How can flexible racquets be powerful?

[ChicagoJack]

Originally Posted by jimbo333

Hi Jack, Yet again superb info, the best technical posts lately on here have come from you, great stuff, just a couple of questions please:-

1. So for the very fastest most powerful volleys, you will need a heavy and stiff racket, and need to hit the ball low in the hoop where the dampner would be, is that correct?

2. One thing you havn't discussed much is where the rackets flex. When measuring the standard racket RA, there is a lot of focus on the throat area of the racket. However I think the reason for the Donnay above, even though having a lower RA reading than the Babolat (mainly due to the Donnay's more flexy throat), demonstrating more power, is because the Donnay has a slightly stiffer hoop than the Babolat, and with the SW being very similar, this makes the difference in power, making the Donnay slightly more powerful than the apparent stiffer Babolat, what do you think about this please?

Originally Posted by jimbo333

Am still hoping ChicagoJack returns to answer my questions from post56 on page 3, he is probably very busy, I will try to be more patient.

Hi Jimbo

1. Sorry for the long delay. Been pinned to the mat with work for a few days. As an abstract concept, that's mostly correct. For stationary racquets, or racquets not moving very quickly, the area of the stringbed that has the most power is called the best bounce, and it's down low near the dampener. See photo provided. But the point of max power rises once the racquet accelerates. That's because on a groundstroke, and especially during the serve, the tip of the racquet is moving faster than the center, so the added velocity creates more power. In the service motion on a 100 mph serve, the tip of the frame is moving around 100 mph, and the center of the strings is moving at around 72 mph. However, in practice, I really cant advocate aiming for the vibration dampener on a volley. I think aiming for the middle of the strings is a much better idea, as it might not be the "most powerful volley" but it will be a clean volley. It does explain however, why you can mishit the ball near the tip of the frame, and still get a decent result. But if you impact up high blocking back a serve, or a volley, the result is often a ball in the bottom of the net. I've also posted, just a few moments ago, quite a few more links and articles, many of which adress this specific issue.

2. Yeah that's a really good point. That Flex Infinity Machine thingamajiggy is something I'd like to have in my Christmas stocking for sure! I think there are a few possibilites explaining why the Donnay Pro One tests as more powerful up high than a stiffer (rdc) frame. The first is your idea that it has a stiffer hoop, but is flexier in the throat. The second might be that it is solid core. Donnay suggestss that the traditional ACOR forumla is valid for hollow frames, but not for solid core frames. I'm not sure how I feel about that assertion, nor can I find the link for the formula they suggest is more correct, but I recall they provided a wikipedia reference (so it must be true lol).



- Jack

[anubis]

Originally Posted by mikeler

As a former user of stiff frames and now an Exo Tour user, I can't believe the difference between a Pure Drive and the Exo with exactly the same string at the same tension is only 1-2 MPH. I'd say it is a few more MPH than that just based upon my own observations (no hard measurements).

I sometimes think the same thing, but after reading ChicagoJack's and Corners' posts, the only way that I can think about squaring these conflicting ideas is: spin production.

Some of the lighter weight, stiffer frames with open string patterns can produce a lot of spin. that extra spin allows you to take bigger cuts at the ball and still keep the ball in play. Therefore, since you are swinging faster, the ball is traveling faster.

But with smaller/flexier/heavier/denser string pattern frames, some people like to slow down their swing speed in order to keep the ball in play, since they don't produce as much spin. Therefore, you're swinging slower and producing a lower velocity shot.

but that's just an assumption on my part.

[ChicagoJack]

Originally Posted by anubis

I sometimes think the same thing, but after reading ChicagoJack's and Corners' posts, the only way that I can think about squaring these conflicting ideas is: spin production.

Some of the lighter weight, stiffer frames with open string patterns can produce a lot of spin. that extra spin allows you to take bigger cuts at the ball and still keep the ball in play. Therefore, since you are swinging faster, the ball is traveling faster.

But with smaller/flexier/heavier/denser string pattern frames, some people like to slow down their swing speed in order to keep the ball in play, since they don't produce as much spin. Therefore, you're swinging slower and producing a lower velocity shot.

but that's just an assumption on my part.

Hi Anubis -

I think you might have just answered your own question you had for me on post #29. I was thinking the exact same thing. Your older generation black and yellow APD has a sw of 316, 16x19, and 100sq. Your IG Rad Mp is 320 sw, 16x19 and the Head 98's are closer to 95 square inches.

The Radical has slight more inherent power, which might have the ball landing a bit deeper. It's also a bit harder to swing, so perhaps, along with the tighter pattern, its more difficult to get the racquet going fast enough to produce spin. Perhaps the adjustment you are then making with the Radical is a shorter, slower, more tentative stroke. But you are able to swing more freely, and with more confidence, with the lighter SW more open pattern APD.

Since you've expressed some discomfort with the APD, I'd consider switching a racquet with the same SW, head size, and pattern, but which is more headlight and flexible. Just shop in that SW 316 area, and play with something that feels good to hit with. Easy Peasy. It's also possible that that the Higher SW of the Rad isn't good for your wrist either, so in switching back and forth from a too heavy frame, to a too stiff one, your wrist is letting you know it's not happy with either frame.

-Jack

[anubis]

Originally Posted by ChicagoJack

Hi Anubis -

I think you might have just answered your own question you had for me on post #29. I was thinking the exact same thing. Your older generation black and yellow APD has a sw of 316, 16x19, and 100sq. Your IG Rad Mp is 320 sw, 16x19 and the Head 98's are closer to 95 square inches.

The Radical has slight more inherent power, which might have the ball landing a bit deeper. It's also a bit harder to swing, so perhaps, along with the tighter pattern, its more difficult to get the racquet going fast enough to produce spin. Perhaps the adjustment you are then making with the Radical is a shorter, slower, more tentative stroke. But you are able to swing more freely, and with more confidence, with the lighter SW more open pattern APD.

Since you've expressed some discomfort with the APD, I'd consider switching a racquet with the same SW, head size, and pattern, but which is more headlight and flexible. Just shop in that SW 316 area, and play with something that feels good to hit with. Easy Peasy. It's also possible that that the Higher SW of the Rad isn't good for your wrist either, so in switching back and forth from a too heavy frame, to a too stiff one, your wrist is letting you know it's not happy with either frame.

-Jack

Thank you very much I appreciate the time and dedication you put into the science behind tennis.

[Power Player]

Little known fact :

Jack's posts were the inspiration for the track "She blinded me with science".

They added an S to He to make it more accessible to the kids.

[mikeler]

It's just seems like some of the science with rackets and strings correlates well with my on court experience while other data does not. Could it just be my perception is wrong? Perhaps.

[ChicagoJack]

Originally Posted by anubis

Thank you very much I appreciate the time and dedication you put into the science behind tennis.

No worries, anubis. I'm happy to help. I know that 4 SW digits, and 10 digit spread in stiffness doesn't seem like much, but when you've got some pain that can be a really big deal. I've got a few Pro One's in my stable that are under spec for balance, mass, SW and flex by a just a smidge. when I was nursing my TE, those slightly easier swinging frames were my favorites for sure.

The relationship of spin to power you mentioned is a big fat piece of the overall puzzle. After all, we still have to keep the ball in the court right? For extra credit reading you might you might check out the article I linked called "The Inch That Changed Tennis Forever", by Rod Cross. The basic premise is that the real revolution from small headed wood frames to larger headed graphite frames wasn't power, but spin. The SW of wood frames is typically in excess of 360
SW. That's power o' plenty right there. It is suggested that the wider head creates the opportunity for more spin. ALOT more spin, about five times more. Couple that with slick co-poly string, and you've got some game changing innovation.

The transition from wood to graphite happened in the late 70's, but it's only been in the last 10-15 years on the tour that players have taken full advantage of that innovation. When muscle mass, fitness, and racquet head speed finally crashed the party, that's when we started to see the game really change. Yes, frames have gotten stiffer, moving in perfect tandem with the dramatic shift. Perhaps this goes along way to explain the common mis-perception, that a super stiff racquet is a super powerful racquet.

-Jack

[Power Player]

W/out a doubt and I know this from experience.

I was hitting with a western grip and heavy spin as a wee lad in the late 80s and 90s and for a while was using a Prince 90 with a rather narrow headshape.

Can't say how many times I clipped the frame coming over the ball while developing my forehand. It felt like 1 million.

[jimbo333]

Originally Posted by corners

I don't know of any published research that contradicts the view he presented. Bottom line: "power", and the role stiffness plays in power, has been grossly oversold by racquet manufacturers. I've posted this before, but in a paper published last year and financed by Prince, an analysis using a finite element computer model found that if you had two racquets, identical in all respects except that one was twice as stiff, say 65 RDC vs. 130 RDC, the stiffer frame would give you about 5 extra miles per hour on a hard groundstroke. But the frames on the market today differ by only 10-15 RDC points, not 65! The difference in power between a flexy (60 RDC) frame and stiff one (70 RDC) is really not that great.

Consider this comparison. 2012 Babolat Pure Drive Roddick vs. 2012 Head Youtek IG Radical Pro. This is a really good comparison because the frames that TW University tested both had the same swingweights (328 ) and nearly identical twistweights.

The Pure Drive Roddick had stiffness of 72 and the IG Rad Pro 64. And yet they pretty much have the same power. The PDR has slightly greater power potential at the three locations 2 inches above the center, and just a little bit greater power to either side of center. But look what this actually means to a player in terms of shot speed:

An extra MPH 2 inches above center, a couple extra MPH if you want to hit right below the tip. You can see from the second graphic that hitting in the center of the strings is where you get your fastest shots. And that is exactly where stiff frames help you the least. Basically, stiff racquets give you a tiny power boost near the tip and toward 3&9. This effectively expands the "sweetzone", in so far as your shots will be slightly faster if you miss the center of the strings. A better way than "powerful" to describe this would be "forgiving".

It should be clear to anyone looking at the above graphs, and even more clear to anyone looking through the TWU Power Potential database, that the key to power is swingweight. But manufacturers won't try to sell you racquets based on swingweight because swingweight is a double edged sword. High swingweight means a racquet is inherently powerful, but it also means that it is harder to swing fast. So if you get a high-swingweight stick in your quest for power you might find your swingspeed to be slower and your shots to end up being the same speed as before. So, in terms of power, there is no free lunch. Well, there is natural gut, but you'll lose a couple lunches to pay for it.

Absolutely superb post, brilliant info thanks!

[jimbo333]

Originally Posted by ChicagoJack

Hi Jimbo

1. Sorry for the long delay. Been pinned to the mat with work for a few days. As an abstract concept, that's mostly correct. For stationary racquets, or racquets not moving very quickly, the area of the stringbed that has the most power is called the best bounce, and it's down low near the dampener. See photo provided. But the point of max power rises once the racquet accelerates. That's because on a groundstroke, and especially during the serve, the tip of the racquet is moving faster than the center, so the added velocity creates more power. In the service motion on a 100 mph serve, the tip of the frame is moving around 100 mph, and the center of the strings is moving at around 72 mph. However, in practice, I really cant advocate aiming for the vibration dampener on a volley. I think aiming for the middle of the strings is a much better idea, as it might not be the "most powerful volley" but it will be a clean volley. It does explain however, why you can mishit the ball near the tip of the frame, and still get a decent result. But if you impact up high blocking back a serve, or a volley, the result is often a ball in the bottom of the net. I've also posted, just a few moments ago, quite a few more links and articles, many of which adress this specific issue.

2. Yeah that's a really good point. That Flex Infinity Machine thingamajiggy is something I'd like to have in my Christmas stocking for sure! I think there are a few possibilites explaining why the Donnay Pro One tests as more powerful up high than a stiffer (rdc) frame. The first is your idea that it has a stiffer hoop, but is flexier in the throat. The second might be that it is solid core. Donnay suggestss that the traditional ACOR forumla is valid for hollow frames, but not for solid core frames. I'm not sure how I feel about that assertion, nor can I find the link for the formula they suggest is more correct, but I recall they provided a wikipedia reference (so it must be true lol).



- Jack

Excellent, thanks very much for the answer Jack!

1. Yes, i wasn't suggesting actually aiming for the dampner on the volleys (I'm certainly not that good), but now I know that for punched volleys at least the most powerful volleys will always be lower in the hoop.

2. I've been thinking about this theory about certain rackets having stiffer hoops (generating more power) for a while, and would really like to see some more examples on the flexinfinity machine. I've said this elsewhere, but would really like to see the Head PT57A compared to the Angell (Vantage) Custom 63RA, because I think they would be completely different (one relatively stiff hoop with flexy throat, one relatively flexy hoop with stiffer throat), and yet both are superb rackets for me to play with, yet feel very different!

Anyway I've learnt so much from this thread, at least more technical info than ever before, thanks especially to ChicagoJack and Corners

[marosmith]

ChicagoJack, I'm not skeptical but since I'm a lemming and can't read I wanted to see if there we actual real, tangible, scientific arguments which would support the use of stiff rackets as a primary means of generating power.

I think it's pretty safe to say that head shape, weight, swing weight and string type and string bed tension are the primary determining factors contributing to power in a racket. That's what I said a few pages back but it seemed to create lots of controversy.

[LeeD]

Why don't you try a PDR vs a Microgel, then you would know.

[Ashley D]

For what it's worth Marosmith, I agree with you. I think the problem was, that Zed guy then came along and made it all about Babs instead of the OT. Loving the info from ChicagoJack and Corners. Seriously, in my case, I'll only be looking at flexi racquets from now on. Just my take on it all.

[LeeD]

I always thought it was a KNOWN fact that players with good strokes almost always hit harder with more flexible rackets, because when they use stiff rackets like PureDrives, the ball goes OUT OUT OUT, so they add more spin or swing more controlled, giving them LESS power.
On a flexi racket, the ball stays IN, so they can swing hard, and the ball goes faster.

[marosmith]

Originally Posted by LeeD

Why don't you try a PDR vs a Microgel, then you would know.

If modded to the same static and swing weight, and string to the same string bed tension and type my guess is probably about 1-2mph difference on off center hits and a different launch angle.

[Ashley D]

Originally Posted by LeeD

I always thought it was a KNOWN fact that players with good strokes almost always hit harder with more flexible rackets, because when they use stiff rackets like PureDrives, the ball goes OUT OUT OUT, so they add more spin or swing more controlled, giving them LESS power.
On a flexi racket, the ball stays IN, so they can swing hard, and the ball goes faster.

I thought that too, but it appears we thought that incorrectly. It's now been shown the flexibility of the racquet makes little difference in terms of power, appart from some minor exceptions, just to drive the point home again.

[LeeD]

Let's see....
Mr.Roddick...
Biggest serves, then and now.
Groundies then..powerful.
Groundies the past 4 years, spinny and weak.
Why?
Because I TOLD YOU SO.

[Ashley D]

Read the Phillipoussis serving study that Chicago Jack posted LeeD.

[LeeD]

While the pursuit of knowledge is often a worthwhile endeavor......
In this case, it's pure esoteric.
Fact... Pros hit hard.
Fact... Few pros use the siffest rackets.
KISS

[Ashley D]

Originally Posted by LeeD

While the pursuit of knowledge is often a worthwhile endeavor......
In this case, it's pure esoteric.
Fact... Pros hit hard.
Fact... Few pros use the siffest rackets.
KISS

Ok then, so wouldn't the logical conclusion then be that flexibility doesn't necessarily have much to do with power?