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Addressing the Ball

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Researchers use finite element analysis for clubhead design. Golf authorities regulate the dimensions and volumes of clubheads, so within those parameters, the team studied hundreds of possibilities, using computer simulations of club and ball actions, down to the bounces of simulated shots.
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After addressing the dynamics that go into a better-designed club, researchers turned to the intricacies of the golf ball and what makes it fly higher, faster, and farther. One variable is the clubface material: Titanium produces the maximum “hotness,” the spring-like effect as the ball jumps off the club. In 2001, though, golf’s ruling bodies—the U.S. Golf Association and the Royal & Ancient club of Scotland—put limits on “hotness.” Once the ball jumps off the club, the backspin on a normal shot generates lift due to greater pressure below the ball than that above it. “This pressure difference is the way you generate lift in airplanes, and it works the same way for a golf ball,” says Michael Amitay, assistant professor of mechanical, aerospace, and nuclear engineering at Rensselaer.

Meanwhile, a golf ball’s familiar dimpled pattern is no hoary tradition, but a clever bit of engineering. Indeed, dimples provide another of golf’s great counterintuitive science facts. All things being equal, the dimpled ball will fly farther precisely because it does not have what is commonly thought of as an aerodynamic shape. “The dimples create a more turbulent boundary layer,” says Cackett. This localized turbulence keeps it aloft longer.

Amitay says his undergraduate students almost always say the smooth ball will fly farther before he demonstrates the principle in a wind-tunnel lab. The underlying issue, whether it pertains to airplanes or golf gear, is that there are not really optimal aerodynamic designs that exist apart from the situation in which a piece of equipment is used. There may be a Platonic ideal of a golf driver out there, but in reality the imperfection of golfers dictates club design. If players had a robotic ability to repeat perfect swings and strike the ball exactly on the “sweet spot” of a club, equipment could be designed accordingly. Instead, designers focus on producing a large moment of inertia and minimizing the gear effect precisely because golfers are so inconsistent.

“It would be easy if it weren’t for the people,” says Cackett jokingly. “The human user is responsible for delivering the clubhead to the ball. And there are a whole host of things that can go wrong in the process.”

In fact, Callaway does robotic testing of equipment, to simulate real swings. But researchers also perform player testing. And some pros, including Mickelson, enjoy trying out new inventions. “Phil loves to experiment with his driver configuration and set makeup, which is kind of unusual,” says Cackett. “Pro golfers in particular tend to be conservative in this regard. But Phil is pretty adventurous.”

This underscores the paradox of golf-club design. The ideal mass-market product creates straighter shots for recreational golfers but, in so doing, may not suit the needs of the pros, who may want to bend and shape shots on more difficult courses. A more strategic—and creative—design for the pro golfer led to one of the company’s finest moments. Working with Hocknell, Mickelson made the unusual decision to play the 2006 Masters with two drivers in his bag—one for standard tee shots and one for the more creative drives. The strategy paid off with Mickelson’s second Masters title.

As club technology moves to the next level of complexity and leading-edge research, so, too, do changes in golf courses themselves—added length, more roughs and hazards, and twisting holes, for example—put an even greater demand on researchers like Cackett to innovate even more. Merging golf technology with the human golfer gives Cackett the opportunity to advance research and design with, well, playing a game.

Cackett says he remembers then-President George Low ’48 exhorting his class at the Senior Banquet in 1982 to “get out onto the factory floor and touch the hardware.”

“I’m fortunate that I’m able to get out on the golf course and touch the hardware,” Cackett says.

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Rensselaer (ISSN 0898-1442) is published in Spring, Summer, Fall, and Winter by the Office of Strategic Communications and External Relations, Rensselaer Polytechnic Institute, Troy, NY 12180-3590. Opinions expressed in these pages do not necessarily reflect the views of the editors or the policies of the Institute. ©2008 Rensselaer Polytechnic Institute.