TrackMan Golf Case Study – February 8, 2013 – “Reducing Spin Loft”
Subject: RH Male, early 50’s, in very good shape and physically strong. Career best score of 74, but last season averaged 84 strokes per round. In our pre-session interview, he mentioned being a very high ball hitter. Since he plays most of his 50+ rounds per year on a course that is known for windy conditions, the high flight of his shots can be problematic.
We gathered a set of 12 test shots with his 7 iron. Analysis of that series revealed an average spin rate of over 8100 rpm – far too high for a 7-iron and a key contributor to “ballooning” flight trajectories. Upon further analysis, we were able to drill down and reveal the culprit behind these sky-high spin rates: extremely high spin loft values.
Spin loft is often referred to as the difference between dynamic loft and attack angle, as pictured below. Strictly speaking, this definition is incomplete. Spin loft incorporates not only the vertical components of attack angle and dynamic loft, but also the horizontal components of club path and face angle. In other words, the movement of the club through impact in 3 dimensions. However, for practical purposes, we can work effectively with just the vertical components.
In the test series, this golfer produced an average attack angle of -3.3*. That’s pretty “textbook” performance. However, the average dynamic loft was 29.5*, far too high – optimally, these numbers would be in the low-20’s. The resulting spin loft values (DL – AA = SL) were far too high. In essence, the ball thought it was being hit by a 9-iron or wedge, instead of a 7-iron and the spin rates responded accordingly!
BEFORE: Average DL: 29.5* | Average AA: -3.3*| Average SL: 32.9*
I placed a hula hoop about 6 feet ahead of the ball directly on the target line and had him try to hit balls through it. The only instruction I offered was to “hit the ball lower”. With a simple and measurable instructive bottom-line, the golfer has the opportunity to tap into their intuition. As the instructor, my job becomes one of soliciting their feedback and helping the student interpret what they are feeling. It’s not always cut and dried, but why not start by trying the simplest and most direct path to the root of the problem? The ball is flying too high, therefore, let’s see how our instincts respond to the directive of hitting it lower.
In this case, the results came fairly quickly. After some practice with the hoop and some conversation, we gathered another test set.
AFTER: Average DL: 23.9* a drop of almost 6* | Average AA: -2.7*, slightly shallower | Average SL: 26.8*, a drop of 6*. Very good changes. More to the point of our discussion here, his spin rate dropped by about 2000 rpm – from an average of 8100 to about 6100.
As an added bonus, the hula hoop drill improved not only his trajectories, but the directional control as well. The resulting ball flight is more piercing and should prove to be much more stable and predictable in the wind.