Category Archives: String
All string information
Questron Cycle Update
Every string that enters the World Headquarters of Racquet Quest goes through the Questron cycle. We have posted images of the product of the cycle, but not the entire process that the Questron goes through to create these posts.
The following video is the entire process from start to post. We look forward to your comments!
If you have a string, or strings, that you would like to know more about, please let us know. We may have already put them through the Questron Cycle.
I mistakenly said “Z” axis when I meant “X” axis, if you caught it.
NG Strings – Part Two: Natural Gut Knot Strength
Any string that goes into a tennis racquet is, at some point, going to be tied off using a knot. Creating a string knot is normally not an issue, however, some strings are more sensitive to this process than others.
This plot will show the relative difference between gauges, and other properties. We can see that NG17 gauge did not quite make it to the stress/strain ceiling of 50 pounds. That is why there is only a single line while the other two (2) go through the cycle before the knot fails.
This is a tough test for natural gut due to the coefficient of friction (COF) being pretty high meaning the overlapping strings are like sawing at each other as the knot is being pulled tight. The knot strengths in the 60 pound range are suitable and will not, typically, be a problem. Be very careful with values less than that, however.
Natural Gut Knot Strength
And, while we are talking about knots, we need to consider the best practices for tying off other strings on natural gut. The best practice is don’t! Find a grommet that can be suitable for tying off another material type on itself…not the natural gut. Obviously if the entire string bed is natural gut it is a good idea to find a suitable tie off on a cross string.
There are other considerations when typing off on natural gut and we will have look at these in a future post.
The power potential of the NG Strings has beed added to the String Power Potential page and can be seen here.
Just type in NG Strings in the search field if you don’t feel like scrolling!
NG Strings
Several months ago we tested some small samples of NG natural gut string. The results were not exciting so the data was not published.
Recently we tested some new versions of NG Strings, the PROV5+, and have some results to post.
First, the packaging is top notch.
Second, the two (2) 12m lengths per set is perfect, in our opinion, since all racquets should be strung using two (2) pieces of string, no one piece or ATW. There may be a manufacturing component to the 2 piece decision, also.
The “squiggles” we see in the two (2) NG Strings may be the tiny changes in the bonding agent(s) that occurs under load. We have seen this in some early Luxilon gut. We refer to it as a “break-in period”. Pre-stretching the entire piece length will reduce the break-in period.
Third, the gauge is much more consistent than previous samples.
This initial post will include stress/strain and ultimate tensile strength plots compared to Babolat VS Touch 17, our most used natural gut.
The first plot is UTS:
Natural Gut UTS
This visual tells the story but if you want the numbers they are at the failure end of each string. The stress/strain cycle shows the relative “softness” of each string. The higher the deflection the softer the string, so NG16 is the stiffest of the three and NG 17 is the softest.
We will be adding Knot Strength so check back soon the see how each string reacts to knots!
We will do several other tests before the string goes into a racquet for player feedback.
In summary this version shows tremendous improvement over the first version we tested… give it a try.
Accuracy Index…What is it?
For several years, Racquet Quest has been testing racquets we have strung for an “Accuracy Index.” Click here to see an example, and then we will discuss it.
For several years, Racquet Quest has been quantifying racquet string bed behavior using our internally developed Accuracy Index. This post was drafted in 2019 but not posted util now. Why now? Players, and us, are even more frustrated with the lack of quality racquet preparations than we were in 2019! We are seeing more and more really bad stuff happening so this post may be a way to address the bad stuff and do better!
The first graph presents the relative stiffness of the main and cross string arrays, as well as the average composite stiffness. On the following page, the Accuracy Index data grid provides a segmented view of the string bed, with each color-coded cell corresponding to a specific impact zone.
This grid allows us to analyze local stiffness variations, where, for example, light blue cells typically correlate with premature failure points in topspin-oriented play. The example shown references a standard 16×19 string pattern, but the analytical framework is applicable to any string configuration.
Why does the Accuracy Index matter?
In performance terms, control is effectively a function of predictability. That is, the extent to which the string bed returns the ball along an expected trajectory with minimal variability. The Accuracy Index quantifies this by comparing actual deflection characteristics across the bed to idealized stringbed behavior. Higher accuracy values imply lower angular deviation and more consistent ball exit vectors.
We also report an Efficiency Index, which assesses how effectively the stringing process preserved the frame’s intended geometric and mechanical properties. A lower efficiency score (e.g., 71) indicates that the racquet had to internally redistribute loads—compensating for distortions incurred during stringing. This can result in non-uniform string tensions and unintended stiffness profiles across the bed, reducing both playability and predictability.
At Racquet Quest, our stringing systems utilize frame stabilization techniques that eliminate distortion during tensioning. As a result, our stringbeds exhibit minimal deviation from target parameters, allowing both Accuracy and Efficiency indices to remain at consistently elevated levels.
Implications for Racquet Technicians
Regardless of the equipment used, technicians can leverage the Accuracy Index as a diagnostic tool to identify inconsistencies introduced during stringing. Adjustments to clamping sequences, pull timing, frame support, or pre-stretch protocols can measurably improve stringbed linearity and reduce compensatory distortion.
In essence, a higher Accuracy Index isn’t just a number—it’s an indicator of a racquet’s ability to perform as engineered, shot after shot.
Racquet Quest, LLC
