Category Archives: String – Old
Old string information
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 FXP is a string that seems to be largely overlooked and I am surprised after seeing the results of the installation and testing!
|String Name||Category||Gauge||Ultimate Tensile Strength/Lbs||Knot Strength/Lbs||Country of Origin|
|Head FXP||Multifilament - Nylon||17||165.9||93.4||Japan|
Both the tensile strength and knot strength are exceptional and the graph shows that this string is very “elastic” which is a good thing for tennis racquet string but sometimes just not considered.
The area under the solid red lines is considered a stress-strain curve and indicates the “elasticity” of string by how close the lines fit from 0 to 50 three (3) times. A perfectly elastic material would be one line even though it went through three (3) cycles. What you see here is quite good and one of the reasons it is the winner!
Racquet Quest is going to add a “winner” of the week to our website as a way to develop a fun way to look at string!
Each week we will select a string that has exhibited outstanding properties from one of five (5) major categories:
- Synthetic Gut
- Natural gut
- PEEK Monofilament
- Polyester Monofilament
The winning string must have been installed in the most recent week either in a client or demo racquet.
We will include as much information as possible including graphs and the country of origin.
We will try to post “And the Winner is…” on Friday so take look!
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!
For the past fifteen (15) years or so, most string discussion centered on polyester. By now, you know our position on polyester, so we won’t go through that again right now. What we will go through right now is the difference(s) in a polyester string!
PET, polyethylene terephthalate, is the standard “material” in the better quality polyester string, so how can there be so many different versions of the same material?
Can you say “additives”? Luxilon has made it part of their brand to use acronyms for materials in each string’s description. ALU, for example, is aluminum, Timo is titanium/molybdenum, and I don’t know what 4G is.
So let’s take a look at the differences in a couple of polyester stings. Shown here are two (2) polyester strings, Luxilon ALU Power and Volkl V-Star. You can see the difference in stiffness between them, the V-Star being “softer,” but what you can’t see is the V-Star package does not say “co-polyester” but instead Co-Polymer!
We know “co” is two or more and “poly” is many, so how many of anything does any material have in it? We may never know and probably shouldn’t care as long as we have the presented data.
What can we see from this graph?
- ALU Power reaches 50 lbs quicker (stiffer)
- ALU Power exhibits good elasticity
- V-Star is more linear (consistency)
- V-Star has a greater tensile strength
- V-Star is softer (takes longer to reach 50 lbs)
How would a player know this by just looking a the package? I am not sure! Adding the word “soft” or “comfort” or “feel” may persuade a player to try the string, but what if a better decision could be made before spending the time and money?