Category Archives: Tension
How’s the shape of your string?
Is it round, square, hexagonal, octagonal, triangular, or something else?
The string pictured here is square. The dimension across the flat sides is roughly .048 inches/1.22mm, which means the largest dimension is about .063 inches/1.6mm but due to the rounded edges it is less than that. The wear is happening on the “flat” side (.048/1.22),
A flat-sided string shape can create some issues when trying to achieve consistent string tension.
This is expected because the string will want to align with the flat side, not the edges. This may cause the string to twist and create added friction when tensioning.
So, we can expect the “edges” to be exposed to the ball, and the “edges can create friction on the ball, which causes rotation!
Yea! How much and for how long is hard to know.
I believe it is safe to say “square” is a good “shape” for your string to be in for polyester monofilaments which we are looking at here.
Head Radical MP 2023
You have seen the pretty pictures; now see the specs of this new Radical series!
We are starting our property review with the Head Radical MP 2023. The MP version will probably be the most popular due to the very lovely weight and “player” style head size of 98 inches!
As you look at the following specifications you may notice the addition of some “numbers”, specifically “beam width”.
We have been taking this number for many years but now believe it is time to expose it to you, the readers.
Briefly, the beam height-to-width ratio contributes to in-plane stiffness which is important for consistent string bed stiffness (SBS).
|Racquet Model||Head Radical MP 2023|
|String||MonoGut ZX Pro|
|Machine Used||True Tension Professional|
|String Bed Stiffness - RDC||53.0 Units|
|String Bed Stiffness -FlexFour||64.9 pounds|
|String Bed Stiffness - SBS||51.8 pounds|
|String Bed Stiffness - ERT||35 Kg/Cm|
|Racquet Flex, RDC||65 - After stringing|
|Racquet Flex, FlexFour||44.5|
|Racquet - In Plane Stiffness||379.7 lbs/Inch|
|Head Area, cm2||623.0|
|Head Area, Sq. Inch||96.7|
|Beam Height @ Grip, mm||21.0|
|Beam Height @ Mid, mm||22.5|
|Beam Height @ Tip||20.5|
|Beam Width @ Grip, mm||12.5|
|Beam Width @ Throat, mm||11.5|
|Beam Width @ Mid, mm||12.8|
|Beam Width @ Tip, mm||12.8|
|Number of Main Strings||16|
|Number of Cross Strings||19|
|Main String Grid||7.18|
|Cross String Grid||9.44|
|Density (% of head filled with string)||69.6%|
|Average Cross String Space||.494|
|Average Main String Space||.449
|Dynamic Tension, Kp, ERT||35|
|Dynamic Tension, Lbs/in||195.76|
|First Moment, Nm||.841|
|Swing Weight, Kg/cm2||331|
|Swing Weight, Ounces||11.68|
|Swing Weight Calculated||361.5|
|Head Weight, %||48.5%|
|Center of Percussion||21.1|
|Dwell Time, ms||8.74|
|Efective Stiffness - lbs||29.2|
Our Questron in Action!
As you know, Racquet Quest is a data-driven business, and data requires numbers. To generate those numbers, we have designed and built several devices.
One device is the Questron!
The Questron is used to test every string we receive, and the data is compiled to understand where that particular string fits.
So, instead of talking about it we have included a short video!
Thank you for watching our Questron in Action! If you have a question, or a particular string of interest, please let us know. We may have already taken the data! On GASP.network there are many graphs of previous tests. GASP.network is a membership ($40.00 one time) site.
What’s The Difference?
As tennis players, you must constantly ask “what’s the difference” when it comes to tennis racquets and string! Well, as racquet technicians we ask the same questions!
This post is intended to showcase the differences of string in testing, not playing, however, some of the data may be noticeable to the player in certain situations.
What this graph shows us, in addition to our trying to save a tree by printing on the back of previously used paper, is that each of these stings will provide almost the same performance. This is indicated by the curve and how closely related the strings are.
The differences you do see here can be attributed to the gauge, or diameter, of the string, with the largest diameter (Tour Bite) having the highest tensile strength. Down in the “hitting” displacement range (way below the 39.9mm!), there is very little difference.
The tensile strength can be a factor as the string begins to “notch” or otherwise come apart. Each of the strings in this graph is monofilament so notching would be the failure mode in a racquet.
What Can Pictures Tell Us About String?
It is said that “a picture is worth a thousand words,” which may be true as long as the picture tells a story.
This story is about natural gut string, and the pictures will show what we can achieve, informationally, with our testing equipment. The two (2) strings are Babolat VS Touch 17 and Luxilon Natural Gut 125.
Our Questron software scales the images to suit the data so the graphs will not be the same size.
Our testing loads the string from 0 pounds force to 50 pounds and back to zero then up to 50 pounds three (3) times. This is the “stress/strain” curve. Fifty (50) pounds is arbitrary and because we are using the same methodology for all string materials it is a good number. The closer these lines are together the better.
The farther it takes to reach 50 pounds the “higher elongation” the string is. In this case it is about 44mm.
The important property of this string is the linearity! That is the “straightness” of the line from beginning to end. This indicates predictability, stability, and consistency.
This picture tells us the tensile strength and the knot strength. In this case the knot strength is 52.3 pounds and takes a stretch to very close to 60mm before failure.
What is, probably, the first thing you notice about this “picture”? Could it be the squiggly lines? What could be causing this?
We believe it is the “break-in period” players associate with Luxilon gut! We have heard it from the players but have not been able to “see” it! It could be the bonding agents realigning as the load is applied.
You will notice a couple of things: the similarity of the “stress/strain” curve and the displacement to “knot strength” of the two strings. This string will feel a little less “soft” than the Babolat VS Touch 17. The linearity is quite good up to failure.
So, based on these pictures, could you make a recommendation? If so, let us hear them!