Golf ball
A golf ball is a ball designed to be used in golf. Under the rules of golf, a golf ball has a mass no more than, has a diameter not less than, and performs within specified velocity, distance, and symmetry limits. Like golf clubs, golf balls are subject to testing and approval by The R&A and the United States Golf Association, and those that do not conform with regulations may not be used in competitions .
History
Early balls
It is commonly believed that hard wooden, round balls, made from hardwoods such as beech and box, were used for golf from the 14th through the 17th centuries.Though wooden balls were no doubt used for other similar contemporary stick and ball games, there is no definite evidence that they were actually used in golf in Scotland. It is equally likely, if not more so, that leather balls filled with cows' hair were used, imported from the Netherlands from at least 1486 onward.
Featherie
Then or later, the featherie ball was developed and introduced. A featherie, or feathery, is a hand-sewn round leather pouch stuffed with chicken or goose feathers and coated with paint, usually white in color. A standard featherie used a gentleman's top hat full of feathers. The feathers were boiled and softened before they were stuffed into the leather pouch. Making a featherie was a tedious and time-consuming process. An experienced ball maker could only make a few balls in one day, so they were expensive. A single ball would cost, which is equivalent to US$10–20 today.Guttie
In 1848, the Rev. Dr. Robert Adams Paterson invented the gutta-percha ball. The guttie was made from dried sap of the Malaysian sapodilla tree. The sap had a rubber-like feel and could be made spherical by heating and shaping it in a mold. Because gutties were cheaper to produce, could be re-formed if they became out-of-round or damaged, and had improved aerodynamic qualities, they soon became the preferred ball for use.Accidentally, it was discovered that nicks in the guttie from normal use actually provided a ball with a more consistent ball flight than a guttie with a perfectly smooth surface. Thus, makers began intentionally making indentations into the surface of new balls using either a knife or hammer and chisel, giving the guttie a textured surface. Many patterns were tried and used. These new gutties, with protruding nubs left by carving patterned paths across the ball's surface, became known as "brambles" due to their resemblance to bramble fruit.
Wound golf ball
The next major breakthrough in golf ball development came in 1898. Coburn Haskell of Cleveland, Ohio, had driven to nearby Akron, Ohio, for a golf date with Bertram Work, the superintendent of the B.F. Goodrich Company. While he waited in the plant for Work, Haskell picked up some rubber thread and wound it into a ball. When he bounced the ball, it flew almost to the ceiling. Work suggested Haskell put a cover on the creation, and that was the birth of the 20th-century wound golf ball that would soon replace the guttie bramble ball. The new design became known as the rubber Haskell golf ball.For decades, the wound rubber ball consisted of a liquid-filled or solid round core that was wound with a layer of rubber thread into a larger round inner core and then covered with a thin outer shell made of balatá sap. The balatá is a tree native to Central and South America and the Caribbean. The tree is tapped and the soft, viscous fluid released is a rubber-like material similar to gutta-percha, which was found to make an ideal cover for a golf ball. Balatá, however, is relatively soft. If the leading edge of a highly lofted short iron contacts a balatá-covered ball in a location other than the bottom of the ball a cut or "smile" will often be the result, rendering the ball unfit for play.
Addition of dimples
In the early 1900s, it was found that dimpling the ball provided even more control of the ball's trajectory, flight, and spin. David Stanley Froy, James McHardy, and Peter G. Fernie received a patent in 1897 for a ball with indentations; Froy played in the Open in 1900 at the Old Course at St. Andrews with the first prototype.Players were able to put additional backspin on the new wound, dimpled balls when using more lofted clubs, thus inducing the ball to stop more quickly on the green. Manufacturers soon began selling various types of golf balls with various dimple patterns to improve the length, trajectory, spin, and overall "feel" characteristics of the new wound golf balls. Wound, balatá-covered golf balls were used into the late 20th century.
Modern resin and polyurethane covered balls
In the mid-1960s, a new synthetic resin, an ionomer of ethylene acid named Surlyn was introduced by DuPont as were new urethane blends for golf ball covers, and these new materials soon displaced balatá as they proved more durable and more resistant to cutting.Along with various other materials that came into use to replace the rubber-wound internal sphere, golf balls came to be classified as either two-piece, three-piece, or four-piece balls, according to the number of layered components. These basic materials continue to be used in modern balls, with further advances in technology creating balls that can be customized to a player's strengths and weaknesses, and even allowing for the combination of characteristics that were formerly mutually-exclusive.
Titleist's Pro V1, Taylormade TP5, and Callaway Supersoft exemplify modern advancements in golf ball aerodynamics. The Titleist Pro V1 boasts a tightly wound 388-dimple design, minimizing gaps between dimples for better aerodynamics. On the other hand, the Taylormade TP5 features a combination of circular and hexagonal dimples to reduce drag. Lastly, Callaway balls showcase a sleek, completely hexagonal design for straighter ball flights.
Liquid cores were commonly used in golf balls as early as 1917. The liquid cores in many of the early balls contained a caustic liquid, typically an alkali, causing eye injuries to children who happened to dissect a golf ball out of curiosity. By the 1920s, golf ball manufacturers had stopped using caustic liquids, but into the 1970s and 1980s golf balls were still at times exploding when dissected and were causing injuries due to the presence of crushed crystalline material present in the liquid cores.
In 1967, Spalding purchased a patent for a solid golf ball from Jim Bartsch. His original patent defined a ball devoid of the layers in earlier designs, but Bartsch's patent lacked the chemical properties needed for manufacturing. Spalding's chemical engineering team developed a chemical resin that eliminated the need for the layered components entirely. Since then, the majority of non-professional golfers have transitioned to using solid core golf balls.
The specifications for the golf ball continue to be governed by the ruling bodies of the game; namely, The R&A, and the United States Golf Association.
Biodegradable golf balls
The early wood, featherie, and guttie balls were made from biodegradable materials. However, as a result of the Industrial Revolution and the invention of vulcanization, balls increasingly became made from non-biodegradable materials. During the late 2000s, a few new biodegradable golf balls came into the market, including some made from wood, lobster shells, or cornstarch.Regulations
The Rules of Golf, jointly governed by the R&A and the USGA, state in Appendix III that the diameter of a "conforming" golf ball cannot be any smaller than, and the weight of the ball may not exceed. The ball must also have the basic properties of a spherically symmetrical ball, generally meaning that the ball itself must be spherical and must have a symmetrical arrangement of dimples on its surface. While the ball's dimples must be symmetrical, there is no limit to the number of dimples allowed on a golf ball. Additional rules direct players and manufacturers to other technical documents published by the R&A and USGA with additional restrictions, such as radius and depth of dimples, maximum launch speed from test apparatus and maximum total distance when launched from the test equipment.In general, the governing bodies and their regulations seek to provide a relatively level playing field and maintain the traditional form of the game and its equipment, while not completely halting the use of new technology in equipment design.
Until 1990, it was permissible to use balls of less than 1.68 inches in diameter in tournaments under the jurisdiction of the R&A, which differed in its ball specifications rules from those of the USGA. This ball was commonly called a "British" ball, while the golf ball approved by the USGA was simply the "American ball". The smaller diameter gave the player a distance advantage, especially in high winds, as the smaller ball created a similarly smaller "wake" behind it.
Aerodynamics
When a golf ball is hit, the impact, which lasts less than a millisecond, determines the ball's velocity, launch angle and spin rate, all of which influence its trajectory and its behavior when it hits the ground.A ball moving through air experiences two major aerodynamic forces: lift, and drag. Dimpled balls fly farther than non-dimpled balls due to the combination of these two effects.
File:Drag coefficient on a sphere vs. Reynolds number - main trends.svg|upright=1.75|right|thumb|Drag coefficient Cd for a sphere as a function of Reynolds number Re, as obtained from laboratory experiments. The dark line is for a sphere with a smooth surface, while the lighter line is for the case of a rough surface. There is a range of fluid velocities where a rough-surfaced golf ball experiences less drag than a smooth ball. The numbers along the line indicate several flow regimes and associated changes in the drag coefficient:
•2: attached flow and steady separated flow,
•3: separated unsteady flow, having a laminar flow boundary layer upstream of the separation, and producing a vortex street,
•4: separated unsteady flow with a laminar boundary layer at the upstream side, before flow separation, with downstream of the sphere a chaotic turbulent wake,
•5: post-critical separated flow, with a turbulent boundary layer.
First, the dimples on the surface of a golf ball cause the boundary layer on the upstream side of the ball to transition from laminar to turbulent. The turbulent boundary layer is able to remain attached to the surface of the ball much longer than a laminar boundary with fewer eddies and so creates a narrower low-pressure wake and hence less pressure drag. The reduction in pressure drag causes the ball to travel further.
Second, backspin generates lift by deforming the airflow around the ball, in a similar manner to an airplane wing. This is called the Magnus effect. The dimples on a golf ball deform the air around the ball quickly causing a turbulent airflow that results in more Magnus lift than a smooth ball would experience.
Backspin is imparted in almost every shot due to the golf club's loft. A backspinning ball experiences an upward lift force which makes it fly higher and longer than a ball without spin.
Curvature of the ball flight occurs when the clubface is not aligned perpendicularly to the club direction at impact, leading to an angled spin axis that causes the ball to curve to one side or the other based on difference between the face angle and swing path at impact. Because the ball's spin during flight is angled, and because of the Magnus effect, the ball will take on a curved path during its flight. Some dimple designs claim to reduce the sidespin effects to provide a straighter ball flight.
Other effects can change the flight behaviour of the ball. Factors such as dynamic lie, strike location if the player is using a wood due to the curved face, and external factors such as wind and debris.
To keep the aerodynamics optimal, the golf ball needs to be clean, including all dimples. Thus, it is advisable that golfers wash their balls whenever permissible by the rules of golf. Golfers can wash their balls manually using a wet towel or using a ball washer of some type.