The basic requirements for a golf ball are set out in The Equipment Rules :
- The weight of the ball must not be greater than 1.620 ounces (45.93 g).
- The diameter of the ball must not be less than 1.680 inches (42.67 mm).
- The ball must not be substantially different from the traditional and customary form and make.
- The ball must not be designed, manufactured or intentionally modified to have properties which differ from those of a spherically symmetrical ball.
Construction of modern golf ball
The outer cover of the golf ball is made of a durable thermoplastic material. Most often it is an ionomer resin or urethane. The surface of this cover is designed with various dimple patterns. Their task is to increase the lift force and keep the ball in the air longer. A smooth golf ball hit by a good golfer travels about half as far as a golf ball with dimples does.
Most golf balls have between 300 and 500 dimples. The number, shape and dimensions of the dimples depend on the specific ball model. Usually the dimples are 0.13 to 0.16 inch (3.3mm to 4.1mm) in diameter and about 0.01 inch (0.25mm) deep.
The dimensions, shape and pattern of the dimples affects the behavior of the ball in flight. Individual manufacturers constantly optimize the dimple patterns to suit the way to hit a ball and other preferences of various groups of golfers.
The inner part of the ball under the outer cover is made of various types of elastomers from synthetic rubber to polymers. Manufacturers use the various combinations of materials with different properties: hardness, specific weight, etc.
The number of layers of the golf ball defines the number of parts a ball is made of. Balls filled with a homogeneous material under the cover are called 2-layer balls. Balls containing a core wrapped in multiple inner layers can be 3-layer, 4-layer or 5-layer. Examples are shown in the figure below.
The flight of the ball in the air
The trajectory and behavior of the ball in flight after impact depends on the design of the ball, the impact details and the weather conditions.
The influence of environmental conditions such as temperature and atmospheric pressure on the ball flight is described on Influence of weather and altitude on a ball flight. The calculator available there allows you to estimate the shot distance depending on the weather conditions.
update: April 2022