-Sean Foley
Understanding Ball Flight in Relationship to the Swing:
If you are like me who regularly watches the PGA and LPGA tours on television, I always used to wonder how the unique looking swings (ex: Jim Furyk, Ai Miyazato, Bubba Watson) hit the ball straight or consistently towards the target they are aiming for. In addition, recently I have been astounded by how Tiger rehearses his really "cut across/ over the top" swing and hits his shots so pure, far, and accurate. Well, with the introduction of top of the line club and ball measurement systems, Trackman and Flightscope, these mysteries and common myths about golf have been debunked.
PGA & LPGA Tours Trackman Insight
The Physics Behind A Straight Shot
Trackman is promoting a
numbers feel to the game of golf. These
numbers including club path, club face, angle of attack, (and more!!!) give
facts about a good or bad golf swing. In these numbers there are no teaching
philosophies or opinions, just facts that result in the ball flight that you
see. While critics think this technology will create more technical thoughts, top instructors Sean Foley and Martin Hall believe that it allows the player to invent their own feel. With no guessing involved through the scientific understanding of cause and effect, there isn't much need for video analysis. This means that you can control & feel your swing's clubface control and clubpath to get the numbers to produce the desired ball flight.
The use of this device “gives more trust between the player and the
teacher, which leads to safety, which leads to learning as quickly as possible
(because this eliminates predetermined fears or doubts swing changes hurting
scores etc.).” – Sean Foley
“Video shows style, but Trackman shows skill. It helps the
student invent feel. Trackman puts every
swing theory on trial.” – Martin Hall
Club Path vs. Club Face
Basically the initial starting line of the golf shot is with the club face. So wherever you point the face at impact is where the shot goes. [The specifics: for an iron the initial starting line is about 75% due to the clubface at impact and the club path is about 25%. With the driver the initial starting line is about 85% due to the clubface at impact and the club path about 15%]. So when you are watching on the range or the course, figure that the reason your shots start left or right is because of the clubface (also see Driver Gear Effects below). The club path directly causes the spin of the golf ball (the horizontal spin axis tilts). Backspin does not counteract sidespin because there is no such thing as "sidespin." Backspin just tilts on an axis (see picture below).
Club-Path-Spin relationship
The D-plane is the wedge-shaped plane between two 3-dimensional directions: 1) clubhead direction at impact which is described by attack angle and club path and 2) clubface orientation at impact which is described by dynamic loft and face angle. In the figure above, the opaque shaded wedge-shaped plane is the
D-plane. Note that the angle of the D-plane is actually the spin loft.
Basically, to hit the ball straight and apply maximum force to the ball, a tour pro has his face angle and clubhead path perfectly square. To hit a draw, the tour pro will either adjust the face angle or the path so that the face angle at impact is from 1 to 2 degrees closed to the path. Since face angle is more of a determining factor in initial ball direction than clubhead path (80% vs. 20%); the tour pro will almost always keep the face angle square to the target and swing from 1 to 2 degrees inside out. This starts the ball slightly right of the target and the balls slight draw spin curves it back toward the target. Easier said than done. 1 degree produces a very slight draw and 2 degrees a normal draw. Over 3 degrees is a hook and over 4 degrees is a terrible hook. So you see that controlling clubhead and path properly and consistently takes some skill because we are dealing with very small amounts of angle change that affect big amounts of ball flight change.
As you can see, the clubface directs the initial starting line, while the swing path (since it is more to the right of the clubface) causes the ball to spin right to left. {The old views on how the ball flew was that the path influenced the initial starting line the most, however through Trackman technology, this view was proven false.}
Bubba Watson's shot out of the pine straw on hole 10 in the 2012 Masters playoff was a big push overdraw or "hook" shot. He had the clubface at impact pointing well to the left of the flag, while he had his clubpath point way further out to the left to get the amount of curvature that it did (see below).
The correct visual of clubface to clubpath relationship.
The D-plane is the wedge-shaped plane between two 3-dimensional directions: 1) clubhead direction at impact which is described by attack angle and club path and 2) clubface orientation at impact which is described by dynamic loft and face angle. In the figure above, the opaque shaded wedge-shaped plane is the
D-plane. Note that the angle of the D-plane is actually the spin loft.
Basically, to hit the ball straight and apply maximum force to the ball, a tour pro has his face angle and clubhead path perfectly square. To hit a draw, the tour pro will either adjust the face angle or the path so that the face angle at impact is from 1 to 2 degrees closed to the path. Since face angle is more of a determining factor in initial ball direction than clubhead path (80% vs. 20%); the tour pro will almost always keep the face angle square to the target and swing from 1 to 2 degrees inside out. This starts the ball slightly right of the target and the balls slight draw spin curves it back toward the target. Easier said than done. 1 degree produces a very slight draw and 2 degrees a normal draw. Over 3 degrees is a hook and over 4 degrees is a terrible hook. So you see that controlling clubhead and path properly and consistently takes some skill because we are dealing with very small amounts of angle change that affect big amounts of ball flight change.
As you can see, the clubface directs the initial starting line, while the swing path (since it is more to the right of the clubface) causes the ball to spin right to left. {The old views on how the ball flew was that the path influenced the initial starting line the most, however through Trackman technology, this view was proven false.}
Bubba Watson's shot out of the pine straw on hole 10 in the 2012 Masters playoff was a big push overdraw or "hook" shot. He had the clubface at impact pointing well to the left of the flag, while he had his clubpath point way further out to the left to get the amount of curvature that it did (see below).
The clubface was closed to the clubpath which caused the ball to spin left to right, causing a hook.
Impact occurs in about 4/10,000 of a second while the blink of an eye is about 4/10 of a second. Thus impact is a thousand times quicker than a blink of an eye. There is no way we could possibly rotate/ roll/ flipping the clubface to create spin.
Overall look at Bubba's Swing Path. The flag is 45 yards right from this angle!
The ball spun on a 38 degree tilted axis to get the ball spinning back to target.
Bubba's 45 yard hook: Sports Science
Attack Angle & Swing Planes
See this video for an easy explanation: https://www.youtube.com/watch?v=G5JYjNsyDpk
If you have an attack angle of -5 degrees down you will need to shift the Horizontal Swing Plane (the exit point of the club left or right) to the left -2.5 degrees to have a neutral clubpath and thus hit a straight shot (pending your clubface is neutral at impact as well). With the driver, since we want to catch the ball on the upswing, say +2 degrees, we would have to shift the Horizontal Swing Plane +2 degrees to the right to have a neutral clubpath and thus hit a straight shot (again pending your clubface is neutral at impact as well). The reaso
This figure above shows the effects of the "angle of attack-horizontal swing plane" relationship for a 6 or 7 iron. If you swing how you generally should with these clubs, then you should have about a -5 degree angle of attack with a 60 degree vertical swing plane.
So if you have an attack angle of -5 degrees down and your horizontal swing plane (the exit point of the club left or right) is 0.0 degrees, your effective clubpath would be +2.5 degrees to the right and you would hit a draw (pending your clubface is neutral at impact as well).
These charts and figures can be rather academic. Can you explain it in a very down to earth way?
I can try: We can say that with the driver you need the same value for attack angle and horizontal swing plane in order to obtain a 0° club path – for example if your attack angle is +3°, the horizontal swing plane needs to be +3° to obtain a club path of 0°. And for irons it is half effect – for example if attack angle is -4°, the horizontal swing plane needs to be -2° to obtain zero club path. In short, aim left when hitting down on the ball and aim right when hitting up upon the ball. And remember when I say ‘aim left’ I mean the swing plane, the face angle should always be aligned towards the target line. Ball position is an issue here as well?
Absolutely. If you move the ball back towards your right foot for the same horizontal swing plane, the effect will be a steeper attack angle (more negative) and a more inside-out club path (more positive). So, in order to maintain a zero club path while moving the ball further back in your stance, you simply have to rotate your
horizontal swing plane towards the left (more open stance). Before we discussed that the shorter the club and the steeper the vertical swing plane, the less you had to compensate your horizontal swing plane away from the target line.
If you are hitting down -5° with every iron, the shorter the iron you hit the steeper your vertical swing plane will be and the lesser you’ll have to compensate your horizontal swing plane to the left to achieve a club path of 0°.
The shorter the iron with the same attack angle, the more direct at the target you should aim. In other words, it is more important to compensate – swing left – with the 3 iron than with the 8 iron.
This figure above shows the effects of the "angle of attack-horizontal swing plane" relationship for a 6 or 7 iron. If you swing how you generally should with these clubs, then you should have about a -5 degree angle of attack with a 60 degree vertical swing plane.
So if you have an attack angle of -5 degrees down and your horizontal swing plane (the exit point of the club left or right) is 0.0 degrees, your effective clubpath would be +2.5 degrees to the right and you would hit a draw (pending your clubface is neutral at impact as well).
These charts and figures can be rather academic. Can you explain it in a very down to earth way?
I can try: We can say that with the driver you need the same value for attack angle and horizontal swing plane in order to obtain a 0° club path – for example if your attack angle is +3°, the horizontal swing plane needs to be +3° to obtain a club path of 0°. And for irons it is half effect – for example if attack angle is -4°, the horizontal swing plane needs to be -2° to obtain zero club path. In short, aim left when hitting down on the ball and aim right when hitting up upon the ball. And remember when I say ‘aim left’ I mean the swing plane, the face angle should always be aligned towards the target line. Ball position is an issue here as well?
Absolutely. If you move the ball back towards your right foot for the same horizontal swing plane, the effect will be a steeper attack angle (more negative) and a more inside-out club path (more positive). So, in order to maintain a zero club path while moving the ball further back in your stance, you simply have to rotate your
horizontal swing plane towards the left (more open stance). Before we discussed that the shorter the club and the steeper the vertical swing plane, the less you had to compensate your horizontal swing plane away from the target line.
If you are hitting down -5° with every iron, the shorter the iron you hit the steeper your vertical swing plane will be and the lesser you’ll have to compensate your horizontal swing plane to the left to achieve a club path of 0°.
The shorter the iron with the same attack angle, the more direct at the target you should aim. In other words, it is more important to compensate – swing left – with the 3 iron than with the 8 iron.
| Attack angle: the descent of the clubhead into the ball |
 |
| The horizontal swing plane (in red "hsp") and the vertical swing plane (in blue "vsp"). In this section we are discussing shifting the horizontal swing plane to the left when we have a steep angle of attack. On the contrary, when swinging the driver, we shift the horizontal swing plane to the right because we have a shallow angle of attack. |
So the change in "angle of attack-vertical & horizontal swing plane" relationship is why Tiger rehearses that "cut across/ over the top" swing and still hits his shots far and straight. For his "stinger" low penetrating shot he may be swinging -9 degrees down, so he'll have to shift the Horizontal Swing Plane (the exit point of the club left or right) to the left -7.0 degrees to have a neutral clubpath and thus hit a straight shot (pending his clubface is neutral at impact as well).
I've seen these concepts in action when some amateur golfers who swing way "across/ over the top" hit straight irons with deep divots pointing way left, yet still slice the ball heavily with the driver. This is because their angle of attack-horizontal swing plane relationship is the 2:1 ratio that produces neutral clubpath. With the driver there is the incentive to sweep the ball off the tee (in an effort to maximize distance). Thus, they don't swing with such a steep attack angle, however they still swing across the ball, so the 2:1 iron ratio becomes a 2:10 driver ratio, resulting in massive slices. While it leaves them dumbfounded, the "angle of attack-horizontal swing plane" relationship is the underlying cause. Remember with the driver, since we want to catch the ball on the upswing, say +2 degrees, we would have to shift the Horizontal Swing Plane +2 degrees to the right to have a neutral clubpath and thus hit a straight shot (pending your clubface is neutral at impact).
This figure depicts hitting a straight shot. But an open clubface to clubpath causes a slice right?
Not necessarily, given the attack angle is about -5 degrees down, the shot will be straight.
|
| Another view of shifting the horizontal swing plane (this picture shows a shift to the left) |
Driver Gear Effects
The process of the ball spinning up or down the clubface (horizontally or vertically) is like a gear
Vertical Gear Effect
When the ball is hit above the center of gravity, the impact of the clubface-ball causes the face angle to tilt back slightly resulting in the ball spinning down the face a little bit. This results in a low spin, high launching golf shot which will maximize distance.
As a general rule, you want to tee the ball where half of the ball's equator is above the clubface.
Drill: Use a dry erase marker or impact tape to see where you are catching the ball on the clubface.
Drill 2: Observe the ball flight in relation to where you felt you hit the ball on the clubface (heel, toe, sweet spot). If you are hitting the ball in the sweet spot yet still hitting slices or hooks, then take a look at your swing plane, clubface control, etc.
The fix you will see in the case study video (link below) was to simply tee the ball up higher. Other causes of Low Launch and High Spin driver shots: not enough loft on the club, angle of attack is too steep, ball position too far back, de-lofting club at impact.
Horizontal Gear Effect
Heel Contact:
Ball flight for strike on heel should be a shot that starts left and slices/ fades further right.
Heel contact of the clubface-ball causes the clubface to twist close slightly. The ball rides towards the center of the clubface causing a the spin axis tilting to the right (slice for right-handed golfer). The ball will start more to the left than if it were struck in the center.
Toe Contact:
Ball flight for strike on toe should be a shot that starts right and then hooks/ draws back left.
Toe contact of the clubface-ball causes the clubface to twist open slightly. The ball rides towards the center of the clubface causing a the spin axis tilting to the left (hook for right-handed golfer). The ball will start more to the right than if it were struck in the center.
IF you've ever wondered why club manufactures engineer Drivers and Woods with a slight concave bulge, it is because it counteracts the severity of this gear effect. So if you hit the ball out on the heel, the bulge (on the heel it makes the clubface slightly closed) negates some of the spin generated by the ball riding towards the center of the clubface.
IF you've ever wondered why club manufactures engineer Drivers and Woods with a slight concave bulge, it is because it counteracts the severity of this gear effect. So if you hit the ball out on the heel, the bulge (on the heel it makes the clubface slightly closed) negates some of the spin generated by the ball riding towards the center of the clubface.
Drill for Steep Attack with the Driver:
Move the pelvis as far forward as you can where your right foot is banked to the left; your weight should be about 90-95% on front foot, and there should be some axis tilt. Move the clubshaft slightly forward (see above). Hit half punch shots with hips and weight forward. On the downswing the arms should be straight. When you bend the elbows the angle of attack tends to go down while the path of the swing direction goes more to the left.
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