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Old Jun 10, 2009, 10:09 AM   #11
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Here is a golf sequence with what you should expect.

http://www.todaysgolfer.co.uk/upload...e-golf-tip.jpg
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Old Jun 10, 2009, 10:43 AM   #12
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Originally Posted by DaveLeeNC View Post
Is that always true? The question came up on a golf discussion board regarding the following image.

http://www.pbase.com/bret/image/113518953/original

The question (obviously) being "is the shaft really that much flexxed forward at impact"? The camera used was a Canon 5d2.
Absolutely. During a swing, the hands are actually traveling faster and don't slow down until after the club has hit the ball. If anything, the club would be bent slightly back so the head would be behind the hands, not in front of them.

Most focal plane shutters have shutter curtains that travel from left to right (or, in this case, since the image is vertical and the camera was rotated 90, from top to bottom.) The curtains actually take about 1/1000 second to travel across the focal plane, so for faster shutter speeds, the second curtain covering the image sensor is released before the first curtain exposing the image has finished. As a result, the right side of an image (or, in this case, the bottom of the image) has been exposed long after the left side (or top) of the image (relatively speeaking.) See http://en.wikipedia.org/wiki/Focal_plane_shutter for more info.

So, when recording that golf swing, the club head appears ahead of the rest of the club only because it was the last part of the club to be exposed on the image sensor. When the club head finally got exposed, the golfer's hands were much further along on the swing than they appear in the photo.

In fact, the Wikipedia article contains an image that demonsrates teh effect quite well, and resembles the image of the golf club. See http://en.wikipedia.org/wiki/File:Fo...istortions.jpg
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Old Jun 10, 2009, 6:49 PM   #13
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No offense intended here, guys/gals. But basically every single golf thing stated previously is wrong.

1) The hands slow down toward impact as momentum is transferred to the club (at least in 'good' golf swings).

2) In virtually every 'good' golf swing, the head of the club is at or ahead of the shaft approaching impact. The degree of this can change (obviously) as a function of how much flex is in the shaft, the timing of the golfer, etc.

3) Contrary to what you might think, a shaft that is too flexible will cause a typical golfer to hit the ball too far to the left and too high (for a right hander). This is because the club will get too far ahead of things at impact. Now too much flex can also induce (wanted or unwanted) changes in swing mechanics that can over-ride this principle. But a VERY common way to get more loft from a given club is to weaken (make more flexible) the shaft so the face will be more 'tilted forward and rotated left' at impact. When I swing my wife's (very flexible) clubs, the ball goes a mile high and a mile to the left.

These are well known and well established facts in the world of club fitting and club design.

References

Theordore Jorgenson, The Physics of Golf, ISBN 0-387-98691-x

Cochran and Stobbs - Search for the Perfect Golf Swing - ISBN 1-57243-109-1

Tom Wishon - Search for the Perfect Golf Club - ISBN - 1-58726-185-5

dave

ps. The swing pic referenced is K.J. Choi - get one that shows his clubface right BEFORE impact (in a typical golf swing the shaft will be straight around 1/4 second before impact - goes forward from there-on). Hitting a golf ball with a driver at "professional speeds" puts upwards of 1000 pounds of force on the ball. There is a clubhead rebound going on.

I have attached a picture of Mike Weir where the green line (straight) was added by me.
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Old Jun 10, 2009, 7:00 PM   #14
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I'm more than happy to be wrong as it is good to learn so if you have any further information online that would be great. The photo you've attached shows that the club head is still behind the shaft just before impact so that concurs with what I believed.
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Old Jun 10, 2009, 7:19 PM   #15
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I'm more than happy to be wrong as it is good to learn so if you have any further information online that would be great. The photo you've attached shows that the club head is still behind the shaft just before impact so that concurs with what I believed.
The shaft is flexxed forward. What is going on is that the center of gravity of the clubhead (which is toward the rear) is 'attempting to line up with the shaft, causing the clubhead to try to 'move forward', twist, and to 'droop downward'. This is combined with the dynamics of a typical golfer where the golfer him/herself is actually slowing down.

On online reference is from Ralph Maltby http://www.ralphmaltby.com/38

although his description of 'the release' part is pretty sketchy.

Look carefully at the picture - the shaft is lagging the straight line connecting MW's hands and the hosel of the club. The shaft is bent forward (by a little).

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Old Jun 10, 2009, 7:38 PM   #16
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In any event, using a high speed shutter option will give a better image of high speed motion.
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