Category Archives: co-polyester
I suspect we all have heard that expression!
It means there is something that everyone tries to ignore, but it is too large to do so!
I recently read an article in Racquet Sports Industries authored by Georgetta L. Morque. The title is “Tackling Tennis Elbow.” Tennis elbow is an important topic and deserves much attention. Georgetta is writing about ways to mitigate tennis elbow after the fact.
Let’s try to prevent tennis elbow, so it does not need to be treated!
When we say stiff, it means a string with less than 4% elongation at 60 pounds which is our testing parameter. Most strings, and for this discussion, strings exhibiting that property will be monofilament PET-based (polyester).
Fully understanding this required a lot of testing, both lab and play, for many playing styles and racquets. To make a long story short, as a racquet technologies business, we decided not to promote polyester strings for most players. That sounds silly, but why take a chance when you don’t have to!
Our success is based on helping you, the player, perform the best you can, so it does not make sense to promote something contrary to that philosophy. Probably 75% of our clients have come to us for something different, so we have a “head start.”
So why do so many players use it or want to use it?
We believe it is because they have not been exposed to alternative string materials. Some outstanding players at the pro level use it, so it must be good, and it is for about 10-11 games. Of course, manufacturers and marketers of polyester string stand to make a nice profit! It is in their best interest to promote products by adding some terminology and material to make the string less stiff.
A polyester string is deficient in power and needs to be walloped, and the harder it is hit, the stiffer it becomes, which is the problem. Developing bodies can’t tolerate that level of impact for long.
Several weeks ago we received the first sets of Head Lynx Touch 17 gauge strings. Yesterday we received the Lynx Touch 16 gauge version and want to share the differences…numerically!
Quickly, this string is composed of two (2) separate but “combined” filaments. So, is this a monofilament or a multifilament? The numbers indicate it reacts like a monofilament as we have become familiar with it.
Let’s start with the 17 gauge version:
The area under the heavy red lines is the “stress/strain” curve and we see that this string takes 23.5mm to reach the 50-pound mark. This is just a number unless it is compared to other strings so it is neither good nor bad, right now!
You can see that the string will hold up to 149.8 pounds before it breaks. This is tensile strength and may be important when considering the amount of “notching” that can occur. The “knot” strength of this version is 132.4 pounds.
Now let’s look at the 16 gauge version:
The difference is subtle. The 16 gauge version is a little stiffer (expected) and a little stronger in tension (also expected). The “knot” strength of this version is 133.6 pounds.
What is interesting is the “grouping” of the stress/strain cycles on both strings. They indicate a good elasticity. The closer to the “zero” point on unloading the better!
In our opinion, both versions of the string would be considered “stiff” and suitable for the player looking for a stiff but stable string as our creep test confirmed.
If you currently use stiff strings and would like better consistency this would definitely be a candidate ./
As tennis players, you must constantly ask “what’s the difference” when it comes to tennis racquets and string! Well, as racquet technicians we ask the same questions!
This post is intended to showcase the differences of string in testing, not playing, however, some of the data may be noticeable to the player in certain situations.
What this graph shows us, in addition to our trying to save a tree by printing on the back of previously used paper, is that each of these stings will provide almost the same performance. This is indicated by the curve and how closely related the strings are.
The differences you do see here can be attributed to the gauge, or diameter, of the string, with the largest diameter (Tour Bite) having the highest tensile strength. Down in the “hitting” displacement range (way below the 39.9mm!), there is very little difference.
The tensile strength can be a factor as the string begins to “notch” or otherwise come apart. Each of the strings in this graph is monofilament so notching would be the failure mode in a racquet.
Of course color matters! Brands have made history on color! Prince Green, Head Orange, Babolat Blue, for racquets but what about string?
Sure, again! Luxilon Silver, Babolat Black, Solinco Green, Victrex Putty…what? Which of these monofilament strings do not have any color pigment?
If you guessed the Victrex you would be correct. But why not? The natural color of the polymer is probably the very strongest a string can be, however, without color they would not be at all interesting or recognizable! The natural Victrex color is typically what we use when evaluating the string because it is visually different.
Victrex does make strings with black-pigment, but this post is about the difference pigmentation can make in a string. In a previous post some years go we determined that color had very little affect on string properties and this evaluation shows pretty much the same result in a different format.
You can see by this graph there is very little difference between the two Volkl V-Star strings. In fact it would be safe to say the strings are identical.
In Part Un we discussed the difference between shanking (mis-hit) and friction failure. It was obvious that the string was broken. But what happens when it is not so obvious?
Part Deux, this part, will examine the frictional notching failure of monofilament string and how we can be prepared for it! To further refine this discussion we will be comparing PET polyester has PEEK monofilament string. The reason is that each material while both will notch one requires more time to reach the critical dimensional decrease that is a failure!
In almost every Racquet Quest Podcast we talk about tension v string diameter and agree that once 50% of the string diameter is notched away the string is vulnerable! So a .050 (1.27mm) diameter string that has a tensile strength of 120 pounds at 50% notching will have 60 pounds of tensile strength remaining.
This graph is a string that was broken during use. The string was removed from the racquet. The top line is the tensile strength in the area of no notching so you can see that it is pretty strong still and has stabilized due to use. That stabilization is indicated by the very tight stress/strain grouping.
However, things go sideways when the notched area of the string is put under stress. The string failed at a force of 63.8 pounds, or about 59% of the used tensile strength. Not bad!
So, notching is failure-inducing but how long it takes to create the fatal notch differs with string material. This particular set of strings had about six (6) hours of play.
In Part Trois, we will look at PEEK material under the same conditions!