Eccentric Engineer: How the golf ball got its dimples
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This month, we look at the way the design of golf balls evolved, with their aerodynamic properties contributing to the sport’s enduring popularity.
Golf has produced a number of engineering innovations, which hopefully offset the sport’s baleful contribution to fashion. But perhaps most charming and effective are simple dimples.
The earliest golf balls were probably made of wood, but the first recognisable ‘type’ was the ‘featherie’, a hand-sewn leather pouch, stuffed, as you might expect, with feathers – in fact ‘a gentleman’s top hat full’ of goose feathers. The ‘featherie’ had some obvious drawbacks – it wasn’t usually all that round, it flew less far when wet and had a tendency to explode on contact with a hard surface, turning the game into something resembling a pillow fight.
Fortunately, in 1848, Robert Adams Paterson noted that gutta-percha, the dried sap of the Malaysian sapodilla tree, formed a hard rubber-like substance that could be moulded into balls, was resistant to damage and didn’t go soggy when wet. Of course, these balls weren’t perfect. Hit the ball at an angle and a dent or chip would result, but golfers noticed that these abrasions seemed to make the ball fly straighter and farther. Golfers always love a gimmick, so manufacturers began making their gutta-percha balls with various patterns of grooves, gouges and pimples, the latter nicknamed ‘brambles’ due to their similarity to the fruit.
The first to try an indentated surface were David Stanley Froy and a group of friends, who patented a ball “with isolated indentations”. Froy tried this out at the 1900 Open at St Andrews, but he didn’t win and his next patent was for doorknobs.
It would be an intervention from an unexpected quarter that eventually gave us the modern dimpled ball. Thomas Smithies Taylor was an optician who, with his brother, ran a successful business manufacturing lenses and measurement machinery in Leicester and, later, New York. When Taylor’s doctor advised he take up a hobby to help him relax, the hobby he chose was golf. However, Taylor was not a man to simply buy some eye-catching trousers and hack a ball around a field. He was determined to find out why dented and damaged balls flew better than new ones.
Using his optical skills, Taylor built a glass-fronted test chamber where smoke could be blown over various ball surfaces to study eddies and vortices in the airflow around them. In effect, this was an early wind tunnel. He soon noticed that the haphazard nature of dents on damaged balls, and even on brambles, did not produce a regular result, so designed a series of indentations that covered the ball evenly.
With these he found that the indentations created a boundary layer on the ‘upstream’ side of the travelling ball with fewer vortices and eddies, creating a narrower low-pressure wake behind the ball, and hence less pressure drag. The result of this was that the ball flew further. But there was a secondary effect too. Striking the indented ball created backspin, which made it curve in the air – the Magnus effect – and this produced lift, again carrying the ball further. Further experiments led him to finalise the steepness of each hollow: shallow enough not to collect dirt, which would alter the aerodynamics, but deep enough to give the desired drag effects.
Taylor patented his design in 1905 but, rather than licensing it, he went on to design his own machine for making moulds to form the indentations on the surface of the new ‘wound’ balls, made with a solid or liquid core around which was wound rubber thread. As for the indentations themselves, they needed a name. The form they took was like a small crater; it was his wife who suggested calling them ‘dimples’.
Which arrangement of dimples would work best? Again, Taylor put this to a practical test, building an automatic, weight-operated driving machine that could always strike a ball in the same place with the same force. He fired off thousands of shots using balls with different dimple configurations until he settled on the longest flying. He also found that his surface geometry improved the flexibility of the ball and helped to prevent the risk of bursting, at a time when many balls were filled with highly caustic liquid.
Taylor lived for another 33 years after creating the dimpled ball, suggesting that either golf or engineering must be good for you.
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