William L. Coney Blog: MyGolfSpy Labs: The Horizontal Impact Location Study

By: Tony Covey

A couple of weeks ago we published a study that showed what was likely obvious to most of you; impact location matters.

The data we published backed-up much of what we've been taught since our indoctrination to the game, but quantifying the intel proved interesting enough that many of you asked us to take a closer look at our horizontal (heel/toe) impact location data.

And since you asked nicely, we obliged.

There is a bit of a requisite disclaimer. As with our vertical impact study, looking at horizontal impact location in a vacuum makes it impossible to paint a complete picture of the full influence impact location has over ball flight.

Nevertheless, it is, again, interesting to look at some actual numbers behind the theories.

About the Data

Before we get to the data, here's a quick recap of where it comes from.

Data was gathered during this season's Most Wanted Driver test.
Included are data points from over 5000 shots (for this sample, it's just under 5700), generated by 20 golfers hitting 25 different drivers.
Ball data was gathered using Foresight GC2 Launch Monitors, while the head data, including impact location, comes from an attached Foresight HMT unit.
All testers hit Bridgestone B330-RX Golf Balls.
For this analysis, we again defined the center region as +/- 4.5mm from face center. Arguably this is a generous definition, and we would expect more significant ball speed decreases if we redefined center more narrowly (+/- 2mm for example).
The header graphic (top) shows the impact pattern from our test, though representative of the actual data, it's not exactly to scale with the clubface.

IMPACT LOCATION: ALL SHOTS

Observations:

Interestingly, center face strikes were produced by swing speeds that were approximately 2 MPH faster than those leading to heel and toe contact.
Differences in launch angle aren't likely directly related to horizontal impact location, but rather the general tendency for toe strikes to be high on the face, while heel strikes tend to be low on the face.
As with our vertical impact study, the greatest ball speeds are generated by center face contact.
As you would expect, heel struck balls started more leftward (Side Angle) than those struck on the center or toe - the latter producing the most rightward starting direction.
Balls struck on the heel side produced a right tilted spin axis (fade spin), while toe struck balls resulted in significantly negative axis tilt (draw spin).
As you would expect, center struck ball produced the greatest distance, while heel shots resulted in a loss of 18.1 yards on average, compared to a loss of just over 5 yards on toe struck balls.

IMPACT LOCATION: SWING SPEEDS OVER 100MPH

Observations:

Again, center contact occurred on the fastest swings. We believe this speaks to overall benefits of what we would describe as more efficient swings.
As heel impacts are generally low on the face, we see a correlation with our vertical impact study which suggests that a comparatively more positive Attack Angle corresponds with low face contact.
Ball speeds are again highest on center face contact.
While vertical launch angles are nearly identical, we again see significant differences in starting line (Side Angle), with toe strikes starting the most right of the target line.
While the players in this group created what could be described as draw spin at each impact position, the most negative axis tilt was created by toe struck shots, while the least axis tilt was created by heel struck shots.
Interestingly, this group generated nearly identical distance with center and toe struck balls. This is attributable to marginal differences in average ball speed coupled with lower spin generated by what we presume is often slightly high toe contact.

IMPACT LOCATION: SWING SPEED BELOW 100 MPH

Observations:

For our sub-100 MPH group, the fastest swings, on average, resulted in toe-sided contact.
Again we see clear differences with the slower swing speed group as Attack Angle less positive for heel struck balls.
Center contact resulted in the greatest ball speeds, while heel contact resulted in significant degradation of ball speed and distance.
For this group, we see significant differences in launch angle between toe and heel shots. Again, this is likely attributable to the tendency for heel contact to below face while toe contact also tends to be high face.
As with the full cohort and our faster swingers, this group reinforces the fact that toe struck balls will start appreciably more to the right than heel struck balls.
Again the axis tilt numbers confirm the correlations between heel contact and positive axis tilt (fade spin), and between toe contact and negative axis tilt (draw spin).
As we would expect, for this group, the greatest average distance was produced by center contact, while a nearly 15-yard average distance penalty was incurred for heel-sided contact.

Additional Notes:

The horizontal impact data is not nearly as evenly distributed as it is for vertical (high/low) impact. Over the course of our driver test, more than twice as many balls were hit on the toe than on the heel.
Center face contact occurred only slight more often than heel impact.

The Verdict:

The data shows exactly what we would expect:
Balls struck on the heel side generally start more to the left (a pull for right-handed golfers), and result in a more right tilted axis (fade spin or less draw spin).
Balls struck on the toe side generally start more to the right (push) and result in a more left tilted axis (draw spin or less fade spin).
Differences in Attack Angle, Dynamic Loft, and Launch Angle are more closely tied to vertical impact locations (high/low face contact).
Center struck balls produced the greatest distance. While the data suggests the penalty for toe impact is comparatively small, heel contact invariably results in the most significant average distance penalty.
Combined with our Vertical Impact Study, it is reasonable to conclude that vertical impact location has a greater influence on trajectory, while horizontal impact location has the greater influence over directionality.