While the Spin Loft of a shot is important, our interest usually lies in how it changes what the ball will do. This post will focus on the spin of the ball for standard, full shots (there are additional factors when talking about shorter, green side shots); which way the ball will spin and how quickly.
As with a lot of my posts, checking out this page of definitions might help with some of the technical terms used.
If you haven't already, you'l probably want to read Spin Loft: Part I - Smash Factor and Ball Speed, as it defines Spin Loft and has some other helpful in there.
A golf shot's Spin Rate is a function of Spin Loft, Clubhead Speed, and contact location. More Spin Loft will result in more spin, as will more Clubhead speed. Less Spin Loft will result in a lower Spin Rate, as will slower Clubhead Speeds. [For complete info on contact location, please refer to my blog post on miss hits.]
These two shots would have identical Spin Rates, all else being equal (assuming no Horizontal Differential):
1) VPath (Angle of Attack): -3.0°, VFace (Dynamic Loft): +9.0°, Spin Loft = 12.0°.
2) Vertical Path: 1.0°, Vertical Face: 13.0°, Spin Loft = 12.0°.
The golf ball doesn't know if it was hit down on or up on, it just knows that it was hit with a 12.0° glancing blow.
So, while changing your Angle of Attack may affect your Spin Rate, it won't if the Dynamic Loft changes by the same amount, since you'd end up with the same Spin Loft (although it would result in a higher launch, since both the Face and Path are more upwards). This means that just hitting more up with your driver will only help you reduce your Spin Rate if you can prevent the Vertical Face (Dynamic Loft) from increasing at the same time.
In simplest terms: the closer the 3D Face and 3D Path are to each other, the lower the Spin Rate will be (also, the higher the Smash Factor and Ball Speed).
Now, the Spin Axis tells us how tilted the D-Plane was, and how sideways the ball will be spinning. A perfectly straight shot, with no sidespin, is spinning perfectly backwards, around a perfectly horizontal Spin Axis (0.0°). A theoretical shot with a perfectly vertical, 90.0° Spin Axis (either Left or Right) would be spinning straight sideways.
The Spin Axis will tilt any time the Horizontal Path and Face are not going in the same horizontal direction. How much it tilts depends on the Horizontal and Vertical Differentials.
Two different golf shots could have identical Horizontal Path and Face numbers, but experience very different Spin Axis numbers, depending on the difference between the vertical components (Vertical Differential). Shots with very high Vertical Differentials (like wedge shots) stretch the D-Plane upwards resulting in flatter, less tilted Spin Axis numbers than low Vertical Differential shots (like drivers), which will tilt much more.
For example: two shots could share the same Horizontal Differential (difference between path and face, as if viewed from overhead), let's say 3.5°. The lower Spin Lofted shot (say, with a VDiff of just 5.5°) will experience a tilting of its Spin Axis of 32.7°! This would not be a useful golf shot at all. However, the same Horizontal components could result in a Spin Axis tilt of only 6.6° (slight curvature) if its' VDiff was much higher (31.5°). This sounds like a lot of specific numbers, but it explains why drivers spin sideways way more than wedges.
This is the trade-off between distance and accuracy; lower spin lofted shots will tend to carry further due to higher ball speeds and lower spin rates, but the same shot will tend to spin sideways more if the Path and Face get out of line much. Given this information, one might decide to try and hit shots with lower Spin Lofts on open driving holes where distance is a priority and hit shots with higher Spin Lofts on holes where you'd want more control. In fact, Bubba Watson (admittedly, one of the more creative players on Tour) has been measured varying his Vertical Path between -7.5° and +5.0° during competition (Trackman Newsletter #2, Pg. 12), suggesting that he employs this kind of strategy (whether he knows it or not).
So, in summary, a golf ball's spin (amount and direction) is largely controlled by its Spin Loft, which is simply the difference between the Face and Path.
-Mark
@StrongerGolf
Tuesday, 22 November 2011
Wednesday, 9 November 2011
Thoughts on your Setup
We all know that the setup is important to our golf games, but I'm not sure that enough people know how important it really is.
If you continue to read some of my material (or have already read some), you'll see me often refer to the D-Plane and its components, Path and Face. These are two of the main factors that control our golf ball. Well, even though there's a lot going on in a golf swing and things can change, your Club Face aim at address and the Face at impact will correlate highly with each other. Also, your shoulder alignment at setup and your Path at impact are closely intertwined. In a nutshell, these are the reasons that I feel that your Club Face aim and shoulder alignment are two main aspects of your setup that should be constantly checked.
A phrase I find myself repeating on the lesson tee all the time is, "Never blame anything in your swing for a bad shot before you've eliminated the setup as a source of error." For example: a pulled shot can be more easily explained by that ball position being too far forward than "coming over the top," "flipping with the hands," or "lifting my head." I'm always happy to hear students assessing their setup before trying to figure out what went wrong with their swing after a poor shot.
I feel that you need to 1) set up in such a manner that allows you to 2) make a good swing AND 3) get a good result. Setting up with improper alignment or aim does not allow this to happen.
Another example: if you set up to a straight, 10 foot putt with your putter face aimed to the right of the hole, you will have two (or more) options: either make a great stroke and roll the ball to the right of the hole, or make a compensated stroke to get the ball rolling on line. Since a good stroke won't reward you with a holed putt, you're likely to change your stroke in a way that will help you make putts. Perhaps you start to flip the putter head closed or develop a pull stroke from this rightward setup since you'd make more putts doing so.
I also feel very strongly that your setup should strive to be 1) customized to your swing and 2) as consistent as possible. You can't expect to have a consistent swing without a consistent setup. In my opinion, practicing without a target can be harmful for most golfers, since they won't get accurate feedback.
Often, in order to affect change in the stroke or swing, the setup will need to be changed first - not only to allow for the physical differences in the motion, but simply to reward the better swing/stroke with a better result. New behaviours are more likely to be adopted if you get rewarded (with better shots) for doing so.
A little off-topic: The TV commentators that analyze swings in 30 seconds after one quick look do not have an easy task, so I don't mind cutting them some slack (although you do hear some pretty questionable info from time to time). However, I don't understand why a commentator has never suggested, "his alignment looks a little closed," when a poor shot is being replayed and analyzed. Instead of saying something like "he was late with his hands," why not suggest that the same player may have simply been aligned a bit right? If all the Average Joe's out there are listening to the commentators, golfers will always be analyzing their swings, and always neglecting their setups.
Those are my opinions, nothing more.
-Mark
@StrongerGolf
If you continue to read some of my material (or have already read some), you'll see me often refer to the D-Plane and its components, Path and Face. These are two of the main factors that control our golf ball. Well, even though there's a lot going on in a golf swing and things can change, your Club Face aim at address and the Face at impact will correlate highly with each other. Also, your shoulder alignment at setup and your Path at impact are closely intertwined. In a nutshell, these are the reasons that I feel that your Club Face aim and shoulder alignment are two main aspects of your setup that should be constantly checked.
A phrase I find myself repeating on the lesson tee all the time is, "Never blame anything in your swing for a bad shot before you've eliminated the setup as a source of error." For example: a pulled shot can be more easily explained by that ball position being too far forward than "coming over the top," "flipping with the hands," or "lifting my head." I'm always happy to hear students assessing their setup before trying to figure out what went wrong with their swing after a poor shot.
I feel that you need to 1) set up in such a manner that allows you to 2) make a good swing AND 3) get a good result. Setting up with improper alignment or aim does not allow this to happen.
Another example: if you set up to a straight, 10 foot putt with your putter face aimed to the right of the hole, you will have two (or more) options: either make a great stroke and roll the ball to the right of the hole, or make a compensated stroke to get the ball rolling on line. Since a good stroke won't reward you with a holed putt, you're likely to change your stroke in a way that will help you make putts. Perhaps you start to flip the putter head closed or develop a pull stroke from this rightward setup since you'd make more putts doing so.
I also feel very strongly that your setup should strive to be 1) customized to your swing and 2) as consistent as possible. You can't expect to have a consistent swing without a consistent setup. In my opinion, practicing without a target can be harmful for most golfers, since they won't get accurate feedback.
Often, in order to affect change in the stroke or swing, the setup will need to be changed first - not only to allow for the physical differences in the motion, but simply to reward the better swing/stroke with a better result. New behaviours are more likely to be adopted if you get rewarded (with better shots) for doing so.
A little off-topic: The TV commentators that analyze swings in 30 seconds after one quick look do not have an easy task, so I don't mind cutting them some slack (although you do hear some pretty questionable info from time to time). However, I don't understand why a commentator has never suggested, "his alignment looks a little closed," when a poor shot is being replayed and analyzed. Instead of saying something like "he was late with his hands," why not suggest that the same player may have simply been aligned a bit right? If all the Average Joe's out there are listening to the commentators, golfers will always be analyzing their swings, and always neglecting their setups.
Those are my opinions, nothing more.
-Mark
@StrongerGolf
Tuesday, 8 November 2011
Spin Loft: Part I - Smash Factor and Ball Speed
Have you ever been told to hit up more to make your drives fly further? Ideas like these are fine, but are only correct if you understand what else is going on at the same time. Hopefully I'll make things a little more clearer in this blog post regarding 3D Spin Loft, Smash Factor, and Ball Speed.
As with a lot of my posts, checking out this page of definitions might help with some of the technical terms used.
There are a lot of directions that you could go when talking about Spin Loft: how it affects the Smash Factor and Ball Speed, how it affects the Spin Rate of the shot, or how it affects the Spin Axis and the curvature of the shot. Before we go there, I'd like to define Spin Loft.
Trackman defines Spin Loft as the difference between dynamic loft and the attack angle (Pg. 7, Trackman's Glossary). Unfortunately, this is incomplete as they are only looking at the vertical components (dynamic loft = Vertical Face, attack angle = Vertical Path), and disregarding the horizontal aspects of the shot. Spin Loft needs to be measured/considered in 3D, combining both the Vertical and Horizontal Differentials (think: perpendicular to the Spin Axis, instead of just an arbitrary direction like up), in order to properly account for its effects on ball flight. Spin Loft is actually the angle between the 3D Path and 3D Face, which is different than just looking at the vertical components, as if from a face-on view.
As an example of 3D Spin Loft, let's take a shot with a downward VPath of 5.0° and a VFace of 25.0°. The Vertical Differential, or Trackman's Spin Loft, is 30.0 degrees. However, if this same shot had an HFace of 5.0°R (Face is aimed 5 degrees right of the target line) and an HPath of 10.0°L (Path is going 10 degrees left of the target line), we have to take the 15.0° Horizontal Differential into account. The difference between the horizontal components stretches the Spin Loft and, in this case, combines with the Vertical Differential to result in a 3D Spin Loft of 33.5°. While it's not a monumental difference, we've still discovered more than 10% extra to the measurement that only took the vertical components into account; this higher number will more closely correlate with other measurements such as Spin Rate and Smash Factor.
Another definition: Smash Factor is easy to figure out; it's simply a ratio of the resulting ball speed to the shot's club head speed (Smash Factor = Ball Speed / Clubhead speed, eg. 145mph Ball Speed / 100mph Clubhead speed = 1.45 Smash Factor). Newer drivers have been maxed out in terms of their COR (trampoline effect), so you won't see too many Smash Factors over 1.5, with legal golf clubs, anyways.
Lower spin lofts create more compression, so we get higher resulting ball speeds (and, therefore smash factors). Higher Spin Lofts are more of a glancing strike, so less energy goes into propelling the ball, and you get slower ball speeds. While there are a few factors in play (shorter shafts resulting in slower clubhead speeds, for one) causing wedge ball speeds to be significantly lower than wood ball speeds, Spin Loft is the major one.
In terms of maximizing our driving distance with a given swing speed, lower Spin Lofts have the double benefit of increasing Ball Speed and decreasing the Spin Rate; both of which will increase driving distance for almost anybody out there. I'll discuss how the Spin Rate comes into play, as well as talk about the downside of lower Spin Lofted shots in the next Blog post, Spin Loft: Part II - Spin Rate and Spin Axis.
Summary:
As Spin Loft decreases, effective compression increases = Smash Factor and Ball Speed increase.
As Spin Loft increases, effective compression decreases = Smash Factor and Ball Speed decrease.
Thanks for reading, feel free to ask any questions.
-Mark
@StrongerGolf
Nov. 27th Follow Up:
Here's a chart showing the relationship between Smash Factor and Spin Loft. Since the data is from Trackman, it isn't 3D Spin Loft being measured, but Vertical Differential. I have no doubt that, if the data for these shots' horizontal components were available, the correlation would be even stronger between Smash Factor and 3D Spin Loft.
As with a lot of my posts, checking out this page of definitions might help with some of the technical terms used.
There are a lot of directions that you could go when talking about Spin Loft: how it affects the Smash Factor and Ball Speed, how it affects the Spin Rate of the shot, or how it affects the Spin Axis and the curvature of the shot. Before we go there, I'd like to define Spin Loft.
Trackman defines Spin Loft as the difference between dynamic loft and the attack angle (Pg. 7, Trackman's Glossary). Unfortunately, this is incomplete as they are only looking at the vertical components (dynamic loft = Vertical Face, attack angle = Vertical Path), and disregarding the horizontal aspects of the shot. Spin Loft needs to be measured/considered in 3D, combining both the Vertical and Horizontal Differentials (think: perpendicular to the Spin Axis, instead of just an arbitrary direction like up), in order to properly account for its effects on ball flight. Spin Loft is actually the angle between the 3D Path and 3D Face, which is different than just looking at the vertical components, as if from a face-on view.
As an example of 3D Spin Loft, let's take a shot with a downward VPath of 5.0° and a VFace of 25.0°. The Vertical Differential, or Trackman's Spin Loft, is 30.0 degrees. However, if this same shot had an HFace of 5.0°R (Face is aimed 5 degrees right of the target line) and an HPath of 10.0°L (Path is going 10 degrees left of the target line), we have to take the 15.0° Horizontal Differential into account. The difference between the horizontal components stretches the Spin Loft and, in this case, combines with the Vertical Differential to result in a 3D Spin Loft of 33.5°. While it's not a monumental difference, we've still discovered more than 10% extra to the measurement that only took the vertical components into account; this higher number will more closely correlate with other measurements such as Spin Rate and Smash Factor.
Another definition: Smash Factor is easy to figure out; it's simply a ratio of the resulting ball speed to the shot's club head speed (Smash Factor = Ball Speed / Clubhead speed, eg. 145mph Ball Speed / 100mph Clubhead speed = 1.45 Smash Factor). Newer drivers have been maxed out in terms of their COR (trampoline effect), so you won't see too many Smash Factors over 1.5, with legal golf clubs, anyways.
Lower spin lofts create more compression, so we get higher resulting ball speeds (and, therefore smash factors). Higher Spin Lofts are more of a glancing strike, so less energy goes into propelling the ball, and you get slower ball speeds. While there are a few factors in play (shorter shafts resulting in slower clubhead speeds, for one) causing wedge ball speeds to be significantly lower than wood ball speeds, Spin Loft is the major one.
In terms of maximizing our driving distance with a given swing speed, lower Spin Lofts have the double benefit of increasing Ball Speed and decreasing the Spin Rate; both of which will increase driving distance for almost anybody out there. I'll discuss how the Spin Rate comes into play, as well as talk about the downside of lower Spin Lofted shots in the next Blog post, Spin Loft: Part II - Spin Rate and Spin Axis.
Summary:
As Spin Loft decreases, effective compression increases = Smash Factor and Ball Speed increase.
As Spin Loft increases, effective compression decreases = Smash Factor and Ball Speed decrease.
Thanks for reading, feel free to ask any questions.
-Mark
@StrongerGolf
Nov. 27th Follow Up:
Here's a chart showing the relationship between Smash Factor and Spin Loft. Since the data is from Trackman, it isn't 3D Spin Loft being measured, but Vertical Differential. I have no doubt that, if the data for these shots' horizontal components were available, the correlation would be even stronger between Smash Factor and 3D Spin Loft.
Monday, 7 November 2011
The Effects of Miss Hits
Most of the literature you read regarding Golf's Ball Flight (D-Plane geometry, Impact Plane geometry, etc.) offer explanations of ball flight based on centred (sweet spot) contact. I think it's very important to understand how that relationship works, but also think that being aware of all the effects of non-centred contact has on a golf shot is fairly important, given that a fair number of any average golfer's shots are not hit on the Sweet Spot.
When we look at analyzing miss hit shots, we'll consider shots missing the sweet spot in 4 directions: towards the toe, towards the heel, high on the face, and low on the face. Of course, you can combine these influences should you want to look at a high-toe miss, for example.
When the clubface impacts with the ball, the surface of the ball is in contact with the face for mere milliseconds, but this is when all the influence happens. When the ball is not hit on the centre of percussion (sweet spot), the face will rotate towards the direction of contact, even as the ball is still compressed against it. Since the face will be more open at separation (when the ball leaves the face) than it was at impact, the Effective Face angles (the ones we use in D-Plane calculations) will come from where they were in the middle of the Impact Interval (also the time when the ball is at maximum compression). Also, the twisting open of the face has the effect of spinning the ball in the opposite direction. This is called Gear Effect.
If we break the golf ball's flight down to it's initial components, we'll have: Ball Speed, Vertical Launch, Horizontal Launch, Spin Rate, and the Spin Axis (indicates how sideways a ball is spinning). This list takes care of pretty much everything that the golf ball will do upon being launched. We'll look at how the different miss hits affect each component.
Smash Factor: Not too surprisingly, when we hit the ball away from the sweet spot we see a lower Smash Factor, which is the ratio of ball speed to club speed (Smash Factor = Ball Speed / Club Head Speed, eg. 147mph Ball Speed / 100mph Club Head Speed = 1.47 Smash Factor). The higher the Smash Factor, the higher the resulting Ball Speed (Driver shots have much higher smash factors than wedges). Shots hit towards the heel will see a lower ball speed than sweet spot contact. Shots hit towards the toe will also see a reduction in ball speed, but less so since the face at the toe of the club is actually moving slightly faster than the face at the sweet spot (since the face is rotating around the hosel). As a side note: higher smash factors are a result of higher COR and lower Spin Loft numbers, but that's for another blog...
Toe hits: When the ball impacts the face towards the toe, the face opens immediately, and this opening is what causes the following effects:
Smash Factor/Ball Speed - lower, but higher than heel hits
Launch - more right*
Spin Rate - slightly higher
Spin Axis - tilted more left
Heel hits: face rotates closed and:
Smash Factor/Ball Speed - lower
Launch - more left*
Spin Rate - slightly higher
Spin Axis - tilted more right
Hit high on the face: face rotates upwards and:
Smash Factor/Ball Speed - lower
Launch - higher
Spin Rate - lower
Spin Axis - unchanged
Hit low on the face: face rotates downwards more than normally:
Smash Factor/Ball Speed - lower
Launch - lower
Spin Rate - higher
Spin Axis - unchanged
*I've put asterisks on two effects that Trackman (a leader in this area of research) disagrees with me on. They still maintain that the effects of off centre contact do not include a change in horizontal launch (Trackman Newsletter #5, pg. 3). I believe that Trackman would agree that low-face contact will result in a lower launch, and that high-face contact will result in a higher launch. It would be due to the same effect that happens in the horizontal frame, so why the difference? I think it has something to do with the way that Trackman calculates and presents their Face numbers, likely displaying the Effective Face angles from the middle of the impact interval (but that has twisted from its "delivered" condition).
They could consider showing two sets of numbers for the Face - "delivered" (by the player) and "effective" (post-twisting). A small difference in the numbers would indicate better contact.
Dave Pelz found that the effects of heel impact on putts sent the initial launch of the ball to the left (RH golfers) and that toe hits sent the ball to the right (Dave Pelz's Putting Bible, pg 354). I think it's fair to assume that the same principles apply to the initial launch of a golf ball in putting, as well as full shots.
Interestingly enough, the combination of hitting a drive off the high-toe is not necessarily a bad miss hit for a lot of people. The combined effects of more draw spin (leftward tilted spin axis), higher launch, and less spin can actually help certain people hit it further and straighter than they normally would.
Side Note: Clubs are now being designed with higher Moment of Inertia (MOI), which will increase the club head's resistance to twisting. Less twisting means smaller effects on off centre hits, in terms of spin and launch. Club with different Centres of Gravity (COG) will experience different degrees of twisting and Gear Effect; the further behind the face that the COG sits (like in fairway woods and drivers), the more twisting that will occur on those off-centre hits, and the more exaggerated these effects will be.
So, if you're watching ball flight on the range, and are trying to figure out what the club is doing to cause that flight, you might want to consider non-centred contact (it happens a lot).
Thanks for reading (sorry for all the brackets)!
-Mark
@StrongerGolf
References:
Jorgensen, T. (1994). The Physics of Golf. AIS Press
Cross, R. (2006). Physics of Golf.
Retrieved from http://www.physics.usyd.edu.au/~cross/GOLF/GOLF.htm
When we look at analyzing miss hit shots, we'll consider shots missing the sweet spot in 4 directions: towards the toe, towards the heel, high on the face, and low on the face. Of course, you can combine these influences should you want to look at a high-toe miss, for example.
When the clubface impacts with the ball, the surface of the ball is in contact with the face for mere milliseconds, but this is when all the influence happens. When the ball is not hit on the centre of percussion (sweet spot), the face will rotate towards the direction of contact, even as the ball is still compressed against it. Since the face will be more open at separation (when the ball leaves the face) than it was at impact, the Effective Face angles (the ones we use in D-Plane calculations) will come from where they were in the middle of the Impact Interval (also the time when the ball is at maximum compression). Also, the twisting open of the face has the effect of spinning the ball in the opposite direction. This is called Gear Effect.
Image taken from: http://www.physics.usyd.edu.au/~cross/GOLF/GOLF.htm
If we break the golf ball's flight down to it's initial components, we'll have: Ball Speed, Vertical Launch, Horizontal Launch, Spin Rate, and the Spin Axis (indicates how sideways a ball is spinning). This list takes care of pretty much everything that the golf ball will do upon being launched. We'll look at how the different miss hits affect each component.
Smash Factor: Not too surprisingly, when we hit the ball away from the sweet spot we see a lower Smash Factor, which is the ratio of ball speed to club speed (Smash Factor = Ball Speed / Club Head Speed, eg. 147mph Ball Speed / 100mph Club Head Speed = 1.47 Smash Factor). The higher the Smash Factor, the higher the resulting Ball Speed (Driver shots have much higher smash factors than wedges). Shots hit towards the heel will see a lower ball speed than sweet spot contact. Shots hit towards the toe will also see a reduction in ball speed, but less so since the face at the toe of the club is actually moving slightly faster than the face at the sweet spot (since the face is rotating around the hosel). As a side note: higher smash factors are a result of higher COR and lower Spin Loft numbers, but that's for another blog...
Toe hits: When the ball impacts the face towards the toe, the face opens immediately, and this opening is what causes the following effects:
Smash Factor/Ball Speed - lower, but higher than heel hits
Launch - more right*
Spin Rate - slightly higher
Spin Axis - tilted more left
Heel hits: face rotates closed and:
Smash Factor/Ball Speed - lower
Launch - more left*
Spin Rate - slightly higher
Spin Axis - tilted more right
Hit high on the face: face rotates upwards and:
Smash Factor/Ball Speed - lower
Launch - higher
Spin Rate - lower
Spin Axis - unchanged
Hit low on the face: face rotates downwards more than normally:
Smash Factor/Ball Speed - lower
Launch - lower
Spin Rate - higher
Spin Axis - unchanged
*I've put asterisks on two effects that Trackman (a leader in this area of research) disagrees with me on. They still maintain that the effects of off centre contact do not include a change in horizontal launch (Trackman Newsletter #5, pg. 3). I believe that Trackman would agree that low-face contact will result in a lower launch, and that high-face contact will result in a higher launch. It would be due to the same effect that happens in the horizontal frame, so why the difference? I think it has something to do with the way that Trackman calculates and presents their Face numbers, likely displaying the Effective Face angles from the middle of the impact interval (but that has twisted from its "delivered" condition).
They could consider showing two sets of numbers for the Face - "delivered" (by the player) and "effective" (post-twisting). A small difference in the numbers would indicate better contact.
Dave Pelz found that the effects of heel impact on putts sent the initial launch of the ball to the left (RH golfers) and that toe hits sent the ball to the right (Dave Pelz's Putting Bible, pg 354). I think it's fair to assume that the same principles apply to the initial launch of a golf ball in putting, as well as full shots.
Interestingly enough, the combination of hitting a drive off the high-toe is not necessarily a bad miss hit for a lot of people. The combined effects of more draw spin (leftward tilted spin axis), higher launch, and less spin can actually help certain people hit it further and straighter than they normally would.
Side Note: Clubs are now being designed with higher Moment of Inertia (MOI), which will increase the club head's resistance to twisting. Less twisting means smaller effects on off centre hits, in terms of spin and launch. Club with different Centres of Gravity (COG) will experience different degrees of twisting and Gear Effect; the further behind the face that the COG sits (like in fairway woods and drivers), the more twisting that will occur on those off-centre hits, and the more exaggerated these effects will be.
So, if you're watching ball flight on the range, and are trying to figure out what the club is doing to cause that flight, you might want to consider non-centred contact (it happens a lot).
Thanks for reading (sorry for all the brackets)!
-Mark
@StrongerGolf
References:
Jorgensen, T. (1994). The Physics of Golf. AIS Press
Cross, R. (2006). Physics of Golf.
Retrieved from http://www.physics.usyd.edu.au/~cross/GOLF/GOLF.htm
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