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Bob Ratliff
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Aerospace engineer seeks the perfect dimple
Dimples and bluff bodies may sound like they belong in the world of high fashion models, but they are actually part of the world of Bob Thurman, an aerospace engineer whose designs would not be at home on the fashion runway or the airport runway.
Thurman is Wilson Sporting Goods principal engineer of aerodynamics and manager of the company's golf research testing function in Humboldt, Tenn. A big part of his job is designing dimples, the little indentations that cover the surface of golf balls. His career as an aerospace engineer for a major sporting goods manufacturer began at Mississippi State University.
Thurman worked with Martin Marietta Corporation in New Orleans as a cooperative education student following his freshman year as an aerospace engineering major at MSU. At that time, the company was building fuel tanks for the space shuttle --exciting work for an engineering student. It was also somewhat discouraging.
"I learned a lot, but I also saw that there were several hundred engineers working on the same project," he said. "It was not the kind of
environment where I felt I could make a dent."
When he returned to campus, however, Thurman discovered an aspect of aerospace engineering that combined his desire to be an engineer and his interest in sports.
"The first time I walked into Dr. Koenig's lab I knew I had found what I wanted to do," he said, referring to the research with baseball bats and other athletic equipment conducted at MSU by aerospace engineering professor Keith Koenig.
Following graduation with a bachelor's degree in 1992, Thurman was headed for graduate school, but fate steered him in another direction. He applied for a summer job at Wilson's golf ball plant in Humboldt. His resume made its way to the company's U.S. headquarters in Chicago at the same time the company's research and development operations were being reorganized. The new plan called for an engineer to design and test balls and other golf equipment at the west Tennessee facility. Thurman was hired, and he's been using his aerospace training to seek a better golf ball ever since.
"Engineering school teaches you how to solve problems," he noted. "They can't teach you everything, but they can provide you with a good sound foundation. When it comes to particular applications you go back and recall things you've learned."
One of the things Thurman learned at Mississippi State is that a round sphere, such as a golf ball, is called a bluff body and is a complicated object when it comes to aerodynamics.
"Even though an airplane may be pitching or rolling, the geometry is basically very static and under the influence of powered flight," he said. "The flight of a golf ball is very different. After leaving the club face the ball immediately begins to slow down and the spin begins to decay."
Dimples help a ball it in its flight from tee to hole.
"The dimples create turbulence, which keeps the airflow attached to the ball, producing a smaller wake and reduced aerodynamic drag," Thurman said. "With a smooth ball the wake separates much earlier, creating a large wake and tremendous drag forces."
A good golfer might drive a properly dimpled ball about 250 yards, while the same individual might get only about 120 yards from a smooth ball, he explained, adding that there are lot of options when it comes to dimple patterns. Finding the best options is part of his job.
Thurman has been very successful, as noted by the two U.S. patents for golf ball designs hanging on the walls of his office. There are also boxes and baskets of golf balls covered with lines, dots and other felt pen markings scattered around the office.
With a few strokes on his keyboard the engineer can bring up the image of his latest creation on a large computer screen. Horizontal and vertical lines map a new dimple pattern on the screen.
Adjacent to the office is a lab crisscrossed with computer cables and dominated by two "Iron Byrons," machines that mimic the swing of Byron Nelson, the legendary golf pro whose swing in the 1930s and 1940s was reputed to be close to perfect.
Detailed testing is necessary in the competitive world of golf equipment manufacturing.
"Most companies come out with one or two new golf ball designs each year," Thurman said. "Ball designs that were in production four years ago are no longer being produced."
Manufacturers must adhere to weight and diameter standards established by the U.S. Golf Association, but dimple design can be used to customize balls for different types of players.
"You have balls manufactured for higher handicapped players that are primarily just for distance," Thurman said. "Tour players, on the other hand, are not as concerned with distance as they are with the feel of the ball and the ability to control it on the green."
The diversified demand promises to keep Bob Thurman busy for years to come, and it's a prospect he looks forward to.
"When you go to the best courses in this country or even overseas and you see someone playing with that little golf ball that started in the computer here in Humboldt, that makes this a great job!"
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