Racquet with the lowest swingweight ever?

Discussion in 'Racquets' started by corners, Jan 19, 2013.

  1. corners

    corners Legend

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    Nice McGyver action.

    For high swingspeeds on rotational swings, yeah, the fact that the swingspeed is greatest at the tip and least at the throat ends up balancing out the fact that ACOR is greatest as the throat and least at the tip. Of course, spin is greatest near the tip because the racquet is moving fastest there, and least at the throat, so we might expect to find shots hit near the tip to land very short on topspin shots. But low ACOR (low hittingweight) also means a higher launch angle. So the shot hit near the tip will rebound at a higher angle and then the greater spin will bring it down to approximately the same depth on the court as the combination of greater ACOR, lower rebound angle, and less spin at the throat will.

    But this is all most true for very high swingspeeds and low incoming ball speeds. So on serve you really don't lose much speed if you hit near the tip, if at all, and the extra spin is very welcome. But as the swingspeed slows down and the incoming ball speed increases, the low ACOR near the tip starts to penalize you. On a hard groundstroke, like 70mph shot speed, you might lose 2-4 mph if you hit 2 inches above the center with a traditionally weighted player's stick. And on a volley, where the incoming shot might be 70 mph or so, and your racquet is traveling only 15, things are worse. And made worse by the fact that volleys are relatively linear swings, so the tip isn't usually moving much faster than the throat, unlike with serves and rotational groundstrokes. So on a volley you might lose 5-7 mph on a shot struck near the tip compared to one struck in the center. Worse still, if we instead compare a volley struck 2" above center and one struck 2" below center we're looking at a possible difference of 15 MPH or so. And now the differences in launch angle and speed start to combine to produce shots landing several feet or more apart from each other on the court. So not only are you getting widely variable shot speeds at net but you're losing accuracy unless you can hit in the center of the strings each time, which you can't.

    So this gradient business is mostly about volleys, but also could be important on groundstrokes if you're into equipment optimization or just generally geeking out on this stuff. And if you get the tip leaded up and ACOR improved up there you might be able to get a couple extra MPH on serve because most people tend to hit high in the hoop when serving. Stiff hoops also liven up the upper hoop, but doing it with mass is a more arm-friendly approach, (as long as your shoulder can handle the heft.) The poster Travlerajm introduced me to this topic, and if you're familiar with his experiments you'll know that he weights the hell out of the top of the hoop. He plays the net a lot so this probably really helps him achieve consistent power and accuracy up there. From that perspective it's pretty interesting. Sampras gained a lot by adding so much mass at 3&9, but I wonder if his volleys would have been even better had he put more mass higher in the hoop.

    On the other hand, to my knowledge Edberg used a stock PS 85 without a bumper guard, which meant his swingweight was very low, with a steep ACOR dropoff near the tip. And he maybe had the best volleys of all time. So a strong case could definitely be made that we're here ridiculously overthinking this stuff. :)

    All the "data" in the first couple paragraphs was generated with TWU's Shot Maker simulator. I've learned a lot from playing around with that thing.
     
    Last edited: Feb 23, 2013
    #51
  2. JohnB

    JohnB Rookie

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    Thanks, Corners.

    Today, I moved the weights to 10 and 2 and tried to be as precise as possible to achieve the same twistweight. No matter how I shifted the weights around 10 and 2, I could get a predictable launchangle. No comes the interesting part. When attached the weights to spots around 10 and 2 where the launchangle was least unpredictable, I added 12 grams total also at 10 and 2 (on top of the weights), the launchangle, speed and depth were constant again. This makes me believe that with higher swingweights, higher twistweights are needed to generate a constant spinrate across the face from 3 to 9.

    Estimated final specs. 437grams, 39cm, sw.600+, so not very playable obviously.
     
    #52
  3. corners

    corners Legend

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    Interesting findings John. Maybe there is some optimal ratio of swingweight/hittingweight and twistweight. But yeah, 600 swingweight won't work for play, but you might be onto something. :)
     
    #53
  4. JohnB

    JohnB Rookie

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    I was hoping you came up with a formula or something:)

    Although the swingweight increase is enormous, the twistweight increase isn't that much higher, relatively speaking. So it might be that a certain twistweight is optimal for this purpose and that just a little finetuning is needed. If you want to combine this experiment with a proper power gradiënt towards to tip, you have to start with a very, very light frame.
     
    #54
  5. corners

    corners Legend

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    i wish I was that clever.

    An extraordinarily light frame. If we're looking at 60 grams to balance spin generation from side to side I think the only way to simultaneously liven the upper hoop would be with frame stiffness. With so much mass concentrated at 3&9 the frame would probably have to counterbanced at the buttcap with a massive wad of tungsten or spent uranium. All that buttweight should soften the frame enough so that a superstiff tip might not be uncomfortable. Or, someone could make a 100% graphene racquet that weighs 1 oz with 150 swingweight that could easily be leaded up with massive amounts from 4 all the way round to 8, creating the perfect stringbed. I'm calling a patent attorney;)
     
    #55
  6. tyu1314

    tyu1314 Semi-Pro

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    How to add 60 grams at 9&3? That is 120inch of .5gram,or 240 inch of.25 gram lead?? If you use the .5gram/inch, thats 30layers of lead:shock:
     
    Last edited: Feb 26, 2013
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  7. spaceman_spiff

    spaceman_spiff Hall of Fame

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    If you use 5" long strips on all four sides of the frame (both sides of the strings at 3 and 9), and if your frame is wide enough to fit the 1/2" wide tape on both sides of the strings, then it's 6 layers in each position.

    It's a fairly sizable stack of lead, but it's still doable.
     
    #57
  8. corners

    corners Legend

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    I'm thinking of squirting something into the grommet holes. Travlerajm has done it with silicone but I don't think that will be dense enough for this project. Researching other materials.
     
    #58
  9. spaceman_spiff

    spaceman_spiff Hall of Fame

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    Maybe a combination of liquid and lead tape. Squirt the silicone and measure the mass gained. Then add the remaining mass with layers of lead tape.
     
    #59
  10. travlerajm

    travlerajm Hall of Fame

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    I just found this thread. It’s an interesting topic.

    I discovered 5-6 years ago an interesting phenomenon, and I confess that I still cannot fully explain the physics of it.

    If you start with a stock racquet (doesn’t really matter what the starting specs are, it could be a light tweener, or it could be a players racquet, as long the swingweight is in the typical range), and then proceed to add mass gradually to the upper hoop, it will tend to become more powerful and less spin-friendly.

    But as you continue to add mass, eventually you reach a “tipping point”, where further additions of mass start to have the opposite effect on spin and power level a groundstroke. Continued addition of mass beyond this tipping point result in a heavier, spinnier response from the stringbed (I had previously termed this zone beyond the tipping point as “SW2”).

    I found it uncanny that the tipping point almost always occurs at a swingweight near 360 (but it can vary, depending on the starting specs of the frame). It seems to be at least in part a swingweight effect, because the “spin reversal” (that is, the increased spin with further mass increase) happens regardless of whether I place the extra lead at 3-&-9 or at 12. But I have also noticed that the heavy ball effect (seemingly effortless natural spin) is most pronounced when a significant fraction of the added mass is at 3 and 9.

    I had presumed in the past that this “spin reversal” effect must be somehow related to the effects of ball flattening. But now I’m not so sure – I think ball flattening is part of the story, but these other effects discussed by TW professor (rotation effect, shortside effect, could also be contributing to this phenomenon).

    The TW Professor’s experiment looked at what happens when you add 100g, which pushes you far past the tipping point, into the realm of very spin-friendly racquets. But I think the experiment is jumping over the more interesting question of what is happening in between. In my experience, it doesn’t take 100g addition to enjoy these heavy-spin effects – all it takes is pushing the swingweight of your racquet up to around 370 SW.

    Doing the experiment on court (or even against a wall) is fun and easy to do. Just grab a roll of lead tape, and start adding a couple grams at a time, and observe the difference in ball response. When you finally get past the tipping point, and the ball starts to really dip after it leaves your stringbed, it is a strange sensation.

    As for creating more consistent spin across the face from 3 to 9, I have never specifically tried to optimize that. However, I can tell you that whenever I try to play with a frame of stock swingweight (325 or so), I am never completely comfortable with the predictability of spin and launch angle. For me, the difference in control (with ‘control’ defined here as predictability of ball response) between 325 SW and swingweight in high 360s is night and day. Maybe part of the reason is that the high 360s swingweight range is where spin rate is nearly equalized across the face from 3 to 9?

    Once you combine predictability of ball response (which for me comes with combining high enough swingweight and stiff enough stringbed) with the ability to control the racquetface through the contact point (which for me can be achieved by carefully tuning the MgR/I parameter), tennis becomes a lot easier.
     
    Last edited: Feb 27, 2013
    #60
  11. corners

    corners Legend

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    Yeah, that might be the way to go. Thanks. I'd also like to figure out a way to squeeze tungsten putty into the grommet holes.
     
    #61
  12. corners

    corners Legend

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    Good stuff Trav. Do you think the tipping point is actually a particular effective hitting weight? I'm wondering if you reach it earlier if you use a shortened frame or have a contact point lower in the stringbed.

    What's the deal with Fed - his MgR/I seems optimal according to your hypothesis, but his stringbed is very soft? Compensatory genius?
     
    #62
  13. corners

    corners Legend

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    Have you noticed any difference in spin generation on high and low impacts when going from a mid to an oversize? As I mused above, it would seem that the short-side effect in particular would be minimized if impacts occured further from the frame edge, as they generally would with an oversize. Also, your technique of eliminating the outer mains might do this as well by reducing the stringbed stiffness near the edge. I've been wondering about the Wilson Blade Team/Blade 104 because of it's power holes at 3&9 for this reason.
     
    #63
  14. JohnB

    JohnB Rookie

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    As for creating more consistent spin across the face from 3 to 9, I have never specifically tried to optimize that. However, I can tell you that whenever I try to play with a frame of stock swingweight (325 or so), I am never completely comfortable with the predictability of spin and launch angle. For me, the difference in control (with ‘control’ defined here as predictability of ball response) between 325 SW and swingweight in high 360s is night and day. Maybe part of the reason is that the high 360s swingweight range is where spin rate is nearly equalized across the face from 3 to 9?

    I don't think that the 360 swingweight range is the reason for constant spinrate. In my experiment with the weights at 4 and 8, when the swingweight must have been at least 400 and I really had to adjust the twistweight to get a nice, even ball response.(Or maybe the swingweight has to be precisely around 360). When I moved the weights to 10 and 2, I had to add 12 grams total on top of it to get a nice, even ball response. Because of the locations being as close as possible from the same distance from the top to bottom line of the racket, I increased the twistweight with 12 grams. Then, I also varied grippositions up to including the throat. The throat was the location where the swingweight felt normal (with the weights at 10 and 2). At this gripposition, the launchangle, speed and depth was the same when struck from 3 to 9, I only had less plow with this gripposition.
     
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  15. newyorkstadium

    newyorkstadium Semi-Pro

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    I thought swingspeed contributed to spin. Do you not lose swingspeed going up to 370 SW?
     
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  16. corners

    corners Legend

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    I'm going to jump in here. Trav has written many times that spin tends to decrease as you go up in swingweight because swingspeed decreases. But, at a certain point, extra mass in the head starts to improve spin greatly, and when you reach a certain swingweight threshold - 365 or so - that extra head mass overcomes the lessened swingspeed and total spin increases compared to low-swingweight setups.
     
    #66
  17. newyorkstadium

    newyorkstadium Semi-Pro

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    Okay. Thanks corners.
     
    #67
  18. travlerajm

    travlerajm Hall of Fame

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    Yes, I think the tipping point is mostly a function of effective mass. So yes, I would expect a shorter frame should get there at a lower swingweight. It's been awhile since I experimented with this though.
    [/quote]
    A soft stringbed is great for serving big and hitting explosive heavy forehands. But the achilles heel of a soft stringbed is heavy incoming spin.

    I think Federer's struggles dealing with Nadal have more to do with his string setup than to the fact that he has a one-handed backhand.

    The way to neutralize Nadal-type heavy spin is to string your racquet like a paddle. James Blake strung his 18x20 frame with poly at 68 lbs, so it played like a wooden paddle. I don't think it's coincidence that in his prime, Blake had no trouble dispatching Nadal whenever they met in big matches.

    Djokovic also strings his 18x20 frame in the 60s, and he doesn't seem to be bothered by Nadal's forehand either.

    When a ball with heavy incoming spin hits a stringbed, the amount of torque applied to the racquet by the ball is a function of how deep the ball sinks into the stringbed. The softer the stringbed, the longer the moment arm for the rotating ball to apply torque to the racquet. The longer dwell time of a soft stringbed compounds the problem, and the increased rebound angle due to denting compounds it further!

    Even when neglecting the torque effect, the denting effect is a major factor in control. But you don't have to take my word for it -- you can simply look at the data from the 2004 paper by Goodwill and Haake on oblique impacts on a clamped stringbed. The authors failed to notice it, but their data clearly show that rebound angle is much more sensitive to incoming spin rate when the stringbed is looser. The less your rebound angle depends on incoming spin rate, the more control. In other words, the data show empirical evidence for the old adage: string tighter for more control!

    Whenever Federer played Nadal at the French, you could see how frustrated he was that he simply could not control the rebound angle when he tried to use his slice backhand against Nadal's spinny shot.
    Had Federer tried stringing his racquet 10 lbs tighter, I think his results vs Nadal at the French Open in his prime might well have been different.
     
    Last edited: Mar 3, 2013
    #68
  19. travlerajm

    travlerajm Hall of Fame

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    Since my goal is to make contact in the center of the stringbed, I think it's difficult to perceive differences in spin generation as a function of impact point.

    One thing I did notice though, that agrees with some of the things you mentioned earllier in this thread:

    When I shortened my POG Longbody to 26.75" and concentrated 40g at 3&9, the racquet performed very well on serves (and even better when I add a gram at 12, which seemed to stiffen the upper hoop). I could really serve big heavy serves with it, despite the shortened length. It also hit a really naturally heavy ball on groundies. It turned out that the swingweight was in the low 350s when I measured on an RDC machine. But I abandoned the setup with all the hoop weight at 3-and-9 when I found how much the power level dropped off on volleys near the tip.

    This thread makes me want to get my POG LBs out again and try some more things with lots of weight at 3&9 - maybe I can minimize the dead tip problem on volleys by adding just a few more grams at the tip? My shortened POGs have unleaded swingweight of around 270.

    As a fun side note, I was feeling humbled this morning after I couldn't win the set I played against the teaching pro at the Buenos Aires Sheraton when my rusty serve let me down. Then afterward, he told me he was top 900 in the world 4 years ago when he was 18 (Kevin Sosa). I actually matched up fairly evenly in the baseline games to 11 today, winning one of them and losing the rubber game 14-12, so I didn't feel so bad anymore!
     
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  20. JohnB

    JohnB Rookie

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    Did you have a chance to test it already?
     
    #70
  21. newyorkstadium

    newyorkstadium Semi-Pro

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    Corners, did you find the perfect racket for this experiment? The problem I have with adding all the lead at 3/9 is that lead at 10/2, 11/1 or 12 is better for the serve, based on what i've read over the years.

    A flipside of lead at 3 and 9, over 10/2 or above, is that it doesn't raise the sweetspot as much. Which is good for me, as fuzzy residue on the stringbed confirms I hit mostly in the centre of the stringbed.
     
    #71
  22. corners

    corners Legend

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    Yeah, there is a post upthread a little ways about that, and I think the benefit of more lead at the top of the hoop vs. 3&9 is mostly felt on volleys - shots with low swingspeed. I don't think it matters very much with groundstrokes and serves because of how rotational those strokes are and how much faster the tip is moving relative to the center of the stringbed.

    I think it's a good idea to have the vibration node where you tend to hit the ball. On the other hand, it may be that you tend to hit the ball where the vibration node is. :)

    And no, I never found the perfect frame. I got of got distracted from this project by the ever-exciting monogut ZX.
     
    #72

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