Author Archives: RacquetQuest
For the past few years and certainly the past year Racquet Quest has been committed to tennis racquets and yours is included!
Hopefully the days of the “mask”are over and we can resume actually talking to each other and be understood! Of course if you prefer to wear a mask that is OK, too!
Here is what is not OK!
Not caring about your tennis racquet is not OK, and by that I mean keeping it in the best possible condition. That includes string, grip, grommet sets, overgrips and general reactions of beating it against the ground or net!
We have seen five year old racquets that look brand new and five day old racquets that are in really poor shape! One of the most damaging “strokes” in tennis is the ball pickup stroke! This is not a stroke at all but a way to keep from bending over to pick up balls!
Using the racquet head to scoop up the balls is easy and cool! It is also the quick way to ruin the bumper guard which is there to protect the Racquet from normal stroke, not pick-ups!
So, what do you do about it? The next time you consider scooping up balls with the racquet consider tapping the ball to start it bouncing or simplpy use the fingers on your hand to pick up the ball…that would be good!
The following table will shed some light on the numbers we use and hopefully shed some light on what they can mean in terms of your racquet.
|Manufacturer||Yonex||What it Means|
|Racquet Model||Yonex VCore Pro 97 HD||Racquet being reviewed.|
|Reference Tension||55 lbs - 24.9 kg||Stringing machine tension setting. Not, necessarily, the string bed stiffness.|
|String||Ashaway MonoGut ZX Pro||String brand name and gauge (Pro being 17Gauge)|
|Machine Used||True Tension Professional||Stringing machine used.|
|ASPS, RDC||56||The stiffness of all the strings as a unit. Normally between 30 and 65.|
|ASPS, FlexFour||64.5||The stiffness of the string bed as tested on this device.|
|Racquet Flex, RDC||57 - After stringing||50 is low (flexible) and 70 is high (very stiff). Clash 100 is 52 on this device. As is a Head Speed model.|
|Racquet Flex, FlexFour||50||35 is low (flexible) 70 is high (very stiff). Clash 100 is 26 on this device.|
|Racquet - In Plane Stiffness||353.8 lbs/Inch||This is how stiff the racquet head is across the middle. 300 is soft and 500 is very stiff. This affects the string bed stiffness.|
|Weight, Grams||336||285 is light and 360 is heavy.
315 is minimum target weight for performance.
|Weight, Ounces||11.85||The racquet weight in ounces, typically used in US.|
|Balance, mm||322||This is the center of gravity from the butt cap. If you put the racquet on a round rod this would be how much is hanging toward the butt cap.|
|Balance, Inch||12.68||This is the CG in ounces for US. Points head heavy or head light is part of this.|
|Length, Cm||68.5||This is the total length of the racquet and is the typical standard adult length.|
|Length, Inch||26.968||This is length in inches for the US.|
|Head Width, Inches||9.57||The inside width of the hitting area.|
|Head Length, Inches||12.54||The inside length of the hitting area.|
|Head Area, cm2||625.8||The advertised hitting area in centimeters squared.|
|Head Area, Sq. Inch||97.0||The advertised hitting area in inches squared.|
|Number of Main Strings||18||The main strings are the vertical strings when looking at a standing racquet. Typically the longest strings.|
|Number of Cross Strings||20||The cross strings are the horizontal strings when looking at a standing
racquet. Typically shorter.
|Ratio Cross/Mains||.687||The natural ratio of the string pattern (calculated).|
|Main String Grid||7.25||The total distance between right and left main string.|
|Cross String Grid||10.18||The total distance between the first cross string and the last cross string.|
|Density (% of head filled with string)||.783|
|Average Cross String Space||.509||The higher this number the more the string will move. This number is used to help select the best string setup.|
|Average Main String Space||.403||The higher this number the more the string will move. This number is used to help select the best string setup.|
|Properties of a moving racquet.|
|Dynamic Tension, Kp, ERT||37||This is the stiffness of a string bed in kilograms per centimeter based on a frequency.|
|Dynamic Tension, Lbs/in||206.94||This is the above converted to pounds per inch.|
|First Moment, Nm||.831||This is how heavy the racquet feels in the hand. The higher the number the heavier the racquet will feel.|
|Polar Moment||340||This is the resistance to rotating about the center of the racquet on, say a mimes-hit. The higher the better.|
|Torsional Stability||16||This is the derived stability number. The higher the better within reason. Anything below 14 would need some help.|
|Swing Weight, Kg/cm2||324||This is the "inertia" of the racquet and probably the most important number in the review! The higher the number the more momentum through the ball but less manueverability.|
|Swing Weight, Ounces||11.43|
|Swing Weight Calculated||348.4||This number will be larger than the previous swing weight because it is calculated from the very end of the racquet as if there is no one holding it. A very important number.|
|Power, RDC||42||Calculated by the RDC. High is 100|
|Control, RDC||59||Calculated by the RDC. High is 100|
|Manueverability, RDC||71||Calculated by the RDC. High is 100|
|Power, Calculated||1740.5||This number is calculated based on a bunch racquet properties, Including length.|
|Head Points||6.46 (negative = head heavy)||This number is how positive or negative the balance is. A "point" is ⅛ of an inch so this racquet is a little over ¾ of an inch head light.|
|Head Weight, %||47.0%||Calculated based on weight distribution and length.|
|Center of Percussion||21.0||This is the spot on the string bed that returns a "solid" hit.|
|Dwell Time, ms||8.50||This is how long the ball and string are in contact with no swing. A big swing will reduce this number by about half.|
|Efective Stiffness - lbs||28.2||This number is calculated from the string bed stiffness and the racquet stiffness. Anything under 30 will be "soft" feeling and over 35 will be "harsh".|
|K, Lb/In||179.5||This is how many pounds it takes to deflect the string bed one (1) inch.|
|Recoil Weight||160.8||This number is the racquets resistance to rotating backward. The higher the number the better for volleys.|
|Twist Weight||230.8||This is the racquets resistance to twisting in your hand. The higher the better.|
|End Weight||139.8||This weight is used to calculate the precise balance of the racquet.|
|Tip Weight||196.2||This weight is used to calculate the precise balance of the racquet.|
|9 O'Clock||100.4||This is the weight of that position on the racquet head and is used for precise customization.|
|3 O'Clock||99.6||This is the weight of that position on the racquet head and is used for precise customization.|
|Butt Cap||135.6||This is the weight of that position on the racquet and is used for precise customization.|
The little video you see above is just a reminder that we do not promote polyester based string for underage players! So, what is underage? Oh, under 100 would be a good number, I think!
OK, smart alec what are the options?
- No Polyester
Well, there are many, however, if the option is only relative to “no polyester” the best option is PEEK material. This material is usually referred to by the brand name Zyex which is the fiber division of Victrex of England and known by the Ashaway name as well. This material is normally found as a monofilament construction as is most polyester materials.
PEEK/Zyex offers exceptional durability and energy!
- Premium Playability
Natural gut still is the number one playing string available. We use Babolat and Luxilon natural gut but there are other options like Pacific, Klip, and others.
- Excellent Playability
Multifilament construction can act as a spring and return both performance, power, and comfort. Typically the more individual fibers the better. These fibers are usually bonded with a soft adhesive and show signs of “fraying” during use.
Strings in this category include Tecnifibre, Ashaway, Babolat, Head, Yonex, and Gosen and others. Expect to pay $42.00 + for these strings installed.
These multifilament strings are typically constructed using fewer larger diameter fibers to enhance durability. The same “fraying” occurs with this grade of string as well however the larger diameter will last a bit longer usually.
Strings in the category include Tecnifibre, Babolat, Head, Yonex, IsoSpeed, Gamma, and others. Expect to pay between $35.00 and $40.00 for these strings installed.
There are probably 10000 strings that fall under this umbrella! 9999 of these strings will be a nylon core with one or two overwraps bonded to the outer surface. This material and construction has been around for many, many years and has offered great service to millions of tennis players…and is still in major use today!
Strings in this category include at least one, and probably many more, set from every major brand! If you are really cost-conscious do not overlook this material. Expect to pay $27.00 to $35.00 for these strings installed.
And lastly, what is our gripe with polyester? Click on the link below to find out!
As always, our position is “there are no bad strings just bad applications!”
Grip size, in this case, does matter! However, for several years the largest grip size available has been a 4 ⅝, or just 5 for short.
This is simply the circumference of the finished grip forward of the butt cap. Of course the butt cap is of a size that will capture the butt of your hand for comfort and control.
But what happens if you need a grip size larger than 4 ⅝? In years gone by a shrink tube was applied to the current grip pallet and the size was increased accordingly. Typically only two (2) shrink tubes could be used and even then the grip facets became “rounded”.
Lucky for us, and you of course, we can now print grip pallets in any size required! The largest one so far is a 5 1/4 for a player in New York using a Babolat Pure Aero.
Each printed pallet is made specifically for a racquet, not just a “one size fits all” approach due to very subtle variations in size, especially the inner shaft.
In this case the pallets were longer to accommodate large hands so the length of the racquet was increased through the use of these pallets and a printed extender.
The printed pallet must fit securely and the best way to assure the fit is to have the racquet.
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!