Category Archives: Technology

Mr. Dailey Makes a Visit!

The Racquet Quest World Headquarters had the pleasure of having Curt Dailey, CEO of LaserFibre Strings, visit today!

Racquet Quest, LLC will be doing a little evaluation work on LaserFibre string made in the United States!  LaserFibre is the only string supplier committed to making all of their string products in the United States.  Right now this is not the case, but they are headed in that direction.

Curt has been in the tennis business for many years and is trying hard to bring updated string products to the market.

Welcome to Racquet Quest, Curt!

 

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

 

What’s New?

It has been incredibly busy this winter at Racquet Quest, but that is no excuse to keep you wondering what is here and what is coming your way soon!

You know the new Wilson Ultra series, both the CV and the Tour are in the shop along with the new Head Radical and Head Prestige. I have racquets for your evaluation now.

This website is consumer-centric, but I want to point out some new diagnostic equipment and stringing machines while we are here.

Gosen, one of the premier string manufacturers in the world, sent a GM One Diagnostic machine for evaluation. If you have been to the World Headquarters of Racquet Quest, LLC you have seen several pieces of equipment we use to certify that your racquet is in the very best playing and physical condition.

The Gosen GM One is a swing weight device that has extended the precision to .5 units! And, the included scale measures in the .1 gram range. This is extreme accuracy!

 

 

 

We have the Babolat Racquet Station stringing machine in for evaluation.  A state of the art machine physically and electronically.

We are using this machine to evaluate different string formats, i.e., hybrids with polyester mains/multi-filament crosses, the reverse format, gut/polyester, polyester/gut and straight multi-filament.

The results are exciting and enlightening.

Let’s Talk About This!

I decided to write about this again after reading some posts asking questions, good ones by the way, about string tensions when stringing a racquet.

What we are discussing is not a simple matter, in fact, it is challenging to quantify many things we believe are real.  It is difficult, if not impossible, to tell a stringer how to string a racquet for a new client.  These are the obvious player/stringer questions that need to be answered:
a. What racquet type?
b. What string type?
c. What main and cross string tensions should be pulled?
d. What stringbed (SBS) stiffness is wanted?
e. What racquet weight, swing weight, and CG is wanted?
f. What stringing machine should be used (yes this matters, but is rarely considered!)?

There are also many player-specific questions that are in the mix, including:
a. Do you want more or less power?
b. Do you want more or less control for that power?
c. Do you want to hit with more spin?
d. Do you have any physical problems influencing your play (sore shoulder/arm, elbow, strength, etc.)?

The task/responsibility for a good stringer, or, racquet technician preferably, to his player is quite daunting if the goal is to “string responsibly.”

With answers to these questions, and a stringers plan in place to achieve these goals, one of the most important attributes a stringer can deliver is repeatability. Once a player has settled on a path (racquet, strings, tensions, stringbed stiffness (SBS), etc. you want, as a client and stringer, that customized performance to repeat with every re-stringing. So the stringer must have a process, with metrics, that will guarantee that repeatability. This repeatability is also the foundation for changes from that norm (for example, what happens if I replace my strings with another type, or if I stay with the same strings but switch racquets, etc.)

My comments that follow is the plan I have developed for my stringing process for the players I try to support.

One of the most important influences on how a racquet plays is the stringing machine that is used to string a racquet.

About twenty years ago I developed a machine evaluation procedure for understanding what happens during, and after, the stringing process.

Every machine is treated in the same way. The same racquet, the same string, and the same tension settings, and the same testing devices. I am not going into detail here because it is quite a lengthy path.

Here is what we need to know:
1. When stringing a racquet with main and cross strings, every racquet has a “natural ratio” of the final cross tensions to the final main tensions. That is what the cross string tension is relative to the main string tension of a finished racquet.
2. Nearly every machine tested allowed considerable distortion of the racquet in the three and nine directions. As much as .380 (9.62mm)! You want to minimize that distortion for the final strung racquet.
3. Almost every machine reacted slightly differently when the racquet was removed, i.e., some easier than others.

Why does this matter:
1. Due to the distortion, with the racquet in the machine, every machine produced main string only tensions of about 55% of the machine tension setting. That is the machine is set on 60 for example, and the measured tension is approximately 33 in the middle and increasing slightly going toward the 5th and 6th string. It never reaches 60 with only the main strings installed.

2. When the cross strings are installed, they begin to pull the racquet head back into shape but not significantly until nearing the 11th or 12th cross string.

3. When the racquet is finished and depending a little on the number of strings, it will, hopefully, return to close to the original unstrung shape and dimensions.

4. This “reshaping” can have damaging effects (stress failures) on the racquet.

Here is the question that started this whole discussion again.”

So, do I want to increase or decrease cross string tensions? My opinion is that until you know how the racquet, any racquet, is going to react don’t change tension settings at all. The key here is a responsible stringer wants repeatable metrics first.

We have an “Accuracy Index” procedure for every string pattern, that is the number of main strings and number of cross strings, that calculates the accuracy of the entire string bed based on where the ball is impacting the string bed. The accuracy index is a measure of the ball rebounding normally to a deflected string bed. For example, if a ball were to hit in the geometric center of an elliptical head racquet that was strung with main and cross string tensions that minimized racquet stresses and frame distortion the accuracy index would be 1.0. For the same racquet, if some of the strings were at low tensions (perhaps a break) the accuracy index would be less than 1.0.

Based on “observed breakage locations” we can see the accuracy of that small area of the string bed where most breaks occur.

Most machines I have evaluated will return accuracy indices of 87 to 95 percent.

I have, however, included in this test an “Efficiency Index” which shows me how much the racquet had to “move around” to achieve the accuracy index number and reach some equilibrium. This value is typically in the 70 to 75 percent range! So the racquet is working hard to get back into shape.

If you are a stringer or racquet technician, please note that after the racquet is setup in the stringing machine properly do not make adjustments to the supports during the stringing process. In some cases, the supports will not be in contact with the racquet. Don’t adjust.

Unless the racquet is mounted on a solid annular plate, like the top image, do not restrict the expansion of the racquet by placing a restrictive member across the 3 and 9 o/clock positions which in this image are the top and bottom.  The red knobs are the 12 and 6 o’clock positions

True Tension Professional

True Tension Professional Machine

baiardo

Wilson Baiardo

Yonex Protech 8 Contact Points

Babolat Racquet Station

Head Visit

The World Headquarters of Racquet Quest was pleased to have Erika and Federic from Head visit recently. Erika is with Head in Phoenix and Frederic is from the Headquarters in Kennelbach, Austria.

Team Head player, Jack Anthrop was on hand to provide a players perspective.

Jack Anthrop

“Champion”

The purpose of the visit was to discuss a “grassroots” program that can effectively address, and contribute to the growth of tennis worldwide.

I was commenting on racquets and string selections, of course, when it dawned on me that Head has done an extraordinary job in designing racquets that have vast player appeal! A prime example is the Adaptive Series, introduced about a year ago, consisting of a “Speed” and  “Instinct” model.

Head Adaptive Length Extenders

This series can go from a lightweight standard length racquet to a more substantial, longer racquet in a few minutes! Plus this series can be either a 16 x 19 or a 16x 16 string pattern!

This concept is valid, and one that allows players to maximise the performance of the racquet. And the implementation is easy. Some changes can be made at courtside!

So, while I believe more can be done to get players into the correct racquet, the Head Adaptive Series is very close to being perfect!

Get real!

A lot of players are anxious for new tennis racquets this time of year and have, maybe, asked for one as a gift.  A great idea, of course.

However, be sure the gift giver, or yourself, gets real!  There are some real bargains out there, but the bargains may not get you what you expect.  This can happen to any brand and the more popular the racquet, the more likely there are to be fakes!

Fake Blade 98

This is an image of a fake Wilson Blade 98 compared to a real Wilson Blade 98.

I am showing this image because without seeing this detail the fake racquet graphics will look nearly identical to the real Wilson racquet.

One of the best ways to confirm a fake or real racquet is to “bend” it, that is to check the stiffness of the racquet.  In almost every case the fake will be quite a bit more flexible.  For example, this fake racquet has a stiffness of RDC 41 whereas the real racquet has a stiffness of RDC 63.   If your racquet technician does not have a device for checking stiffness the next best thing is to look at the “insides.”  A qualified racquet technician will know what the insides of the real racquet look like.

Another sign of fakery is the grip pallet.  Most performance racquets will have a foam pallet molded over the graphite shaft or a two-piece pallet that is attached to the racquet shaft.

Fake racquets may very likely have a continuous graphite pallet.  You can quickly look under the first couple of inches of the grip and see if it is foam or graphite.

Clamshell grip pallet

If you are requesting a new tennis racquet be sure you get it from a local business, if possible, or an otherwise reputable source.

If you have any questions at all, please call your local dealer or us (407.491.4755) to be sure you “GET REAL.”

What is Important?

I spend hours each day dealing with tennis racquets, strings, machines and questions of all sorts!

By doing this I am learning what is important to tennis players but it should not require a one-on-one discussion to learn this, in my opinion.

So, what is important to you?  Here is what I am discovering.

Comfort.  It goes without saying that you don’t want to play tennis if you are hurting!  Players are requesting racquets that are more arm friendly.  But wait, the racquet really holds the string which has a huge impact on comfort.  So should we begin with string?  I think so!

String.  Every string I have has undergone a comprehensive testing procedure to determine elongation which in turn is converted to Power Potential.  The higher the elongation the higher the power potential and the less stiff the string bed will feel when the ball is hit hard, all other settings being equal.  If you have a stiff racquet it is important to select a string and tension that will mitigate the racquet stiffness to some extent.  Every racquet we do has the “effective stiffness” calculated which is the combined stiffness of the racquet and string bed. Once we have the preferred effective stiffness for a customer we can achieve that even if a new racquet is added to the mix.

Durability.  We try to associate the cost of racquet stringing to “cost per hour” of play time.  What is your threshold?  $1.00 per hour or $10.00 per hour?  When considering durability do not confuse “performance” with “durability”!  There are several strings that may not fail for several months however the performance is gone in a few hours.  This is typical of polyester based strings.  So, even if the string is still intact the performance is way gone!

Cost.  The cost of tennis racquets is increasing, sometimes justified, sometimes not but are rising none the less.  If cost is your “driver” some navigation around the market is important, however, we do not suggest you buy the “cheapest” thing you can find without a thorough understanding of what you are getting.  We can assist you in evaluating racquets from any source.

Is This the Perfect Combination?

It seems like Ashaway had this very racquet in mind when they developed their Dynamite Soft 18 string!  This blue string is a perfect match to the blue accent color on the Ultra 100 CV and Ultra Tour!

And, the gauge, a very thin 18, is a perfect match to the very stiff frame (73 RDC, 70 FF stiffness).

I think the 18 gauge string may not be durable enough for hard hitters but this combination could be very good for many players.

You can be the judge of that, of course.

The string tension of 48 lbs (21.7 kg) combined with the racquet stiffness returns an effective stiffness of 30.3 which is a very comfortable number.

This stiff, 100 square inch racquet, should pack a powerful punch with a weight of 318 gr (11.2 oz) and swing weight of 318 kg/cm^ (11.2 oz).

New! Head Adaptive Tuning Models!

I have been working on these new models for a few days and will post more data as it is available but right now here a few points about this fascinating racquet concept.

dsc04103

The two (2) models are Speed Adaptive and Instinct Adaptive.  The racquets are both new versions of the current models with slightly newer graphics, that are, in my opinion very cool!  The Instinct has new graphics which will appeal to more players.

First, the Adaptive Tuning can create thirty-two (32) possible combinations, including increasing the overall length of the racquet.

The racquets are shipped in the lightest (285 gram), 16×19, 27.0-inch length format, and swing weight 287.

The Adaptive Tuning Kit is required and costs $29.00.   In the “kit” you will find a “heavy” butt cap insert, three (3) sets of grommet inserts to add weight and change string pattern, and three (3) sleeves that go onto the shaft to create length.

The length modification can be made quickly by the player, if necessary, however, the other modifications require the racquet to be unstrung.

These modifications should be left to your racquet technician.

Head Adaptive Length Extenders

Head Adaptive Length Extenders

Below is a spreadsheet representing the various combinations as they are applied.  This does not include all the options because the 16×16 grommet set did not participate in this session.

This was done at Racquet Quest, LLC and represents actual data, not calculated characteristics.

screenshot-2017-01-18-20-57-59

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

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