New TWU Article: Spin and String Friction

Discussion in 'Strings' started by TW Professor, Aug 27, 2010.

  1. TW Professor

    TW Professor Administrator

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    Check out the new TWU article based on our experiments with interstring friction. We have measured the coefficient of friction on about 30 strings (and will strive to do many more as time permits and make a full-fledged tool out of it).

    http://twu.tennis-warehouse.com/learning_center/COF.php
     
    #1
  2. vamos2050

    vamos2050 New User

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    great tool! thanks for taking your time
     
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  3. Bud

    Bud Bionic Poster

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    Some string company should create a natural gut with a durable Teflon™ coating :)
     
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  4. GPB

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    What a report! Thanks for spitting out all this info into your learning center.
     
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  5. olliess

    olliess Semi-Pro

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    Fascinating results. Thanks for this post.
     
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  6. Gasolina

    Gasolina Professional

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    I was hoping to see Tour Bite in the test.

    Great article. One thing that needs to be taken into account here is even though a gut/poly hybrid would produce the biggest spin, it won't necessarily give you that "just before the line" dropping of a full poly.

    As much spin as you could generate with a hybrid, you still need the dampening of power from a poly to effectively use that spin.
     
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  7. Gasolina

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    I wonder if a multi/poly hybrid would get as much spin as a gut/poly hybrid?
     
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  8. scotus

    scotus Legend

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    So it looks like a gut-M and RPM-Blast-X would be the ultimate spin monster...

    ... for the über rich.
     
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  9. Don't Let It Bounce

    Don't Let It Bounce Hall of Fame

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    t does look like it, assuming that the slipperiest poly will always make the slipperiest gut/poly hybrid. I wonder if we can assume that? (I hope not, given how much less Cyclone costs than RPM Blast.)
     
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  10. Buckethead

    Buckethead Banned

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    So TW Professor,
    the strings that retain tension better,meaning less string movement,therefore less spin potential,am I right?
     
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  11. wrxtotoro

    wrxtotoro Rookie

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    Then what about Kevlar? It's known to produce extreme bite on the ball but does it increase any spin in reality?
     
    Last edited: Aug 29, 2010
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  12. GameSetMatch

    GameSetMatch Banned

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    How can a gut hybrid produce more spin that a full bed poly? That just makes no sense.

    I think you need to a test a full bed of natural gut as a 'control' factor to the experiment.

    Interesting that X1 is one of the worst spin producing strings you can get.
     
    Last edited: Aug 29, 2010
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  13. bad_call

    bad_call Legend

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    wait a while to see if u know what i mean. ;)
     
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  14. Gasolina

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    True... but what about the remaining 95% of the population?

    Given that TCS was #2 based on the test, it would make sense as the poly cross for a "reasonable" setup.

    How about the mains? Since the reason why gut@mains made #1 was because of it allows the poly to freely move... would the Dynamite be a good alternative since it offers the closest to gut feel? Maybe a POGS would work too?

    String both at around 45lbs and maybe we have a winner.
     
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  15. gatorbait01

    gatorbait01 Rookie

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    Has anyone here done a side by side comparison with rackets strung up with full poly and gut mains, poly crosses?? Does the hybrid really produce more or equal spin to the full bed of poly?
     
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  16. Gasolina

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    Didn't they just do that in the article? Well they tested the lowest COF which contibutes to spin.

    Although what good is a spin if you can't dampen your power well to use it right? Maybe that's why a lot of people would claim that full poly = more spin.
     
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  17. JediMindTrick

    JediMindTrick Professional

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    Now we know why Federer and Djokovic put the gut in the mains and the poly in the crosses.
     
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  18. AR15

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    Perhaps string savers will provide even more spin by allowing the strings to move back into position, after impact, faster.
     
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  19. Gasolina

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    I don't think that's the complete story. I think on order to produce the spin, the strings would have to go back first and then snap back with little friction. If you had string savers, then won't the string movement be prevented?
     
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  20. Xenakis

    Xenakis Hall of Fame

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    Interesting stuff, thanks.
     
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  21. gatorbait01

    gatorbait01 Rookie

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  22. Buckethead

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    I can't agree with the fact that some strings were rated better than the SP Tornado.I have tested so many strings and the Tornado really grabs the ball and generates more spin than some of those mentioned on the article.
     
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  23. Centered

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    But there's no oil being exuded from polyester, so what accounts for its lower COF? If oil is good, will we see people oiling their strings before matches in the future? What about teflon coatings?

    Plus, the bottom chart shows two nylon strings with a lower COF than VS Team. That would imply gut doesn't have "super-slipperiness" in comparison with those two nylon strings:

    Prince Synthetic Gut Original 16, Nylon, 0.124
    Gosen OG-Sheep Micro Super 16L, Nylon, 0.145
    Babolat VS Team 17, Gut, 0.147

    If sideways movement of the mains is so important, what about lowering string tension? It also seems like strings that move around more would be better for spin, making what people call "excessive string movement" a good thing. Is there a chart that shows the difference between strings with an actual tension of 40 lbs versus strings with an actual tension of 60?

    Also, what's the second hypothesis?
    Hmm. I'm confused. The first part makes it sound, along with the "gut oils" hypothesis, that surface condition (slippery surface) is really important. The second part makes it sound as if the surface condition makes little difference.
    Please be more specific about this. Does polyester "retain its elastic energy" better than other strings, which accounts for its greater spin potential? If so, how?
     
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  24. Gasolina

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    I think the reason why power spin hitters (Nadal / Verdasco) stay away from Gut/Poly hybrids is because it's too lively. Contrary to popular belief, your ball can have a lot of spin, but still fly out of the park.

    A lot of us when we hear spin, we think its the thing that magically makes the ball fall down before the baseline and jump back up making the shot hard to return. In reality, spin, for all it's intents and purposes is just the ball spinning, even if the ball sails long or not.

    People use full poly because #1 control and #2 spin. A gut/poly hybrid might produce the most spin but the full poly might produce the most useful spin. Meaning the low powered poly would actually contribute to the ball coming down before the baseline.

    Can you imagine Nadal and Verdasco's forehands with a gut hybrid? It would fly all the way to the 5th row.
     
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  25. Centered

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    Not really. Topspin causes a ball to arc from low to high and then down. Hitting flat causes the ball to go straighter/deeper. It's the spin in the topspin shot that keeps it in the court.

    Sure, it's possible to hit a heavy spin ball that's out, but that doesn't mean the spin isn't helping to keep the shot in the court.
     
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  26. Gasolina

    Gasolina Professional

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    Yes of course, topspin helps in keeping the ball in play. But I'm willing to bet the low powered poly contributes more than the spin.

    Also, the poly allows you to take gigantic windshield wipers to generate the spin in the first place.
     
    #26
  27. Centered

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    No, it's the spin RPMs that have increased. Borg's topspin RPMs were much lower than Nadal's, and Borg's shots were less powerful. The combination of greater muscle, a larger stiffer lighter racquet, a more extreme western grip, poly, and very high racquet speed have enabled Nadal to hit with more topspin than his predecessors.

    Kevlar is less powerful than poly, being much stiffer, and it did not enable the same level of spin production and big hitting, according to Agassi who used it and then switched to poly.

    Anyway, back to my first post. Here is the part of the chart that shows gut with a less impressive COF than two nylon strings:

    [​IMG]
     
    #27
  28. Gasolina

    Gasolina Professional

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    I stand corrected. The Gut rating leaves me confused as well. But my thinking is the slipperyness of the Poly makes the COF lower. I mean if you just run your fingers over some gut, it is pretty sticky.
     
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  29. Gasolina

    Gasolina Professional

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    This makes a POGS/TCS experiment a lot more viable
     
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  30. Centered

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    The chart just doesn't make much sense with the description of gut as being "super slippery". Gut also comes with various coatings, some of which may reduce slickness.
     
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  31. Gasolina

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    I thought the article pointed out that the gut's oils (which came from the poly slicing into it) made the the gut slide a lot easier?
     
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  32. gatorbait01

    gatorbait01 Rookie

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    A lot of us when we hear spin, we think its the thing that magically makes the ball fall down before the baseline and jump back up making the shot hard to return. In reality, spin, for all it's intents and purposes is just the ball spinning, even if the ball sails long or not.

    People use full poly because #1 control and #2 spin. A gut/poly hybrid might produce the most spin but the full poly might produce the most useful spin. Meaning the low powered poly would actually contribute to the ball coming down before the baseline.

    Can you imagine Nadal and Verdasco's forehands with a gut hybrid? It would fly all the way to the 5th row.[/QUOTE]

    Something tells me that if a gut hybrid would produce more spin, then hardly anyone would use full poly. I think nadal and vedasco could adjust there swings to take advantage of the added spin and added comfort of gut mains. I could be wrong. I was hoping if anyone has done a good side by side comparison where the only variable would be the different strings. I'll do one soon, just gotta get some thicker guage cyberflash.
     
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  33. AR15

    AR15 Professional

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    Not sure. I have limited experience with string savers, but I recall that my strings still slipped with them.
     
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  34. JediMindTrick

    JediMindTrick Professional

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    TW Professor,

    Can we please get the numbers for Prince Recoil? Since Prince is claiming that this is a very slippery string, it would be interesting to see this claim quantified.

    Thanks!
     
    #34
  35. JediMindTrick

    JediMindTrick Professional

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    All strings move, but the slippery ones (like polys and Recoil) snap back, making it look likey didn't move. Because they snap back, they give more spin. So "excessive string movement" = "strings didn't snap back" = "less spin" = "a bad thing'.
     
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  36. Racer41c

    Racer41c Semi-Pro

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    So does this explain why my racquet smells like WD-40 all the sudden?
     
    #36
  37. olliess

    olliess Semi-Pro

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    It's smooth, among other reasons.

    I think Prince Recoil (mentioned by another poster) and Babolat N.Vy (among others) are already trying slippery coatings, so probably yes. WD-40 I don't know about.

    Gut was only "super slippery" in the special case of gut mains sliding against poly crosses, right? COF can be different between two materials than between instances of the same material and also be sensitive to exactly how those surfaces engage (hence the "slippery oil" hypothesis).

    Lowering string tension should reduce the friction if the COF stays roughly the same. However, the "snapping" action of the string in the horizontal (which seems to be the mechanism for imparting spin) also comes from the tension, so these two effects ought to run counter to each other.

    I thought excessive string movement referred to strings which move out of place and don't come back (so that you have to sit there and twiddle with your strings between points like they all did in the old days).

    When your multifilament gets knocked out of place and doesn't come back, it retains its elastic energy but it doesn't release it back to the ball. The poly, despite being less elastic than other strings, is able to slide back and immediately return the elastic energy built up by deflecting the string sideways.
     
    Last edited: Sep 1, 2010
    #37
  38. DE19702

    DE19702 Rookie

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    Although lower tensions may make it easier for the stings to slide apart, as posted above, this also has the effect of reducing the speed at which they snap back. Apparently, it is this snapping back that imparts spin upon the ball.

    With regard to the question why full gut is not more slippery than a gut/poly hybrid, it may be because of adhesion between the mains and the crosses since they are both the same material.

    It should be relatively a simple matter to chop up a bunch of gut, mix it with some kind of solvent, boil away the solvent and then measure the amount of oil in the string. I haven't seen any evidence that says that there is oil in gut, but it makes sense.

    It was interesting to note that the Prince Synthetic Gut has a coefficient of friction less than the multis and overall looks like a half-decent string from that point of view.
     
    #38
  39. Centered

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    Some of these explanations don't seem to add up, like the sections of the article I highlighted.

    Not all poly is smooth and some nylon strings are very smooth, plus the article said it doesn't matter what the shape of the poly is. Well, a round string is going to be smoother than a hexagonal one because it lacks sharp edges.

    Plus the article said rough textured strings don't make a significant difference.
    I think it's still too fuzzy in the way it's explained/documented to make good sense. I fail to see why gut would exude special oils when it's used with poly and not something else, or why it has a lower COF than two of the tested nylon strings if it exudes oil and gets "super slippery".
    Why/how? That's what I'd like to see explained, too.
     
    #39
  40. Centered

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    Head claims some of its strings that have Teflon coatings are more powerful because of slipperiness, too. The grommets in some of its racquets are a similar case.
     
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  41. tarkowski

    tarkowski Professional

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    I've played a gut main and poly cross for quite a while and have always felt that it is extremely spin friendly. More than my all gut setup, and more than the full bed of black code that I just tried. I chalked it up to the fact that for me, it is the most familiar and what my swing path is grooved to. But based on TW findings, it looks like it is indeed more spin friendly in absolute terms.

    Outside of the 'oil release due to gut notching on poly theory', there is also the fact that gut is a much more elastic string than poly. Compared to a full poly setup, gut on the mains with a poly cross provides that combination of poly keeping the string bed from deforming backward for more forward launch, and giving the gut the best chance to bend sideways for maximum spin.

    This is how I feel it when playing it as well. I also feel that with this set up, I really need to be 'on' my game, swinging full and confident to maximize this set up. I also need to swing flatter. Catching a ball late, or exaggerating the low-to-high motion in this set up really sends the ball long. I think this may also be what Chris (TW) was eluding to when he said that for him, an all poly set up provides more controlled spin because the launch angle is quite a bit less.

    Just my humble opinions and ramblings as we all grapple with the issue!
     
    #41
  42. Gasolina

    Gasolina Professional

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    Maybe because the gut was tested as a hybrid only with a poly? They didn't really test the gut in a hybrid with a syn gut or with a multi.
     
    #42
  43. Buckethead

    Buckethead Banned

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    This article also makes no sense in some parts.
    * String texture or shape makes no difference to spin
    Didn't it show that ALu Rough Produces more spin than Alu Power??
    * String pattern makes no difference to spin
    It does make a huge difference.
    Why don;t tey make a racket with 45 mains and 50 crosses and play with that racket and then go play with a 16x19?I bet you could get more spin from a 16x19.
    * String tension makes no difference to spin
    On the very same article it shows the same string strung at 62 and 52 and the one with 52 had low COF therefore producing more spin.
    * String gauge makes no difference to spin-
    Same string at lower gauge can produce more spin.
    * String material makes no difference to spin
    Didn't it say the polyester produces more spin than nylon?
    I don't really believe some of what they said at all,very contradictory.
     
    #43
  44. Centered

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    Yeah, I think some major retooling is needed. To me it looks a bit like a convoluted advertisement for RPM Blast. I will assume that wasn't intentional.
     
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  45. bsandy

    bsandy Hall of Fame

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    Another reason to wax your gut.

    . . . Bud
     
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  46. kcjim

    kcjim New User

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    I've tried gut mains and poly crosses twice. I loved it on my serves....way more spin. Really abrupt (only word that comes to mind) spin that just snapped as it cleared the net. The problem with this setup is my forehands kept going just long. It felt great, but in the end I just didn't have the sense or ability to reign in my forehand side. Probably a form issue with my forehand. I don't know.
     
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  47. TW Professor

    TW Professor Administrator

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    Several points of clarification:

    This quote echoes several others equating low COF and spin. COF is only one of the facilitators of string movement, snap back, and spin. But other properties of a individual string can act to negate or reverse benefits of the low COF. The COF experiments simply distinquish the slippery strings from the sticky ones. Other experiments will distinquish strings from each other on the other spin facilitating properties. The goal being able to decipher which strings have the greatest NET spin potential. Determining the COF ranking is just one step along the way. So do not simply interpret a low COF as "the best spin string," but rather, that it has one very important property that acts in favor of spin. It may or may not be the "best."

    For a given string, higher tension will tend to increase the COF between strings, first because the tension pushes the strings together with greater force and second because the stiffer stringbed will create a greater normal force at impact which also pushes the strings together more.

    COF depends on the TWO surfaces. The COFs given in the quote are for each string on itself. The hybrids involve two different materials. In each instance the surfaces will interact differently both atomically and morphologically.

    There are two completely different situations here: the ball-to-string friction interaction and the string-to-string interaction. The first is a special case because, as the article explains, friction tends to disappear before the end of the impact in the first case but not in the second. So string shape, texture, gauge may make a difference in spin in the string-to-string interaction but not in the ball-to-string interaction.

    There will be more COFs coming....

    Lowering tension will reduce inter-string friction but it also tends to lower the energy return in the string (you can see this by going to http://twu.tennis-warehouse.com/learning_center/reporter.php and searching energy return at the different tensions). This means the string will snap back more slowly. Thus, it may or may not snap back quick enough, far enough or with enough force to significantly affect the spin. It will depend on the string.

    Friction not only puts torque on the ball to create spin, but it slows the ball down as it travels across the strings. String movement and snap back will do the same. The more the ball is slowed down parallel to the strings, the steeper the launch angle will be and the farther the ball will travel farther.

    Much of the answer to this is explained above with respect to all these properties having a different significance depending on whether you are talking ball/string interaction or string/string interaction. Before it was determined that string movement and snap back were so important to topspin, the statement that COF, material, pattern, etc. did not matter to spin was "correct" as far as it went. But given that string movement is important, each of these needs to be experimentally revisited, but for different reasons and from a different point of view. So the COF article has revisted COF, the material articles (http://twu.tennis-warehouse.com/learning_center/spinexperiment.php and http://twu.tennis-warehouse.com/learning_center/stringmovement.php have revisted material, and we are presently conducting experiments on patterns.

    Stay tuned...
     
    #47
  48. Centered

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    Then you had better do some tests with hybrid setups that don't just involve gut + poly, given that two nylon strings had lower COFs in your chart than VS Team gut.

    Also, please test the new Dynamite Soft and also regular Dynamite 17 for the String Database. Thanks.
     
    #48
  49. JT_2eighty

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    That's really probably not necessary:

    1) we know low friction *helps* the spin of a shot. (technique, ability, grip, etc still play their role).
    2) we know that gut is the most elastic string type. (multi will always be 2nd place to gut).
    3) we know that strings that are NOT monofilaments (gut, multis, syn gut), will notch, thus increasing the friction between strings over use (they typically start notching after an hour or few), while monofilaments (i.e. polys), do not notch in the same way, preserving their low friction qualities (polys are known for maintaining an even stringbed because of both their stiffness and smoothness and resistance to notching).

    Therefore, gut mains (most elastic for most movement and snap back) and poly crosses (resistance to notching and low friction) is the best setup for pure spin, while also benefitting in the power and feel departments due to gut mains. Having just half the stringbed be poly is enough to create a low-friction, good-spin setup. Try it yourself and use it for days/weeks. You will see how the gut continues to slide back in place, unlike what will occur with the same gut in a full bed. The obvious downside to not using full poly is control, due to the launch angle discussions. More spin does not always equate to more control, this gets into player differences now, as some prefer max spin, and some just amped spin.

    Thus, multi mains on poly crosses will be similar, but not as good as gut mains (see 1-3).

    Everyone give the Prof a breather, dang. You should all be able to take the info here, and extrapolate to your favorite string or hybrid if not included. Keep experimenting, and if your oncourt results defy the results in a lab, that's FINE, actual results > theory.
     
    Last edited: Sep 3, 2010
    #49
  50. JT_2eighty

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    Of course they *could* adjust their swings, but that is another piece of the puzzle as to why some use full poly and some gut/poly hybrid. The full poly typically allows for a more controllable shot, due to the trajectory (launch angles) off the stringbeds that will vary from hybrid or full beds of x,y,z.

    I do love all the science about how this all works and value it's importance and what we can learn from it to help our games, but let us not forget how much things like technique, talent, subjective likes and dislikes, personalities, etc play into a player's choice of equipment and style. All of these more intangible aspects of one's game still make up the majority of the puzzle. Equipment changes will only get you so far; there's no mystery why one man's trash is another's treasure. We see it on these boards, on the tour, and at the club.
     
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