Measuring the Optimal String Tensions of String Materials Under Different Conditions

Abstract

Almost all of the previous research conducted on the effect of environmental conditions on the strings of a tennis racket (i.e. temperature and relative humidity) has taken place in a laboratory setting that does not adequately capture the environment experienced by players. Therefore, this study examines the effects of temperature and relative humidity on tension and stiffness of a variety of string types, as well as on how much tension will decrease over time, through experimentation using an array of string materials. In the experimental trials conducted for this study, natural gut string showed the highest amount of loss in tension at 3 hours post-stringing, with a loss of 28-34%. Nylon was approximately 18-22% and polyester lost around 11-14%. When comparing warm, humid conditions (30 degrees Celsius / 80% relative humidity) to cool, dry conditions, the tension lost after 3 hours increased by 40%-55%, and the rate of creep increased for all string types: polyester by roughly 1.8 times; nylon by roughly 2.3 times; and natural gut by approximately 3.1 times due to these conditions. In addition, elastic moduli values measured at high humidity were lower for: polyester (12% drop); nylon (19% drop); and natural gut (31% drop). Consequently, based on the data collected in this study, it is recommended that players adjust the tension of their string by +3-5 lbs in humid climates and -2 to -3 lbs in hot, dry climates to ensure that their racquets maintain consistent performance. Research supports the concept that String Tension is determined by playing Environment. Players and Stringers can use this Data to make informed String Tension adjustments specific to their needs; therefore, improving the optimal Rack and String functionality, extending the usable life of the Strings in relation to String Adjustment Cost.