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Three Important Things
When dealing with tennis racquets, there are many significant performance parameters. We are going to list our three (3) most important ones:
- Swing Weight
- Overall Weight
- Effective Stiffness
These particular parameters are based on machine testing, physics, and experience.
- Swing Weight: we refer to this as a dynamic weight, meaning how heavy or light the racquet feels during the swing to the ball.
- Overall Weight: This is normally considered to be the weight found on a scale, electronic, or balance. Weight is your friend if properly associated with your capabilities and stature.
- Effective Stiffness: is a calculable and measurable stiffness of the ball hitting the string as you are holding the racquet and hitting a ball.
Why is it Important?:
- Swing Weight: contributes to power and stability, which contributes to control. A higher swing weight of, say, 320 to 340 will handle most incoming balls with ease. Swing weights of 300 to 319 will be easier to maneuver and require a little more energy from the player to handle aggressive incoming balls.
- Overall Weight: contributes to ease of movement and long play time and must be associated with the stature and style of the player. The heavier racquet will provide more power with less energy expended by the player.
- Effective Stiffness: this is a metric we use to ensure the racquet is within the stiffness range needed by the player. For example, if you come into the World Headquarters of Racquet Quest for the first time with your current racquet and the strings are intact, we can determine the effective stiffness and, based on your satisfaction with the current playability, arrive at a corresponding effective stiffness…not on a reference tension. A range of 24 to 30 pounds is acceptable. Anything over 30 becomes quite stiff and should be avoided by most players.
If you look at our racquet reviews, you will see a lot more than three (3) performance parameters! We believe they are all important, but players should understand the three (3) described here.
Strings are made to Work (and wear out)!
If tennis strings are doing what they should, they will wear out!
What happens between the time strings are installed and the time they need to be replaced?
- Strings are under tension (stress)
- Strings are subject to fatigue due to hits
- Strings are subject to frictional notching due to sliding
- Strings are elastic but will lose tension
- Strings break
All of the above actions are subject to many variables, of course!
- String Bed Pattern (16×19, 18×20,,,)
- Sring Bed Size (90, 95, 98, 100, 110… square inch)
- Racquet head speed
- Racquet head angle
- String wear
- Environment (wet, dry, hot, cold…)
What does this actually look like, though?
This will give an idea of what a really good wear pattern will look like
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- COP View
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- Full String Bed
after about ten (10) weeks of use. This is a 17-gauge multifilament in a 98-square-inch head size at a reference tension of 55 pounds (24.9kg).
In fact, the COF (coefficient of friction) is greater than when the string was fresh!
COF_ M: 23%, X: 31.5% greater! This means if you have the nerve (no fear of breaking string), you can continue to play and enjoy the grabbing of the ball by the tiny tentacles that get caught in the ball fuzz.
This will not last forever, though!
COP View
This wear pattern is typical of high-quality multifilament strings.
When making a string selection, think about how long you want the string to perform well, not necessarily how long it will stay in your racquet.
If you need some ideas, go to our String Frequency Calculator. This will give you some high performance stringing cycle recommendations.
Have fun … and use up your string!
Power vs String Bed Stiffness
We have been testing strings for power potential since 1984! Currently, we have over 500 strings registered on our website, and we will put a link in this post that will take you there. Over the years, we have tested that several times that number but need to remove some strings that simply do not need to be in this data while keeping “legacy” strings for reference to today’s offerings.
What does the power potential of string have to do with String Bed stiffness? While a single strand of string tells us a lot about the performance characteristics of any string, it is the total string bed that you play with, not a single string!
We test for String Bed Stiffness in four (4) different ways: Babolat RDC, Flex Four, Master Tensometer, and our proprietary String Bed Master.
What we want to clarify is the power of the string bed stiffness, and to do that, we need to include the tennis ball, which is, by design, not very efficient. I believe the rebound percentage is about 53 to 58 percent. If the rebound percentage were closer to 100 percent, the ball would not stay in the court!
The graph below helps us understand what String Bed Stiffness will work in any given player situation.
Power vs String Bed Stiffness
I know there are a lot of lines, but I am certain you can understand them. We will help you along and explain why this is very important to you and us!
The vertical axis (Y) is Power, and the horizontal axis (X) is String Bed stiffness in pounds per inch. Every device we use for string bed stiffness presents the force in pounds per inch. The green dotted box represents the “normal” range (≈ 160. to 210.0) for string bed stiffness.
If we want to maximize the power of the ball contact and string, we would need a string bed stiffness of about 100 pounds per inch, which is achievable but not “normal.
The upper curve (brown or red) represents the sting bed only. So you see a power range of 20.0 down to 6.67. The lower curve (blue) introduces the ball and, due to the ball design, does not add any power but detracts from power. So you see a power range of 13.7 down to 8.38. Because we don’t know how hard the ball is being struck, we prefer to use the string bed-only curve. It is, however, critical for us to know how the ball is participating.
An interesting and important value of the graph is the power value. As the string bed becomes stiffer than the ball (≈ 210.0 pounds per inch range), the ball will provide more power than the string bed. Not much, but at least the ball will not detract from the power!
Yonex V-Core 100
The Yonex V-Core is a great opportunity to review the racquet with IsoSpeed Professional 17 gauge string. If you know anything about the racquet you will know it is a great platform for many player types.
But what about IsoSpeed strings? These strings, and there are a series of them, are unusual in the material and construction, therefore not very well considered!
The string is polypropylene fibers bonded together then stretched and packaged on a stiff molded reel to retain some of the stretching.
If you have seen our previous review on our Questron data you will notice some similarity to natural gut.
| Manufacturer | Yonex |
|---|---|
| Racquet Model | Yonex V-Core 100 |
| Reference Tension | 55 |
| String | IsoSpeed Professional 17 |
| Machine Used | True Tension Pro |
| String Bed Stiffness - RDC | 41 |
| String Bed Stiffness -FlexFour | 53 |
| String Bed Stiffness SBS | 48.6 |
| String Bed Stiffness - ERT | 31 Kg/Cm^ |
| Racquet Flex, RDC | 66 |
| Racquet Flex, FlexFour | 48.6 |
| Racquet - In Plane Stiffness | 423.7 lbs/In |
| Weight, Grams | 321 |
| Weight, Ounces | 11.32 |
| Balance, mm | 324 |
| Balance, Inch | 12.76 |
| Length, Cm | 68.8 |
| Length, Inch | 27.08 |
| Head Width | 9.87 |
| Head Length | 12.82 |
| Head Area, cm2 | 641.3 |
| Head Area, Sq. Inch | 99.4 |
| Beam Height @ Grip, mm | 22 |
| Beam Height @ Mid, mm | 25.6 |
| Beam Height @ Tip | 25.5 |
| Beam Width @ Grip, mm | 16.3 |
| Beam Width @ Throat, mm | 15.2 |
| Beam Width @ Mid, mm | 10.3 |
| Beam Width @ Tip, mm | 11.6 |
| Number of Main Strings | 16 |
| Number of Cross Strings | 19 |
| Ratio | .649 |
| Main String Grid Inch/mm | 7.50 / 190.5 |
| Cross String Grid Inch/mm | 10.15 / 257.8 |
| Density (% of head filled with string) | .747 |
| Average Cross String Space | .529 |
| Average Main String Space | .461 |
| Dynamic Tension, Kp, ERT | 31 |
| Dynamic Tension, Lbs/in | 173.4 |
| First Moment, Nm | .800 |
| Polar Moment | 328 |
| Torsional Stability | 15 |
| Swing Weight, Kg/cm2 | 313.0 Kg/Cm^ |
| Swing Weight, Ounces | 11.094 |
| Swing Weight Calculated | 337.0 |
| Power, RDC | 58 |
| Control, RDC | 41 |
| Manueverability, RDC | 78 |
| Power, Calculated | 2073.9 |
| Head Points | 5.98 |
| Head Weight, % | 47.2% |
| Center of Percussion | 21.1 |
| Dwell Time, ms | 7.31 |
| Efective Stiffness - lbs | 25.3 |
| K, Lb/In | 131.4 |
| Recoil Weight | 154.2 |
| Twist Weight | 233.8 |
| End Weight | 130.7 |
| Tip Weight | 188.4 |
| 9 O'Clock | 90.5 |
| 3 O'Clock | 89.4 |
| Butt End | 140.2 |
| COF, Main | .392 |
| COF, Cross | .321 |
Racquet Quest, LLC
