I started a thread over at Brian Manzella’s site talking about the future of the D Plane.  As a model, I think it needs a little refining to handle the off center hits.  I’m not exactly sure what that refining will turn into but I have a theory.

I was talking with David Colclough about this topic and he really got me thinking.  I’ve asked some very smart people about my theory and will discuss the results after I hear back.

Ok, so here’s my theory.  The D Plane suggests that the spin axis on the ball will be perpendicular to the plane formed by the 3d club path and clubface normal.  It also suggests that the lift forces will be perpendicular to the spin axis.  This model works wonderfully for center hits.  However, for off center hits, the spin axis and lift forces are not in the D plane because of the gear effect caused by the off center hit.

My theory, which allows for center hits and off center hits to be accurately described is to use the 3d direction of the spin axis as the top vector and not the clubface normal.  This would allow for a properly shaped D Plane for any outcome.  I don’t know if I’m right and I’m pretty sure someone much smarter than me will come up with the right model.

I can say this.  The email I received from Fredrick Tuxen  shows agreement that the D Plane model is not sufficient to explain off center hits

Let the tweaking begin.

I’ve talked a bunch about how to hit straight iron shots using the D Plane as a guide.  I have assumed in my previous cases that I was dealing with a level lie.  Let’s look at the situation of an uphill lie.  This post will not talk about a ball above your feet as in a sidehill lie.

D Plane for Uphill Lies:  In order to hit these shots well, there are some things we have to do with our setup and swing to account for the slope.  Typically, we are told to aim a little to the right, get the shoulders at the same angle as the slope, move the ball a little forward and try and swing with the slope.  What does this do to the swing?  Because we are swinging with the slope, we end up with positive angle of attack relative to the target line.  The club reaches it’s lowest point before it strikes the ball.  How can the club reach it’s lowest point before the ball if I take a divot after the ball?  It’s possible because of the slope of the ground.  So, if my swing is directly at the target at low point, when the club gets to the ball the club has started to come inward and upward.  The more positive the angle of attack also gives us more time to close the face.  For these two reasons, these shots will tend to go left.  This is the why of aiming a little to the right for a right handed golfer for an uphill lie.