Editor’s note: This story originally ran in the April 4 issue of Golfweek.
Any time you can make someone with a doctorate in applied mathematics smirk and say, “That’s a good question,” you know you’re on to something.
I had asked Paul Wood, Ping Golf’s vice president of engineering, a seemingly simple question: “Where does distance come from with a driver?” But like a lot of simple questions, it has a complicated answer.
“It’s ball speed first,” he said. “The correlation between ball speed and distance is extremely strong. If you get more speed, all things being equal, you get more distance.”
Most golfers already knew that, but “all things” on a golf course rarely are equal. A player’s swing changes from shot to shot, and environmental conditions fluctuate. Two things that are constant throughout a round: the clubhead and the ball.
“Today, everything is basically optimized,” said John Oldenburg, Aldila’s vice president of engineering and product development. “The heads can’t get bigger, and the faces can’t get springier.”
In an effort to limit a driver’s ability to generate ball speed, the U.S. Golf Association capped the springiness of a driver’s face (expressed by coefficient of restitution, or COR) at .83, meaning that no more than 83 percent of the energy created at impact can be transferred to the ball.
The greatest transfer of energy typically takes place toward the middle of the clubface – the sweet spot. However, many recent advances have focused on making more of the clubface approach the USGA limits of COR farther away from the center, effectively broadening the hitting area.
For example, Nike and Titleist have channels in the sole of their drivers that allow the bottom of the face to flex more at impact, which pulls the sweetspot down.
Bridgestone’s latest drivers have Power Ribs in the crown, near the seam between the face and the top of the club, which helps provide more ball speed on shots hit high in the face. Callaway, TaylorMade and the other major manufacturers have developed technologies that allow the face to effectively flex across a larger area.
One part of the distance-generating equation that the game’s governing bodies do not limit is clubhead speed. This is the reason why several companies have made big investments in aerodynamic research in recent years.
For example, Ping engineers tested the aerodynamic qualities of the Turbulators on the crown of the G30 driver in a wind tunnel at Arizona State University. Callaway worked with Boeing, the aerospace corporation, to create the Speed Step on the crown on the Callaway XR 16 driver to help it flow through the air more easily. TaylorMade, Titleist, Cobra and most of the others have worked extensively to create designs that are more aerodynamic and therefore faster.
Finally, driver distance also comes down to technique. According to data collected by TrackMan, maker of sophisticated radar-based launch monitors, the average player on the PGA Tour hits down on driver tee shots – a negative angle of attack. It’s very slight, in the neighborhood of minus-2 degrees. But the longest drivers hit up on the ball and create a positive attack angle. Bubba Watson and Dustin Johnson commonly have an upward attack angle greater than 4 degrees.
When the driver is swinging downward into impact, the launch angle decreases and the spin rate increases, robbing shots of distance. Swinging up on a drive increases launch angle, decreases spin and adds yards. As the accompanying chart based on 90-mph clubhead speed shows, changing from a minus-3 degree attack angle to a plus-3 degree attack angle would result in adding 13 yards without swinging any faster.
So it would seem the answer to, “Where does distance come from with a driver?” is really a fast, ascending swing that creates as much ball speed as possible. Thanks to improved designs and better materials, today’s drivers convert that clubhead speed into ball speed more efficiently.
With proper custom-fitting, the combination of the right clubhead, shaft and ball can help achieve optimal launch conditions more easily and more often.
See Paul . . . was that so complicated?
Optimized distance per clubhead speed
This chart is based on data collected by TrackMan. It shows how increases in clubhead speed, when combined with the ideal launch angle and spin rate, lead to gains in ball speed and distance. These optimized carry distances are the farthest a player can expect to carry a ball for the associated clubhead speeds.
|Clubhead Speed||Ball Speed||Launch Angle
|Spin Rate (RPM)||Carry Distance
This chart shows how attack angle affects launch angle, spin and distance, based on TrackMan data. It’s a common refrain that a high launch with low spin creates optimal launch and distance; this chart shows that correlation.
|Clubhead Speed||Attack Angle (Degrees)||Launch Angle (Degrees)||Spin Rate (RPM)||Carry Distance (Yards)|