Category Archives: co-polyester

Head Lynx Touch! Two for One?

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.

Head Lynx Touch

Visually the string components are obvious.

The inner filament is black and the outer covering is translucent.

 

Let’s start with the 17 gauge version:

  Lynx Touch 17

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:

Lynx Touch 16

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 ./

What’s The Difference?

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.

Tensile Strength Comparison

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.

 

In a string does color matter?

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.

We will continue to evaluate strings with pigmentation to determine if any color does exhibit an affect on the properties.

What Can String Failure Tell Us – Part Deux

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.

Notched v un notched string

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!

 

What Can String Failure Tell Us?

Well, in the simplest terms, failure tells us it is time to have the request strung! However, there may be subtleties in string failure that can help us in our quest for tennis racquet performance.

Such as?

Is the failure shear related or tensile strength related? Was friction the major contributor to the failure? Where did the failure occur (on the racquet, not the court)? Was the failure during play or in the bag?

Shear-related failure is when the string breaks very near the racquet frame. This failure is called a mis-hit or shank! It is like cutting the string with a pair of scissors!

Shear Failure

Friction Failure

Friction failure is caused by just that, friction!  Friction is caused by the string moving on each other. That rubbing creates friction and notches the string where it will fail.

If the racquet failed during play and it is not shear-related, the tensile strength of the string was exceeded. If a string has a tensile strength of 120 pounds and the tension is 60 pounds leaving 60 pounds to be used to hit the ball. Some big hitters can generate at least that much force on a solid forehand!

The graphs show the tensile strength and relative elongation of different material.

This graph shows the tensile strength of the string to be about 115 pounds.  Given the movement of this string-on-string, the frictional notching can contribute to relatively early failure based on the hitters force.

This graph shows the tensile strength of the string to be about 155 pounds but it has to travel (stretches) further to reach that force.

So, you can see, with this information we can make better decisions when asked to suggest a string, or strings, for a client!