The Scientific Side of Ball Striking
By Randy Peterson
Callaway Golf Director of Fitting and Instruction
As I've said previously here on CallawayGolf.com, there is no universally correct tee height for all golfers and it's important to identify your own personal optimum tee height. After all, how high you tee the ball has a big effect on where you hit the ball on the clubface (within the context of your individual swing characteristics and club parameters). And where you hit the ball on the clubface, especially with a driver, dramatically affects the resulting shot.
Launch Angle and Backspin
Today, most golfers are familiar with terms such as "launch angle" and "backspin"—especially as they relate to hitting a driver. These terms are mentioned often during golf telecasts and covered regularly in golf magazines. The majority of retail golf shops and pro shops now have launch monitors capable of measuring these and many other parameters. Launch monitors are routinely used during club fitting sessions. For the record, launch angle is defined as the angle the ball leaves the clubface relative to horizontal and is measured in degrees. Backspin is the rate the ball spins backward around its rotational axis and is measured in revolutions per minute (rpm). Optimizing these two parameters, along with ball speed, allows you to achieve your maximum driver distance. Optimum launch angle and backspin rate vary depending on ball speed. However, a launch angle of 10°-14° and a backspin rate of 2200-2600 rpm can be considered in the optimum range.
So, what are the critical factors contributing to the optimization of launch angle and backspin? Obviously the loft of the club plays a crucial role and is vital to determine when being fit for a driver. As a point of reference, a 1° change in loft will result in a change of 1° in launch angle and 300 rpm of backspin, assuming a center clubface impact. That means if you move from a 9° driver to a 10° driver, and hit a shot with each club in the center of the clubface, you can expect the 10° driver to launch a degree higher and the backspin rate to have an increase of 300 rpm. This 1° difference in launch angle and 300 rpm difference in backspin is enough to cause a 5-6 yard net difference in distance. And I don't know anyone who would turn down an additional 5-6 yards off the tee.
The Importance of Impact Location
Another important factor in determining launch angle and backspin is impact location: the exact point on the clubface that makes contact with the ball. In fact, the variability in launch angle and backspin caused by various impact locations is enormous. Impact location has a much more dramatic affect on launch angle and backspin with a driver than loft alone. And since no one hits the ball in the same place on the clubface every time—not even Tour Professionals and certainly not average golfers—we must account for the effects of impact location when talking about launch angle and backspin.
For the purposes of this article we're only talking about varying impact locations in the vertical plane, from top-to-bottom on the clubface.
Woods and hybrids, unlike irons, do not have flat clubfaces. They have curved clubfaces. The curvature is called "roll". Because the clubface on woods is not flat, the club doesn't have the same loft on all points of the clubface. For example, a driver will have more loft at the top of the club head and less loft at the bottom. The loft you read stamped on the bottom of a given driver is the loft measured in the center of the clubface. Hitting the ball above the center of the club face will result in a higher launch angle than if you had hit the ball in the middle of the club face. The higher you hit it on the clubface, the bigger the discrepancy in launch angle when compared to a center impact. Hitting below the center of the clubface will have the opposite effect: the ball will launch lower than if you'd hit it in the center of the club face. And it's not just the launch angle that's affected. Back spin also varies greatly depending on impact location. Relative to impact location, backspin is inversely proportional to launch angle (caused by gear-effect). This means as launch angle goes up, backspin goes down and vice versa. So if you hit a shot high on the clubface with a driver you can expect the ball to launch higher with less backspin than if you'd hit the ball in the center of the club face. Again, the opposite is true for hitting the ball low on the clubface: the ball will launch lower and have more backspin than if it had been hit in the center of the clubface.
What It All Means To You
In extreme cases, where the golfer has a very wide dispersion in impact location, it's possible to see launch angles vary by 8°-10° and backspin by as much as 1500-2000 rpm. Even among accomplished golfers it's not uncommon to see variances of 3-4 in launch angle and 500 rpm in back spin. There can be a 20-30 yard difference in distance with the same club head speed based on impact location alone. Being aware of the significant effect impact location plays on the resulting shot will help you better understand the variance in your driver distance. In fact, we've seen players improve their driving simply by paying more attention to where they to hit the ball on the clubface and making small adjustments to their swing, tee height or ball position.
This is not to suggest that getting fit for the right driver with the correct loft isn't important. On the contrary, it's very important. Rather, the point of this column is to illustrate the effect impact location has on the resulting ball flight.
Understanding the effects of impact location on launch angle and backspin can help ensure you get fit into the correct driver specifications and can also improve your performance with your current driver. Whenever you're comparing two drivers with different lofts or drivers with the same loft but different models/brands, make sure you're paying attention to where you're hitting each driver on the clubface. Comparing shots hit in similar locations will provide you the most accurate feedback, allowing you to truly compare the benefits of each club. Remember, your impact location will have a greater affect on the outcome of the shot than any other individual variable.
For more great tips from Randy, check out his articles on golf tips for your game and hitting better shots from the rough.