Category Archives: Accuracy

String Tension Testers…Friend or Foe?

The StringMeter is a device used to check the tension of an individual string. There are other versions of similar functionality, but this is what we use, and I will start with that.

Interestingly, this device traces its design to a tool that is used to check mainstay tension on a sailing vessel.

It is clear that our devices are well used, so they must be a “friend,” not a “foe”! And to that, I would say yes! The two (2) units shown here are “calibrated” units. One device is “free string,” and the other is “strung string.” These are different scales and very important for accurate information.

String Tension Tester

When we evaluate string or stringing machines, one of the most important values is the string tension with only the main strings installed. Using the “free string” scale, we check every main string and record the number.

Once the racquet is fully strung, we can check some center main strings and center cross strings with the “strung string” scale and see the variation. The difference between the two is the “natural ratio” of the racquet.

In addition to the stringing machine review use of the StringMeter, we also use it to calculate our “accuracy index.”

For this, we use the “strung string” scale and check each main string tension from left to right and every cross string tension from top to bottom and compare the actual numbers to the calculated numbers based on a non-distorted racquet. This spreadsheet shows how accurately the ball will come off of the racquet face.

The “efficiency index” tells us how much the racquet needs to change shape to reach that “index.”  

These are all essential functions of the StringMeter and String Tension Tester from Gamma Sports.

But, what if the StringMeter or other device is used without knowing what it is telling the user?

This is the “foe” part!

This would be the case if a customer with such a device has a racquet strung at say a reference tension of 55 pounds. The customer then uses the method to check the tension and finds that it is not 55 pounds or even close! The customer is not going to be happy!

If the customer knows what to do, they can check the main string tension as soon as they can after stringing, then, later on, to see how much the string has stretched without regard to the reference tension.

It is what it is!

When the racquet is no longer performing it would tell the customer how much the tension can deteriorate before stringing is required.

So, these devices are very useful for individual string tension but no so much for “string bed stiffness,” which is the total string bed as a ball impacts it.

We will look at some of the “string bed stiffness” devices in a future post.

 

 

Head Graphene 360+ Speed MP Lite

The Head Graphene 360+ Speed MP Lite may be the perfect racquet for a player looking for a thin(er) beam, 100 square inch head size, slightly lighter than most MP racquets!

As you will see in the specifications this racquet is about 28 grams (1 ounce) lighter than the MP model, and, just a little more flexible, or better said, less stiff!

Forty-nine point nine percent (49.9%) of the total weight resides toward the head of this racquet, so if you think in terms of “points” it is 0.16 points head light.

Some customization will make this a racquet that you can stay with for a long time. As your skills advance, so can the racquet!

Head Graphene 360+ Speed MP Lite

As I am working on this post I realize how much trouble it is to switch between racquet reviews for comparison so I am including a link to the Head Graphene 360+ Speed Series Comparison.

 

 

ManufacturerHead
Racquet ModelHead Graphene 360+ Speed MP Lite
Reference Tension56 lbs - 25.4 kg
String
Victrex PEEK fiber Experimental 7718
Machine UsedTrue Tension Professional
Static
ASPS, RDC51
ASPS, FlexFour62
Racquet Flex, RDC60 - After stringing
Racquet Flex, FlexFour49
Weight, Grams293
Weight, Ounces10.34
Balance, mm342
Balance, Inch13.46
Length, Cm68.5
Length, Inch26.97
Head Width9.68
Head Length13.06
Head Area, cm2640.8
Head Area, Sq. Inch99.3
Beam Width, mm, Shaft, Center, Tip23, 23, 23
In Plane Stiffness, Pounds/In307.3 Lbs/In.
In Plane Stiffness, Kg/cm 139.4 Kg/cm
Number of Main Strings16
Number of Cross Strings19
Ratio Cross/Mains.624
Main String Grid7.30
Cross String Grid10.62
Density (% of head filled with string).780
Average Cross String Space.559
Average Main String Space.456
Dynamic
Dynamic Tension, Kp, ERT35
Dynamic Tension, Lbs/in195.76
First Moment, Nm.782
Polar Moment323
Torsional Stability15
Swing Weight, Kg/cm2308
Swing Weight, Ounces10.86
Swing Weight Calculated342.7
Power, RDC46
Control, RDC57
Manueverability, RDC81
Power, Calculated 1835.6
Head Points0.16 (negative = head heavy)
Head Weight, %49.9%
Center of Percussion21.0
Dwell Time, ms, No Swing8.91
Efective Stiffness - lbs27.6
K, Lb/In (SBS) RDC163.46
Recoil Weight138.67
Twist Weight205.8
End Weight 105.8
Tip Weight 186.5
9 O'Clock95.1
3 O'Clock94.5
Butt Cap103.0

Head Graphene 360+ Speed S

I think we all know what “Pro and MP” mean but what about “S”?  I am not sure, so we are going to call it “Special”!

The Speed S is indeed special and probably one of the best all-around racquets for 2020!  You will see by the specs why this may be the case but a couple of things stand out.  A 100 square inch head size.  A uniform 16×19 string pattern and 25mm beam producing the stiffness of RDC 64!

The overall weight and swing weight are just right for most advancing players and can be modified when the need arises!  This is really a “players” racquet in disguise!

Head Graphene 360+ Speed S

While I was doing this post I realized how difficult it is to switch between racquet reviews to see a comparison so here is a link to the Head Graphene 360+ Speed Series Comparison.

 

ManufacturerHead
Racquet ModelHead Graphene 360+ Speed S
Reference Tension56 lbs - 25.4 kg
String
Victrex PEEK fiber Experimental 7718
Machine UsedTrue Tension Professional
Static
ASPS, RDC54
ASPS, FlexFour67.5
Racquet Flex, RDC64 - After stringing
Racquet Flex, FlexFour40
Weight, Grams302
Weight, Ounces10.44
Balance, mm328
Balance, Inch12.91
Length, Cm68.5
Length, Inch26.97
Head Width9.68
Head Length13.06
Head Area, cm2641.2
Head Area, Sq. Inch99.3
Beam Width, mm, Shaft, Center, Tip25, 25, 25
In Plane Stiffness, Pounds/In425.2 Lbs/In.
In Plane Stiffness, Kg/cm 192.8 Kg/cm
Number of Main Strings16
Number of Cross Strings19
Ratio Cross/Mains.624
Main String Grid7.35
Cross String Grid9.40
Density (% of head filled with string).749
Average Cross String Space.539
Average Main String Space.453
Dynamic
Dynamic Tension, Kp, ERT37
Dynamic Tension, Lbs/in206.94
First Moment, Nm.764
Polar Moment312
Torsional Stability16
Swing Weight, Kg/cm2296
Swing Weight, Ounces10.44
Swing Weight Calculated324.9
Power, RDC45
Control, RDC57
Manueverability, RDC89
Power, Calculated 1880.4
Head Points4.57 (negative = head heavy
Head Weight, %47.9%
Center of Percussion20.9
Dwell Time, ms, No Swing8.66
Efective Stiffness - lbs29.3
K, Lb/In (SBS) RDC173.08
Recoil Weight141.20
Twist Weight211.83
End Weight 119.7
Tip Weight 182.9
9 O'Clock94.2
3 O'Clock94.2
Butt Cap113.0

Head Graphene 360+ Prestige Tour

When we do the testing and “number taking” for our demo racquets, we try to think as the consumer may think and include comments that may help the consumer make the best decision.

We do not want to make these posts so dull that you go to sleep, but data is essential, so we are going to include it…so stay awake!

Data is particularly relevant to the Prestige Series from Head.

This review is for the Prestige Tour, and it points to the differences between Prestige racquets that may go unnoticed or misunderstood.

The Prestige Tour is a 99 (645 cm²)square inch racquet with an 18 x 19 string pattern. If you have read the post on the Prestige MP, you may wonder, what’s the difference?

You may notice that the Prestige Tour has one (1) fewer cross string. Not a big deal. You may see that the Prestige Tour has one (1) square inch larger head size. Also, not a big deal. What you may not notice is the Prestige Tour has an in-plane stiffness of 400, and the Prestige MP has an in-plane stiffness of 359. That is a big deal! Even with a bigger head and fewer strings, the Prestige Tour has a higher string bed stiffness than the Prestige MP. The higher the in-plane stiffness, the less the racquet will “bend” during impact.

The Prestige Tour is more stiff overall (62 v 58) than the Prestige MP, and the 21.5mm beam contributes to that stiffness.

So, take a look at the numbers for this racquet to see if you can find other exciting differences!

 

 

 

ManufacturerHead
Racquet ModelHead Graphene 360+ Prestige Tour
Reference Tension55 lbs - 24.9 kg
String
Victrex PEEK fiber Experimental 7718
Machine UsedTrue Tension Professional
Static
ASPS, RDC55
ASPS, FlexFour71
Racquet Flex, RDC62 - After stringing
Racquet Flex, FlexFour49
Weight, Grams325
Weight, Ounces11.46

Balance, mm327
Balance, Inch12.87
Length, Cm68.6
Length, Inch27.008
Head Width9.56
Head Length13.12
Head Area, cm2635.3
Head Area, Sq. Inch98.5
Beam Width, mm, Shaft, Center, Tip21.5, 21.5, 21.5
In Plane Stiffness, Pounds/In400.0 Lbs/In.
In Plane Stiffness, Kg/cm181.4 Kg/cm
Number of Main Strings18
Number of Cross Strings19
Ratio Cross/Mains.690
Main String Grid7.81
Cross String Grid10.00
Density (% of head filled with string).724
Average Cross String Space.526
Average Main String Space.396
Dynamic
Dynamic Tension, Kp, ERT35
Dynamic Tension, Lbs/in195.7
First Moment, Nm.819
Polar Moment334
Torsional Stability18
Swing Weight, Kg/cm2316
Swing Weight, Ounces11.15
Swing Weight Calculated347.5
Power, RDC46
Control, RDC55
Manueverability, RDC76
Power, Calculated 1929.2
Head Points4.88 (negative = head heavy)
Head Weight, %47.7%
Center of Percussion20.8
Dwell Time, ms, No Swing8.58
Efective Stiffness - lbs29.1
K, Lb/In (SBS) RDC176.3
Recoil Weight150.9
Twist Weight222.7
End Weight 131.7
Tip Weight 195.3
9 O'Clock100.7
3 O'Clock101.4
Butt Cap124.0

Head Graphene 360+ Prestige MP

We are finally getting the time to work on these marvelous new racquets from Head! In this case, it is the Head Graphene 360+ Prestige MP.

The Prestige is a fascinating series for Head, but I think it is often overlooked when considering a new racquet purchase. I believe the “performance” category excludes a lot of players that could very well use this racquet if it is appropriately set up. Secondly, I think players have the mistaken feeling that the Prestige series is too stiff!

I believe you will see by the following specifications that neither are necessarily true!

The Prestige series is, in my opinion, the best looking new racquet in a long time. However, in a performance racquet, what does “looks” have to do with it? In my opinion, a lot!

This racquet is the “true” 98 square inch (630 cm²) head size with an 18 x 20 string pattern and, of course, the excellent “cap system” that contributes to the performance of this racquet. You will see in the specifications that the swing weight is on the “light” side, allowing for customization to suit any player.

Head is now including a CPI, “Control Power Index,” and this racquet ranks as a CPI 200 compared to the Prestige Pro at CPI 300. The difference is a function of the tight string pattern and flex. The thin 20mm beam throughout contributes to the nice flex of RDC 58 after stringing.

A lower CPI indicates to us that the racquet will do no more than you ask of it! If you want the ball to go fast you swing harder! The racquet will not force to to “fear” your stroke!

If you are considering an 18 x 20 string pattern this racquet should be right at the top of the list.

Our COF numbers are quite good which indicate a positive contribution to “spin” considering the tight string pattern.

 

ManufacturerHead
Racquet ModelHead Graphene 360+ Prestige MP
Reference Tension55 lbs - 24.9 kg
String
Victrex PEEK fiber Experimental 7718
Machine UsedTrue Tension Professional
Static
ASPS, RDC58
ASPS, FlexFour67
Racquet Flex, RDC58 - After stringing
Racquet Flex, FlexFour39
Weight, Grams337
Weight, Ounces11.89

Balance, mm313
Balance, Inch12.32
Length, Cm68.6
Length, Inch27.008
Head Width9.47
Head Length13.05
Head Area, cm2625.9
Head Area, Sq. Inch97
Beam Width, mm, Shaft, Center, Tip20, 20, 20
In Plane Stiffness, Pounds/In359 Lbs/In.
In Plane Stiffness, Kg/cm162 Kg/cm
Number of Main Strings18
Number of Cross Strings20
Ratio Cross/Mains.653
Main String Grid7.50
Cross String Grid10.25
Density (% of head filled with string).792
Average Cross String Space.513
Average Main String Space.417
Dynamic
Dynamic Tension, Kp, ERT37
Dynamic Tension, Lbs/in206.9
First Moment, Nm.803
Polar Moment326
Torsional Stability15
Swing Weight, Kg/cm2311
Swing Weight, Ounces10.97
Swing Weight Calculated330.2
Power, RDC39
Control, RDC62
Manueverability, RDC79
Power, Calculated 1749.9
Head Points9.29 (negative = head heavy)
Head Weight, %45.7%
Center of Percussion21.0
Dwell Time, ms, No Swing8.35
Efective Stiffness - lbs29.0
K, Lb/In (SBS) RDC185.9
Recoil Weight160.4
Twist Weight226.8
End Weight 149.2
Tip Weight 189.9
9 O'Clock98.2
3 O'Clock98.8
Butt Cap140.3