Aerospace grad making his mark on the game of golf -- and on the
golf ball
by Bob Ratliff
photos by Fred Faulk
| Ever wondered why golf balls have all those little dimples, not to mention how they got there? Read on. |
Bob Thurman works in a world of dimples and bluff bodies. No, he's not a high-fashion photographer or a Hollywood producer. Thurman, an aerospace engineer, designs golf balls for Wilson Sporting Goods at the company's Humboldt, Tenn., research and testing facility.
While Humboldt may be a long way from the fashion runways of Rome and the soundstages of Hollywood, it is also far removed from the aircraft plants and NASA facilities where you would expect to find an aerospace engineer.
For Thurman, the road to Humboldt-and a career designing golf balls for a major sporting goods manufacturer-began in his hometown of Dyersburg, Tenn.
"When I was in high school, I really loved math and science and knew I wanted to go into some type of engineering," he explained. "When I applied to MSU, I went down the list of engineering programs and aerospace sounded the best, even though I never was a big airplane buff."
| "Engineering school teaches you how to solve problems. They can't teach you everything, but they can provide you with a good, sound foundation." |
"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 like I could make a dent."
Returning to campus the next fall, Thurman discovered an aspect of aerospace engineering that was more appealing to him than working on huge projects with hundreds of other engineers.
"The first time I walked into Dr. Koenig's lab, I knew I had found what I wanted to do," he explained, referring to research on baseball bats and other athletic equipment being conducted by aerospace engineering professor Keith Koenig.
Although Koenig's work fired his imagination, Thurman also was involved in some of the more traditional activities for aerospace engineering students, including work on a student space plane project.
After receiving his bachelor's degree in 1992, Thurman was headed for graduate school, until fate stepped in.
"I needed a summer job. My father works for a company that sells raw material to the Wilson golf ball plant in Humboldt and he suggested I send the company a resume," he noted.
The resume made its way to Wilson's U.S. headquarters in Chicago at the same time the company was in the process of decentralizing its research and development operations. As part of the plan, an engineer was needed to design and test balls and other golf equipment at the Tennessee facility. Thurman was hired, and he's been seeking a better golf ball ever since.
"My first day on the job, I pulled out one of my aerodynamics textbooks and found one page with a reference to something like a golf ball," he said.
That doesn't mean he wasn't prepared, though.
 Bob Thurman tees up a ball for "Iron Byron" |
One of the things Thurman learned at Mississippi State is that a round sphere, a golf ball for example, 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 says. "The flight of a golf ball is different. After leaving the club face, the ball immediately begins to slow down and the spin begins to decay as well."
The dimples, those little indentations on the surface of a golf ball, help it in its flight from tee to hole.
"With a golf ball, the dimples actually create turbulence, which keeps the airflow attached to the ball, producing a smaller wake and reduced aerodynamic drag," said Thurman. "With a smooth ball the wake separates much earlier from the ball, creating a large wake and tremendous drag forces."
He added that three primary factors determine the performance of a golf ball-the amount of surface covered by dimples, the angle that a dimple breaks from the surface of the ball, and dimple depth.
"The maximum amount of the surface that can be covered with dimples is about 80 percent," he explains. "Changes in how sharp the angle is where the dimple breaks from the surface of the ball and dimple depth provide room for the most variables."
As a general rule of thumb, deeper dimples produce lower, flatter trajectories. Shallow dimples produce higher, ballooning trajectories. The key, Thurman says, is to create a dimple with enough depth to produce air turbulence around the ball as it rotates in flight. That helps the ball penetrate what engineers call "the force barrier"-the resistance that builds up as the ball moves through the air.
Thurman, along with technicians Susan Beachum and Donna Haynes and fellow engineer Ron Borecki, test a variety of ball designs at Wilson's research and testing laboratory, which sits at one end of a 13-acre driving range about a mile from the company's golf ball manufacturing plant.
| "Most companies come out with one or two new golf ball designs each year. Ball designs that were in production four years ago are no longer being produced." |
Thurman works in an office adjoining the lab. Baskets of balls covered with lines, dots, and other felt-pen markings fill some corners in the office. With a few strokes on his computer keyboard, the engineer can bring up the image of his latest creation on the computer screen. Horizontal and vertical lines that map a new dimple pattern dissect the computer image of a golf ball.
What's the perfect number of dimples? It is possible to design a ball with 1,000 or more dimples, Thurman said, but he's designed a 500-dimple ball that's been very successful in Wilson's Staff Titanium and Ultra 500 lines.
"I wasn't trying to develop a 500-dimple ball," he explained. "It just took 500 to properly define the pattern."
He added that a properly dimpled ball will go about 250 yards, while with a smooth ball you would be lucky to get 120 yards. There are a lot of options when it comes to dimple patterns for golf balls. Finding the best options is part of Thurman's job as Wilson's principal engineer of aerodynamics and manager of the company's golf research testing function.
He's been very successful at that job, as noted by the two U.S. patents for golf ball designs hanging on the walls of his office. But it's not a job where you can rest on your laurels.
"Most companies come out with one or two new golf ball designs each year," said Thurman. "Ball designs that were in production four years ago are no longer being produced."
Manufacturers must adhere to certain weight and size standards established by the U.S. Golf Association. Dimple design and other factors can, however, 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 noted. "Tour players, on the other hand, are not as concerned about distance as they are with the feel of the ball and the ability to control it on the green."
Wilson and other manufacturers produce balls that fit the needs of players at all points along the handicap spectrum, as well as customized balls for special events, promotions, and to fit the preferences of players in Japan and other countries.
The diversified demand will likely 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 this computer here in Humboldt, that makes this a great job!"
Golf balls fly through history The Chinese played a game similar to golf 1,000 years ago, but it's the Scots who lay claim to originating the game as we know it today. The game began in Scotland during the Middle Ages as a haphazard sport of hitting a pebble or other somewhat round object with a stick into a hole, often one occupied by rabbits along the high bluffs of Scotland's eastern coastline.
Feather balls were used until gutta-percha, or hard rubber, balls became available in the mid-1800s. The early rubber balls may not have been much of an improvement over feathers. A report on a long-driving competition in 1859 notes that the winning drive, made with a gutta-percha ball, was just 175 yards. Players, however, soon made an important discovery about the new type of balls. "They noticed that as a ball got scarred up, it would go farther," explained Bob Thurman. "So, they began to scuff up the balls before play. The scuffs provided the aerodynamics necessary for good flight performance, just as the stitched seams had for the earlier leather-covered balls" By the late 1800s, players began cutting control patterns, usually square or octagon shapes, on the surface of golf balls. "It took until the 1930s before dimples were generally accepted as the best surface for a golf ball," said Thurman. |
This World Wide Web version of Alumnus was marked up by Chris Brown <brownc@ur.msstate.edu>
For information about Mississippi State University, contact msuinfo@ur.msstate.edu.
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By the 1600s, leather pouches stuffed with feathers became the first real "golf balls." Records of the Glasgow Club in Scotland show that in 1786 a player named John Gibson made a series of drives ranging from 182 yards to 222 yards with a feather ball.