## What is wrong with this picture?

Actually, it is going to be two (2) pictures! One with no narrative and one with an explanation of what is wrong!

No peeking!

Did you see what was wrong with this picture?  If you did, congratulations are in order!

If you didn’t know what was wrong with this picture, here it is!  If you receive a freshly strung racquet that looks like this, take a close look at the strings and do not accept it if there is a “mis-weave” in the string bed!

Sometimes this condition is not easy to spot, so take a good look.

## SBS…what is it and why should we care?

We have made several posts regarding SBS, which is “String Bed Stiffness” and this is another one!

String bed stiffness is the “feeling” when the ball hits the string on a tennis racquet.  Due to the various string materials there will be “soft” and “hard” feelings.  But wait, there’s more!

The string bed is made up of several strings, some longer called the Main string (M)and some shorter called the Cross string(X).  Using “reference” tension each of the sets of string will be pulled at the same machine setting!  It the machine is set at 50 pounds the tension head will stop pulling when it feels 50 pounds of resistance, regardless of what he tension inside the racquet head may be.

SBS is the most effective data for comparing tennis racquet stringing!

Let’s say you come into the world headquarters and we ask you what SBS you would like to have?  Would you know?  Probably not and not many would!  We have grown up using the term “reference tension”, not SBS.

Reference tension is “number” you would ask your racquet technician to set the stringing machine tension system on.  That number will probably be between 30 and 60 pounds (≈13 to 26 Kilo).

So, depending on many other variables, such as string material, string pattern, stringing machine, stringer technique, etc., you can end up with may different versions of the same “reference tension”.

A better way, and one we have been using for over thirty (30) years, is SBS but not everyone has bought into the concept, even though a qualified racquet technician will have a way to measure SBS!  Maybe because it is too much trouble to figure out what your desired SBS from machine X would be from machine A!  It is not!

There have been several really good SBS data collection devices but they have been difficult to use, and pricy!  Not to mention gigantic!

A call to action!
So here is where you come in,

Would you purchase a SBS data collection device?

How much would you pay for such a device?

Would you prefer a mechanical device or an electronic device?

The device must be portable, that is easily carried in a racquet bag or backpack

Yes or It doesn’t matter

It must be easy to use.

If you use an SBS device would you use a racquet technician that did not know what SBS is or how to measure it?

## 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!

## Which Comes First!

We all have heard the question “which comes first the chicken or the egg”?  However, my question is “Which comes first the game or the string”?

I believe they happen simultaneously.  But first a quick story.

In 2005 I was attending a Head product introduction on the island of Mallorca, Spain,  Yes, that one!

The product introduction was exciting but what I am going to tell you about now was even more meaningful.

The Director of one of the top US Tennis Training organizations, at that time, was there and we were discussing teaching techniques and what he said after being in this part of Europe was “we need to start teaching our players how to hit this way!”  Well, “this way” was the way of low-powered strings that were popular in Europe but not so much in the US, yet.

So, it began!  The players could not hit harder, like the Europeans, unless they used the same string material as the Europeans and that was very stiff and mostly PET polyester.

So, the idea was the “egg” and the string was the “chicken”, sort of!  I guess the feeling was that “if Americans are going to compete we must use the same equipment”.

Our history confirms that almost no one plays better with stiff string and durability is suffering!

Now, I believe the professional game can go on about its way but otherwise, we need to consider changing the game by returning to a combination of comfort and playability.

Our history shows us that the “high performance” life span of many polyester strings is about 2-3 hours, or less, maybe about 10-12 games.  We don’t believe this is quite long enough for most players.  But, how do you quantify “performance”?  It may be different things for different players.

There are many components to performance but what if it was associated with UTR data?  Racquet Quest can track UTR numbers and make some determinations based on that data.  If a UTR is stable or increasing it is a good bet that the performance of the player and equipment is OK.  However, if the UTR is slipping it is a good indication that something is not working as it should…but what?

We have found that, in some cases, it is injury or discomfort, that is causing the slippage!  Stop it!  The following data is for a 12 month period and acquired from the UTR website.  Even small positive changes are tough!  But negative changes seem to have an enormous impact more quickly than positive changes!

For example:

PlayerRacquetStringUTR1UTR2Delta
BBabolat Pure AeroPolyester10.919.56-1.35
DWilson Pro Staff 97PEEK5.07.03+2.03
EBabolat Pure AeroPEEK3.85.64+1.84

This information is provided as a small sample comparison instrument and is not intended to pry anyone away from their favorite setup!  Even if it hurts!

## See What We are Talking About?

If you have been listening to the Racquet Quest Podcast you know we have talked about what to NOT accept when you pick up your newly strung racquet.

We know it is hard to visualize sometimes so these pictures are posted to give you a visual aid!  This is the very same string!  One could conclude from these images that the person responsible for these knots has not had any training at all.  It makes you wonder how good the rest of the string job is!