How Club Path and Face Angle Determines Ball Flight

[iacas]

I also have a graphic which illustrates what happens to cause a slice. This is looking over the ball.

Your diagram indicates that the initial direction the ball starts is due to the clubface angle, while I've read several accounts that the initial direction - except in extreme cases - has more to do with the club's path rather than the face angle.

[Ringer]

Your diagram indicates that the initial direction the ball starts is due to the clubface angle, while I've read several accounts that the initial direction - except in extreme cases - has more to do with the club's path rather than the face angle.

Without bringing in an entire article that would possibly just confuse the matter... why does the ball go immediately up in the air with a pitching wedge even though you are making a very sharp decending blow?

Look at my diagram again but instead envision that you are looking at impact from the face on view instead of directly above. They are both doing the same thing. Up/down, left/right.. it's all the same.

[bwinger79]

Initial direction a ball is going to travel is decided by the swing path. Which way the ball is going to curve is decided by face angle relative to swing path. Iacas is right, the diagram is incorrect, no matter what way you look at it.

[Ringer]

Initial direction a ball is going to travel is decided by the swing path. Which way the ball is going to curve is decided by face angle relative to swing path. Iacas is right, the diagram is incorrect, no matter what way you look at it.

Prove it.

[bwinger79]

Prove it.

I do every time I step on the course to play a round.

[Ringer]

I do every time I step on the course to play a round.

So then you hit the ball into the ground on every swing? You must, because you said the initial direction of the ball is determined by the clubhead path. Since the clubhead path is down toward the earth, you must be hitting the ball into the ground.

[bwinger79]

So then you hit the ball into the ground on every swing? You must, because you said the initial direction of the ball is determined by the clubhead path. Since the clubhead path is down toward the earth, you must be hitting the ball into the ground.

We are talking directional(left, right). If you want to talk about descending blows and clubs loft, you should probably start another thread. Possibly the dumbest thing I have ever heard though.

[Ringer]

We are talking directional(left, right). If you want to talk about descending blows and clubs loft, you should probably start another thread. Possibly the dumbest thing I have ever heard though.

So you think the physics change between decending blows vs left/right clubhead path?

[bwinger79]

So you think the physics change between decending blows vs left/right clubhead path?

The physics do change as soon as you add loft to the picture. Please know what you are talking about before starting an argument. Sorry to tell ya buddy, but your diagram is incorrect.

[iacas]

OK guys, calm down a touch.

Ringer, your physics don't work: a 10 degree descending blow with a club that has 45 or 48 degrees of loft does not result in a downward path for the clubface. There's still "positive loft." Hitting down just adds to the backspin. Furthermore, broken into vectors, the pitching wedge is still moving forward many, many, many more times than it is moving down. The x vector is much larger than the y vector.

With a driver, there's very little loft but ideally the ball is struck on a slightly ascending blow. Again, very little y vector, a heck of a lot of x. In this case, the z vector would be the inside/outside.

So yeah, things definitely change when you're talking about left/right or up/down.

As for "prove it," yeah, I also do so every time I step onto the golf course, and I also believe Titleist's science van folks (with whom I spent two days a few years back) as well as the many famous teachers who would disagree with you, Ringer.

Both of you could still calm down a bit please. I've moved these to a new thread so the original poster doesn't have to handle a side discussion.

[greenail]

Your diagram indicates that the initial direction the ball starts is due to the clubface angle, while I've read several accounts that the initial direction - except in extreme cases - has more to do with the club's path rather than the face angle.

with 0 degrees loft the diagram is correct, add loft and it becomes more and more inaccurate.

do a test with a golf ball and a book with a square edge on a smooth surface, open the "book's face" to 45 degrees and see what happens.

[Leek]

Initial direction a ball is going to travel is decided by the swing path. Which way the ball is going to curve is decided by face angle relative to swing path. Iacas is right, the diagram is incorrect, no matter what way you look at it.

Actually, that is a common myth. If you get a monitor, you'll find face angle has more impact on initial direction than path. Not to say path doesn't influence it, just that face angle influences more.

[bwinger79]

Actually, that is a common myth. If you get a monitor, you'll find face angle has more impact on initial direction than path. Not to say path doesn't influence it, just that face angle influences more.

I hit on a monitor all the time. Nothing I have seen supports your claim. But if you make a swing with a path square to your target, and close the face of the club, of course the ball is going to go to the left. You might be talking in extremes, I am not sure, but like I said, I havent seen any launch data that would support your claim.

[greenail]

referencing http://www.wellesley.edu/Athletics/P...l_flights.html



See URL above for the descriptions.

[iacas]

Look at the descriptions of 7 and 4. The initial direction of the ball relates to the clubhead's path and the direction it curves relates to the clubface.

Furthermore, why do a lot of Tour pros - in "Playing Lessons with the Pros" or wherever - suggest that to hit a fade you open your stance, then point the clubface at the target? If it started at the target and then faded, it'd end up right. (They say vice versa for a draw).

Please, too, let's be clear in this: we're not talking about the vertical axis and we're not talking about extreme cases - angles of probably 8 or 10° or less. The club path still influences the initial direction of a shot with a 45° open clubface (the ball won't start off quite 45° to the right)... but not enough to overcome the obvious.

[beisenhauer]

Disclaimer: I am not a physicist (nor did I stay at a Holiday Inn Express last night,) though I do have a degree in engineering and am generally a physical sciences geek.

The only way Ringer's original diagram could be correct, with the initial path of the ball perfectly perpendicular to the club face, would be if the club face was a frictionless surface, which of course it isn't. The diagram assumes that the initial direction is determined solely by the club face angle.

The initial flight of the golf ball at impact is a question of forces. There are forces perpendicular to the club face, but there are also forces parallel to the club face (the ones that make the ball spin.) Both contribute to the direction in which the ball travels.

Attachment 512

This diagram is going to take some explaining.

In figure A obviously the circle represents the ball and the triangular wedge is my representation of a golf club. It doesn't matter if your looking from the side or from the top. (Yes, physics really does work the same in all directions.) The arrow inside the wedge indicates the direction of travel, i.e. the swing path.

At impact the club face imparts force to the ball, which for the sake of analysis, I have broken down into forces normal and tangential to the club face (that's perpendicular and parallel to most people.) Vector 1 represents the normal force and vector 2 represents the tangential force.

In figure B I have removed the "club", leaving only the forces it imparts to the ball. I have also introduced two new vectors. These don't represent forces per se/I], they're just conceptual fictions. Vectors 3 and 4 are equal in magnitude to the tangential vector (#2), but they point in opposite directions and run through the center of gravity of the ball. They could be forces, but they'd just cancel each other out.

In figure C I have combined vectors 1 and 4 to produce a single translational force acting on the center of gravity of the ball. I have also combined vectors 2 and 3 into a rotational torque on the ball. I can do this because they are of equal magnitude but opposite in direction with an offset in their lines of action.

The initial direction of flight will be in the direction of vector T, while the spin of the ball will be determined my the magnitude of the torque R.

Diagrams D, E and F show the same analysis but with a different swing path. Note the change in initial direction, despite the identical club face angle.

All of this assumes of course that the ball is a rigid body (which in the context of impact, it isn't) and that it is also a free body (which if it's sitting on the ground and we're swinging down on it, it isn't.) The exact proportions of the normal and tangential forces imparted to the ball will depend on club head speed, compression of the ball, friction between the ball and the club face, etc.

Conclusion: For the time being, I'm siding with the "swing path" people. The initial path of the ball is determined to some extent by both the swing path and the face angle, in combination with the surface characteristics of the club and ball. For the most part we're talking about deviations in swing path and face angle of a few degrees from the target line. In that range, I think the swing path is going to be the primary determinant, particularly with lesser lofted clubs.

I know there are at least a couple of books on the physics of golf, The Physics of Golf by Theodore Joergensen and Newton on the Tee by John Zumerchik. Has anyone read either of these, and if so, do they have anything to say about what goes on at impact?

[Ringer]

My diagram is not exact. From the physics calculations I've read it's a minimum of 5/7 in favor of the face. That means at least 71.4% of the initial direction is from the face of the club.

But the diagram is not meant to be precise, it's meant to give you a better understanding, or impression.

Trying to indicate all the other factors invloved for impact would be very difficult to explain without making it twice as big and difficult to read.

[greenail]

I think you also need to define "initial direction".

If initial direction is in the first 10/1000 of a second than you may be correct that the compression, and friction influence the direction of the ball more in relation to the club path, but if you mean the first 1-2 seconds and after the ball and clubface have restored their original shape and the ball has left the clubface but before the resistance of the air has caused deflection then I think it will be a different story. There is also the gear effect to consider in the different swings.

Prime example is a flop shot, how come the ball doesn't go with your club, if you had a ton of sidespin you'd see it when it hit the green.