(written by: Willy Yanto Wijaya — Jan 2009)
Golf is an interesting sport that involves many aspects of physics, including mechanics of materials. In this writing, we shall focus more at the design and material mechanics of the golf stick, one of the most important equipments in playing golf.
A golf stick consists of three main parts: head, shaft, and grip. When playing golf, several types of golf sticks are usually utilized for different purposes: driver (first hit for long shot), wedges (for wedging out the ball from various terrains, certain accuracy shot), putters (for getting the ball into the hole), and several intermediary-function golf sticks. Head and shaft parts of the golf stick will be our main interest since mechanics of materials plays so significant roles in these parts.
When designing any material (including golf stick), there are many aspects need to be considered, for example: the material properties (either physical or chemical properties); composition of the materials; material processing (temperature treatment, etc). In order to get stiffness (high rigidity) and low weight, material should possess high E (modulus of elasticity) as well as low r (density). Since commonly these two parameters are trade-off each other, a new parameter E/r (specific modulus) is introduced to provide better deal in choosing materials’ characteristics.
Strength of material is defined as the ability to resist the applied s (stress) (either tensile, compressive, or shear stress). Besides depending on the material characteristics, strength is also a function of the engineering process (material processing).
Returning to the golf stick problems, for the driver (long-distance-shot type stick), weight is an important parameter since less weight will enable stick to be swung at the higher speed (and therefore farther distance shot). One possible option is to reduce the weight of the golf stick shaft. Some sport-equipment companies have tried to use graphite shaft (instead of steel shaft). However, since graphite has higher “shaft flex” (amount the shaft will bend when placed under a load) and higher torque, it can result in lower accuracy.
The other possibility is at the golf stick head. In this stick head, some key parameters to mention are weight distribution, size, shapes and design. Several parameters related to the weight distribution are: sweet spot, center of gravity, and perimeter weighting. Weighting the perimeter of the head could help increasing the size of the sweet spot (area on the head that will result in good hit). On the other hand, center of gravity will determine how the directional ability to hit the golf ball into the air. However, to achieve a good swing, there must be a balance between the weight of the head, stick length as well as the weight of the shaft.
To address this issue, titanium could be utilized, which combine light weight and excellent strength. However, since its being expensive, only high-end class of golf sticks could probably employ it. Therefore, in the future, research upon more approaching materials (better strength, less weight, cheaper cost) for the golf sticks is still widely open.
Some possibilities to do this could include the development of new methods/ technology for material strengthening mechanism. Utilizing our understanding in mechanics of materials about parameters that influence the strength and rigidity, we could develop new mechanism (either physically or chemically) to strengthen the weight and cost favorable materials for this golf sticks manufacturing. The mechanism could include the alloying/ changing material impurities level, modifying grain/ boundary sizes, changing the dislocation density, utilizing nano-technology, or even applying suitable chemical compounds (such as aromatic polyamide – used in bullet-proof vest Kevlar) for achieving this purpose.