String Tension:
There are two ways to string your racquet for power, and two ways to string for control. Both thin strings and low string tension make the stringbed more resilient, to generate greater "trampoline effect" and more power. Conversely, thick strings and high tension make the stringbed stiffer, and the flatter surface aids ball control.
So does string gauge really matter? After all, you can make any string, thick or thin, tighter or looser. Or does tension really matter, since you can choose a string that's thinner or thicker?
Yes to both questions, because there are other factors contributing to power and control besides the trampoline effect, and other considerations besides power and control.
Many of us are concerned with durability, from a number of different standpoints. First and most obvious is the cost of replacing strings that have either broken or lost their tension. Second is the probability of a lost point every time a string breaks in the middle of a rally. Third is the inconvenience of getting the stringing done, and perhaps being without your favorite (or only) racquet for a time.
Thicker strings are more durable than thinner ones of similar construction, but tension presents a more complex picture. If you string at high tension and you're a really hard hitter, then you're probably going to pop a lot of strings, and the ones that don't pop will lose tension rapidly. If you string at high tension and you're a touch player, breakage won't be a big problem, and tension loss will be slower. If you string at really low tension, you won't pop a lot of strings, and tension loss won't be a problem, but you may wear them out by abrasion, because at low tension the strings tend to saw back and forth against each other.
The molecules in racquet string fibers tend to be coiled up when they're under no tension, and these coils get straightened as the string is stretched. After the string has been under tension for a while, the molecules take a "set" in their straightened configuration and stop trying to spring back to their original shape. That's what causes tension loss. Because thin strings have to be stretched further than thick ones in order to achieve the same tension, they are more susceptible to tension loss.
But thin strings have several advantages as well. They dig a bit deeper into the surface of the squash ball, generating better traction for more spin control. They create less wind resistance, allowing the racquet to be swung faster. Finally, they weigh less, which should also boost swing speed and racquet maneuverability. (I weighed sets of 17 and 18 gauge strings of similar construction, and the difference was 1.82 grams, or 15%-not a huge difference, but maybe enough to make a difference.)
Thin strings and thick strings feel different at equal tensions. You might think that the thinner string would feel looser, but it doesn't always work that way. Trampoline effect is a function of how much further those molecular coils can stretch when the ball hits the string. Because the coils are already stretched pretty straight in thin string, there is less resilience left in them. So to attain a comparable "feel," you actually have to tension the thinner string a bit lower than the thicker one.
Here's a quick summary:
Thin strings provide more trampoline power, deeper ball penetration, and offer lower wind resistance and weight, while thick strings offer greater control stiffness and durability. High stringing tension provides greater control stiffness, but is more susceptible to "catastrophic" breakage, while low tension provides greater trampoline power, and is subject to more abrasion failures.
David Palmer uses Powernick 18 Red at 27-28 lbs (depending on the conditions).
