In praise of Kevlar/ZX hybrid!!!

Discussion in 'Strings' started by marsh, Dec 10, 2015.

  1. skydog

    skydog Semi-Pro

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    I am thinking racquet dependent. I have 3 identical Prince Tour 98 ESP's I have strung once or twice apiece with no issues. It has just been the fourth one, twice in one week. I also had my first playing string break on the ZX cross in the same racquet only a few days after being strung, but that cross was mid-bed.
     
  2. Shroud

    Shroud G.O.A.T.

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    Very weird and intersting! Well since it has a "tour" designation you are probably just crushing the ball to much
     
  3. Irvin

    Irvin G.O.A.T.

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    I don't understand this, elasticity is by definition "the ability of an object or material to resume its normal shape after being stretched or compressed; stretchiness." If you stretch a string hard long enough it will become permanently pre-stretched and will have less elasticity.
     
    Last edited: Aug 8, 2017
  4. Irvin

    Irvin G.O.A.T.

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    The only time I've broken ZX was at the top when using a starting clamp with and without a spacer. No way that could be the section of string in the gripper. But my machine pulls ZX very slowly. The stiffer the string the faster my machine pulls so it stands to reason it pulls Gut and ZX very slow. I also use a starting clamp to tie knots no matter what type of string I'm using. Because you're using a Wise maybe you should use the slowest pull for tie offs. Maybe the faster pulls weakens the string somehow. Just a though to think about, I'm not saying this is fact.
     
  5. bkfinch

    bkfinch Rookie

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    Got my kevlars in the mail today.

    Thinking to try Kevlar/4G before going through 'ordeal' of setting up and pre stretching zyex homemade style. If something does happens to the zyex- seems to be a bit fragile? At least the half set of kevlar is still intact, lolol

    Yea the stringer who did my first kevlar/zyex complained that the zyex broke and she had to do some patchwork. I've been making sure she doesn't string my rackets anymore since I've had a few recurring problems with her. This used to be a small time place but it's expanded a lot in last years and employees have increased quite a bit. Their two best stringers don't work there anymore and I don't always know everybody on first name basis anymore.
     
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  6. Shroud

    Shroud G.O.A.T.

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    Kev/4g is shroud approved. You can at least string it past 80. But i was pretty disappointed with the tension maintence. Actually i think ashaways non zx monogut is better than 4g as a cross if you take pricing into account!
     
  7. Shroud

    Shroud G.O.A.T.

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    yeah thats why for zx the starting clamp method is something I dont use.

    Pretty sure its on the slowest setting but man that thing is not intuitive. One would think that one was the slowest but IIRC its the opposite or something like that. you are right though that slow pulls are best.
     
  8. ultradr

    ultradr Legend

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    what would be that "hard enough" force for that too much stretching?
     
  9. graycrait

    graycrait Professional

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    With zyex I think you can figure out that "too much" stretch with a calipers but haven't had the discipline to do it. I've measured it before and after but never stuck with it to figure out useful numbers.
     
  10. ultradr

    ultradr Legend

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    I have a feeling that there is an upper bound (although it might vary per player).

    In actually play, I think there is my max force that I apply against incoming balls.
    Then somebody must have measured a range of forces appied during typical tennis match.
    Let me look up the tennis physics book and update here later.
     
  11. bkfinch

    bkfinch Rookie

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    Update:

    I have been hired by the pro shop and I know how to string now. I'm probably terrible but I made it through 3 rackets and one of mine (all polyester). I played with the machine, it can go much higher than 20% pre stretch, you just have to keep pressing the '+' button lol

    So I will be stringing my own kevlars/zx once I feel I have enough competency not to screw it up ! Hahaha
     
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  12. esgee48

    esgee48 Legend

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    Yeah, but if ref tension + prestretch >> 60#, your ZX will break prematurely or during stringing. :rolleyes:
     
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  13. Shroud

    Shroud G.O.A.T.

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    Esgee makes a good point here though i think the numbers are higher. Given my weight leaning against the string has to be over 60#... But something to think about. And always use the slowest pull speed with zx
     
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  14. esgee48

    esgee48 Legend

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    You must be tired or something. ;) 70# over 20' does not damage the string as much as 70# over 20". And then you are pulsing the pull rather than holding the tension constant for 20-30 seconds.
     
  15. Shroud

    Shroud G.O.A.T.

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    Maybe you are right. Though i do lean pretty constantly and pulse at the same time. And given the fat comments i seem to get its got to be more weight than a silly machine

    Fwiw i think i strung zx over 70 once iirc and it didnt break but just continued stretching

    Yeah i am pretty tired.
     
  16. Irvin

    Irvin G.O.A.T.

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    What's the difference? If you have pull 20' of string at 70# every inch will be pulled at 70#. When you apply a tension force T
    T to the string, as long as it doesn't break, the force gets "spread out" and will experience a tension of exactly T at every point on the string. The string will break if the weakest point on the string exceeds it holding strength.

    The longer a string is stretched, the less material there is in any given section (especially in the weaker sections,) and the lower the tensile strength of the string. If you tension (and stretch) a string right up to just below the breaking point but do not exceed it it will not break. But what do you think happens when you hit the first ball?
     
  17. travlerajm

    travlerajm Hall of Fame

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    Monogut ZX can take over 100 lbs tension... as long as it's pulled in the axial direction of the string. The problem with ZX is that it doesn't do well with high tension going around corners - unlike other types of string (like polyester or nylon), it's not malleable enough to flow and distribute stresses to other parts of the cross section, so stress concentrations develop and cause breakage. That's also why it's so fragile when pulling tension on knots.

    The fragility when going around corners at high tension is much worse when the string is not prestretched. If you fuly prestretch it (by lengthening an 18' segment by at least 20"), the string becomes more durable, and you can safely string a racquet at 70 lbs as long as you use blunt-edged clamp jaws that don't damage the string. But at high tension, it's even more important to hand-tie knots.

    The reason prestretching boosts durability: When you pull tension on an unprestretched string, the position of the tensioned sharp bend (where the string corners the first grommet) ends up traveling along the string as the string stretches, increasing likelihood for the string to snap at the tensioned corner. In contrast, if you fully prestretch, the tensioned sharp bend will not travel along the string, so the risk of breakage is much lower.

    Also, prestretching the string evens out the stress distribution across the cross section at all axial points along the string, which reduces the magnitude of stress concentration that might develop at sharp tensioned bends during stringing.

    The lack of malleability and lack of ductility is what makes ZX so fragile. But this property is also what makes it a superior cross string compared to poly. It helps it resist denting (malleability is by definition the opposite of dent resistance), so it's easy on the arm and great for spin.
     
    Last edited: Aug 19, 2017
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  18. skydog

    skydog Semi-Pro

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    Finally settling in on a tension for my Tour 98 ESP's. Looks like 64/50 is going to be the sweet spot. Will string up the knot breaker frame this weekend to see if I can complete the job without breaking the knot, again, on that frame. Other three frames still without any breakage issues after multiple string jobs.
     
  19. marsh

    marsh Rookie

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    So I have a question for all of those wiser than myself. I strung a friends racquet at 60/50 (his request) with the Kevlar Zyex combo. He loves it but is starting to have some elbow discomfort. Normally he plays with gut/ poly at an unknown tension. I know his problem is due to the death grip he swings his racquet, but other than mentioning it I can't say too much more because he is a much better player than myself. Now he has requested that I string one of his racquets at a higher tension because he thinks the dwell time of the lower tenison is partially causing his problem. My question is do I go ahead and string at say 62/55 or something similar or do I I string at 60/40 and offer to comp the job if he doesn't like it? Is it possible that tighter tensions and thus a quicker response might help someone with a death grip?
     
  20. 2nd Serve Ace

    2nd Serve Ace Semi-Pro

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    I would try to honor your friend's request and just go to about 64/54, but do a real thorough pre-stretch on the mains.

    Maybe incorporate a little proportional stringing and do the short outside strings a bit lower tension? Helps some on off center hits.
     
  21. graycrait

    graycrait Professional

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    Go 75/60 if it is 100"+ and open 16/19 or 16 x 18. After an overnight and 2 hours of hitting it will be sublime. That is what I would do on a lockout NEOS 1000 but would want to consider racket head size, flex and string pattern.
     
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  22. Outliar

    Outliar Rookie

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    So would you strung a 95-98 head frame with even more of a differential?


    Sent from my iPhone using Tapatalk
     
  23. skydog

    skydog Semi-Pro

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    I think I found the culprit. Restrung this same racquet this morning and found that the tie off grommet where the breakage had occurred had an edge that rolled over into the grommet leaving a semi sharp edge pointing in toward the strings. Smoothed it out and re shaped the grommet with an awl and strung it up. No knot breakage on the final cross this time around.

    I am thinking that when I snugged the first loop on the Parnell knot it must have cinched over the grommet edge pulling it inward leaving that edge facing the tag end string. When I pulled the tag end, it must have acted like a small blade roughing up the string enough to weaken it when being pulled to the point of breakage.

    Hopefully, reshaping the grommet will solve the issue long term.
     
  24. graycrait

    graycrait Professional

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    Nope, but there is no exactness to this, all subjective and needs to be experimented with or not. I simply do not prestretch the Zyex to the edge if at all and will not string it higher than 60lbs.
     
  25. Shroud

    Shroud G.O.A.T.

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    Nice catch. But its the reason for alot of breakage
     
  26. Shroud

    Shroud G.O.A.T.

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    Sure, why not? I did my ps85 at 60/40 and these days would go more for sure
     
  27. whorng

    whorng New User

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    I've been reading the kevlar / zx hybrid threads and decided to buy a few Crossfire ZX 17 sets.
    I know the kevlar isn't the same as the separate sets, but it was on sale and seemed like a good entry into this hybrid.

    What tension should I string the following racquets, prioritizing comfort?

    Prince Textreme Tour 100T | 16x18 | rec. tension 48-58
    Would 60 kev / 40 zx work? Considering Prince has a tighter threshold.​
    Yonex DR98+ | 16x19 |rec. tension 45-60
    Would 65 kev / 40 zx work? Considering Yonex has a wider threshold.​

    Other questions do I pre-stretch the kevlar 2 inches and the zyex 12 inches?
    Plan on tying it to a door pull up bar, and broom handle or a hand clamp.

    Anything I should tell the pro shop stringers?
    They have teenagers doing the stringing although trained by the resident MRT.
     
    Last edited: Sep 12, 2017
  28. Shroud

    Shroud G.O.A.T.

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    Best approach is to do the prestretching and give them the prestretched strings. 2" is probably 1.8" too much to expect to stretch the kevlar. It doesnt really stretch. 12" sounds ok for the zx.

    On the tension i think a good rule of thumb is to take your usual tension and add 10lbs to the mains and subtract 10lbs from the crosses.

    So 50 lbs becomes 60/40 and 48 becomes 58/38 etc.
     
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  29. whorng

    whorng New User

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    Sounds good, ty for the advice.
    I'll do 60/40 on the Prince for starters since it is brand new.
     
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  30. travlerajm

    travlerajm Hall of Fame

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    I would recommend tighter than that -- since kevlar is 4x stiffer than ZX, the final average stringbed tension for 60/40 will be 4x closer to 40 than to 60 (about 44 lbs), which is really loose for a 16x18. You can use same math for other differentials.
    For example, average stringbed tension for kev/zx at 70/45 = 45 + (70 - 45)*(0.2) = 52.
     
    Last edited: Sep 12, 2017
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  31. whorng

    whorng New User

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    Interesting didn't know about the math.
    I will keep that in mind on the next try if something feels off, maybe 65/45.
     
  32. bkfinch

    bkfinch Rookie

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    I just want to say I have put this stuff in a bunch of my rackets now that I've been doing a stringing job, trying different tensions/differentials.

    Results are varying from setup to setup but overall this stuff is insanely good and I never want to go back to full poly again.

    And it's easy to string (!)
     
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  33. travlerajm

    travlerajm Hall of Fame

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    Agreed. Once you learn how to string it, there is no going back to inferior poly string.
     
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  34. bkfinch

    bkfinch Rookie

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    Could you explain that equation please? :rolleyes:

    Going to string one of my 18x20 this aft. Other one had 53/40, initially stiffish but after an hour or so ohmamama

    Also: 4G crosses are also really great but overall tension should be lower and I think kevlar mains should still be tighter. The tighter cross setup played deader and less spin. It gives a more satisfying sound than ZX crosses though and a more predictable/tempered response.
     
  35. whorng

    whorng New User

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    I decided to go up a smidge to 62/42 on the Prince TT100T and it feels stiff.
    Stiffer than my DR 98+ with 3 or 4 week old YPTP 16L @ 52 / Sheep Micro Super 16 @ 54.
    Not the best comparison due to different variables, but still stiff even after a hour of hitting.
    I'll let it rest for a day or two, then try again.
     
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