Category Archives: co-polyester

2020 is Coming Into Focus!

2019 came and went in a blur!  In a few days it will 2020 and with it will come some exciting new tennis stuff, for sure!

I am not so good at predicting things but I do it anyway!  Here are a few predictions I will make for 2020:

  1. Tennis racquets will become more expensive, but only slightly.
  2. On-line sales of tennis racquets will increase.  See this previous post.
  3. Customer satisfaction with on-line sales will decrease.
  4. Small specialty tennis shops will be the source of information, then #2, and then #3.
  5. Players will stick with a racquet longer, making customizations as needed.
  6. String and stringing will become a more important component of a racquet purchase.  See below!
  7. Tennis related injuries will continue to be a problem for the sport going forward.

    No Underage Polyester, Please!

    Thank you for thinking about the “long term” for all tennis players!

    There are no bad strings just bad applications!

    The right equipment is crucial to the long term enjoyment, and winning, of tennis!

    The local representatives I deal with are committed to our “well being” even though some may feel like they are facing “extinction”!

    An excellent example of what we are talking about just walked in! Two (2) new racquets so poorly strung it is shocking!

    The customer is having serious arm issues with an excellent racquet, with a terrible string setup! But the string setup is probably considered by many to be the ultimate combination, that is RPM Blast in the main and VS Touch in the cross! That combination is coming out in a few minutes!  No more polyester!

    The quality of the stringing is what is so wrong! Had you or I received this racquet, we would have returned it at once! Why? Because it exemplifies the attitude of so many stringers that is “who cares”!

Happy New Year!

String. What is important?

The essential function of string in your tennis racquet is to return energy to the ball as it collides with the racquet. It is evident that if there is no string or a broken one, the racquet can not do what it is intended to do, and your shot is going nowhere or worse, everywhere!

There are about thirty (30) string brands, and each brand has about ten (10) different models, and maybe three (3) different colors, so there are nine hundred (900) possible selections! Nine hundred is way too many strings!

You and we need to consolidate string data so we can make the right decision for you, your playing style, and your physical capabilities.

We test every string for elongation, creep, (stability), with a little bit of elasticity data observed. This testing returns our exclusive Power Potential© for each string, and that is the basis of our decision-making process. Naturally, the higher the elongation, the more power the string will return to the ball, and conversely, the lower the power potential, the less power that “can” be generated. You can observe this fundamental by dropping a tennis ball on a concrete floor and then on a strung tennis racquet from the same drop height and see which one bounces the highest.

I use “can” because power, to a great extent, comes from how hard you swing the racquet, which, of course, brings the prospect of overdoing it and subsequent injury! A low power string demands a more powerful swing that involves the entire arm, hips, and legs.

Low power, in the form of a stiff string, has been associated with control, therefore, the increased use of stiff strings. However, with stiffness comes another downside, and that is stability. Stiff strings typically lose tension quickly and need to be changed frequently. So here is the real problem; the string may not be broken, but it is not playing well at all. There is a difference between durability and performance! If your goal is long term performance, a stiff string is not the answer.

What, then, is the answer?

Choose a string with an elongation of 10% or higher! Oh, great! You say. How am I going to know that!

Well, beginning January 1, 2020, I will be posting the power potential of every string we have tested over the years! There are over 500 items on the current list sorted by brand. The color coding is RED if 5% or less, GREEN if 10% or higher, and BLUE for everything else. Note, however, that natural gut is included in this data and will probably not reach the 10% Power Potential© threshold, but is still the best performance string available.  This is due to the dynamic properties of the natural fibers, so, until there is a separate classification gut will be included as is.

A previous post, “What is Soft?” goes into graphical detail.

As new strings are added, some older ones may be deleted because they are no longer manufactured. However, some very old ones may remain due to their “legacy” status. This chart is a preliminary format but will get us map toward the right decision!

Click here to see all the current power potential data.

 

 

 

 

 

 

 

 

 

And Now This…

In the words of Lord Kelvin (May 1883) “When you can measure what you are speaking about, and express it in numbers, you know something about it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts advanced to the stage of science.”

That is why every racquet we do has over fifty (50) numbers attached to the finished data. Most of these numbers will remain unknown to the client, but for us, it is imperative that we know them.

Numbers Matter!

Which leads me, again, to this very important discussion.

Every day we see a statement from tennis string manufactures claiming, or suggesting, their string is the “softest ever tested” and other claims.  What the heck is “soft” anyway?  There is a lot more to it than meets the eye so we have done significant analysis on bunches of string and can now quantify “soft” as it relates to tennis string.

What is “soft”?
In 1994 I did a presentation for the USRSA in Atlanta. What was the topic?

“Understanding String.”

It is now 2016, and we are still trying to understand string! Especially “soft” polyester based string.

In 1994 PolyStar was the only polyester based string I was familiar with. Since then there are dozens of offerings from anyone that can afford to purchase from manufacturers and market the string. If you have a desire to do it, I applaud you!

In 1989 I started testing string and calculating “power potential.” Why “power potential”? Because “modulus,” “elongation” and “elasticity” didn’t get to the bottom line of string performance quickly enough! The steps to arrive at power potential are many.

For the testing, several calculations take place including “stretching” the string as in a ball impact. The difference between the first calculation and the “stretched” calculation is the power potential!

I have calculated hundreds of power potentials but have not until now quantified “soft.”

I think now is the time!

Under the direction of Dr. Rich Zarda, we have done a tremendous amount of work on this issue so we can now distill this work into the following explanation.

So, what is a “soft” tennis string?

Strings in a tennis racquet carry the ball impact load in two ways:
1) Via the pre-load string tension placed in the strings caused by a stringing machine (and the racquet frame “holding” those tensions in place) and
2) Via additional tensions that develop in the same string caused by the elongation of the strings as they deflect with ball impact.

Both of these conditions occur simultaneously and contribute to the string bed stiffness (SBS, units of lbs./in). Racquet technicians measure SBS by applying a load to the center of a supported string bed and measuring the resulting deflection. Dividing the load by the deflection provides the SBS (lbs./in). The lower the SBS, the more power you have (power here is the ability of the ball to easily rebound from the string bed), but the less control (presumably); the higher the SBS, the less power you have but, the more control you have (presumably).

One more point about SBS: the lower the SBS, the less the load your body will feel for a given swing. But for an SBS too low (less than 50-80 lbs./in), balls will be flying off your racquet going over the fence; and for an SBS too high (greater than 200-240 lbs./in), the racquet will hit like a board with significantly less ball rebound. So the most common SBSs are between 100-200 lbs./in: a balance between control and power.

As already expressed, SBS is a function of the pulled string tension and the string elongation. Here is what is interesting: For large string elongations (for example, greater than 15%) and reasonably pulled string tensions (greater than 30-40 lbs.), SBS only depends on the pulled string tension, and it does not depend on string elongation. Additionally, for this condition, SBS, for these high elongation strings, does not change as a ball is hit with more impact.

linearity_noname

But for a string bed with low elongation strings (less than 5%) under low pulled tensions (less than 20 lbs., or tensions that have been reduced due to racquet deformation and/or string tension relaxing with time), the SBS additionally depends on the string elongation and will significantly increase, in a nonlinear ever-increasing way, for harder ball impacts.

In order to achieve a repetitive feel for a player when hitting with a racquet, it is best to have an SBS that is independent of an increasing ball impact force. This will lead to a more consistent playability of the racquet, which includes a more repetitive feel. This desired “feel” implies using high elongation strings (greater than 10%). If low elongation strings are used (less than 4%), the SBS will significantly increase as the ball impact force increases, resulting in a racquet feeling “boardy” for higher impact loads. And low elongation strings will cause un-proportionally increasing load into the body.

deflections

As you can see by the graph, elongation contributes to SBS in a big way. The red line indicates a stiff string, about 4%, and the blue line indicates a “soft” string, about 15% elongation. You can see the loads increase dramatically as the impact increases. So the harder the hit the higher the loads on the body.

So to the question asked at the start “What is a soft tennis string?” In the context of the SBS discussed above, I would suggest that a soft tennis string is one whose elongation is 10-15%, and a stiff tennis string is 4-6%. And any string under 4% should be categorized as ultra-stiff.

String elongation (soft, stiff, ultra-stiff),  stringing machine strung tension, and string pattern(s) all contribute to SBS and SBS is an important measure of how a racquet plays and should be adjusted for an individual player, stiff and ultra-stiff strings can lead to less-repeatable racquet performance and player injury.

Soft = 10 -15% Elongation                Power Potential Range = 10.0 – 16.0
Stiff = 4 – 6% Elongation                   Power Potential Range = 4.0 – 7.0
Ultra Stiff =  Less than 4%               Power Potential Range = .65 – 3.96

 

Hybrid Stringing…What is it and Does it Matter?

When the discussion is about stiff polyester string, it will always include the word “hybrid”!  Typically this word is used to convince players that by putting a “soft” multi-filament string in the cross position the string bed will be easier on the wrist, elbow, and shoulder.

Intuitively this makes sense, but in reality, the reverse could be true!

I began analyzing hybrid string beds years ago and did many just to test the theory. At the time it did not seem so important because, frankly, the use of polyester based string did not approach the usage of current times.

I have nothing against the polyester string(s)! I do have an issue with bad applications of polyester string(s).

I am bringing this up again because recently an “interviewee” stated that that replacing the polyester cross string with a multi-filament would cure the ills of a very stiff string bed.

The bottom line:

A high elongation string of any material can increase the string bed stiffness of a hybrid string bed!

How can this be?

Stiff (polyester) strings are “stiff” and the tension applied to them during stringing is low. However, high elongation (multi-filament) strings will be influenced more by tension and become “stiffer”.  The cross stings are typically shorter, and there are more of them, so the combined affect is stiffness.

The initial reaction to this conundrum is to automatically reduce tension on the cross string by a certain amount. Again this raises another issue, and that is racquet distortion.

During the installation of the main strings most stringing machines will allow the racquet to become wider, sometimes a lot wider! So, reducing the cross string tension may not return the racquet to the designed shape. What happens then is the racquet will continue to move around trying to find a “safe” place and therefore the string bed stiffness changes.

In summary, the hybrid string bed will not be statistically different than the full string bed of polyester. This is even truer if the initial string tensions of the polyester are very low, such as 35 to 40 pounds.

So if you feel the need to use polyester just go with lower, lower,  tensions.

 

 

What is “Soft”?

What is “soft”?
In 1994 I did a presentation for the USRSA in Atlanta. What was the topic?

“Understanding String”.

It is now 2016 and we are still trying to understand string! Especially “soft” polyester based string.

In 1994 PolyStar was the only polyester based string I was familiar with. Since then there are dozens of offerings from anyone that can afford to purchase from manufacturers and market the string. If you have a desire to do it I applaud you!

In 1989 I started testing string and calculating “power potential”. Why “power potential”? Because “modulus”, “elongation” and “elasticity” didn’t get to the bottom line of string performance quickly enough! The steps to arrive at power potential are many.

For the testing, several calculations take place including “stretching” the string as in a ball impact. The difference between the first calculation and the “stretched” calculation is the power potential!

I have calculated hundreds of power potentials but have not until now quantified “soft”.

I think now is the time!

Dr. Rich Zarda has done a tremendous amount of work on this issue so we can now distill this work into the following explanation.

So, what is a “soft” tennis string?

Strings in a tennis racquet carry the ball impact load in two ways:
1) Via the pre-load string tension placed in the strings caused by a stringing machine (and the racquet frame “holding” those tensions in place) and
2) Via additional tensions that develop in the same string caused by the elongation of the strings as they deflect with ball impact.

Both of these conditions occur simultaneously and contribute to the string bed stiffness (SBS, units of lbs./in). Racquet technicians measure SBS by applying a load to the center of a supported string bed and measuring the resulting deflection. Dividing the load by the deflection provides the SBS (lbs./in). The lower the SBS, the more power you have (power here is the ability of the ball to easily rebound from the string bed), but the less control (presumably); the higher the SBS, the less power you have but the more control you have (presumably).

One more point about SBS: the lower the SBS, the less the load your body will feel for a given swing. But for an SBS too low (less than 50-80 lbs./in), balls will be flying off your racquet going over the fence; and for an SBS too high (greater than 200-240 lbs./in), the racquet will hit like a board with significantly less ball rebound. So the most common SBSs are between 100-200 lbs./in: a balance between control and power.

As already expressed, SBS is a function of the pulled string tension and the string elongation. Here is what is interesting: For large string elongations (for example, greater than 15%) and reasonably pulled string tensions (greater than 30-40 lbs.), SBS only depends on the pulled string tension and it does not depend on string elongation. Additionally, for this condition, SBS, for these high elongation strings, does not change as a ball is hit with more impact.

linearity_noname

But for a string bed with low elongation strings (less than 5%) under low pulled tensions (less than 20 lbs., or tensions that have been reduced due to racquet deformation and/or string tension relaxing with time), the SBS additionally depends on the string elongation and will significantly increase, in a nonlinear ever-increasing way, for harder ball impacts.

In order to achieve a repetitive feel for a player when hitting with a racquet, it is best to have a SBS that is independent of an increasing ball impact force. This will lead to a more consistent playability of the racquet, which includes a more repetitive feel. This desired “feel” implies using high elongation strings (greater than 10%). If low elongation strings are used (less than 4%), the SBS will significantly increase as the ball impact force increases, resulting in a racquet feeling “boardy” for higher impact loads. And low elongation strings will cause un-proportionally increasing load into the body.

deflections

As you can see by the graph, elongation contributes to SBS in a big way. The red line indicates a stiff string, about 4%, and the blue line indicates a “soft” string, about 15% elongation. You can see the loads increase dramatically as the impact increases. So the harder the hit the higher the loads on the body.

So to the question asked at the start “What is a soft tennis string?” In the context of the SBS discussed above, I would suggest that a soft tennis string is one whose elongation is 10-15%, and a stiff tennis string is 4-6%. And any string under 4% should be categorized as ultra-stiff.

String elongation (soft, stiff, ultra-stiff),  stringing machine strung tension, and string pattern(s) all contribute to SBS and SBS is an important measure of how a racquet plays and should be adjusted for an individual player, stiff and ultra-stiff strings can lead to less-repeatable racquet performance and player injury.

Soft = 10 -15% Elongation             Power Potential Range = 10.0 – 16.0
Stiff = 4 – 6% Elongation               Power Potential Range = 4.0 – 7.0
Ultra Stiff =  Less than 4%            Power Potential Range = .65 – 3.96