Birds of a featherie

Updated: Oct 29 2007, 07:28am hrs
Golf is unquestionably one of the worlds great games, possibly the greatest. Its held sway over rich and poor alike for almost 600 years. It attracts tens of millions of weekend players, who spend small fortunes on equipment and membership dues and green fees.

Your correspondent is not one of them. In a moment of weakness, he once agreed to make up a foursome. The experience convinced him hed been right to avoid so masochistic a pastime.

But one thing has continued to fascinate him about golf. The rules, especially those governing the equipment, are a model of common senseand a practical guide for many other things in daily life. They embrace innovation but balance advances in materials and technology with the need to maintain the essential challengeand therefore satisfactionof the game.

Take the replacement of the wooden driver with the far springier titanium club. With its big fat head and thin-skinned face, this added 20 yards or more to a professionals drive. For weekend golfers, it at least made the game much easier to play.

But it also made a mockery of the handicapping system. Worse, it made even challenging courses appear puny. Enlarging them to cope with the longer driver would have been prohibitive environmentally as well as financially.

Faced with such a dilemma, the ruling bodies, the Royal & Ancient Golf Club of St Andrews in Scotland and the United States Golf Association, cannily amended the rules. The springiness, which was getting close to its theoretical maximum, has now been reined back. From 2008 onwards, Promethean drivers like Callaways ERC Plus will be banned from even the amateur game.

But the club is only half of the problem. The ball has also been improving by leaps and bounds. Now the question is, having settled the club issue, will golfs ruling bodies turn their attention to the ball

The conventional wisdom used to be that, after six centuries of hacking away at woodies, featheries, gutties and wounders, the golf ball couldnt be improved much further. Since 1976, when the two bodies last changed the rules about the ball, the book has been essentially closed on the matter.

But the wise men hadnt reckoned with the likes of Steve Ogg, a former Boeing engineer and subsequently a senior scientist at Callaway. Mr Oggs radical ball-design has rewritten the rules of flight for spherical objects.

Whats so clever about the Callaway HX ball is that it has no dimples. Instead, it uses a lattice of tubular ridges that cover its surfaceand not just most of its surface, but quite literally 100% of the surface. That is impossible to do with circular dimples, which leave 25% of surface area between the small craters as smooth, flat lands that contribute nothing to the balls ability to carry.

But why dimples or ridges anyway The answer has to do with the way the air streaming over a ball in flight creates a wake behind it.

Back in the 1600s, when the early wooden ball gave way to the featherie,

it was thought that a smooth ball would create less drag, and would therefore travel further. The featheriemade using a wet leather pouch into which boiled feathers were stuffed and allowed to drywas meticulously stitched inside out so that its surface would be as smooth as possible. But such skilled (and therefore expensive) craftsmanship restricted golf balls to wealthy Scots and, later, Englishmen (James I brought the game south in 1608).

What opened the game to a wider following was the arrival of the gutta-percha ball in 1848. Made by heating and rolling the gum of a Malaysian Sapodilla tree into a sphere, the guttie was much cheaper but did not fly as far as a featherieat least, not until it got pockmarked with repeated use. It did not take Victorian golfers long to realise that by deliberately dimpling their smooth gum balls, they could make them fly a whole lot further. Hence the development of the dimpled ball we know today.

Dimples work by setting up tiny eddies that energise the airflow, forcing it to cling to the ball much further around the backside. The result is a smaller wake and more energy for forward motion.

But dimples are not the only thing that can stir the air into becoming turbulent. Military aircraft use all manner of spoilers to disrupt the orderly airflow over their wings in order to delay separation. This reduces drag for high-speed dashes, while increasing lift for manoeuvring at low speed.

One of the most common spoilers is a kind of fence that churns the air flowing over the back half of the wings. From his days at Boeing, Mr Ogg figured out that a network of raised ridges on a golf ball would have a similar effect.

Because its high-speed drag is so low, the ridged ball travels fast for a much greater distance. Then, as it reaches the apex of its trajectory and slows, the high lift at low speed kicks indecreasing the balls angle of descent and helping it float even further down the fairway.

Callaway is shy about saying just how far an HX ball will carry. But it is interesting that when they recently changed the rules for drivers, the ruling bodies declared that golf balls should not of themselves fly significantly further than they do today. In other words, the balls in your court, sunshine.

The Economist Newspaper Limited 2007