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Old 03-05-2013, 11:52 AM   #355
Join Date: Feb 2013
Posts: 144

Originally Posted by corners View Post
Interesting hypothesis Julian. From various descriptions of Zyex that I've found it sounds like it is, as a material, quite abrasion resistant. Do you think, though, that it is not quite as good as a slippery copoly in this respect?

If your hypothesis of surface scuffing were on target, it would seem that pairing it with natural gut mains would be boon, as TW University testing has show that gut mains with crosses that are at all slippery results in a pairing with lower coefficient of friction than either string strung as a full bed.

Also, would you care to weigh in on the widespread theory that loss of elasticity or resilience is responsible for the perception that a string, particularly a poly, has "gone dead"? TW University tests for tension loss, dynamic stiffness and energy return, all of which seem to converge around "elasticity" but none of which define it. In physics terms, I believe elasticity is defined as the slope of the stress/strain curve. So a loss of elasticity would seem to be a change in the shape of that curve and I haven't seen any studies that have attempted to document such a change. So at this point it seems difficult to objectively evaluate claims that a string has lost elasticity along with lost tension. Has Ashaway quantified elasticity and elasticity loss?

Torres reports that his strings have not lost tension, but I'm not sure if he's established that objectively with a stringbed stiffness measuring device. It seems, given your earlier statement about ZX not changing in stiffness much as it loses tension, that it may feel as though it has not lost tension but in reality could have done. With a poly string, by contrast, the dynamic stiffness drops off in proportion to tension loss, so it's quite easy to tell when strings have elongated as a result of repeated impacts or the passage of time.
I believe Elasticity and Dynamic stiffness are the same. Elasticity is a strings ability to maintain its elongation (or stiffness) after being stressed or stretched out. For example, Nylon streches quite a bit (has a lot of elongation)(is not very stiff). However, after being stressed, it becomes much stiffer (has less elongation)(is not as stretchy). Zyex also stretches quite a bit. After being stressed it does not become as stiff as Nylon. The measure of a strings ability to maintain its stretch (elongation)(lack of stiffness) is elasticy (dynamic stiffness). This is the reason Nylon loses tension fater than Zyex. The more a string stretches and does not return, it actually gets slightly longer resulting in the loss of tension. Thus, Zyex holds tension better than both Nylon and Poly.

As for your first question, it remains to be seen how the abasion properties of Zyex compare to those of Poly in Tennis play. I would suspect that niether present a problem. However, I am reaching for a reason to explain the observations of Torres about loss of spin. Spin is much more related to the surface of the string than the elasticity. You want something to grab the ball. As you mentioned, the contrast created by Hybrid stinging is probably good for this.
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