Have you heard the term D-Plane yet? If you haven't, and you are any kind of golf junkie, you will hear it soon.
If you are old enough to get the Fantasy Island reference ("Dee plane, Dee plane!!!") then you also probably learned to play golf before launch monitors, K-Vests, Trackman, and maybe even video cameras. The introduction of technology to golf instruction has sparked a revolution in our understanding of how the golfer, the golf club, and the golf ball interact to create that elusive perfect shot -- or create the banana ball, duck hook, push-slice, worm burner, etc.
The term D-Plane refers to a physics-based model of the collision between the golf club and the golf ball, the part of the swing we commonly call the impact zone.
The D-Plane is tricky even for golf teachers to conceptualize, primarily because it is a 3-D model. Yes, 3-D, just like Avatar or Toy Story 3. Contrast this with the old ball flight laws (see Fig. 1), which are a simple 2-dimensional representation. The D-Plane model enhances (some would argue contradicts) the old ball flight laws.
Fig.1 -- Old Ball Flight Laws in 2 Dimensions
The new 3-D model is mathematically derived and based on the laws of physics. First mentioned in Theodore Jorgensen's 1994 book "The Physics of Golf", D-Plane is short for Descriptive Plane. Jorgensen used the D-Plane to explain how the golf club imparts velocity, trajectory and spin to the golf ball.
D-Plane discussions heated up following the advent of launch monitors like Trackman and Flightscope. The doppler radar based launch monitors are able to measure club path, face angle, launch angle and spin rate at impact. And data generated by the launch monitors proved the accuracy of the D-Plane model. Thus we learned that our old 2-dimensional ball flight laws have some deficiencies.
D-Plane discussions can get complicated and mathematical enough to satisfy almost anyone's inner engineer geek. In simplest terms the golf club moves in a circle like a Ferris Wheel that is lined up at the target. But in the golf swing, the Ferris wheel is tilted at about 70 degrees, just like the swing plane. This 70 degree tilt means that the club head is only moving directly at the target at one point along the club path. It is this fact that makes the D-Plane different from the 2-dimensional models.
Basically, what we have learned is that the ball's launch direction is based approximately 85% on face angle and 15% on club path (see Fig. 2).
This post is not meant to fully explain D-Plane, but rather to provide an introduction and stimulate curiosity. Try the blogs on John Graham's website to deepen your understanding of the D-Plane, and branch out from there. D-Plane Golf is another useful website. The internet and is loaded with examples of visual explanations of the D-Plane, as is Youtube. You can explore the concept as deeply as you would like.
Strangely enough, I find that the 2-dimensional ball flight laws correspond pretty well with what a golfer "feels" during his or her swing.
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