Saturday, January 21, 2012

Ball Flights and the D-Plane

When I started playing golf (about a year and two months ago), I was plagued by the slice like most beginners. And it still creeps in on occasion when I get lazy with the fundamentals. My slice was always (and still is when it happens) a push-slice or straight-slice…it was never a "classic" slice (i.e., ball starts left and curves to the right). Slicing is associated with open club faces relative to the path the club head is moving. At some point, I started making adjustments and got the ball to start hooking; in some cases, it hooked badly and in others, I would get a nice, tight draw. But I was able to make the ball curve the other way, and that means a lot to the slicer.

For right-handed players, a push-slice means that the club sweet spot--assuming one hits the sweet spot--is moving towards the right, and the club face is open--or pointed further right--at impact relative to that path; if the club face was closed (i.e., pointed to the left) relative to that path, the ball would hook to a greater or lesser degree, depending on the gradient or differential between path and face at impact.

The classical view of ball flight--the so called "old" ball flight laws--state that if you set up with the club face aiming at the target but align and swing to the right, the ball will hook or draw back to the target. High speed video (and good old fashioned physics), however, has put many of the old ball flight claims to bed.

The "new" ball flights laws state that the ball's initial flight is controlled almost exclusively (75-85%) by the club face position at impact (path accounting for the other 25% or so), while the curve of the ball flight is dictated by the aforementioned path-to-face gradient. In other words, setting up to hit a draw with the club face aimed at the target (using the ideas in the old ball flight laws) will most likely cause the ball to hook well left of the target. This is assuming that the club face returns to the ball at impact the way it was at setup, and that's a BIG ASSUMPTION. That assumption accounts for why the "old" ball flight laws still seem to work on occasion; in all likelihood, a player is really catching the ball with the club face slightly open but still closed to the path and drawing the ball back to the target.

A very scientific way of viewing the new ball flights laws is the D-Plane concept. The primary variables in the D-Plane are:

  • The path that the impact point on the club face is moving (includes a combination of up or down along with left or right motion)
  • The direction that the impact point on the club face is pointing (straight, left, or right)
  • The loft of the club itself (lower loft = shorter D-Plane and vice-versa).

The D-Plane is a triangular plane, where one side is created by the direction the club face points and the other side is created by the direction the club travels (path). Each of these two sides can be imagined to originate from the same point on the club face at the moment of impact. The other side of this triangle will, therefore, demonstrate the spin and ball flight placed on the ball (including height), as the ball's axis of spin will be perpendicular to that side of the triangle. Remember, irons place backspin or underspin on a ball, so we're talking about tilted backspin (not sidespin as classically taught). Consider this video explanation:

So, a D-Plane that tilts left will produce a hook and a D-Plane that tilts right will produce a slice, with varying degrees of severity, obviously, depending on the gap or difference between face and path. The more elongated the D-Plane, the greater the loft of the club and the less effect the differential between face direction and cub path have on the ball flight.

Notice what is NOT a variable--the plane of the swing (a plane can be created by the setting up at address to encourage a swing out to the right or a swing inside to the left). The swing plane is usually related to the club shaft--not the club head or club face. However, the swing plane, tilted right or left, can still produce seemingly contradictory ball flights, because the impact point of the club face may be moving in the opposite direction of the plane. This means you can setup aimed right, swing to the right, and still hit a slice or setup left and still hit a draw (and both of those have happened to me before).

In a good iron shot, the impact point of the club face is moving forward and either left or right, but it's ALSO moving DOWNWARD. Downward angles of attack (hitting down with an iron) have the effect of closing the face relative to the plane, while upward angles of attack (hitting up with a driver) have the effect opening the face relative to the plane. These angles of attack, however, do NOT close or open the face; they actually create slight inside-out (downward) or outside-in club motions (upward).

So, how is one to make anything of all this theory on the golf course in order to shape shots usefully? Well, it's much more important to adjust ball position at setup as opposed to trying to adjust the plane (i.e., alignment) at setup. Hooking the ball requires the face impact point to be moving to the right with that impact point facing left, and it's easiest to do that on the back side of the swing arc; the club will be moving rightward on the backside as it moves downward. The contrary is true for a fade.

So you want to draw the ball but start the ball right of the target line (a "push-draw"), so that it draws back towards the target? The club face must, therefore, be OPEN slightly to the target line, but CLOSED slightly to the club head path direction. Move the ball back slightly in your stance to encourage a DOWNWARD angle of attack. As with most things in golf, a few degrees here and there go a long way. Again, this ASSUMES you can return the club face to the same condition it was at address, and this ASSUMES that you know how to get your path moving inside-out, and those are BIG ASSUMPTIONS.


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