Crosses mainly responsible for power?

Discussion in 'Strings' started by TonyB, Feb 18, 2009.

  1. TonyB

    TonyB Hall of Fame

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    I realize that the majority opinion on this forum is that the main strings provide the main feel and power of the stringbed. So, a hybrid of gut mains and poly crosses, for instance, would feel like a "stiff gut". And the reverse, having poly mains and gut crosses, would feel like a "soft poly." At least that's what people keep saying. I just wonder how many of those people have actually TRIED both hybrids, or are just repeating what other people have written before.

    However, my experience with gut and multifilament strings is that the crosses always break in first and often snap before the main strings are even broken in at all. You can tell with gut and multis because the fibers break apart and become cloudy rather than clear or translucent once the strings are broken in. My thought is that it would be impossible for the main strings to bear the brunt of the power if the crosses are the ones that are experiencing the most stress (judging by the condition of the strings). My theory is that the crosses are chiefly responsible for the power and the main strings are responsible for the spin, as it is the tendency of the main strings to deflect and slide over the cross strings when topspin is applied. So if the main strings are somewhat inelastic (like poly), they would deflect and rebound much quicker, applying more spin to the ball. But the main strings would not be responsible for the bulk of the power, unless they were at a dramatically higher tension than the crosses, perhaps as much as 10% or more.

    I guess a consequence of this is that I would agree that the mains should be strung noticeably TIGHTER than the crosses to provide a more evenly-balanced and uniformly-powered stringbed. That is because the crosses are experiencing the higher stress while the mains are too loose by comparison to actually experience enough stress to break them in. This makes sense also because the shorter cross strings, when deflecting an amount equal to the main strings, undergo a higher degree of strain. So, having more elastic cross strings (or otherwise stiffer main strings) makes more sense if you want a balanced stringbed and a larger sweetspot.


    I have also tried hybrids with natural gut mains and poly crosses. The natural gut mains hardly ever break in properly, while the poly goes dead much quicker. But I don't notice any real increase in power with gut mains. Fact is, an all-poly stringbed will have just about as much power as a stringbed with gut mains and poly crosses, strung at similar tensions.

    Aside from a slight increase in feel, I can't see any real benefit to having gut in the mains as compared to, say, a cheap synthetic gut. The REAL benefit seems to be in choosing the proper crosses. If I switch to a soft synthetic gut in the crosses (keeping the same natural gut mains), the stringbed is MUCH more powerful than with the poly crosses. But as I said, if I just go with a straight all-poly stringbed, the power is the same, but I lose some feel/feedback and gain some spin.

    I am curious if anyone has any personal feedback on a particular hybrid that they have tried "both ways", that is with the mains and crosses strung one way, and also reversed. But all of the observations that I have made so far lead me to the conclusion that, assuming equal tensions on mains and crosses, the crosses will provide the power and the mains will provide the spin and control (only by moderating the crosses).
     
    Last edited: Feb 18, 2009
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  2. TonyB

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    60 views and no comments...


    Either my post was too complicated, too lengthy, or nobody knows what I'm talking about.

    I think the lack of replies speaks volumes about the popularly accepted theories regarding cross strings and tension variation on this forum. Everyone "knows" how hybrids work, except when confronted with contrasting information.
     
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  3. TenniseaWilliams

    TenniseaWilliams Professional

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    A lot of people break main strings first, unless using a multi cross hybrid.

    I thought the mechanism was:
    main string slides along the cross and back during impact. The heat from the friction is distributed down the cross string, but mostly on one spot on the main.

    A stringmeter will show you that the crosses are always at a much lower installed tension than the mains.

    I have racquets currently strung ng mains/copoly crosses, and copoly mains/sg crosses. I don't use ng on the crosses because I can't tell the difference enough to justify the cost, storage, and handling differences.
     
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  4. FloridaAG

    FloridaAG Professional

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    Unless you have poly mains and something softer in the crosses, the vast majority of people I have seen break the mains before the crosses. I know I always break the mains first.
     
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  5. Racer41c

    Racer41c Semi-Pro

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    So here's what I can add:

    I've tried a setup that based on TT wisdom would say that I should feel a slight increase (if any) in spin by changing from syn gut A to syn gut B as the cross string. However, I experienced a large increase. The words "any multi cross will give you the same results" comes to mind. I'm not sure it's panning out that way.

    Also, one of the posters who over time I come to agree with through my own experimentation says somthing to the effect of: "I've tried all of the following as a cross string, and the one I use is XXX" Which would indicate that it does matter what you use for the cross string.

    In one experiement, I changed from a fully poly to a poly main syn gut cross. The change in feel was dramatic and I would say closer to a Syn gut feel than a poly feel, although the power/spin was closer to poly.
     
    Last edited: Feb 19, 2009
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  6. bad_call

    bad_call Legend

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    i don't think i've ever broken a cross 1st...always a main. thinking about this post, one must consider shot types and quantity. if one was blocking returns all day then maybe the crosses would break first. think about it.
     
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  7. TonyB

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    I'm thinking that maybe you guys missed the point of my original post. This isn't about breakage. Breakage doesn't occur because of overstress. Breakage occurs because the crosses wear THROUGH the mains (or in other words, "saw" into the mains) due to having the mains constantly sliding over the crosses while applying topspin. I didn't say the crosses BREAK first, I said they BREAK *IN* first, indicating that they are undergoing a higher degree of strain than the mains.

    Breakage has less to do with raw power and more to do with spin. I think that if you hit perfectly flat every single shot, I would be willing to guarantee that the crosses will break first.

    My post was about the responsibility of the crosses in the hybrid. It's about power and feel. The mains are responsible for spin and control... by moderating the power of the crosses. And another point is that it's about relative tensions. Crosses should ideally be strung lower than the mains in order to equalize the strain and balance the stringbed.
     
    Last edited: Feb 19, 2009
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  8. bsandy

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    I agree with TonyB's take on the cross strings being responsible for the power. Not because they provide it, but because their shorter and can diminsh it, if they are too stiff or tight.

    . . . Bud
     
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  9. bad_call

    bad_call Legend

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    not sure what you mean here. can u elaborate?

    then why do i break mostly hitting flat serves?

    but i don't like how that plays. it feels too dead to me. having tried the JC method where the crosses are 4 lbs higher (exceptions exist), i experience a consistent tension. that brings up another point regarding "proportional stringing" or something along those lines.
     
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  10. TonyB

    TonyB Hall of Fame

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    Huh? I'm not sure what you're talking about. Are you saying you hit NOTHING except flat serves and break your strings?

    It seems to me that the shot that applies the most stress to the strings in your case is your flat first serve. If the strings are weak enough, then that powerful shot will break them. However, that's not WHY they break. They break because the mains have been cut into during your topspin rally shots and the final blow is dealt by your hard serves, that's all.


    I'm not sure how you are identifying your "consistent tension". It seems like you have a personal preference towards tighter crosses, which is fine. But that doesn't mean they're equal in tension or even equal FEELING in tension. It just means that you prefer it. It might feel "dead" to you because the pocketing is increased and the overall stringbed feel is more evenly balanced. That means that it's harder to tell when you hit the ball in the center or not, because you don't get the harsh feedback from off-center hits like you would by having the shorter outer strings tighter.

    By the way, proportional stringing involves stringing the shorter outer strings at lower tensions, which is exactly what I'm talking about. Translating this to my observations, the shorter cross strings should be strung LOWER than the mains to equalize strain in the stringbed.
     
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  11. eldub20

    eldub20 Rookie

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    #11
  12. sk8ing

    sk8ing Banned

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    post 2 long 10 char
     
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  13. Nanshiki

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    Crosses are just there to keep the mains or the racquet from breaking...

    IIRC something like 60% of the performance of a string comes from a main. But you can use that 40% to make a poly softer or give more control to gut, but overall performance (especially spin) will still be dominated by the mains.
     
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  14. bad_call

    bad_call Legend

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    1) i hit predominantly flat serves and there is when the main breaks.
    2) i've hit with tighter mains and it does not increase or feel more evenly balanced...quite the opposite.
    3) the link provided indicates that mains provide durability and spin whilst the crosses provide power and comfort. so your notion of crosses providing power is correct per the article.
     
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  15. TonyB

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    Glad you posted. This is what I was referring to in my original post... most people just fire off claims like "60% for the mains" and other similar generalities. Are you just repeating what you've read on the internet, or do you have some sort of factual test data to back up that figure?

    My observations and theoretical conclusions say just the opposite: the crosses are mainly responsible for feel and power, while the mains provide the moderating control and spin potential. The "overall performance," if there is such a thing, would therefore be dominated by the crosses in my opinion.
     
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  16. TonyB

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    Wow, great find! Wish I had discovered that before I went through all the trouble to do the experimental work myself.

    (Info from the link is cut and pasted below):

    --------------------

    Mains and crosses
    Q: Has anyone ever determined what the different roles are of the mains and crosses? I want to start playtesting some different combinations of strings and tensions, and it would be nice to know what to look for so I know what to change once I get some results.

    A: According to Babolat, the main strings contribute durability and spin, while the cross strings contribute power and comfort.

    --------------------


    And this is what I wrote in post #7:

    My post was about the responsibility of the crosses in the hybrid. It's about power and feel. The mains are responsible for spin and control... by moderating the power of the crosses.

    Bottom line is that if you want to make a change to your hybrid, start by working on the crosses first, by experimenting with both the type and tension of the string. Oddly, the "Champion's Choice" hybrid seems to be almost opposite of what everyone believes that Federer is looking for when choosing his hybrid.... most people think he wants a touchy-feely stringbed with lots of power, but that's just about the exact opposite of what he has. With gut mains and poly crosses, he's got a relatively low-powered hybrid with less spin than if he had poly mains. Perhaps the low power is partially offset by him stringing with relatively low tensions. Interesting.
     
    Last edited: Feb 19, 2009
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  17. ronalditop

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    that makes a lot of sense. so thats why fed strings his racquet so loose yet its low powered.

    thanks a lot TonyB for posting this valuable info.
     
    Last edited: Feb 19, 2009
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  18. eldub20

    eldub20 Rookie

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    Tony, FWIW here's what Greg answered when I asked if the mains were mainly responsible for control:

    From what we can tell, control is a function of stringbed stiffness and the impact signature of the string in question.
     
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  19. PED

    PED Legend

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    FWIW, I tried a version of this combo a few weeks back with VS gut mains and alu power crosses and found it a real rocket launcher-I didn't find it low powered at all. I usually play with full alu so it was QUITE a change going to gut/poly so I do bear that in mind ;)

    Not trying to be disagreeable but that was my experience. I generally have my setups strung with the crosses 2 or 3 lbs lower to add to the power and or comfort so I do agree with alot of your points.
     
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  20. ODYSSEY Mk.4

    ODYSSEY Mk.4 Professional

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    you got a sharp mind though i must say.
    great posts, great read
     
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  21. Nanshiki

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    The mains are longer. Which means they stretch more. Which means they provide more power than the crosses. IE, putting gut in mains will give you much more power than putting in the crosses. This is pretty much scientific fact based on physics.

    And the ideal string setup would be nothing but mains, except that would cause either the strings to break or it would cause the racquet to break.
     
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  22. bad_call

    bad_call Legend

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    so the published info in the link is not accurate. wonder what else published there is suspect.
     
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  23. gastro54

    gastro54 Rookie

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    No.

    Since the mains and crosses are interwoven, for a given contact point on the racquet, a main-cross pair will deflect the same distance perpendicular to the regular, undeflected racquet plane.

    Since the crosses are shorter than the mains, this means the crosses experience a greater percentage increase in length than the mains will. This is basic trigonometry.

    Absolute change in length has no relevancy because it doesn't tell you anything about the original length.

    There is nothing scientific about this "fact" you speak of.
     
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  24. iTxMe

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    Tony,

    switch your set up to: mains becoming crosses and crosses are mains. I'm pretty sure the mains will "break in" first. The matter is strings' compositions.

    Personal experience:
    When using all gosen, my mains break over time.
    cyber flash mains, gosen cross... gosen breaks
    cyber flash mains, wilson sensation cross...wilson breaks
    and I'm sure that if i put gosen in mains and poly in cross, I will break the gosen first.
     
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  25. FloridaAG

    FloridaAG Professional

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    I was referring to this statement in your original post:

    "However, my experience with gut and multifilament strings is that the crosses always break in first and often snap before the main strings are even broken in at all. You can tell with gut and multis because the fibers break apart and become cloudy rather than clear or translucent once the strings are broken in. My thought is that it would be impossible for the main strings to bear the brunt of the power if the crosses are the ones that are experiencing the most stress (judging by the condition of the strings)."

    That is all I was responding to -
     
    #25
  26. dman72

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    Interesting thread. I use Ashway Crossfire, which comes with Kevlar mains and cheap synthetic gut crosses. The mains have broken first on 2 sets (every other set I've changed before anything breaks, usually after maybe 3 months of play), and no one will say that synthetic gut is tougher than Kevlar.

    I've used a full Kevlar job once, and it proved to me how much of a difference the crosses made..felt 100% different, performed 100% different.
     
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  27. gastro54

    gastro54 Rookie

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    The crosses are more responsible for power, but:

    The string that breaks first is more dependent on the composition and characteristics of the strings than on the power they give.

    Like someone said earlier, if you use poly and syn gut in a hybrid, the syngut almost always breaks first because it is made of a softer, less durable material.
     
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  28. bad_call

    bad_call Legend

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    interesting point here. since the main-cross pair deflect the same then having a powerful main such as gut and low powered cross such as syn gut should produce the same affect as vice versa. that doesn't appear to be true in the case posted earlier by PED.
     
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  29. bad_call

    bad_call Legend

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    any more thoughts here? no physicists among us?
     
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  30. sims1970

    sims1970 New User

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    Hey TonyB. It wasn't too complicated and it was explained perfectly. I've been down the same road you have in experimenting with different types of string and combinations and came to the very same conclusion. I wouldn't debate you on any part of it :eek:) Its great information for those who are about to try some different string combinations.
     
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  31. gastro54

    gastro54 Rookie

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    That's not what I'm saying

    The crosses experience greater strain than the mains because the crosses are shorter than the mains but deflect the same perpendicular distance as the mains do.

    For this to happen, greater stress needs to be applied to the crosses compared to the mains to get them to deflect the same perpendicular distance.

    This means that in the deformed state (the ball has sunken the maximum distance into the stringbed) the crosses will be exerting more force than the mains to return the stringbed to normal.

    This is why crosses contribute more to power.
     
    Last edited: Feb 20, 2009
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  32. bad_call

    bad_call Legend

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    logical thinking but not correct. btw - thanks for the earlier post which is food for thought.

    refer to Nanshiki earlier post (physics). if in doubt, try gut in crosses with syn gut mains then vice versa...at same tension.
     
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  33. Pusher

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    Good post Tony,

    Keep in mind that the X string tension is severely reduced due to the friction of the weave. IMO, the X's must be set at a higher tension than the mains to get an equal M/X tension. I find that is relevent only if you are concerned with longer string life. Higher X tension will give longer string life-all other variables being constant. I've found little difference in feel, power or spin by using higher X tension.

    You can test my assumption very easily and I have done so many times. In fact, I would not string gut any other way than by using the higher X method. The gut will last about 1/3 longer.

    Concerning poly/gut hybrids-My experience is that gut mains/poly X's give more power than poly mains/gut X's. Of course the X's contribute mostly to power-that's all they are capable of doing. Mains contribute to both power and spin and thus have more input than X's. My conclusion is that the mains will have the most impact on the stringbed.

    Concerning breakage: My experience indicates that M's will always break first unless the X is a mulifilament. This assumption with poly main/ gut X hybrids is mostly irrelevant because the poly mains go dead before any breakage. Same with a syngut X. In fact, using a gut or syngut X with a poly main will give more stringlife than an all poly stringbed.

    But predicting string behaviour with hybrids is tricky. Thats one reason I prefer one string per stringbed. It's too easy to get caught up in various combinations of string composition, gauge and tension. Then you have the uneven tension loss due to different string composition. What you start out with may completely change after the first hour of hitting. Who needs that aggravation?

    But my experience is my experience-not anyone else's. The point is that your particular game can and will change a lot of assumptions we make about string behaviour. Heavy topspin hitters can have a different experience than flat hitters. The type of opponent you play has a major impact as well. Just think of the pressure on strings with two heavy topspin players, each opponent has to reverse the spin of the other whilel adding more spin.

    Good thread.
     
    #33
  34. gastro54

    gastro54 Rookie

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    So where is the flaw? What makes what I said untrue?

    Nanshiki's earlier post concerning "physics" isn't based on a legitimate scientific argument.
     
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  35. ambro

    ambro Professional

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    Based on personal experience, I've used combos with poly/gut and gut/poly, and there is a HUGE difference in power. Poly/gut is much less powered than gut/poly. How does this make sense to you based on your theory? Gut is without a doubt more powerful than poly, and if the crosses are responsible for power, the gut in the crosses should be more powerful, which it is not.

    As for the link published by RSI, the answer clearly states "according to Babolat..." which is purely for their marketing purposes. They know everyone is caught up in the poly mains hype, but they still need to sell their most expensive string, which is well known to be the most powerful string. They know (most) people aren't using gut mains, or even full gut, so the only way to sell it is to say the crosses are responsible for power. This way, people will still buy gut for their hybrids. Simple as that.

    The mains are (mostly) responsible for power, no doubt. Of course, crosses contribute a little bit; i.e. poly/gut will be softer and more powerful than full poly, and gut/poly will be less powerful than full gut. But that doesn't mean they are completely responsible for anything.
     
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  36. ambro

    ambro Professional

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    The flaw is that the crosses are at a lower tension than the mains, no matter what. When tightening the mains, there is no friction to oppose the full pulling force from being applied to the strings. The only tension loss is clamp drawback. However, when stringing crosses, the full pulling force is never applied to the string (not even close), because the the pulling force is dissipated into friction between the cross and main strings. And since the string crosses over/under 14-18 mains, depending on the racquet, there is a lot of force dissipated as friction. So even though the crosses are shorter, they are not experiencing the same tension as the mains are.

    The conclusion you arrived at assumes equal tension between mains and crosses. But since the crosses are at a lower tension, it takes much less force to displace them the same perpendicular distance, even though they are shorter. Therefore, the mains are experiencing a greater force when displaced, and have more potential energy due to stretching than the crosses do. This potential energy is converted into kinetic energy of the ball (fancy physics term for speed, assuming equal mass), so the ball gets more of its speed from the mains. In other words, the mains are more responsible for power.
     
    Last edited: Feb 20, 2009
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  37. bad_call

    bad_call Legend

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    ambro - thoughtful observation. "according to Babolat..." indeed. :)
     
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  38. bad_call

    bad_call Legend

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    ambro - another excellent observation. you're batting a 1000 !!! the other force to this is posted earlier by Nanshiki which contributes to the first instance of stored energy.
     
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  39. gastro54

    gastro54 Rookie

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    I like your argument, it's logical but you're missing something in your friction argument.

    When you are stringing the crosses and pulling them through the mains, the kinetic friction is very noticeable because the crosses are moving through the mains which are applying force normal to the direction of the crosses' travel which creates a force that resist the direction of movement - the string is not under any significant tension yet.

    Once you actually tension the string, based on your argument, static frictional forces should start to dominate and somehow lessen the applied tension to the crosses.

    However: static frictional forces resist impending motion in a certain direction.

    The tension in a stretched string is equal along the string's length, so each "element" in the string is getting pulled in opposite directions by equal forces; therefore, the impending motion has no net direction, so the static frictional force is nil.

    Consider this thought experiment:
    • Imagine a racquet with the mains strung and you are tensioning a single cross by somehow suspending the racquet in midair so that it doesn't move.
    • You pull the cross all the way through and take up the slack.
    • You then hang a 55lb weight attached to the cross and let it pull down due to gravity.
    • You pull a bit on the weight and release it to make sure the cross isn't "catching" on the mains at any point. Sophisticated electronic tensioning machines have a feature that does something analogous to this. "Catching" would appear as the mains getting pulled down in the same direction as the weight due to static frictional forces.
    • Once the weight has come to rest and isn't moving, the string must be by definition at 55lb tension. If it the tension in the string was less than the weight, then the force pulling up on the weight would be less than the force of gravity pulling down and the weight would drop further until the forces become equal.
     
    Last edited: Feb 21, 2009
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  40. TenniseaWilliams

    TenniseaWilliams Professional

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    So if I could remove all the slack in the strings, I could tension the entire stringbed with one pull? Going around corners, through grommets, and at angles over and under mains all have an effect on installed tension.

    The string also elongates under tension, very dramatically in the first 30 seconds or so. Stretchy strings will appear fatter at the end opposite the tension head on crosses unless you somehow press and feed the slack around every main.

    Another reason that the mains have more tension than the crosses is the hoop deformation that occurs on the stringer. The installed mains put tremendous pressure on the hoop, shortening it until the crosses are completed. As crosses are installed, the mains become tighter, and previously installed crosses get looser. With stiff strings it doesn't take much length change to effect tension dramatically.

    An inexpensive stringmeter will show crosses tension lower than mains on any usable racquet.
     
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  41. supertrex

    supertrex Semi-Pro

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    I also tried this month ago, Gut/poly vs poly/gut. on my Pro Staff 85.

    The gut on Mains with higher tension gives me more "power feel"

    Then The Gut on Crosses also with Higher tension than my poly mains, Gave me " Less Power Feel "

    Just my experience experimenting also. but maybe this might change if the Racquet headsize is 95 +

    Since ive only tested this on PS85.
     
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  42. ambro

    ambro Professional

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    I like your argument as well, but that is all theoretical, and we all know pure theoretical physics does not quite transfer all that well to real world applications. There are way too many variables.

    When a cross is tensioned, from the last cross to the tension head, the full tension is being pulled. But going across the stringbed away from it, there is less and less tension on each section of the string precisely due to the static friction from the intersections with the main strings. The tension in each cross string is equal along the string's length assuming no friction. However, there is static friction at each weave. This means that the tension in the string is equal for each section of the cross between any two given mains, but not necessarily along the entire cross string's length.

    Not that I actually know the exact numbers, but here's an example to illustrate. Say there are 16 mains on the given racquet, the reference tension is 55 lb, and that at each intersection there is static friction that prevents 1 lb. tension of being felt by the string. At the edge closest to the pull, the tension is 55 lbs. when pulling. Between the mains 15 and 16, the tension is 54 lbs. because of friction from the 16th main. Between 14 and 15 the tension is 53 lbs., and so on. By the time you get to the opposite edge, the tension felt by the string is only 40 lbs. This does not happen with main strings, because there are no strings it has to cross over/under to apply any frictional force. The tension in a cross would be the same along the entire length IF there was absolutely no friction between strings, which we all know is completely ridiculous.

    You say static friction reduces impending motion, which is exactly right, and also why the total amount of static friction increases as you move across the stringbed. There is 16x the static friction at the opposite end of the pull as at the intersection nearest the pull, because there are 16x as many intersections.

    This means that friction causes crosses to be strung at a lower tension than mains, as I said earlier.

    As has been suggested, buy a cheap stringmeter and test out this observation yourself.
     
    #42
  43. TonyB

    TonyB Hall of Fame

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    Listen to this guy. He knows what he's talking about.

    I was just going to write a reply similar to this, but it's close enough where I won't bother.

    Suffice it to say that the amount of dynamic friction that acts against the cross during tensioning is only a few percent of the target tension anyway. And if you're "setting" the strings while they're under tension, the frictional losses are even less.

    When you're comparing the different lengths of mains vs. crosses, they differ by an average of around 20% for your typical oval-shaped frame head ( measured 11" mains vs. 9" crosses on my Vantage frame). To equalize the strain in the mains and crosses, you'd have to reduce the cross tension by this value (~20%). Even if you consider the full frictional losses of 2-3% for the crosses, it would still be negligible.
     
    #43
  44. TonyB

    TonyB Hall of Fame

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    The only thing ridiculous here is your assumption that there would be 1 lb. of friction at each intersection, or 16 lb. total at one cross string.

    If you see my most recent post, you'll see that I estimate around 1 lb. or so TOTAL for the entire cross string, which I feel is much more accurate. Remember, we're not talking STATIC friction here, we're talking about dynamic friction once the string is already in motion, which is typically only a small fraction of static friction.

    Yes, there is a way to measure the exact frictional loss, and I plan to do exactly that the next time I string my racquet. If you can wait a week or so, I'll report back here with the data.
     
    #44
  45. TonyB

    TonyB Hall of Fame

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    What type of stringing machine are you using that allows the hoop to distort and reduce tension in the mains before the crosses are installed??? You speak as though you're losing several pounds of tension as the hoop squeezes down before the crosses are installed, which is completely untrue.

    Even besides that, let's assume that the hoop which was once oval becomes completely circular in shape before the crosses are installed, allowing the mains to drop from 60 lb. down to 30 lb. Once the crosses are installed and the hoop magically returns to its original shape, the tension in the mains will only return to the original 60 lb.

    The only thing that would cause the mains to increase in tension above the initial set point would be that there is some added deflection of the mains due to the interweaving of the crosses. You could calculate exactly how much increase in deflection there would be for a main string, but I'm too lazy to do that at the moment, and beyond that I'm not sure it would provide any significant insight into the whole stringbed tension argument anyway.
     
    #45
  46. Nanshiki

    Nanshiki Hall of Fame

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    Two different lengths of string pulled to the same tension will have very different amounts of elasticity... and elasticity is the same thing as power in tennis strings. That's why kevlar strings have no power whereas natural gut (which is approximately seven times more elastic) has a great deal of power. This is also why oversized racquets are more powerful.

    And this is why mains contribute more to power than crosses. Assuming your racquet face isn't sideways.
     
    #46
  47. ambro

    ambro Professional

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    First of all, I said I do not know exact numbers, that was just to illustrate. Also, your assumption of 1 lb. total at a cross string is hilarious. Do you actually believe that?

    Second, it absolutely is static friction from the intersection that prevents a certain point on a cross string from moving closer towards that pulling force. In other words, static friction at each intersection prevents the full tension from being felt by the whole string. Tension is NOT the same throughout a cross string. Theoretically, with no friction, this would be true, I agree. And maybe after hitting with it for a while, it does even out, but this would of course lower the overall tension, further reinforcing my point. But this is not frictionless theory we are talking about here, this is real life materials intersecting, causing friction. This happens at every single intersection. The string is not experiencing dynamic friction during tensioning, and even if it did, that is not where the loss of tension comes from. It comes from the static friction of which I mention.

    1 lb. loss from friction though... Wow. Ha what a joke.

    Here's a little experiment I'd like you to do since you're so sure that there's almost no frictional effects on tension:

    Take two identical racquets, and string them at exactly the same tension (reasonable, like 55 or 60). String one of them exactly as you normally would. In the second, do not weave any crosses, rather, on the first cross have it completely above the mains. Put the second underneath, and so on. This would almost avoid all of the static friction from intersections.

    I can guarantee you that the racquet will be seriously deformed when removed from the machine, if it doesn't crack or break right away. Racquets are designed to accommodate the tension differences that I have tried to explain to you, and they will not handle the forces if the mains and crosses are at the same tension. You seem pretty confident with your theory though, so I would love to see your results.
     
    Last edited: Feb 21, 2009
    #47
  48. TonyB

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    Quite frankly, I don't have the time, temperment, or ambition to educate you on this subject. You clearly seem to have all the answers. What I WILL say, however, is that your theory about dynamic and static friction in the strings is completely inaccurate. You have it 100% wrong. Period. When a string is being tensioned, it is in MOTION throughout the application of the tensioning force. The string does not sit statically idle while tension is applied, it MOVES in the direction of the applied load. You cannot use the static friction for your loss estimates when you have a string that is moving. Have you ever even SEEN a string being tensioned?


    Better yet, why not just wait a week until I can actually MEASURE the total frictional loss per cross string as I said in my last post? You can laugh all you want at the data once it's available.
     
    Last edited: Feb 21, 2009
    #48
  49. ambro

    ambro Professional

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    I don't believe I have all the answers. I am just pointing out flaws in your theory.

    Hmm have I seen a string tensioned, good question. I have been stringing my own racquets for 5 years, I've seen it plenty.

    The string does move in the direction of the force applied, I agree... until the pulling force is negated by a COMBINATION of tension in the string AND the static friction at the intersections, causing an equilibrium. When equilibrium occurs, the string is NO LONGER IN MOTION and KINETIC FRICTION DOES NOT APPLY. This is why static friction is the one that affects the lower cross tension. Static friction affects the EQUILIBRIUM of forces, meaning that not all the pull force is transferred as tension in the string.

    I don't want to see your data. For all I know, you might just throw some numbers and say you're right. If you're so confident, take my suggestion from my last post on the different way of stringing, then we'll see. Take some pictures of the racquets afterwards as well, I want to see the racquets.
     
    #49
  50. gastro54

    gastro54 Rookie

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    This doesn't need to be a flame war like every other argument on the internet. Everyone needs to just chill out.

    I don't know how anyone is going to measure the tensions of the mains and crosses separately while they're both installed in the racquet.

    You can't string a racquet then just cut out the mains or crosses and measure whats left.

    They need to be interweaved while the measurement is taken, otherwise the reading will be off.

    The only measuring devices I've seen measure the stiffness of the stringbed and not the mains and crosses separately.

    I did think of one reason why the tension in the mains might be slightly higher than in the crosses if you tension them with the same setting:
    • The mains are tensioned without anything displacing them from running linearly throat to head
    • Tensioning the crosses displaces the mains from linear causing them to be zigzagged and lengthened from their original setting.
    • This lengthening is the result of increased tension on the mains
    • Still, you should be able to even this out if you offset the tension settings you use between the mains and crosses (crosses strung @ higher tension)
     
    #50

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