Questions about Polarized & Depolarized set-ups

[aaron_h27]

no I am at 6.5 pts hl with the leather and two og when putting 2 grams of 12 o clock lead. 7 pts hl when I put 1.5 grams. 7.5 pts hl when there’s no lead. Stock I don’t have enough stability against big serves and put away power.

1g at 12 does not reduce the balance point that much in my experience.

 

[Irvin]

@EasternRocks Each gram @ 12 should increase the balance by about 1 mm not 1 point. Each point is just over 3 mm.

 

[EasternRocks]

1g at 12 does not reduce the balance point that much in my experience.

im being generous to the 2g lead at 12 o clock. It is more like 7 pts like it is with 1.5g lead, which also may be more like 7.5 and no lead being really close to 8.

I’ll experiment stringing 120 and putting lead at 12 to try and try and get closer toward a polarized set up and compare with what I have now.

 

[Brando]

I have now played with a Yonex SV98 plus (27.5 inch long) since they first came out. I have a one hand backhand, therefore, I cut the grip down and
do not use a full length overgrip. Why? With only 5-1/2 inch of the pallet wrapped with a stock grip and an overgrip and the rest of the pallet bare, I reduce the weight of the grip by about 3 to 4 grams.

According to TW's site the SV98 plus is rated at 340 swing weight strung and 5 points head light. With the removal of some of the grip material, I should have a slightly higher swing weight. When playing a natural gut/poly hybrid the swing weight is even higher than full poly. Best racquet setup I have ever played with. Have no intention of using any other racquet in the near future.

Aloha

@kramer woodie, you've likely figured this out in the intervening 3 years, but for the edification of those reading this thread for intel, as I am now, I feel duty bound to clarify that removing mass from the grip doesn't increase swingweight. If anything it decreases it by decreasing the mass of the racquet. For the record, the only way to decrease swingweight is to remove mass from above the balance point.

 

[Karma Tennis]

@kramer woodie, you've likely figured this out in the intervening 3 years, but for the edification of those reading this thread for intel, as I am now, I feel duty bound to clarify that removing mass from the grip doesn't increase swingweight. If anything it decreases it by decreasing the mass of the racquet. For the record, the only way to decrease swingweight is to remove mass from above the balance point.

IIRC, swingweight is directly associated with the mass of the tennis racquet.

Adding mass to a racquet will increase its swingweight. For a fixed amount of additional mass, the closer that mass is added to the top of the racquet, the greater the increase in swingweight.

Removing mass from a racquet will decrease its swingweight. For a fixed amount of reduced mass, the closer to the top of the raquet the mass is removed from, the greater the decrease in swingweight.

So, on that basis, removing mass from below the current balance point will reduce swingweight. But nowhere near as much as removing it from above the balance point.

It is also important to note that removing mass from any part of the racquet except in the immediate vicinity of the current balance point will change the racquet balance. Removing mass from the current balance point will reduce the swingweight of the racquet while retaining the existing racquet balance. More importantly, a quick way to increase the swingweight of the racquet without affecting the current balance is to add mass to the balance point.

 

[Irvin]

More importantly, a quick way to increase the swingweight of the racquet without affecting the current balance is to add mass to the balance point.

No matter what the original specs of a racket are, if you add weight at the balance point your SW increase by .001 kgcm^2 for every gram you add.

SW = RW + mr^2

If RW and r remains the same, SW is directly proportional to m, and if m goes up 0.001 kg SW goes up 0.001. If you want to increase SW without changing balance divide the mass in half and place each half equidistant from the balance point. Then RW increases by I = mr^2.

 

[Karma Tennis]

No matter what the original specs of a racket are, if you add weight at the balance point your SW increase by .001 kgcm^2 for every gram you add.

SW = RW + mr^2

If RW and r remains the same, SW is directly proportional to m, and if m goes up 0.001 kg SW goes up 0.001. If you want to increase SW without changing balance divide the mass in half and place each half equidistant from the balance point. Then RW increases by I = mr^2.

Indeed.

But if the balance point is below the hoop I can see advantages in just adding mass at the one point - particularly in the case of certain racquets. In that situation, splitting the mass can have an impact on the polarisation and twistweight of the racquet ... which could be desirable in some circumstances and undesirable in others.

 

[Irvin]

…if the balance point is below the hoop I can see advantages in just adding mass at the one point - particularly in the case of certain racquets. In that situation, splitting the mass can have an impact on the polarisation and twistweight of the racquet ... which could be desirable in some circumstances and undesirable in others.

If the balance point is below the hoop the only point where you can add mass is on the side throat points which impacts TW. Polarization and TW will change in most cases no matter where where weight is added. If mass goes up and RW remains relatively constant polarization goes down.

 

[Brando]

IIRC, swingweight is directly associated with the mass of the tennis racquet.

Adding mass to a racquet will increase its swingweight. For a fixed amount of additional mass, the closer that mass is added to the top of the racquet, the greater the increase in swingweight.

Removing mass from a racquet will decrease its swingweight. For a fixed amount of reduced mass, the closer to the top of the raquet the mass is removed from, the greater the decrease in swingweight.

So, on that basis, removing mass from below the current balance point will reduce swingweight. But nowhere near as much as removing it from above the balance point.

It is also important to note that removing mass from any part of the racquet except in the immediate vicinity of the current balance point will change the racquet balance. Removing mass from the current balance point will reduce the swingweight of the racquet while retaining the existing racquet balance. More importantly, a quick way to increase the swingweight of the racquet without affecting the current balance is to add mass to the balance point.

Nice catch, @Karma Tennis . In my last sentence I meant to say, "...the only significant way to decrease swingweight..." But without 'significant' all I did was contradict the prior sentence. And if one is going to throw around phrases like, "For the record," one should expect to be held to a higher standard of precision. I stand corrected

 

[Karma Tennis]

If the balance point is below the hoop the only point where you can add mass is on the side throat points which impacts TW. Polarization and TW will change in most cases no matter where where weight is added. If mass goes up and RW remains relatively constant polarization goes down.

For sure. But I imagine a large amount of extra mass would need to be added to the side throat points for a noticeable effect on TW. (And that would also be dependant on the hoop size. The effect on TW would be more noticeable on small hoop sizes than larger ones.

As for polarisation, I've always thought the closer any additional mass is placed to the current balance point of the racquet the least impact there is on the existing polarisation when compared to adding mass to any other part of the racquet. (Of course, adding any additional mass to the racquet is going to alter its polarisation unless the added mass is distributed through the racquet in exactly the same manner as the weight was distributed through the racquet at the point of retail delivery.)

 

[Karma Tennis]

Nice catch, @Karma Tennis

Cheers @Brando. For once, I beat our good friend @Irvin to the punch

 

[Irvin]

As for polarisation, I've always thought the closer any additional mass is placed to the current balance point of the racquet the least impact there is on the existing polarisation when compared to adding mass to any other part of the racquet. (Of course, adding any additional mass to the racquet is going to alter its polarisation unless the added mass is distributed through the racquet in exactly the same manner as the weight was distributed through the racquet at the point of retail delivery.)

No need to add mass all up and down the racket. If you had a 325 g uniform racket the RW would be 127.4. If you had a 325 g racket with a RW of 160 it would be 32.6 kgcm^2 greater than a uniform stick. If you want to add 5 g to that racket you could add it at 19.5 cm above and below the balance point and maintain 32.6 points above the uniform racket value of 129.3.

 

[ryohazuki222]

am I the only person that likes polarized setup on the y axis but a depolarized setup on the x axis?

I loathe the feel of adding weight at 3 and 9. Even adding weight at 12, I prefer shorter stacked strips instead of a longer strip.

 

[Brando]

You kidding? I'm poled up nice with a 174 recoil & 20.1 MgR/I. Re. weight at noon, 'got 5g laid out in two 16.7mm strips, making TW 15.1 from 13.6 stock. So I sport a meatier X than you. But I get what you're saying @ryohazuki222 , polarization is a revelation, a dream. A light, whippy stick that plows through balls like it jus' don't care. What's not to like?
Am curious: do you know your pre and post mod twist weights?

 

[Karma Tennis]

No need to add mass all up and down the racket. If you had a 325 g uniform racket the RW would be 127.4. If you had a 325 g racket with a RW of 160 it would be 32.6 kgcm^2 greater than a uniform stick. If you want to add 5 g to that racket you could add it at 19.5 cm above and below the balance point and maintain 32.6 points above the uniform racket value of 129.3.

I understand that. But the racquet with the added mass at those two points would not play and feel exactly the same as a racquet that had the extra mass distributed through the entire racquet in the same manner as the original stock racquet was. Now the difference in playability / feel might not be noticeable but comparison testing would be required to confirm.

 

[Irvin]

I understand that. But the racquet with the added mass at those two points would not play and feel exactly the same as a racquet that had the extra mass distributed through the entire racquet in the same manner as the original stock racquet was. Now the difference in playability / feel might not be noticeable but comparison testing would be required to confirm.

Spreading the weight out increases SW where at 2 single points gives you the least change in SW. Also you can’t increase the weight uniformly because that would decrease polarization.

 

[Karma Tennis]

Spreading the weight out increases SW where at 2 single points gives you the least change in SW. Also you can’t increase the weight uniformly because that would decrease polarization.

OK, I can accept your first point.

But how does increasing the weight uniformly (ie adding the weight throughout the racquet in identical proportions to the way it was originally manufactured) decrease the polarisation?

Are you saying that if I have two racquets that are manufacted with identical weight distribution but one is say 300g and the other is 315g that the 315g racquet will be less polarised than the 300g one? I can understand that the 315g stick would have a higher SW. But why wouldn't they have the same polarisation?

 

[Irvin]

But how does increasing the weight uniformly (ie adding the weight throughout the racquet in identical proportions to the way it was originally manufactured) decrease the polarisation?

You’re contradicting yourself. All rackets are polar to some extent or their RW would be very low, balance would be even, and there would be no machine needed to measure SW. Therefore, I’m not sure how you go about determining where to place weight up and down the racket to maintain the same polarization.

Are you saying that if I have two racquets that are manufacted with identical weight distribution but one is say 300g and the other is 315g that the 315g racquet will be less polarised than the 300g one? I can understand that the 315g stick would have a higher SW. But why wouldn't they have the same polarisation?

How do you measure weight distribution? Not sure a 315 g racket would also have a higher SW either but I doubt it. Take a look at 305 and 315 Tecnifibre TF40 rackets.

EDIT: Often lighter rackets are more polar and HH which also results in them having a higher SW.

 

[Karma Tennis]

You’re contradicting yourself. All rackets are polar to some extent or their RW would be very low, balance would be even, and there would be no machine needed to measure SW. Therefore, I’m not sure how you go about determining where to place weight up and down the racket to maintain the same polarization.

@Irvin, it is 15 minutes past midnight here on the East Coast of Australia. I'm somewhat distracted by the RG SF that is being played at the moment. It is about 4 Degrees Celsius outside and it has been raining quite a bit here in the past few days. So cut me some slack.

HOWEVER (!), I am talking from a purely theoretical perspective. In a perfect world every specific model of racquet that comes of the production line SHOULD have identical specifications in terms of static weight, balance point, SW and TW. This would mean they all have identical polarisation.

Now if you manufacture a 300g model and a 315g model of the same racquet, they will have different static weight, SW and TW. But if they have the same balance point because the ratio of weight distribution is the same, why would they have different polarisation?

 

[Irvin]

I am talking from a purely theoretical perspective. In a perfect world every specific model of racquet that comes of the production line SHOULD have identical specifications in terms of static weight, balance point, SW and TW. This would mean they all have identical polarisation.

It is call Quality Control. Even a manufacturer has issue keeping the weight the same on 1 model.

Now if you manufacture a 300g model and a 315g model of the same racquet, they will have different static weight, SW and TW. But if they have the same balance point because the ratio of weight distribution is the same, why would they have different polarisation?

Ok say you want to sell a 300 and a 315 g version of the same racket. And you want the balance and SW to be close.

SW = RW + mr^2

If m is .300 for 1 racket and .315 for the other and balance is 32.5 cm then mr^2 is (.300*22.5*22.5) 151.875 for the 300 g racket and (.315*22.5*22.5) 159.469 for the 315 g racket. If you want the 2 rackets to have the same SW the RW of the lighter racket must be higher. RW is telling you how mass is distributed, not the balance point. If RW of a normal racket is 160+ it is very polar no matter what the balance point is.

 

[Irvin]

Now if you manufacture a 300g model and a 315g model of the same racquet, they will have different static weight, SW and TW. But if they have the same balance point because the ratio of weight distribution is the same, why would they have different polarisation?

Maybe many people are confused by weight distribution. Assume you have a racket withe 165 g above and below the center of the racket. If the weight were evenly distributed in both section the racket would have an even balance and non polar. If the weight in the head was DISTRIBUTED more towards the tip the balance point would be higher and the racket would be said to be head heavy but it isn’t the 2 13.5“ sections weight the same. Because you can’t cut the racket in half to check weight the only option you have is to measure inertia. The slower the racket moves under a know force the higher the inertia. I = mr_2 so if the mass is the same but r goes up inertia goes up. HH does not mean the head is heavier it means the balance point is above the center of the racket.

 

[Brando]

If m is .300 for 1 racket and .315 for the other and balance is 32.5 cm then mr^2 is (.300*22.5*22.5) 151.875 for the 300 g racket and (.315*22.5*22.5) 159.469 for the 315 g racket. If you want the 2 rackets to have the same SW the RW of the lighter racket must be higher. RW is telling you how mass is distributed, not the balance point. If RW of a normal racket is 160+ it is very polar no matter what the balance point is.

@Irvin , you meant the numbers (I've 'bolded') to be the balance, 32.5, right? This isn't a gotcha' question; I'm looking to truly understand mr^2, and I think I understand it far better after reading this discussion. (And thanks for taking to time to go into it here.)

 

[Irvin]

@Irvin , you meant the numbers (I've 'bolded') to be the balance, 32.5, right? This isn't a gotcha' question; I'm looking to truly understand mr^2, and I think I understand it far better after reading this discussion. (And thanks for taking to time to go into it here.)

Mass times radius squared. The mass is in kg so 300 grams is 0.3 and the radius is distance from the SW pivot of 10 to the balance point Of 32.5 cm or 22.5.

 

[Brando]

Thanks for clarifying that, @Irvin . I had it wrong! But now it makes sense that it's distance from your hand (as the pivot point) to the axis of rotation, being the balance point on this axis. And suddenly your equation SW = TW + MR² adds up, too. For the first time I may actually be grasping the Moment of Inertia. Sweet.