I've used a Kevlar hybrid for a long time and have just recently been using poly strings. I'm noticing that my experiences with the strings are wildly different than what is expected.
Kevlar breaks way easier. It doesn't snap all at once, but, because it is a multi, it gets frayed and eventually breaks. I broke kevlar strings about once every 3 to 4 weeks. Although I've only been hitting with it for about 2 months, I've never broken a polyester string.
Kevlar is not any harsher than Polyester. For a long time, I played with a kevlar hybrid strung at around 60 and never had any serious arm issues. I don't have any issues with poly either, but I'm stringing it around 50.
I do think the polyester seems to have more spin potential. However, Kevlar seemed to maintain roughly the same playability until it broke. The polyester because horrible to play with much before it breaks.
Just wanted to get some feedback and see if anyone else has found the common claims about kevlar/poly to seem inaccurate.
Hi HunterST -
It's not a matter of "claims being inaccurate". Kevlar is what it is. It's the stiffest string available, and is 2.5 to 5 times stiffer than polyester. It's just that we have an exceptionally wide variety of arms, technique, fitness, and age, all contributing feedback. My own history with Kevlar can serve as a fairly good example.
1. I do understand where you are coming from. I used a Kevlar hybrid for 3 years, beginning somewhere in 2001. It was Forten Aramid Gear, which is pre-packaged as Kevlar mains, Forten Sweet 16 crosses. Back then, I didn't think that Kevlar was any harsher feeling than any of the polyesters I tried, and I was stringing Lux BB original at 62 lbs, and playing 5 times per week. I was 100% certain that TE was 100% about technique. But I'm now 13 years older, and my arm is much more sensitive to such things. Back then, I could not distinguish a difference in comfort between Kevlar and Poly. Today, even slight differences between neighboring polyesters seem like night and day to me. Was my user experience in 2001 any more "accurate" than my user experience in 2013? .IMO, It's not a matter of "claims being inaccurate" It's just that we have an exceptionally wide variety of arms, technique, fitness, and age providing feedback.
2. I'll never debate what somebody feels or does not feel, because that's entirely subjective, is likely to change over the course of time, and my own history with Kevlar is no better example. But from a stand point of physics, comparing one string to another, apples to apples, Kevlar is not "just a soft as poly". It's actually 2.5 to 5 times stiffer than polyester. See screen grabs below, from the
2012 RSI String Selector.
3. Stiffness (by definition) is a measure of rigidity. It's the extent to which an object resists deformation in response to an applied force. The complimentary concept is flexibility, or pliability. The more flexible an object is, the less stiff it is. We measure string stiffness and pliability by measuring the amount of pounds it takes to deflect a string a distance of one inch. Gut requires roughly 80-120 lbs to deflect 1 inch. Nylon requires 130-230 lbs., Polyester 165-300 lbs, and Kevlar requires 500-980 lbs.
4. When you impact a tennis ball at 90 degrees perpendicular to the racquet face, a more pliant string deflects ie. "pockets" more. This creates a softer landing for the ball, and there is less impact shock. Friction can contribute to impact feel, because when you brush up on the ball as in a top spin FH, low friction strings allow the mains to slide. The sliding increases dwell time, and this decreases impact shock. This provides us an explanation for why many players feel decreasing comfort as the string bed ages, even though tension is dropping simultaneously. As string bed ages, friction typically increases du to knotching, wear and abrasion.
Gut and Nylon Sorted By Stiffness, From RSI 2012:
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Polyester and Kevlar Sorted By Stiffness, From RSI 2012:
