Actually, it's the True Face that defines the top of the D-plane keeping in mind that planes extend to infinity, and assuming that True Face is above the True Path.
Slices & Hooks - Trackman Style
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Actually, it's the True Face that defines the top of the D-plane keeping in mind that planes extend to infinity, and assuming that True Face is above the True Path.
Kevin Shields
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The higher the speed the more the ball with be influenced by the path....which is responsible for curve. A slow swinging driver that has a face open will kinda just richochet mostly toward the face without much "squash". The same conditions, only, faster, will grip the ball more and start it slightly closer to the path.
mjstrong
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Yeah, but the bottom vector is defined by the true path...so both of these contribute to the "stretched-out" d-plane that reduces the tendency to tilt spin loft.
Dynamic Loft = 20°
AoA = -5°
Spin Loft results in 25°
Dynamic Loft = 25°
AoA = 0.0°
Spin Loft results in 25°
So, you have to consider both when talking about a shot's tendency to tilt the spin axis. The higher the spin axis, the lower a shot's tendency to have a tilted axis.
mjstrong
New
Right, so the initial flight of the ball will be influenced closer to the path, both vertically and horizontally, but will that change the spin axis at all? Both vectors of the D-plane remain where they are, independent of ball speed.
I understand the spin axis to reflect the tilting of the D-plane. Is there more to it than that?
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Kevin Shields
Super Moderator
Good question.... as soon as it starts to remind me to much of school my brain shuts down
Kevin Shields
Super Moderator
I would think the only reason it curves more is the additional clubhead/ballspeed. Once the ball starts to curve it now will fly further in that direction because of more speed.
Tuxen's rule of thumb defines curvature as relative to the length of the shot.
Like a 10 yard draw on a 100 yard wedge is the same curvature as a 20 yard draw on a 200 yard shot.
Tuxen's rule does not factor in clubhead speed.
Is it fair to say clubhead speed does not effect the "geometry" of the shot? It just makes everything proportinally larger.
Like a 10 yard draw on a 100 yard wedge is the same curvature as a 20 yard draw on a 200 yard shot.
Tuxen's rule does not factor in clubhead speed.
Is it fair to say clubhead speed does not effect the "geometry" of the shot? It just makes everything proportinally larger.
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The other day I found a presentation with graphs I assume from a flight trajectory calcuator. But I was surprised about the ball flight downfield (speed and angle) and other matters of decay on page 22 and 23. Consequently, I would have some doubt about rules of thumb that apply near the end of a ball's flight.
http://sections.asme.org/canaveral/Special/golf/asmegolf.pdf
http://sections.asme.org/canaveral/Special/golf/asmegolf.pdf
mjstrong
New
This is what I'm thinking...
That and whatever else causes the ball to slow down (heat/work??).
To be complete, depending on what was being compared, those calculations could be done for the two shots in question and then see if a rule of thumb can be concocted. And with better ball tracking nowadays, maybe real data could be used.
But in any case, I know I think a lot about impact conditions and tend to ignore the downstream conditions.For a complete trajectory, it appears that velocity decays linearly for about 2/3 of the flight, and so maybe that zone is what the rules of thumb were created for - however, I'm not sure if the originator was thinking about that linear zone or a vacuum/no gravity zone. However, after that period, when the ball is plummeting, there are bound to be other effects.
Also, would need to know about the spin decay.
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In my humble opinion, there is no way in the world the Trackman guys used anything other than looking at a few hundred shots, noticed that curvature is proportional to axis tilt, then took the average to come up with the constant 0.7% side distance compared to linear distance. Just observations and taking the average.
I'll bet the only criteria that it was a calm day.
No drag calculations, no air pressure, no other flow calcs or any other of that "non-sense".
I'll bet the only criteria that it was a calm day.
No drag calculations, no air pressure, no other flow calcs or any other of that "non-sense".
Maybe I missed some definitions. If for example the Dplane is tilted 1 degree (what I assume you mean by axis tilt), then curvature is 0.7 degrees. What is curvature...an alternate starting direction?
I was hearing curvature and thinking that it varies through the flight, and the side distance might be increasing per yard of forward distance as the ball flight decays.
Maybe as somewhat seen in trajectory 8 in this diagram
[media]http://womensgolfcenter.com/files/images/Golf%20shot%20paths-small.preview.jpg[/media]
Ahhh, you're close - it's 0.7 percent (not degrees).
Yes, ball spin axis IS the tilt of the D-plane
Examples:
150 yards; spin axis = +3*
150 x 3 x 0.007 = 3.15
Ball will curve 3.15 yards to the right
250 yards; spin axis = -6*
250 x -6 x 0.007 = -10.5
Ball will curve 10.5 yards left
Yes, ball spin axis IS the tilt of the D-plane
Examples:
150 yards; spin axis = +3*
150 x 3 x 0.007 = 3.15
Ball will curve 3.15 yards to the right
250 yards; spin axis = -6*
250 x -6 x 0.007 = -10.5
Ball will curve 10.5 yards left
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