According to the laws of aerodynamics, a smooth surface provides the least wind resistance. It stands to reason, then, that a smooth-surfaced ball would fly faster and farther through the air than one with a rough surface. If that were true, golf balls would cost a dime a dozen.
But with aerodynamic properties similar to the wing of an airplane, golf balls are perhaps the most complex spheroids in sports today. A golf ball’s performance is largely determined by its dimple pattern, a feature that was developed through astute observation and has evolved over time.
Early golf balls were made of wood. Seeking a softer feel, the Scottish founders of the game stuffed leather pouches with boiled feathers. Hard rubber balls–gutta-perchas–came into the game about 1848. When players noticed that nicks and marks on the surface of the smooth balls caused them to fly farther, ball makers began to mold them with indented or raised surface patterns.
With the introduction of the wound ball at the turn of the century–a rubber core with elongated rubber bands wound around it and a balata cover–dimples became a part of the construction. In the 1950s, the average number of dimples was 336. Today, balls can have as many as 500 dimples covering more than 70 percent of the surface.
Dimple patterns work with the ball’s spin to move the ball through the air. The backspin on the ball is determined by its construction and the club-head angle–its degree of loft–and is a crucial contributing factor to the ball’s trajectory, or flight pattern. As the ball is spinning backward, the dimples create a turbulence pattern in front of the ball and a dragging tail that generates an airfoil much like that of an airplane wing. The air pressure is higher on the bottom of the ball and lowers on the top, thus creating an upward lifting force.
Dimples are, in essence, one of man’s attempts to manage air, and the golf ball is considered a triumph of design. A ball with no dimples will travel 130 yards and behave much like a bullet, with a straight trajectory. A dimpled ball, on the other hand, can travel 280 yards, rising through the air because of its lift.
Dimple design has become quite sophisticated, and patterns are now complex geometric constructions, such as icosahedrons, octahelixes, and cuboctahedrons. Symmetry is a key element because it ensures that no matter how the ball is spinning, it will fly straight.
Designers have become obsessed with fitting more and more of these impressions on the spheroids. Ball designers at Spalding hit on the concept that one way to fit more dimples was to increase the surface area. Because the USGA has a standard that balls can be no smaller than 1.68 inches in diameter, but no restriction on how large a ball can be, the solution was obvious: make a bigger ball.
Most oversize balls measure 1.72 or 1.74 inches in diameter, but that seemingly minute expansion presents yet another contradiction to the accepted laws of aerodynamics–a larger mass moves through the air more slowly–and a debate has ensued over claims of increased distance made by manufacturers of oversize balls. Terry Melvin, vice president of research at Spalding, contends that the increased drag created by the larger ball is compensated for by the increased number of dimples on its surface, which help it fly farther. Spalding markets the Magna line of oversized balls. On the other hand, Wilson’s Carl Scheie says that larger balls provide. no advantage, but rather have greater air resistance.
Frank Thomas, technical director of the USGA, says only that hard-hitting hackers may get more distance from an oversize ball. Marketing claims aside, he considers it a breakthrough’ in design that manufacturers have created a larger golf ball that performs much the same as a traditional one.–D. H. C.
Quantifying The Club
Until now, designers created new golf clubs based on trial and error. The USGA research uses computer analysis to quantify how different club-head designs will perform. The solid object in the form of an ellipsoid, which has the same principal moment inertia as the club head, is superimposed over two different club-head designs in these computer-generated drawings, The ellipsoid helps club designers visualize how different club heads may perform depending on where the ball makes contact on the club face. Club designs can thus be compared from an inertial point of view. Special note to duffers: At this stage, researchers can only tell that clubs will perform differently, but not which design is superior.