Category Archives: Tensile Strength
A Picture is Worth a 1000 Words?
Yesterday @ the World Headquarters was full of interesting stringing! So we decided to do some testing of some of the strings that were just waiting to be broken!
The chosen strings are Ashaway MonoGut ZX Pro 17, Tecnifibre Triax 17, and Volkl V-Star 18—three totally different materials. Our purpose is to determine a string’s properties before it goes into a tennis racquet. Our testing quantifies these properties, and then the “feel” component comes from the player.
A 1000 Words?
We normally do not do more than two (2) overlays because it is a little messy, but these strings begged to be compared, so here it is!
Our Questron can cycle automatically, so the stop points are pretty precise. All strings are cycled from two (2) pounds to fifty (50) pounds and then until they fail or ultimate tensile strength (UTS).
In the Displacement axis (X), the shorter the distance in mm to 50 ponds, the stiffer the string. The straighter the line is to fail, the more consistent the feeling until failure.
The testing confirms that Tecnifibre Triax does contain some stiffer fibers. The other strings are monofilaments, so there are no fibers.
Racquet Quest uses a bunch of each of these strings for obvious reasons and, of course, depending on the player.
Monofilament Material Comparison
Most monofilament tennis strings are polyester, a blend of polyester, or PEEK.
As you know, we believe there is no wrong string, just wrong applications. The graph will show the comparative stiffness of three (3) materials. The string is pulled at a rate of 1mm per second. The resultant spreadsheet for this particular test is about 5300 rows long.
With our spreadsheet, we have access to every mm of data. Maybe sometime we can post some of the individual data points.
Blast is polyester, V-Star is a unique blend of material (I do not know what it is), and MonogutZX is PEEK (polyetheretherketone).
The graph shows the cycle from 0 to 50 pounds three (3) times, then to failure (UTS). The quicker (shorter distance) the string reaches the 50-pound mark, the stiffer it is. MonoGut ZX did not fail in the 180mm excursion. You can see, in this case, the stiffer string fails at a higher force but shorter excursion.
Stiffer strings deliver less power and have a higher shock value. The midrange stiffness shows exactly what would be expected, and the softest string also indicates expected results.
Now for some GOOD news!
It seems that I am recovering from this cold or whatever it is, so now we can return to a relatively normal schedule!
I want to start with some comments from Willie B. regarding string. After you read Willie’s comments, we can talk about the string and why it does what it does: to allow players of any level to play without discomfort.
Here is from Willie:
“FYI, my inability to play tennis more than 1-twice a week due to the pain for over 4 years impacted my game. The last time I was ranked was 5.0, but now at 47, probably more like 4.5 (No tournament for the previous 5 years)
The good news is that with the feel of those strings, I can hit back (I practiced with a top player last Sunday, and he even felt it as I am not scared to go big… I have played with him for over a decade)”.
Willie’s racquet technician is Henry Hamels of String MD. Thank you, Henry, for sharing!
If you have not already guessed, the string material is PEEK, polyetheretherketone, which was marketed as Zyex by Ashaway under the MonoGut ZX and ZX Pro models! This monofilament format offers an alternative to stiffer monofilament strings while providing, in most cases, better performance and durability!
- The raw material is expensive.
- Some
racquet techniciansstringers simply don’t know how to handle PEEK.- The high elongation of PEEK is a surprise to the first-time stringer.
- Marketing hype is not strong.
- Very few players and stringers know about this alternative.
- See Marketing Hype above!
- Stringers may have had a poor experience before and are wary.
- The material does not change shape; therefore, knots are not as tiny as some stringers prefer.
- PEEK will “tighten” its own knots.
- Beginning stringers may over-tighten the knot, causing failure…never to be used again!
- Currently, the material is available in two (2) colors, tan and black.
- MonoGut ZX is 16 gauge
- MonoGut ZX Pro is 17 gauge
Depending on the player’s tennis intentions, we may start them on PEEK at age nine (9) but no later than twelve (12).
Thank you, Willie, for your comments!
To see if this material will benefit your game now and for the long term, ask your racquet technician.
- Please text us if you need additional information: 407.491.4755
- Comment on this site, and we will respond to specific questions.
- If, based on our player history, your application may not be the best, we will tell you.
- Very beginning players and those players experimenting with various strokes creating mis-hits need to be recognized.
An Inside Look at String Evaluation
In this series, we will look at the various characteristics of tennis string without the tennis racquet!
Racquet Quest evaluates every string we use plus strings submitted from other sources. These evaluations are “No Prep” and “Prep”, which simply means the Prep string has been pre-stretched in the entire length. It has not been through a tennis racquet…yet!
The following images represent a string that has not been “prepped.” After these plots are fully understood we will do the same string in the”prepped” format to see if there is a difference.
Ultimate Tensile Strength
What we notice immediately is the string is very “soft” as seen in the deflection of 47.8 mm to reach 50 pounds. Also, the elasticity, the ability to recover to the original length, is fairly low.
The area under the 50-pound and 47.8 mark is the stress/strain curve that shows how the string behaves in three (3) cycles. The load and number of cycles can be changed.
The long run (linearity) from the 50-pound mark to failure is quite good and suggests consistency.
The UTS, the ultimate tensile strength, of 127.1 pounds is good for this thin string.
The following plot shows the knot strength of this string.
Knot Strength
This plot is overlayed on the previous image so a quick comparison can be made. It is common for knot strength to be lower than un-knotted string. Knot strength is primarily important to the person tying the knot. Knots rarely fail after they are successfully tied. Pulling a knot too tight or jerking can break a knot.
This plot says to us that this string needs to be handled carefully when it comes to knots! We would expect a knot strength of at least 80 pounds for typical monofilament strings, however, if this string exhibits extraordinary play characteristics anyone can learn to tie the knots!
Based on this information we would suggest this string for a player looking for extraordinary comfort, power, and relatively short life!
Racquet Quest, LLC
