame.

Link [2] Raw Racquet Power, By Rod Cross

Nutshell: From this perspective, it's not so much a matter of making a gut wrenchingly difficult choice between Power vs Comfort, with a huge sacrifice at either end. It is more a matter of finding a racquet that feels good to hit with, within a specific swingweight/power range that suits your game. If you tend to swing slow and smooth, and that's your groove, then a higher SW frame might suit your style, and you'd get max power without incurring more unforced errors by swinging out of your comfort zone. You will get added stability on off center hits as an added bennie. If you want to swing faster, a lower sw frame will frame will help you do this. A faster swings speed might make for an increase in unforced errors, but you will get additional spin out of the trade off.



Ashley D 02-18-2013 05:17 PM

All I can say is "wow".
Thanks so much for all the info Jack.
Based on what you've stated I will be staying with the lower flex racquets simply because I like the feel, and in the knowledge that it's not really going to effect my power levels at all, unless I hit near the tip of the frame, which unfortunately I do from time to time :(
Thanks again.

LeeD 02-18-2013 05:24 PM

Wow, flexible rackets force the player to swing out on every ball, so he learns he can do it on every ball, does it, and the ball goes fast.
Very stiff rackets might have more "theoritical" power, but if the player constantly hits "out" all the time, he learns to reign IN his power, so when he plays, the ball stays IN, and he doesn't swing as fast, so he creates about the same power, but less consistently.

ChicagoJack 02-18-2013 06:14 PM

Ashley - I tend to add on a little more info every time I answer the same question, after a few years I become a little long winded, as I'm always learning from other folks here too. I think I might need an editor soon LOL.

Lee - Your reply seems to indicate that flexible racquets "force players to swing out" to compensate for lack of power. That's not the case, nor is it my point.

prjacobs 02-18-2013 06:17 PM

Thanks so much, ChicagoJack! Very informative...

ChicagoJack 02-18-2013 06:21 PM


Originally Posted by prjacobs (Post 7223420)
Thanks so much, ChicagoJack! Very informative...

prjacobs - No Problemo! Racquet Power is one of my favorite topics of conversation, I'm happy to share what I know.

Ashley D 02-18-2013 06:52 PM


Originally Posted by LeeD (Post 7223346)
Wow, flexible rackets force the player to swing out on every ball, so he learns he can do it on every ball, does it, and the ball goes fast.
Very stiff rackets might have more "theoritical" power, but if the player constantly hits "out" all the time, he learns to reign IN his power, so when he plays, the ball stays IN, and he doesn't swing as fast, so he creates about the same power, but less consistently.

LeeD, I suggest you read Jack's post again. If you understand it properly, you'll come to realise your words above embarrass you. If you don't understand the words, take a look at the picture. Pay particular attention to the power levels of A and D, which vary a lot in stiffness, but not so much in swing weight. Which one is the more powerful racquet? If you still don't understand, take a look at A and B, which are nearly identical swingweights but vary a lot in stiffness. Aside from the tip and base of the racquet, which Jack explained, which one is the more powerful racquet? If you still don't understand.........well that wouldn't surprise me.

LeeD 02-18-2013 07:16 PM

As per usual, you see only one way, black or white.
But what is more powerful?
Are you isolating the racket characteristics from the PLAYER's kinetics?
CAN they be judged separately, or does one actually become linked with the other?
Say a baseball batter look for pure power for hitting home runs. Can he just look for a heavier bat? For more power? Or can he use a lighter bat, choke up on it, and still get the power?
What do you think? I know BarryBonds uses the lightest bat of all the homerun hitters, and get's his power from bat speed, not bat kinetic energy.
So there may be more than one way to look at the power equation.

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