2014 Articles

Ever since I read in Ben Hogan’s Five Lessons book about the low trajectory high spinning wedge shot that appears to be skulled over the green, yet takes a hop or two then stops, I’ve been interested in how this shot actually is stuck. Hogan said that all the great players could hit this shot. After fiddling around with different ideas for years, I’ve come up with a rough, unrefined way to teach it using a Casio but still the exact micro mechanics of the impact conditions of this shot eluded me. So I looked online for some ideas and found a noted teacher’s Trackman representation of how the shot is performed. Here’s his prescription:

• 40 degrees of dynamic loft at impact
• 30 degrees launch angle
• Magic number of over 8000 rpm
• Spin loft of 45 for max spin
• Shaft lean of 10 degrees
• Shallow angle of attack

All of this sounds good except for a couple of things. I have found that too much shaft lean (10 degrees as recommended) might be counterproductive to spin. This also makes the 40 degrees of dynamic loft to be rather impossible. So I set up an experiment over the holidays to try to get some good Phantom high speed camera footage of this shot.

   

Phantom High Speed Video

To understand the low trajectory, high spinning (let’s call this the low spinner) shot I took videos of several different styles of hitting a 35 yard shot. To highlight the differences here it is vs. the high floater shot that many people use.

This was shot at 24,000 frames per second in order to measure spin rate, dynamic loft, attack angle and launch angle. Both players were using Titleist Vokey “M” grind 56 degree sand wedge for this shot. Both shots stopped within a few feet of landing near the hole but with two very different trajectories and backspin.

Analysis shows this.

Low trajectory high spinner on a 35 yard shot
51 degrees dynamic loft approx. and decreases .5 degrees in the impact duration
Shaft leaning 6 degrees forward
4 degrees downward angle of attack (pre-impact to initial contact)
Changes to 6 degrees downward angle of attack during the impact duration!
8200 rpm spin
29 degree launch angle
Slight opening of the clubface through impact
11 frames or .00046 seconds of ball contact
39 mph ball speed
54 mph club speed at toe

This is 300 fps Casio of this shot.

Here’s another player there who uses the bounce on those types of shots so I shot his impact too.

I thought this was very interesting. Here’s analysis of his high floater/low spin rate shot.

49 degrees dynamic loft
No change to dynamic loft during impact duration
9 degree shaft lean forward
1.4 positive angle of attack
Increase in angle of attack of .4 degrees during impact duration
3000 rpm backspin
43 degree launch angle
Slight closing of the clubface through impact
15 frames or .00063 seconds of ball contact
35 mph ball speed
45 mph club speed at toe

This is the 300 fps Casio of the high floating shot.

This shows two different ways of stopping the ball on a green; one relying on high spin rate while the other uses a higher launch angle and descent. But these videos just shows the differences between shots. We’re far from understanding this phenomenon just yet. So I shot even higher speed videos of these two different types of shots.

   

Observations of Phantom Ultra High-Speed Video of the Spinning Wedge Shot

At higher frame rate of 100,000 fps, the Phantom videos show that the impact duration can be broken down into three phases.

At the initial contact, the first thing we see is compression. The club remains on a constant angle of attack which on this shot was about 4 degrees down.

The second phase shows a stretching of the skin/outer layers of the ball followed by spinning. As the spinning of the ball starts, there is a noticeable change in the angle of attack. In this shot it dives down an additional 4 degrees. Thus, the angle of attack changes to about 10 degrees down while the ball is beginning its rapid spin. There is also a slight .6 degree decrease in the loft in this phase.

The third phase begins as the soft, elastic outer layers of the ball begin to “snap back” into its original form. This plus the club’s sharper descent appears to pull the ball down and lower the trajectory or launch angle of the golf ball while it spins rapidly.

   

Observations of Phantom Ultra High-Speed Video of the High Floater

When we compare the high floating shot to the spinner, we can see the differences.

The first phase of the high floater shot shows a shallower, slightly positive attack angle that creates higher launch angle. There is a similar compression as in the low trajectory spinning wedge shot.

But in the second phase, maybe due to the bounce coming into contact with the turf well before impact and then “bouncing” back up. Also there is no diving down of the club and instead the angle of attack increases a bit during the impact duration. This causes a more direct strike of the ball with more compression causing the ball to launch more in the direction the clubface is pointing.

In the third phase, there are less of the outer layers of the ball being stretched, therefore there is less spin.

   

Discussion

So we’re getting closer to some understanding. Angle of attack (AoA) is important but is not a static number or event. Phantom world shows us that the AoA can and does change during the impact interval. This must be affecting launch angle and spin therefore we shall call this “dynamic AoA.”

Also, the club’s dynamic loft can change during the impact interval. Shall we call that the “dynamic dynamic loft” since it is changing during the impact interval? Dynamic loft decreased by a half degree on the low spinner while it stayed roughly the same on the high floater.

Face angle opened slightly on the low spinner while it slightly closed during impact duration on high floater. What’s the significance of this?

Clubhead speed just before contact on the low spinner was higher to fly the same distance as the high floater (54 mph to 45 mph). Does this point toward a faster but more glancing strike on the low spinner?

Contact time was substantially less for the low spinner (11 frames vs 15 frames).

The experts always talk about good, clean contact to get most friction to create spin. Sure some grass clippings/dirt appeared to get in between the clubface and ball but this cannot completely explain the over 5000 rpm difference in spin rate and the 14 degree difference in launch angle. So what causes backspin?

   

What Causes Backspin?

Looking for answers, I ran across Dave Tutelman’s site. Here’s Cochran and Stobbs illustration of how backspin is created. Is that correct representation of the actual events during the impact interval?

Just as in the flight of the bumble bee, scientists (Cochran and Stobbs) didn’t have the benefit of ultra high speed video, so it is understandable that they had to guess at what conditions were like in the impact duration. But just for mental exercise let’s see how right they were. 

1. Initial sliding – incorrect. Phantom video shows compression first
2. Compression/rolling – incorrect Phantom video shows no rolling
3. Rebound and release – correct but not very specific

Since this doesn’t appear to match Phantom reality, understanding spin will require more study. I’ll do some experiments in the next few weeks to see if we can get more understanding of spin from other sports.

   

How To Hit the Low Spinner

Thus for now, let me give my best guess prescription for how you can hit this shot. But first, let me explain what it is not. If you have too much shaft lean and do not have the club passing your hands near impact, you will hit a punch shot (pitch and run shot) with low trajectory and low spin rate. If you let the club flip past your hands too early, you will hit a high floating shot with low spin rate. Somewhere in between is the magical place where you can hit this shot that tour pros can hit with their eyes closed.

Set up with weight on left side – only lob (higher than high floater) would be set up with the majority of your weight to the right. Hands should be slightly forward. Clubface slightly open.

One’s body should be constantly rotating through impact. Without the body rotation through impact, you are likely to flip a bit early and hit the high floater.

Then you must hold enough lag to get near impact with some shaft lean then release so that somewhere around 5-7 degrees exists at impact. Once you have that lag, you must relax your hands/arms just before impact to stop drive/holding and let the club swing past your hands. 

This increases the speed differential of the sole of the club and the top line of the head. If the sole is moving much faster, there will be more spin due to the bottom of the ball being compressed more than the top. If moving same speed it is more likely to be a floater. Or if top line moves faster, it will be more of a punch shot.

I’ve seen this shot done with path right or left. Swing plane can be flat like Stricker, steep or “on plane.” It’s all in the impact zone dynamics. 

As shown in the ultra high speed video the clubface slightly de-lofts. This suggests more of a low on the face contact point. This one was centered on the third line from bottom. Low contact point helps lower the trajectory by lowering the loft slightly. Too high and you’re striking the ground earlier and will hit either fat shot or high floater shot. Too low on bottom and you can get a skulled shot.

Loose grip pressure is important to allow the club to swing past your hands. If grip pressure is too firm, it’ll be a punch shot.

The clubface does not close during the impact interval. Stays steady or opens slightly. This can be easily done if slightly hit toward the toe of the club as in the above picture. If closing, it will decrease backspin.

Low point of the swing must be just after impact in Phantom world. This allows the clubhead to dip downward during the impact duration but be careful not too much downward or you will hit a punch shot. If low point is behind the ball, you can only hit a skulled shot or a high floater.

Swing speed is higher due to more glancing blow with low spinner. All things being equal the punch shot requires the lowest speed to achieve the same distance due to low trajectory, low spin and therefore more roll.
   

	Lo Spinner	High Floater	Punch shot
Dynamic angle of attack	Slightly down to more sharply down	Slightly up	More sharply down
Low point	Post impact	Pre-impact	Post impact
Dynamic, dynamic loft	Around 50 degrees with slight de-lofting	Around 50 degrees or more and constant	45 degrees or less and decreasing
Shaft lean forward	5-7 degrees	Can be anywhere between 10 and 0. Depends also on amount clubface is open.	10 or more
Contact point	Low 2nd or 3rd groove and slight toe	5th groove or higher	Can be anywhere on bottom half
Dynamic clubface angle	Square to slightly opening	Open and slightly closing	Closed slightly and closing faster
Clubhead speed	Fast	Medium	Slow
Speed differential	Sole faster	Similar speeds	Top line faster
Path	Any but generally slightly left	Straight or slight right	More right
Hand pressure	Hold lag then loose	Loose	Hold lag then stay firm
Body motion	Rotating through impact	Stalling	Rotating

   

Things That Don’t Appear To Matter As Much

• Ball placement – can be middle, forward or back in stance. Tour guys are doing this with impact zone dynamics not simply ball position.
• Path – can swing left or right. Tour players can spin it with draw or fade spin axis.
• Plane – good to think of being “on plane” but again tour guys can hit with any plane.
• Stance direction – since tour players are using all sorts of planes/paths the stance can be open, square or even closed (if steep with path left).
• Release style – Hard to say it has to be any one release style. Only thing that could be said is it is not a drive/hold and not a flip or flip/roll. I’ve seen players use underflip, right side rolling and even a flip/drive release (if body is leaning left enough). It’s all about controlling the impact zone mechanics.
• Wrist cocking on backswing – some players use lots of wrist cock like Ben Hogan and Graeme McDowell or some barely hinge the wrists like Steve Stricker or Jason Day. Once again, it doesn’t seem to matter if you can control the impact.