Tuesday, March 10, 2009
Golf ball
A golf ball is a ball designed to be used in the game of golf.
Under the Rules of Golf, a golf ball weighs no more than 1.620 oz (45.93 grams), has a diameter not less than 1.680 in (42.67 mm), and performs within specified velocity, distance, and symmetry limits. Like golf clubs, golf balls are subject to testing and approval by the Royal and Ancient Golf Club of St Andrews and the United States Golf Association, and those that do not conform with regulations may not be used in competitions (Rule 5-1 — also see rules of golf)
A golf ball is a ball designed to be used in the game of golf.
Under the Rules of Golf, a golf ball weighs no more than 1.620 oz (45.93 grams), has a diameter not less than 1.680 in (42.67 mm), and performs within specified velocity, distance, and symmetry limits. Like golf clubs, golf balls are subject to testing and approval by the Royal and Ancient Golf Club of St Andrews and the United States Golf Association, and those that do not conform with regulations may not be used in competitions (Rule 5-1 — also see rules of golf)
History
Wooden balls were used until the early 17th century, when the featherie ball was invented. This added a new and exciting feature to the game of golf. A featherie is a hand sewn leather pouch stuffed with goose feathers and coated with paint. The feathers in the ball were enough to fill a top hat. They were boiled and put in the cowhide bag. As it cooled, the feathers would expand and the hide would shrink, making a compact ball. Due to its superior flight characteristics, the featherie remained the standard ball for more than two centuries. However, an experienced ball maker could only make a few balls in one day, so they were expensive. A single ball would cost between 2 shillings and sixpence and 5 shillings, which is the equivalent of around 10 to 20 US dollars today [1]. Also, it was hard to make a perfectly spherical ball, and because of that, the ball often flew irregularly. When playing in wet weather, the stitches in the ball would rot, and the ball would split open after hitting a hard surface.
In 1848, the Rev. Dr. Robert Adams (or Robert Adam Paterson)[2] invented the gutta-percha ball (or guttie). The gutta was created from dried sap of a Sapodilla Tree. The sap had a rubber-like feel and could be made round by heating and shaping it while hot. Accidentally, it was discovered that defects in the sphere could provide a ball with a truer flight than a pure sphere. Thus, makers started creating intentional defects in the surface to have a more consistent ball flight. Because gutties were cheaper to produce and could be manufactured with textured surfaces to improve their aerodynamic qualities, they replaced feather balls completely within a few years.
In the 20th century, multi-layer balls were developed, first as wound balls consisting of a solid or liquid-filled core wound with a layer of rubber thread and a thin outer shell. This idea was first discovered by Coburn Haskell of Cleveland, Ohio in 1898. Haskell had driven to nearby Akron to keep a golf date with Bertram Work, then superintendent of B.F. Goodrich. While he waited for Work at the plant, Haskell idly wound a long rubber thread 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 golf ball. The design allowed manufacturers to fine-tune the length, spin and "feel" characteristics of balls. Wound balls were especially valued for their soft feel.
They usually consist of a two-, three-, or four-layer design, (named either a two-piece, three-piece, or four-piece ball) consisting of various synthetic materials like surlyn or urethane blends. They come in a great variety of playing characteristics to suit the needs of golfers of different abilities.
Regulations
The current regulations mandated by the R&A and the USGA state that diameter of the golf ball cannot be any smaller than 1.680 inches. The maximum velocity of the ball may not exceed 250 feet per second under test conditions and the weight of the ball may not exceed 1.620 ounces.
Until 1990 it was permissible to use balls of no less than 1.62 inches in diameter in tournaments under the jurisdiction of the R&A[3].
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 two effects:
Firstly, the dimples delay separation of the boundary layer from the ball. Early separation, as seen on a smooth sphere, causes significant wake turbulence, the principal cause of drag. The separation delay caused by the dimples therefore reduces this wake turbulence, and hence the drag.
Secondly, backspin generates lift by deforming the airflow around the ball, in a similar manner to an airplane wing. This is called the Magnus effect. Backspin is imparted in almost every shot due to the golf club's loft (i.e. angle between the clubface and a vertical plane). A backspinning ball experiences an upward lift force which makes it fly higher and longer than a ball without spin.[1] Sidespin occurs when the clubface is not aligned perpendicularly to the direction of swing, leading to a lift force that makes the ball curve to one side or the other. Unfortunately the dimples magnify this effect as well as the more desirable upward lift derived from pure backspin. (Some dimple designs are claimed to reduce sidespin effects.)
In order to keep the aerodynamics optimal, the ball needs to be clean. Golfers can wash their balls manually, but there are also mechanical ball washers available.
Design
Dimples first became a feature of golf balls when a certain Taylor patented a dimple design in 1908. Other types of patterned covers were in use at about the same time, including one called a "mesh" and another named the "bramble", but the dimple became the dominant design due to "the superiority of the dimpled cover in flight".[4]
Most golf balls on sale today have about 250 – 450 dimples. There were a few balls having over 500 dimples before. The record holder was a ball with 1,070 dimples — 414 larger ones (in four different sizes) and 656 pinhead-sized ones. All brands of balls, except one, have even-numbered dimples. The only odd-numbered ball on the market is a ball with 333 dimples, called the Srixon AD333.
Officially sanctioned balls are designed to be as symmetrical as possible. This symmetry is the result of a dispute that stemmed from the Polara, a ball sold in the late 1970s that had six rows of normal dimples on its equator but very shallow dimples elsewhere. This asymmetrical design helped the ball self-adjust its spin-axis during the flight. The USGA refused to sanction it for tournament play and, in 1981, changed the rules to ban aerodynamic asymmetrical balls. Polara's producer sued the USGA and the association paid US$1.375 million in a 1985 out-of-court settlement.
Golf equipment maker Callaway has introduced a ball with hexagonal dimples to increase the dimpled area on a golf ball, as hexagons tesselate unlike circles.
The United States Patent and Trademark Office's patent database is a good source of past dimple designs. Most designs are based on Platonic solids such as icosahedron.
Golf balls are usually white, but are available in other high visibility colours , which helps with finding the ball when lost or when playing in frosty conditions. As well as bearing the makers name or logo, balls are usually printed with numbers or other symbols to help players identify their ball.
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