Dear James,
Nice to hear from you!
Not to put too fine a point on it, the point Brad Redding appears to be making appears strained in an effort to justify the arcing style. A greater appreciation of the phenomena involved shows the straining.
There are THREE dimensions of space, and changing the presentation of the putter face to the back of the ball at impact from square at address can happen in none, one, two, or three dimensions. And some dimensions are better than others!
The X dimension is left-right. The Y dimension is near-far. The Z dimension is up-down.
The ball-to-target line is the same as the X dimension.
There are also "planes" in space: The X-Z plane is like a clear sheet that rises vertically out of the line of the putt. The X-Y plane is the same as the (flat) surface. The Y-Z plane runs like a vertical sheet perpendicular to the line of the putt.
In a straight-back and straight-thru stroke, the putter head rises going back from the ball in the X-Z plane, and then coming into impact the putter head it sinks back to the bottom before impact. The ball is forward of the bottom of the stroke some distance (more later), never behind the bottom. Once the putter head reaches the bottom, the putter head starts rising again. The golfers key is "where is the bottom." It is stupidly always in the same place, where the stroke is lowest, and this is usually in the middle of the body and stance where the putter initially rests at address unless thew golfer has weird technique or grip form, etc. Knowing where the bottom is could not be simpler. Everything about the human body in space cries out when you get there: the tempo, the levelness of the shoulders, the centering of the putter head between the feet, the full extent of hang of the arms and hands, the closest approach to the grass of any point in the swing, and about another dozen obvious cues.
Thus, in a straight-back and straight-thru stroke, with the whole heaven and earth helping the golfer know where the bottom of the stroke is, and with the ball played forward of that, the following points are obviously true:
1. The ball is never hit downward;
2. The ball might be hit up, but that depends on how far forward of the bottom the ball is played; and
3. The putter face angle will be square the whole time it moves in contact with the ball.
You can do the test yourself to see what happens to the roll of the ball: play the ball right at the bottom, then 1 inch ahead, then 2 inches ahead, then 3 inches ahead, then 4 inches ahead, then 5 inches ahead. Just make a stroke that has the putter head bottom out in the same neutral place each time and then rise into the back of the ball. In every case, with a straight-back and straight-thru stroke, all of these putts will roll the ball straight on the same line. The farther the ball is played from the bottom of the stroke, the more the impact dynamics will present more effective loft to the back of the ball. However, the added loft is not that much, AND the solidness of the blow diminishes the farther forward the ball is played. The experiment should show that -- starting with a conventional putter loft of about 3 degrees on a normal green -- NOTHING TERRIBLE happens to the ball from the increases of effective loft. The ball rolls straight, even though there is a minor increase in launching of the ball.
The added loft is not that great because of the circumference of a putting stroke, as extended into a complete circle around the golfer. this circle is over 9 feet in diameter, and the radiusing upward of this stroke from the bottom all the way to 5 inches in front of this is on the order of 1/8th of an inch to 1/4th of an inch. This means that the "normal" impact point on the putter face (about 1/2 an inch high) ends up just a little lower than normal, but hardly in danger of missing the ball.
The launching of the ball off the ground is also not near as much as expected. Playing the ball farther forward alters the physics of impact: the blow is NOT directed thru the center of gravity of the ball, but above it more and more the more the ball is played forward of the bottom. This means the blow is both not as solid as otherwise and also tends to get the ball rolling (at least so long as the putter's COG remains lower than the impact point on the face). The less-solid blow keeps the launching down, and so does the over-roll action. Hence, changes in the X-Z plane don't affect the straighhtness of the roll much at all, if any.
In contrast, the inside-inside arcing / gating stroke may remain a little lower throughout the stroke path, but so what? There will still be some rising, unless the golfer uses manipulations to prevent this, so the arcing stroke merely has "less" up-down that the other style.
More importantly, the gating stroke "swipes" thru the ball, with the face angle changing while the ball and putter are still in contact. This contact period last nearly one-third of an inch. The face angle change (in the X-Y plane, heaven help us!) over this radiusing can be pretty significant in terms of angle, and even tiny angle changes matter more and more the longer the putt.
If you asked me which is more dangerous to putting accuracy and consistency -- a minor launching that does not appear to affect the straightness of the putt (and has never been shown to effect the straightness) or a minor varying in the face angle due to gating -- physics is pretty clear that the face angle change is the more dangerous of the two.
There is also the issue of timing precision. The gating stroke requires VERY tight precision to get rid of bad face angle changes, and even then, since the putter and ball stay in contact briefly, there is really nothing a true gating putter can do. In contrast, the straight-back and straight-thru stroke presents a very easy timing problem; bottom out and then head up, so play the ball sufficiently ahead of the bottom that you have a generous margin of error. The trade-off of tiny launching versus greater margin of error in timing the bottom is actually a welcomed comfort to the putter's accuracy and repeatability.
It strikes me that "apologists" for the gating stroke strain to make putting phenomena fit their view, and it is easier to make the shoe fit if the apologist doesn't really understand the phenomenon he is commenting on.
But again, I have to repeat that I do not personally teach EITHER a straight-back and straight-thru stroke OR an inside-inside arcing stroke. I teach a straight forward stroke thru the impact zone. Personally, my teaching has a little up-rising in the X-Z plane past the bottom, and NO X-Y change, but that is because I just don't see the benefit of the trade-off of trying to eliminate any up-rising at impact. It's too mild and inconsequential to spend precious resources on. However, you COULD eliminate the up-rising if you felt compelled to do so -- just use a little "tangential blow" as Harold Swash teaches, either with a minor forward press or a slight hingeing of the rear wrist at the top of the backstroke to swipe the square putter face in a delofted manner across the top quadrant of the back of the ball.
No problem. Just seems a bit much to me -- not enough payoff for the trouble.
Cheers!
Geoff Mangum
Putting Coach and Theorist
PuttingZone
http://puttingzone.com
Golf's most advanced putting instruction -- you're either in the PuttingZone, or not.
