Vertical precision of a racquet

zalive · Apr 20, 2016

Starting this thread was something that was on my mind for a days, however I'm not exactly sure how to formulate it in a good manner.

For a introduction, let's say that my first racquet long time ago was a precise one, Head Elektra Pro 600, 18x20, 93 sq.in with 18x19 pattern I think. Ball actually went where you wanted it to go, provided you have hit the sweet spot, and creating spin was not a problem even with nylon strings back then. With this racquet I was able to see how even using a damper worsened its precision, so I didn't use it.

The next racquet was Prince Precision Spectrum 630 (mp). Although with larger head (97 sq.in., which actually helped my game because I never completely dialed in with the hitting precision I needed to hit the tiny sweet spot of my Head), although the beam was 25 mm wide and especially although the string pattern was mere 14x18, this was still a racquet with decent precision. It was not scalpel like as Elektra, but still I could hit the height I wanted to, when I wanted to. Which was important back then when dealing against guys at the net, to send them the lowest possible ball barely clearing the net. And I was able to do it pretty consistently using this racquet.

Back then it was normal to me, I thought that certain level of precision to be something inherent to a racquet, at least if the head size was moderate. And then I bought my third one, Erbacher Kevlar M110 which is something like 103-104 sq.in 16x19. I'm not precisely sure about the head size and it is hard to find info. But I still couldn't complain at all for it's precision. Even a larger head size didn't harm it significantly, I could still hit what I wanted (and besides, Erbacher was my first racquet that I could call being stable, so it made things even easier).

And then I stopped to play tennis, for some 12-13 years. Returned to the tennis at the end of the last year. And decided it was a time for me to buy a new racquets. So I did, in fact, I bought more than one, lol.

And found out that some of them were not that precise at all. I could not hit the height I wanted any more. I couldn't quite predict what will be coming out of the string bed, no matter how hard I tried to hit my most precise ball.

So, I'm wondering what are the elements that makes a racquet vertically precise (meaning, predictable). For simplicity and focusing, let's leave alone the left to right precision, because I guess that things here may get a bit more complicated, but also they may have some different aspects and elements that influence them.

In the next post I'll mention some of the elements that may influence. And I hope that guys with much more experience than me and with decent knowledge can kick in to shed a light in what so far still looks a bit misterious.

Shroud · Apr 20, 2016

zalive said:
Starting this thread was something that was on my mind for a days, however I'm not exactly sure how to formulate it in a good manner.

For a introduction, let's say that my first racquet long time ago was a precise one, Head Elektra Pro 600, 18x20, 93 sq.in with 18x19 pattern I think. Ball actually went where you wanted it to go, provided you have hit the sweet spot, and creating spin was not a problem even with nylon strings back then. With this racquet I was able to see how even using a damper worsened its precision, so I didn't use it.

The next racquet was Prince Precision Spectrum 630 (mp). Although with larger head (97 sq.in., which actually helped my game because I never completely dialed in with the hitting precision I needed to hit the tiny sweet spot of my Head), although the beam was 25 mm wide and especially although the string pattern was mere 14x18, this was still a racquet with decent precision. It was not scalpel like as Elektra, but still I could hit the height I wanted to, when I wanted to. Which was important back then when dealing against guys at the net, to send them the lowest possible ball barely clearing the net. And I was able to do it pretty consistently using this racquet.

Back then it was normal to me, I thought that certain level of precision to be something inherent to a racquet, at least if the head size was moderate. And then I bought my third one, Erbacher Kevlar M110 which is something like 103-104 sq.in 16x19. I'm not precisely sure about the head size and it is hard to find info. But I still couldn't complain at all for it's precision. Even a larger head size didn't harm it significantly, I could still hit what I wanted (and besides, Erbacher was my first racquet that I could call being stable, so it made things even easier).

And then I stopped to play tennis, for some 12-13 years. Returned to the tennis at the end of the last year. And decided it was a time for me to buy a new racquets. So I did, in fact, I bought more than one, lol.

And found out that some of them were not that precise at all. I could not hit the height I wanted any more. I couldn't quite predict what will be coming out of the string bed, no matter how hard I tried to hit my most precise ball.

So, I'm wondering what are the elements that makes a racquet vertically precise (meaning, predictable). For simplicity and focusing, let's leave alone the left to right precision, because I guess that things here may get a bit more complicated, but also they may have some different aspects and elements that influence them.

In the next post I'll mention some of the elements that may influence. And I hope that guys with much more experience than me and with decent knowledge can kick in to shed a light in what so far still looks a bit misterious.

On these new rackets you have bought, what kind of strings are you using and what tensions?

zalive · Apr 20, 2016

Everybody mentions string pattern as a key to precision. Which more precisely comes to the density of the pattern in the sweet zone used to hit the ball. The denser the pattern in the sweet zone, the more predictable the ball. And also there is string(s) type and tension - the more tense the string bed, the more predictable the ball will come out. Quite expected. There's also a head size. The tighter the size, the more precise the racquet is. Pretty much everybody knows all this, and it would be nice if these explained it all.

However, it's not happening completely. All this is true, but when I take two racquets of a same/similar head size, string them with the same strings using the same tension, have their specs in the same range, and experience quite a different result, something's clearly missing.

So, there is another additional element when it comes to string bed: grommets. Some use wider holes to help create the spin. And off course it affects precision too, because string bed actually will behave closer to a larger head size string bed with increased string movement. There are also special types of grommets, too (not on my racquets).

There's also the element of a twist stability. Makes sense: the variance in the hitting spot creates forces that twist racquet's face a bit on impact, directly resulting in loss of a vertical precision. So the lack of precision happens if a player is not able to hit precisely the same spot in a racquet.

I have still Volkl X8, customized to be very stable to twisting (TW is above 16, I guarantee, on volleys it is rock stable). Pattern is 16x19 at 100 sq.in. and it gets pretty dense in the sweet zone as well. I don't see a problem there, it should still have a reasonable precision. Yet it isn't there from the baseline. Any answer I can think of boils down to grommet holes: it uses bigger grommet holes. Seems like it's all that it takes to lose its vertical precision completely. One note: on volleys it's quite oposite, it's pin-point precise. And on flat shots it's decent. It's when you utilize ground stroke brushing is where it loses all its precision.

Another one is my Mantis 250 customization project. It's head size is similar, it's pattern is the same, although less dense in the middle. But grommet holes are narrower. And even with 14 grams added at 3+9 o'clock, seems that it still lacks twist stability. So, my guess that the biggest factor for its loss in vertical precision in it is the lack of stability, still. It should not be the string pattern by itself. 14x18 at prince, not specially dense at the middle, performs with enough precision, Volkl doesn't get even close.

Any other ideas? What are the other factors, missed here? It seems to me that one bad thing can spoil all the rest and mess the racquet up when it comes to precision.

zalive · Apr 20, 2016

Shroud said:
On these new rackets you have bought, what kind of strings are you using and what tensions?

Co-polies strung at 25/24 kg on each. I used so far Solinco TB, Yonex PTP and Signum Pro Plasma Hextreme. All in 1.25 diameter. All pretty good at keeping the tension. TBH much better at keeping the tension than strings I used with the older racquets. And those strings were less harsh: I used Polystar Classic on Spectrum and Erbacher, 26/25 and 27/26...but Polystar massively loses tension, losing 3 kg and more is standard to Polystar. I didn't restring Spectrum. But with clearly looser tension and much more power from the string bed, even with 14x18 pattern this racquet is still more precise than Volkl or Mantis.

Now, PK Destiny FCS is quite a different story, it is precise. 16x19 denser than Mantis in the middle and about the same density as Volkl, 98.5 sq.in. headsize, it's pretty precise.

I used also a new old stock Prince Precision Pro Graphite 600 MP. I can place it somewhere in the middle. It has exactly the same head shape as Spectrum (they're from the same line), but uses 16x19. But it's inherently less twist stable. In the end, Spectrum is still more precise even with couple of grams added to Graphite Pro enhance the twist stability. But Graphite Pro is still better than Mantis or Volkl in terms of vertical precision from the baseline as long as I don't miss its sweet spot.

prostaff1 · Apr 20, 2016

Interesting you never mention the actual level of the player holding the racquet...seems like the most important variable of all.

Shroud · Apr 20, 2016

zalive said:
Co-polies strung at 25/24 kg on each. I used so far Solinco TB, Yonex PTP and Signum Pro Plasma Hextreme. All in 1.25 diameter. All pretty good at keeping the tension. TBH much better at keeping the tension than strings I used with the older racquets. And those strings were less harsh: I used Polystar Classic on Spectrum and Erbacher, 26/25 and 27/26...but Polystar massively loses tension, losing 3 kg and more is standard to Polystar. I didn't restring Spectrum. But with clearly looser tension and much more power from the string bed, even with 14x18 pattern this racquet is still more precise than Volkl or Mantis.

Now, PK Destiny FCS is quite a different story, it is precise. 16x19 denser than Mantis in the middle and about the same density as Volkl, 98.5 sq.in. headsize, it's pretty precise.

I used also a new old stock Prince Precision Pro Graphite 600 MP. I can place it somewhere in the middle. It has exactly the same head shape as Spectrum (they're from the same line), but uses 16x19. But it's inherently less twist stable. In the end, Spectrum is still more precise even with couple of grams added to Graphite Pro enhance the twist stability. But Graphite Pro is still better than Mantis or Volkl in terms of vertical precision from the baseline as long as I don't miss its sweet spot.

Could it be stiffness of the frames?

zalive · Apr 20, 2016

prostaff1 said:
Interesting you never mention the actual level of the player holding the racquet...seems like the most important variable of all.

Less precise a player is definitely more demanding when it comes to racquet's accuracy. Still, any player benefit if the racquet is more precise itself.

The point is, some racquets do it better, some racquets do it worse. You can pair two racquets of pretty similar specs and have one of them much less accurate then the other. So which one you will pick between them? It's a no brainer.

The idea behind the thread was to try to pin point all the most important elements that make the racquet accurate, when it comes to the launch angle accuracy. It might help avoiding some racquets from the start. Pretty much every player wants a racquet that will be closer to the definition of the extension of his arm. Without decent accuracy it will never happen.

Shroud said:
Could it be stiffness of the frames?

I'm not sure how it would affect the vertical accuracy. I can see that it might affect horizontal accuracy, as the flex might affect horizontal angle.
Anyhow, I have or have had racquets both soft and stiff that I could call accurate, so I don't see a connection. Polar examples are Elektra (very soft!) and Destiny (rated at 69 RA).

Especially interesting is Volkl, because of the difference. At volleys it's so stable and precise that it makes long volleys ridiculously easy even to a player with no particular skill at the net like me. And yet, when it comes to baseline topspin shots, everything reverses. Its stability as a problem is simply excluded, string pattern in the middle is dense, stringing at 25/24 is tight enough and I don't see any other reason aside from grommet holes width to contribute its launch angle unpredictability.

Or...there is indeed something else, that I never thought of, until now. String pattern density difference between its middle (sweet spot) and around it. X8 does not have a classic string pattern geometry. It's clearly denser in the middle and with more space in between strings towards the sides. Perhaps this specifical pattern changes launch angle undesireably when you hit with different spots? Might be that, to be honest.

Shroud · Apr 20, 2016

zalive said:
Less precise a player is definitely more demanding when it comes to racquet's accuracy. Still, any player benefit if the racquet is more precise itself.

The point is, some racquets do it better, some racquets do it worse. You can pair two racquets of pretty similar specs and have one of them much less accurate then the other. So which one you will pick between them? It's a no brainer.

The idea behind the thread was to try to pin point all the most important elements that make the racquet accurate, when it comes to the launch angle accuracy. It might help avoiding some racquets from the start. Pretty much every player wants a racquet that will be closer to the definition of the extension of his arm. Without decent accuracy it will never happen.

I'm not sure how it would affect the vertical accuracy. I can see that it might affect horizontal accuracy, as the flex might affect horizontal angle.
Anyhow, I have or have had racquets both soft and stiff that I could call accurate, so I don't see a connection. Polar examples are Elektra (very soft!) and Destiny (rated at 69 RA).

Especially interesting is Volkl, because of the difference. At volleys it's so stable and precise that it makes long volleys ridiculously easy even to a player with no particular skill at the net like me. And yet, when it comes to baseline topspin shots, everything reverses. Its stability as a problem is simply excluded, string pattern in the middle is dense, stringing at 25/24 is tight enough and I don't see any other reason aside from grommet holes width to contribute its launch angle unpredictability.

Or...there is indeed something else, that I never thought of, until now. String pattern density difference between its middle (sweet spot) and around it. X8 does not have a classic string pattern geometry. It's clearly denser in the middle and with more space in between strings towards the sides. Perhaps this specifical pattern changes launch angle undesireably when you hit with different spots? Might be that, to be honest.

Yeah if you have a pattern that is more open around the edges or curves then you will get some weird reactions.

I made my POG a 14x10 pattern and while it was pretty awesome for spin it was really a crapshoot in that you would get weird launch angles sometimes and not others. I ditched it because of that.

TW has several reviews of current rackets where they talk about this phenomenon but never explains where it comes from.

travlerajm · Apr 21, 2016

If a racquet has pinpoint precision on volleys (which, as you noted, is largely a function of stringbed stiffness and stability), but the racquet is not so precise on groundstrokes, that's a give-away. This usually means that the impact dynamics are not the problem, and that the swing dynamics are not quite right. It's quite fixable, if you're willing to take the time to tune the MgR/I value so that the angular acceleration of the racquet about the wrist axis is perfectly synched with the timing of your swing (to produce minimal change in racquetface angle through the hitting zone, thereby making your targeting insensitive to timing errors).

A racquet can only be precise if both impact dynamics and the swing dynamics favor precise targeting.

Another factor that helps precision on all shots is minimizing dwell time (this is not necessarily coupled to the stringbed stiffness). Long dwell time may be good for healthy elbows (and in some cases good for spin potential), but it's the enemy of precision because it allows the racquet to twist more before the ball leaves the stringbed.

Adding mass to the butt end of the racquet will increase dwell time (and reduce the impact dynamics component of precision) for two reasons:
1. It increases the distance between the vibration nodes, which lowers dynamic stiffness.
2. It increases the distance between the balance point and the impact point, which softens the impact on the stringbed even if the frame is very stiff.

On the other hand, adding mass to top of handle will tend to have the opposite effect on dwell time as adding to the butt (it will decrease dwell time by increasing dynamic stiffness, which will improve the impact dynamics component of precision). Adding mass to top end of handle will also have strong effect on MgR/I value, so it's important to stay aware of both impact dynamics effects and swing dynamics effects.

zalive · Apr 21, 2016

Shroud said:
Yeah if you have a pattern that is more open around the edges or curves then you will get some weird reactions.

I made my POG a 14x10 pattern and while it was pretty awesome for spin it was really a crapshoot in that you would get weird launch angles sometimes and not others. I ditched it because of that.

TW has several reviews of current rackets where they talk about this phenomenon but never explains where it comes from.

It's the stringbed unpredictability in this case, 10 crosses are simply not enough. But there are some patterns with 15-16 crosses as a minimum, right?

Dark Knight plays with this and points out it's the best racquet he has ever played with:
http://store.vortextennis.com/Vortex_ES_116_p/es116.htm

14x15 pattern on 116 sq.in. head , wow

zalive · Apr 21, 2016

travlerajm said:
If a racquet has pinpoint precision on volleys (which, as you noted, is largely a function of stringbed stiffness and stability), but the racquet is not so precise on groundstrokes, that's a give-away. This usually means that the impact dynamics are not the problem, and that the swing dynamics are not quite right. It's quite fixable, if you're willing to take the time to tune the MgR/I value so that the angular acceleration of the racquet about the wrist axis is perfectly synched with the timing of your swing (to produce minimal change in racquetface angle through the hitting zone, thereby making your targeting insensitive to timing errors).

A racquet can only be precise if both impact dynamics and the swing dynamics favor precise targeting.

Another factor that helps precision on all shots is minimizing dwell time (this is not necessarily coupled to the stringbed stiffness). Long dwell time may be good for healthy elbows (and in some cases good for spin potential), but it's the enemy of precision.

Adding mass to the butt end of the racquet will increase dwell time (and reduce the impact dynamics component of precision) for two reasons:
1. It increases the distance between the vibration nodes, which lowers dynamic stiffness.
2. It increases the distance between the balance point and the impact point, which softens the impact on the stringbed even if the frame is very stiff.

On the other hand, adding mass to top of handle will tend to have the opposite effect on dwell time as adding to the butt (it will decrease dwell time, which will improve the impact dynamics component of precision). Adding mass to top end of handle will also have strong effect on MgR/I value, so it's important to stay aware of both impact dynamics effects and swing dynamics effects.

I'll check for Volkl, but as far as I remember, its MgR/I was in the right range. However I didn't personally tune it precisely. One more thing, I don't have problems with left to right accuracy with Volkl. It's the height that sprays.

I'm not sure it's the same thing. I understand that without right MgR/I you'll more easy mistime or miss the sweet spot.

But what I consider is what happens when you do miss the sweet spot. Some racquets still remain decently (vertically) precise/accurate. Some others completely change the launch angle.

I'm aware that with each racquet it gets more precise when I get more precise. For example, hitting session on the wall. At the end of the session I can get decent height precision with any of my racquets, because I'm more accurate when it comes to hitting the middle.

But also, some of those racquet remain accurate even when I don't hit the perfect middle. Not if I completely miss it, of course, but they have a reasonable sweet zone margin within which they stay precise. While with the others, if you don't hit it precise, launch angle becomes unpredictable.

And I don't talk about swing mechanics here, I talk about what happens after you hit the ball with different spots on the string bed (regardless of the reason why this happens).

zalive · Apr 21, 2016

Shroud said:
Yeah if you have a pattern that is more open around the edges or curves then you will get some weird reactions.

I forgot to comment this: since my experience is good with 14x18 97 sq.in. racquet (Spectrum) when it comes to its accuracy (and funny, this racquet is not perfect in stock form when it comes to twist stability, which you feel when you get to hit against hard balls, or at volleying), it may mean that its the distribution is what counts. There's a something that looks like a traditional string density distribution. And of course that even with traditional string patterns strings are denser in the middle. But Volkl doesn't deal with this classic. Its strings are further denser in the middle, and more open towards out, ending in larger holes on the sides near the frame than it's typical. And I can feel the difference in behaviour in the effective spin window. With Volkl I don't have the perfect brushing feel and forgiveness I get with some other racquets. In theory you have decent spin window, in the effect you have much less spin window that remains decent.

travlerajm · Apr 21, 2016

zalive said:
I'll check for Volkl, but as far as I remember, its MgR/I was in the right range. However I didn't personally tune it precisely. One more thing, I don't have problems with left to right accuracy with Volkl. It's the height that sprays.

I'm not sure it's the same thing. I understand that without right MgR/I you'll more easy mistime or miss the sweet spot.

But what I consider is what happens when you do miss the sweet spot. Some racquets still remain decently (vertically) precise/accurate. Some others completely change the launch angle.

I'm aware that with each racquet it gets more precise when I get more precise. For example, hitting session on the wall. At the end of the session I can get decent height precision with any of my racquets, because I'm more accurate when it comes to hitting the middle.

But also, some of those racquet remain accurate even when I don't hit the perfect middle. Not if I completely miss it, of course, but they have a reasonable sweet zone margin within which they stay precise. While with the others, if you don't hit it precise, launch angle becomes unpredictable.

And I don't talk about swing mechanics here, I talk about what happens after you hit the ball with different spots on the string bed (regardless of the reason why this happens).

The whole point of tuning MgR/I is to have better "vertical precision". Using the left-right accuracy with loose wrist (and not compensating) is just a good way to diagnose whether you are lagging or leading. And as I've said before, having MgR/I in the "right range" (a tenth or so away from your optimum) but not spot on is actually worse for accuracy than having it a few tenths lower than your optimum:

http://tt.tennis-warehouse.com/inde...-review-ratings-vs-mgr-i-measurements.559553/

Shroud · Apr 21, 2016

zalive said:
It's the stringbed unpredictability in this case, 10 crosses are simply not enough. But there are some patterns with 15-16 crosses as a minimum, right?

Dark Knight plays with this and points out it's the best racquet he has ever played with:
http://store.vortextennis.com/Vortex_ES_116_p/es116.htm

14x15 pattern on 116 sq.in. head , wow

If its uniform its more manageable, but I wouldnt put much faith in the Dark Knight. He has also said that he doesnt want to hit hard, and that he is more of a Mac finesse player. For his type of game it might be stellar, but for someone who takes a cut at the ball and hits with spin maybe maybe not. Its a 116" frame with an open pattern. You think you can control that with a decent cut? I bet I cant. I struggle with 110"s and a less open pattern, unless I just try to push.

I think I have a 14x16 racket by prince and I havent noticed any sort of issues with it not being uniform in the string bed.

Also I think you may be a better tennis player than I am. Maybe it happens subconscious, but I dont really aim for a spot above the net, or a clearance above the net. I just aim in the back court and try to hit where I want it. And even then, its more a direction than a specific point on the court. The exception is when I serve. Then I have a specific target in mind, but not a target above the net.

Though when I hit the wall I do try to hit a certain target.

zalive · Apr 21, 2016

travlerajm said:
The whole point of tuning MgR/I is to have better "vertical precision". Using the left-right accuracy with loose wrist (and not compensating) is just a good way to diagnose whether you are lagging or leading. And as I've said before, having MgR/I in the "right range" (a tenth or so away from your optimum) but not spot on is actually worse for accuracy than having it a few tenths lower than your optimum:

http://tt.tennis-warehouse.com/inde...-review-ratings-vs-mgr-i-measurements.559553/

I don't think this is the key in actual examples. Though I can accept that it may be important too.

I'll tell you the argument here why. I've changed MgR/I on my Destiny by adding about10 SW points (3 grams at 12 o'clock). It changes quite MgR/I, right? So if it was by some chance (pure luck) right for me, it could not have stayed right (tuned for me) after adding 3 grams at 12 o'clock...am I right?

But the vertical precision remained. I'm not talking about nuances here, that may have changed and I'm not sure about it TBH. But the difference to my other racquets of a similar spec range is huge. When it sprays big you can't miss the conclusion

zalive · Apr 21, 2016

Shroud said:
If its uniform its more manageable, but I wouldnt put much faith in the Dark Knight. He has also said that he doesnt want to hit hard, and that he is more of a Mac finesse player. For his type of game it might be stellar, but for someone who takes a cut at the ball and hits with spin maybe maybe not. Its a 116" frame with an open pattern. You think you can control that with a decent cut? I bet I cant. I struggle with 110"s and a less open pattern, unless I just try to push.

I think I have a 14x16 racket by prince and I havent noticed any sort of issues with it not being uniform in the string bed.

Also I think you may be a better tennis player than I am. Maybe it happens subconscious, but I dont really aim for a spot above the net, or a clearance above the net. I just aim in the back court and try to hit where I want it. And even then, its more a direction than a specific point on the court. The exception is when I serve. Then I have a specific target in mind, but not a target above the net.

Though when I hit the wall I do try to hit a certain target.

I'm certainly no better player than you, you can trust me.
But racquet accuracy is good because consistency comes from accuracy, among other reasons, and whenever you aim to build the point you need at least certain levels of accuracy. If you aim for a long ball and launch angle fails you, you'll probably hit long.

The situation why I wanted height accuracy was specific. I used to play before doubles against guys of a typically 3.5 (up to 4.0 at most) level which were typically not that great at volleys when it comes to the balls below the net height. And those guys are the kind that park themselves at the net, so if you wanted to give them such a ball you needed to accurately clear not more than 20 cm above the net, but preferrably less, to hit hard, and to have the ball on the descent when they lay their racquets on it. Preferrably if the ball was lower or even height with the net when they touch it. With enough power this was in most cases the direct point against such guys, even if their left to right position was ideal. And if they returned it it was not likely to be one of the best volleys but more likely something that can be attacked hard with the next strike. So it paid off to be able to pull something like that. But the keys are intention to clear the certain height, the racquet that is accurate enough to do it and with enough power to put combo of power and spin on the ball needed, all the rest is practice. However, against skilled volleyer it won't work as good, but it's still a tougher shot to volley than something of a standard height. After all, even pro players who recieve volleys more away from the net have the most trouble if the ball falls at their feet height when they reach it. And for this to happen ball has to clear the net low. So it's actually a nice shot to have.

However, with most current racquet I use I cannot do it. I cannot be consistent on angles either, because you have to have both vertical and horizontal accuracy to pull big angles. And I'm still playing with those less then perfect racquets, while trying to learn as much as I can from it, which includes both me and different equipment.

Irvin · Apr 21, 2016

With all the different rackets, patterns, strings, and tensions you can get a vast difference in launch angles. Launch angles are directly related to string bed stiffness. If you want a higher angle lower you tension (which lowers DT) and if you want a lower angle raise you tension. Consistency comes from finding the DT, racket, and strings that work best for you and practice.

zalive · Apr 21, 2016

It's no about launch angle itself, Irvin, because whatever it is, you can get used to it. It's about launch angle variance / lack of predictability. It's about spraying of the launch angle.

BretH · Apr 21, 2016

zalive said:
...And then I stopped to play tennis, for some 12-13 years. Returned to the tennis at the end of the last year...
...And found out that some of them were not that precise at all. I could not hit the height I wanted any more. I couldn't quite predict what will be coming out of the string bed, no matter how hard I tried to hit my most precise ball.

This begs the question is it really the racquets?

zalive · Apr 21, 2016

BretH said:
This begs the question is it really the racquets?

Yes.
Easy to answer, because the same present me sees a strong difference in accuracy of the different racquets I currently use.

However, because I'm currently unable to hit almost every ball with the sweet spot, I certainly test the racquets harder. But some of them comply in these conditions, while some of them don't, no matter how hard I try to hit the ball precisely.

BretH · Apr 21, 2016

Ah, got it. Thought you didn't have your old racquets any more. In any case there's folks here who can expound at length on launch angle, etc, so I have no doubt you will get all the info you want

Irvin · Apr 21, 2016

zalive said:
It's no about launch angle itself, Irvin, because whatever it is, you can get used to it. It's about launch angle variance / lack of predictability. It's about spraying of the launch angle.

That requires practice. You need to contact the ball in the same relative position (when you can) with the racket face at the same angle. A lot of the time when you spraying your shots into the net or long it is not as much you fault as it is your opponents fault. If they are changing up the speed and ball bounce along with moving you back and forth and side to side you're going to produce a lot of errors. Ever notice how well you hit warming up with a good player that sets the ball up for you just perfect every time. Then when the game starts your game goes south. Or you're warming up and doing great then it the match you start pushing the ball all over the place. After the match you trying hitting with a hitting partner and your game come back to life.

EDIT: Could also be little seemingly insignificant things like switching rackets. When the balance, or SW is off you unconsciously make little changes to correct the difference sometimes. You may start hitting with a bent arm to correct for a heavier SW. It works at first then you start getting wristier any shots start going every where, or rolling the racket over the ball.

travlerajm · Apr 21, 2016

zalive said:
It's no about launch angle itself, Irvin, because whatever it is, you can get used to it. It's about launch angle variance / lack of predictability. It's about spraying of the launch angle.

It may not be obvious, but launch angle and launch angle variance are the essentially the same thing. What I mean by that is that the launch angle variance (and lack of predictability) is directly correlated to the launch angle. If you have high launch angle, you also have high unpredictability of launch angle. And if you have low launch angle, you have more reproducible and predictable launch angle.

This is true because of several reasons:
1. With a softer stringbed, the launch angle is more sensitive to the ball's incoming angle.
2. With a softer stringbed, the launch angle is more sensitive to the ball's incoming velocity.
3. With a softer stringbed, the launch angle is more sensitive to the ball's incoming spin rate.
4. With a softer stringbed, the launch angle is more sensitive to the racquethead velocity at impact.
5. With a softer stringbed, the launch angle is more sensitive to the steepness of the swingpath.
6. With a softer stringbed, the launch angle is more sensitive to the the racquetface angle at impact.

In other words, controlling the trajectory of your shot with good precision requires a player to simultaneously calculate the contributions of all 6 of these factors and then compensate for the net combined result by precicely adjusting the racquetface angle at impact. It's not easy to do on every single shot, which is why tennis is a difficult game. But a very stiff stringbed can nearly eliminate the sensitivity to all 6 of these factors, which greatly enhances "vertical precision" and makes controlling your shot trajectory much easier.

Did you ever wonder why a softer-stringbed guy like Federer (who strings his 16x19 frame in the 40s) makes uncharacteristic errors when he plays against Nadal's spin, but stiff-stringbed 'paddle tennis" guys like James Blake (68 lbs full poly on 95" head with 18x20 in his prime) were immune to Nadal's extreme spin and had excellent records against Nadal even when ranked much lower? Djokovic also strings a very dense-pattern frame at high tensions, and is able to tame Nadal too.

Shroud · Apr 21, 2016

travlerajm said:
It may not be obvious, but launch angle and launch angle variance are the essentially the same thing. What I mean by that is that the launch angle variance (and lack of predictability) is directly correlated to the launch angle. If you have high launch angle, you also have high unpredictability of launch angle. And if you have low launch angle, you have more reproducible and predictable launch angle.

This is true because of several reasons:
1. With a softer stringbed, the launch angle is more sensitive to the ball's incoming angle.
2. With a softer stringbed, the launch angle is more sensitive to the ball's incoming velocity.
3. With a softer stringbed, the launch angle is more sensitive to the ball's incoming spin rate.
4. With a softer stringbed, the launch angle is more sensitive to the racquethead velocity at impact.
5. With a softer stringbed, the launch angle is more sensitive to the steepness of the swingpath.
6. With a softer stringbed, the launch angle is more sensitive to the the racquetface angle at impact.

In other words, controlling the trajectory of your shot with good precision requires a player to simultaneously calculate the contributions of all 6 of these factors and then compensate for the net combined result by precicely adjusting the racquetface angle at impact. It's not easy to do on every single shot, which is why tennis is a difficult game. But a very stiff stringbed can nearly eliminate the sensitivity to all 6 of these factors, which greatly enhances "vertical precision."

Did you ever wonder why Federer (who strings his 16x19 frame in the 40s) makes uncharacteristic errors when he plays against Nadal's spin, but stiff-stringbed 'paddle tennis" guys like James Blake (68 lbs full poly on 95" head with 18x20 in his prime) were immune to Nadal's extreme spin and had excellent records against Nadal even when ranked much lower? Djokovic also strings a very dense-pattern frame at high tensions, and is able to tame Nadal too.

It all makes sense to me, but 2 things:

1. If this is true, it can't be because EVERYONE knows Fed looses because of his 1 hander, not his racket

2. Why the ESP? It produces a low stringbed stiffness compared to traditional methods. Is your theory that the tight kevlar compensates? Said another way, my Kevlar/poly 86/86 string bed has a DT of 56, but my 86/46 ESP bed has a DT of just 40.

Anyhow I am willing to wager that no one at TT has played with a stringbed with a DT of 56. I think you are 100% right in your 6 points.

travlerajm · Apr 21, 2016

Shroud said:
It all makes sense to me, but 2 things:

1. If this is true, it can't be because EVERYONE knows Fed looses because of his 1 hander, not his racket

2. Why the ESP? It produces a low stringbed stiffness compared to traditional methods. Is your theory that the tight kevlar compensates? Said another way, my Kevlar/poly 86/86 string bed has a DT of 56, but my 86/46 ESP bed has a DT of just 40.

Anyhow I am willing to wager that no one at TT has played with a stringbed with a DT of 56. I think you are 100% right in your 6 points.

On point 2:
I think to get the full benefit of an ESP setup, you need to have a stiff stringbed. The real advantage to ESP is that you can still get the advantages of a stiff stringbed (as outlined above) without giving up spin potential. That is, simply stringing a dense pattern very tightly will give you a stiff stringbed. But the tightness of the stringbed tends to restrict lateral mainstring movement, which can limit spin. The ESP stringbed also give improved comfort for a given stringbed stiffness.

As for you OS frame, I think the pattern is simply far too open to take full advantage of the ESP concept. I have never measured my stringbed stiffness, but I suspect that my preferred spec is probably stiffer than 56.

Also, on the 6 points above, there is published data to prove this (see Haake & Goodwill 2004). I didn't just theorize.

Shroud · Apr 21, 2016

travlerajm said:
On point 2:
I think to get the full benefit of an ESP setup, you need to have a stiff stringbed. The real advantage to ESP is that you can still get the advantages of a stiff stringbed (as outlined above) without giving up spin potential. That is, simply stringing a dense pattern very tightly will give you a stiff stringbed. But the tightness of the stringbed tends to restrict lateral mainstring movement, which can limit spin. The ESP stringbed also give improved comfort for a given stringbed stiffness.

As for you OS frame, I think the pattern is simply far too open to take full advantage of the ESP concept. I have never measured my stringbed stiffness, but I suspect that my preferred spec is probably stiffer than 56.

Also, on the 6 points above, there is published data to prove this (see Haake & Goodwill 2004). I didn't just theorize.

You may be right. The Profile 95 seems to work better with ESP tensions though I used mosquito bite at 46 and kev at 86.

FWIW a Dynamic Tension of 56 is not like a racket strung at 56. Infact I am pretty sure the meter maxes out at 56...which is equivalent to 86lbs (could go higher but the conversion chart only goes to 56). FWIW I am betting my 86/46 kev mosquitobite profile has a stiffer stringbed than your similar ones but using zx, and that only measures a DT of 40.

here is an example pict with a 43 measurement equating to 62lbs for a midsized racket:

Its useful to monitor tension loss and get an idea of what range you can play in best.

dgoran · Apr 21, 2016

Me: "Hey Martin what do you think about your "Vertical precision of your racquet"..."
(Deadly silence fills the Argentinian air ..)
JMDP

slowly turns around)

JMDP: "are you serious bro..."
JMDP: "Get the **** out, now...get out, NOW!"
ME: "ok ok I'll see my self out, don't get up..."
(Runs towards the door)

Backhanded Compliment · Apr 21, 2016

I think predictability of response is very important and a lot of it has to come from a torsional stability as well as smaller amounts of head deformation on impact.

It is very rarely talked about but low deformation was a quality that was talked a lot about on the max 200 g which was an incredibly precise yet relatively powerful for its tiny head size racquet.

zalive · Apr 21, 2016

travlerajm said:
It may not be obvious, but launch angle and launch angle variance are the essentially the same thing. What I mean by that is that the launch angle variance (and lack of predictability) is directly correlated to the launch angle. If you have high launch angle, you also have high unpredictability of launch angle. And if you have low launch angle, you have more reproducible and predictable launch angle.

This is true because of several reasons:
1. With a softer stringbed, the launch angle is more sensitive to the ball's incoming angle.
2. With a softer stringbed, the launch angle is more sensitive to the ball's incoming velocity.
3. With a softer stringbed, the launch angle is more sensitive to the ball's incoming spin rate.
4. With a softer stringbed, the launch angle is more sensitive to the racquethead velocity at impact.
5. With a softer stringbed, the launch angle is more sensitive to the steepness of the swingpath.
6. With a softer stringbed, the launch angle is more sensitive to the the racquetface angle at impact.

In other words, controlling the trajectory of your shot with good precision requires a player to simultaneously calculate the contributions of all 6 of these factors and then compensate for the net combined result by precicely adjusting the racquetface angle at impact. It's not easy to do on every single shot, which is why tennis is a difficult game. But a very stiff stringbed can nearly eliminate the sensitivity to all 6 of these factors, which greatly enhances "vertical precision" and makes controlling your shot trajectory much easier.

Did you ever wonder why a softer-stringbed guy like Federer (who strings his 16x19 frame in the 40s) makes uncharacteristic errors when he plays against Nadal's spin, but stiff-stringbed 'paddle tennis" guys like James Blake (68 lbs full poly on 95" head with 18x20 in his prime) were immune to Nadal's extreme spin and had excellent records against Nadal even when ranked much lower? Djokovic also strings a very dense-pattern frame at high tensions, and is able to tame Nadal too.

Ok, I get this. However, I still think there are other factors that strongly contribute to lack of predictability of the launch angle, to the point of ability of changing the whole picture

So I'm naming four of my current racquets I use currently, and the string bed that's on them and with approx specs. And at the same time I'll sort them according to their precision, the first being least precise:
1. Mantis 250 100 sq.in. 16x19 customized to SW around 355, 366 grams - Solinco TB 1.25 at 25/24 kg
2. Volkl X8 315 100 sq.in. 16x18 customized to SW around 350, 367 grams - Gamma Moto 1.25 at 25/24 kg
3. Prince Graphite Pro 600 97 sq.in. 16x18 customized to SW around 350, 368 grams - Yonex PTP 1.25 at 25/24 kg
4. Pro Kennex Destiny FCS 265 98.5 sq.in. 16x19 customized to SW around 360, 355 grams - Yonex PTP 1.25 at 25/24 kg

I'm not sure about exact 1. - 2. order, most honest to say would be that they approximately share the position, however Volkl is enormously more precise at the net (this order is for the baseline topspin hitting). But the thing is that the two which uses the softest string (Yonex) are more precise (when it comes to hitting from the baseline), with PK being far most precise among all, when it comes to launch angle. And yet, I can sense that launch angle is higher at them than the upper two. Especially Prince has the highest launch angle that stands out among them.

As for the Mantis, the suspect reason is twist stability, regardless of 14 grams added to 3+9 o'clock, which sounds incredible, at least to me. Still it had a pretty light hoop stock. But this racquet doesn't feel unstable. It's like during the impact it takes a tiny deflection of the racquet's head angle to result with change of the launch angle. And the fact is that I can see even when I bounce with it that off center hits towards its sides cause twitches (most between these four).

And when it comes to Volkl, it might be possible that this racquet would benefit from the stiff string like TB, as MOTO seems softer to me - and its launch angle has been higher as well. However, aside from wider grommet holes, I really see no other reason why this happens. Twist stability of Volkl is the highest among them all (it should be around 16.5). Anyhow, those wider grommet holes allow stronger snapback and higher spin, but also a high launch angle, closer to Prince's launch angle (bit less but still a higher one). Anyway, I'm gonna try stringing it with a stiff string, with this racquet it actually might help. I'll try even with higher diameter string.

As you see, lack of predictability in those examples is not predictable at all, because how come PK with a soft string like YPTP remains pretty precise? So I can allow that none of the racquets above is really precise (although I'm more than satisfied with PK), but in that case we're talking about stronger issues than string softness that bother them.

zalive · Apr 22, 2016

Here on Volkl X8 315 review you can see how most of the playtesters struggled bit with the higher launch angle, it seems that they sometimes couldn't quite predict how high the ball will be flying off the string bed. It's also because of X8's bit unusual springiness (they prolly put more Organix in it than they should lol

).

So when it comes to X8 you might be pretty right, travlerajm. Because when you count the wider grommet holes in, string bed probably bed behaves as if the string was even softer than it actually was (MOTO is not that soft; initially it's stiffer, but it gets softer after some use, probably some tension drop).

bkr · Apr 22, 2016

Interesting discussion.I have started playing with Pure Strike 16*19 which is dense in the middle and open at the ends.I may be experiencing inconsistent launch angle compared to my Head Instinct.

I feel like there is less control on Head Instinct but atleast I know when it's going out but with Pure Strike sometimes I'm not sure what's happening with my shots.

May be I'm thinking too much after reading thoughts from you.May be I need more time adjusting to new racquet but I do agree with zalive thoughts here

SpinToWin · Apr 22, 2016

zalive said:
Ok, I get this. However, I still think there are other factors that strongly contribute to lack of predictability of the launch angle, to the point of ability of changing the whole picture

So I'm naming four of my current racquets I use currently, and the string bed that's on them and with approx specs. And at the same time I'll sort them according to their precision, the first being least precise:
1. Mantis 250 100 cm2 16x19 customized to SW around 355, 366 grams - Solinco TB 1.25 at 25/24 kg
2. Volkl X8 315 100 cm2 16x19 customized to SW around 350, 367 grams - Gamma Moto 1.25 at 25/24 kg
3. Prince Graphite Pro 600 97 cm2 16x19 customized to SW around 350, 368 grams - Yonex PTP 1.25 at 25/24 kg
4. Pro Kennex Destiny FCS 265 98.5 cm2 16x19 customized to SW around 360, 355 grams - Yonex PTP 1.25 at 25/24 kg

I'm not sure about exact 1. - 2. order, most honest to say would be that they approximately share the position, however Volkl is enormously more precise at the net (this order is for the baseline topspin hitting). But the thing is that the two which uses the softest string (Yonex) are more precise (when it comes to hitting from the baseline), with PK being far most precise among all, when it comes to launch angle. And yet, I can sense that launch angle is higher at them than the upper two. Especially Prince has the highest launch angle that stands out among them.

As for the Mantis, the suspect reason is twist stability, regardless of 14 grams added to 3+9 o'clock, which sounds incredible, at least to me. Still it had a pretty light hoop stock. But this racquet doesn't feel unstable. It's like during the impact it takes a tiny deflection of the racquet's head angle to result with change of the launch angle. And the fact is that I can see even when I bounce with it that off center hits towards its sides cause twitches (most between these four).

And when it comes to Volkl, it might be possible that this racquet would benefit from the stiff string like TB, as MOTO seems softer to me - and its launch angle has been higher as well. However, aside from wider grommet holes, I really see no other reason why this happens. Twist stability of Volkl is the highest among them all (it should be around 16.5). Anyhow, those wider grommet holes allow stronger snapback and higher spin, but also a high launch angle, closer to Prince's launch angle (bit less but still a higher one). Anyway, I'm gonna try stringing it with a stiff string, with this racquet it actually might help. I'll try even with higher diameter string.

As you see, lack of predictability in those examples is not predictable at all, because how come PK with a soft string like YPTP remains pretty precise? So I can allow that none of the racquets above is really precise (although I'm more than satisfied with PK), but in that case we're talking about stronger issues than string softness that bother them.

Just to be a bit nitpicky…

I doubt that you're playing 100cm^2 racquets

zalive · Apr 22, 2016

Oh shoot...

I'll correct this lol

I've decided going further, I've added another 4 grams at 3+9 o'clock to Mantis. I feel it now becoming nice stable. So this is 18 grams altogether to Mantis lol...finally coming to the threshold of some predictability? We'll see...

travlerajm · Apr 22, 2016

Balances?

zalive said:
Ok, I get this. However, I still think there are other factors that strongly contribute to lack of predictability of the launch angle, to the point of ability of changing the whole picture

So I'm naming four of my current racquets I use currently, and the string bed that's on them and with approx specs. And at the same time I'll sort them according to their precision, the first being least precise:
1. Mantis 250 100 sq.in. 16x19 customized to SW around 355, 366 grams - Solinco TB 1.25 at 25/24 kg
2. Volkl X8 315 100 sq.in. 16x19 customized to SW around 350, 367 grams - Gamma Moto 1.25 at 25/24 kg
3. Prince Graphite Pro 600 97 sq.in. 16x19 customized to SW around 350, 368 grams - Yonex PTP 1.25 at 25/24 kg
4. Pro Kennex Destiny FCS 265 98.5 sq.in. 16x19 customized to SW around 360, 355 grams - Yonex PTP 1.25 at 25/24 kg

I'm not sure about exact 1. - 2. order, most honest to say would be that they approximately share the position, however Volkl is enormously more precise at the net (this order is for the baseline topspin hitting). But the thing is that the two which uses the softest string (Yonex) are more precise (when it comes to hitting from the baseline), with PK being far most precise among all, when it comes to launch angle. And yet, I can sense that launch angle is higher at them than the upper two. Especially Prince has the highest launch angle that stands out among them.

As for the Mantis, the suspect reason is twist stability, regardless of 14 grams added to 3+9 o'clock, which sounds incredible, at least to me. Still it had a pretty light hoop stock. But this racquet doesn't feel unstable. It's like during the impact it takes a tiny deflection of the racquet's head angle to result with change of the launch angle. And the fact is that I can see even when I bounce with it that off center hits towards its sides cause twitches (most between these four).

And when it comes to Volkl, it might be possible that this racquet would benefit from the stiff string like TB, as MOTO seems softer to me - and its launch angle has been higher as well. However, aside from wider grommet holes, I really see no other reason why this happens. Twist stability of Volkl is the highest among them all (it should be around 16.5). Anyhow, those wider grommet holes allow stronger snapback and higher spin, but also a high launch angle, closer to Prince's launch angle (bit less but still a higher one). Anyway, I'm gonna try stringing it with a stiff string, with this racquet it actually might help. I'll try even with higher diameter string.

As you see, lack of predictability in those examples is not predictable at all, because how come PK with a soft string like YPTP remains pretty precise? So I can allow that none of the racquets above is really precise (although I'm more than satisfied with PK), but in that case we're talking about stronger issues than string softness that bother them.

zalive · Apr 22, 2016

All 4-5 pts HL, except Prince which is about 8 pts HL (and 370 g, just checked).

travlerajm · Apr 22, 2016

zalive said:
All 4-5 pts HL, except Prince which is about 8 pts HL (and 370 g, just checked).

Try this:
1. For each racquet, measure the distance in mm between the 8 central mains.
2. Measure the distance in mm between the 8 central crosses (from 4 above the widest point to 4 below the widest point).
3. Multiply the two measurements together, and then divide by 49. This will give you a useful measure of stringbed density (in units of sq.mm/per opening) for the zone bounded by the 8x8-string central rectangle. This is the number I go by when I compare stringbed densities.

I expect the ranking of these stringbed density values might tell you something.

zalive · Apr 23, 2016

Interesting...

PK: 1.31 (density in the middle per sq.cm.)
Volkl: 1.34
Mantis: 1.49
Prince: 1.51

Btw. I corrected specs I have written above, Prince and Volkl are 16x18.

edit: I don't have currently the old Prince Spectrum since my partner plays with it now. But it's vertical precision was nice and its string bed density is I think lower than all these four (it's 14x18 but head size is the same size and shape as Graphite Pro, so I guess it's even less dense in the middle)

travlerajm · Apr 23, 2016

zalive said:
Interesting...

PK: 1.31 (density in the middle per sq.cm.)
Volkl: 1.34
Mantis: 1.49
Prince: 1.51

Btw. I corrected specs I have written above, Prince and Volkl are 16x18.

edit: I don't have currently the old Prince Spectrum since my partner plays with it now. But it's vertical precision was nice and its string bed density is I think lower than all these four (it's 14x18 but head size is the same size and shape as Graphite Pro, so I guess it's even less dense in the middle)

Good. That ranking order should correspond with the precision level on volleys and blocked returns, as these shots tend to impact near the center of the stringbed.

Now try this:
1. Again measure the distance in mm between the 8 central mains.
2. Measure the distance in mm between the 8 uppermost crosses.
3. Multiply these two measurements together and again divide by 49. (and again by 100 if you prefer)

This will give a you a stringbed density value (in sq.mm/ opening) for the upper part of the stringbed where groundstrokes typically impact. Again rank the results.

My guess is that your Prince is probably denser in the upper part of the stringbed compared to your Volkl, explaining why the Prince plays more precise on groundies than it's central stringbed density would suggest, and it might leapfrog up above it in your ranking.

zalive · Apr 23, 2016

travlerajm said:
Good. That ranking order should correspond with the precision level on volleys and blocked returns, as these shots tend to impact near the center of the stringbed.

Now try this:
1. Again measure the distance in mm between the 8 central mains.
2. Measure the distance in mm between the 8 uppermost crosses.
3. Multiply these two measurements together and again divide by 49. (and again by 100 if you prefer)

This will give a you a stringbed density value (in sq.mm/ opening) for the upper part of the stringbed where groundstrokes typically impact. Again rank the results.

My guess is that your Prince is probably denser in the upper part of the stringbed compared to your Volkl, explaining why the Prince plays more precise on groundies than it's central stringbed density would suggest, and it might leapfrog up above it in your ranking.

Results:
Volkl: 1.65
Mantis: 1.67
PK: 1.74
Prince: 1.83

Volkl is especially mysterious all together.
Perhaps part of reason lies in spacing density change towards the outer mains? You can take into account that I'm not precise in hitting the center, so I guess I miss vertically also when I hit topspin. And as spacing changes much in this direction with Volkl, this might explain the launch angle variance.

travlerajm · Apr 24, 2016

zalive said:
Results:
Volkl: 1.65
Mantis: 1.67
PK: 1.74
Prince: 1.83

Volkl is especially mysterious all together.
Perhaps part of reason lies in spacing density change towards the outer mains? You can take into account that I'm not precise in hitting the center, so I guess I miss vertically also when I hit topspin. And as spacing changes much in this direction with Volkl, this might explain the launch angle variance.

Thanks, that helps rule that out as a factor.
I now have my diagnosis:

Based on the central stringbed density measurements, the Prince was the only one that is "out of order" (accuracy outperforming its stringbed density ranking).

There is a reason I asked for the balances earlier.

For a given mass and swingweight, you can calculate the balance that maximizes ACOR. In general, the closer the balance is to the "power-optimized balance," the shorter the dwell time, the crisper the feel, and often better accuracy.
For the Mantis (355 SW and 366g, 4.5pts HL), the balance is 0.3" more HH than the maximized-ACOR balance.
For the Volkl (350 SW and 367g, 4.5pts HL), the balance is 0.45" more HH than the max-ACOR balance.
For the Prince (350 SW and 370g, 8pt HL), the balance is 0.1" more HH than the max-ACOR balance.
For the PK (360 SW and 355g, 4.5pts HL), the balance is -0.1" more HH than the max-ACOR balance.

So ranking these in inches HH relative to max-ACOR balance (from best to worst):
Prince: 0.1
PK: -0.1
Mantis: 0.3
Volkl: 0.45
ThePrince and PK rate very well for this parameter, and the Mantis and Volkl rate very poorly, especially the Volkl.

Now revisit you central stringbed openness values:
PK: 1.31
Volkl: 1.34
Mantis: 1.49
Prince: 1.51

The Mantis is the only one of the 4 that rates poorly in both stringbed density and distance way from max-ACOR balance, so it makes sense why you rated it the worst for precision.
The PK is the only one of the 4 that rates well in both of these parameters, so it makes sense why you rated it the best for precision.
The Prince was the only one of the 4 that is "out of outer" (outperforming its stringbed density); taking into account the distance away from max-ACOR balance explains why the Prince leapfrogged the Mantis and the Volkl in you precision rankings.

I also find it interesting that the Prince (the only one outperforming its expected rating based on stringbed density) is the only one of the 4 that has MgR/I value of 21.0.

bkr · Apr 24, 2016

Hi Travlerajm,

As always great post and thanks for the insights.Now I have a question on how one should calculate the balance that maximizes ACOR.

For a given mass and swingweight, you can calculate the balance that maximizes ACOR. In general, the closer the balance is to the "power-optimized balance," the shorter the dwell time, the crisper the feel, and often better accuracy.

travlerajm · Apr 24, 2016

bkr said:
Hi Travlerajm,

As always great post and thanks for the insights.Now I have a question on how one should calculate the balance that maximizes ACOR.

For a given mass and swingweight, you can calculate the balance that maximizes ACOR. In general, the closer the balance is to the "power-optimized balance," the shorter the dwell time, the crisper the feel, and often better accuracy.

The formula for ACOR can be derived from momentum balances (source: Brody. The physics of tennis. III The ball-racket interaction. Am. J. Phys. 65, 981, 1997):

e = -(mbb + Im/M - ICOR)/(mbb + I + Im/M)

e = ACOR
m = ball mass (0.057kg)
b = distance from impact point to racquet balance point. I usually assume 54cm for impact point on groundies.
I = racquet moment of inertia about balance point (recoil weight).
M = racquet mass.
COR = coefficient of restitution of ball-racquet impact (assumed to be constant at 0.85 for calcuation, since variation is small).

The value of ACOR at the impact point on the stringbed will typically be between 0.35 and 0.4. And even though the value of ACOR will change very little with change in balance, the feel and dwell time of the impact will be very sensitive to the distance between the actual balance and the max-ACOR balance.

Once you have your spreadsheet set up to calculate ACOR as a function of mass, balance, and SW, you can use a solver macro (or trial and error) to determine the balance that maximizes the value of ACOR for a given mass and SW.

zalive · Apr 25, 2016

@travlerajm :
Thanks a lot! This was quite insightful, and this analysis is excellent! You shed much light into this obviously complex field.
Also, thanks a lot for the ACOR formula! I'll try to implement the use in my excel calculation table...

zalive · Apr 25, 2016

Some impressions related to Prince, during different customization setups:

at stock form precision was pretty good; but the power was not sufficient to me when strung at 25/24 kg
when I used customization mainly based on 3+9 o'clock lead plus much blue tac at the tail (it was even more HL than now), things got completely messed up and racquet lost it's playability; and even the balance felt kind of odd in the hand
then I switched to mainly the 12 o'clock and it got better, aside from more power, also added a bit more on the head; the balance got better as well; precision was better, but not as it should be
currently it's some combination with customization mass spread over the hoop, and the precision came around again (close to the stock precision)

So it makes a lot of sense what your analysis shows, that combination of parameters decided the outcome of precision and help the racquet outperform its string bed precision.

As for Volkl, I also used couple of different setups, but it's a frame that kind of narrows your space for customization, because aside from being heavy from the start (mine is 319 grams unstrung) whatever you added to the hoop starting from stock, this racquet becomes unbearably heavy in the hand (high static moment, I guess). So I had to put much weight at the tail to improve its feeling (bearability) in the hand. Anyway, whatever modification I implemented (started from 3+9 o'clock only, ended in distributed 3+9+12 o'clock with a bit of protection tape from 10 to 2 o'clock), the impresion was similar: Volleys, returns, flat strokes were excellent in precision (and only became better the more customizaton mass I used). When it came to brushing, things get worse.

I'll use this formulas and approach to try to improve Volkl.

As for Mantis, it's the only racquet that I tried to get MgR in the suggested range. In one modification alteration it got closer to this goal. But I was never satisfied completely and when it finally improved its precision some (not just vertical one, of course), it became clunky as well as I had to weighten its middle a lot to get MgR closer to the right value, but the real precision was still not there. Perhaps fine tuning might have improved it but I didn't find that point in many alterations. But because of its string bed, I don't think it's worth trying. Although I'll try this latest modification to see how it is now with further improved twist stability.

I went to TW calculations again, it's actually funny how much you need to put at 3+9 o'clock to convert a racquet with bad twist stability into a high TW range. Latest modification adds over 2.5 points to TW. Unfortunately I don't know the stock value, but if it was not high at stock, no wonder that it takes that much.

I'll also do calculations for Mantis to see what I can do with the optimum balance in current range.

bkr · Apr 25, 2016

Thanks travlerajm.You have been a great help on Tennis insights.

zalive · Apr 27, 2016

With increased twist weight and with removed depolarizating weight (remaining now polarized) Mantis now shows a bit more consistency - and this consistency now setlles in pretty high launch angle. Yeah, it's the string spacing density in the middle that causes the problems with precision. I believe it could be further improved by power optimizing its balance and optimizing its MgR/I to make it something similar to Prince, but there's no point, at least not for me. I might still do it for fun, though. I will make calculations during the week.

Vertical precision of a racquet

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