Geoff,
Thanks for your thoughts on this topic.
I would like to raise a couple of questions and issues I don't see addressed in your message:
First, do you think more skidding leads to more bouncing on a putt?
Second, whatever leads to a putt bouncing, does bouncing affect accuracy or not?
Third, what are the psychological impacts of skidding and bouncing vs. roll on the golfer's confidence level in putting?
Also, have you used the GR 2 bar putters and how do they "feel" in comparison to other putters to you?

I applaud you raising the question of whether skid hurts the line of roll (your response to item #10). It's pretty easy to blindly accept the putter-maker's assertion that skid is bad if one doesn't really think about this! On a level surface, I certainly believe a skidding ball should hold the line as well as a true roll (good analogy is billiards perhaps).

But, greens are rarely level and my experience tells me skidding can have a clear impact on amount and timing of break on the putt (good analogy is pinball perhaps). People who play pinball hate surfaces that allow the ball to skid too much because the ball tends to go in a straight line much longer than they expect. The pinball then starts rolling (and breaking) at an unpredictable spot on the slanted pinball field. This hurts their ability to accurately control the pinball to hit the targets they want.

For me, a skidding or bouncing golf ball tends to go straighter than a rolling one on a slanted surface. The more skid that a putter/ball/green produce on anything but a straight putt, the harder it is for me to accurately play the right amount of break. I simply can't predict when the ball is going to stop skidding and thereafter roll and break. Although I haven't seen anyone prove this in a study, I certainly believe this from my own experiments with different putters.

I have a Guerin Rife 2 Bar and before I bought it, I compared it to a couple of other putters that "feel" good to me to see which were more accurate. These experiments are along the lines of "hit twenty 25-foot putts with each putter and see how many you sink and how tight the distribution of misses are." I do this with putts that have some break, on real greens --- not fake, flat putting surfaces in the store or at home. A tightly controlled experiment? No, but probably a step beyond what most players take when buying putters. My little experiments showed the Railgun to be the most accurate putter for me from about 5 ft up to 12 ft or so. With a 20 or 30 ft putt, the Guerin Rife produced better results for me than others I've tried. Inside 5 ft, it seems I can make any putter work equally well once I'm used to it.

Another good analogy to think about is bowling. There, many excellent bowlers that WANT LOTS of skid, in order to delay the roll and the hook on the ball, until the ball is very far down the lane. The bowling ball goes in a fairly straight lane while it is skidding with LOTS of sidespin, then hooks abruptly when it starts rolling. The best bowlers can control this skidding and roll timing very accurately, but only when the very controlled surface of a bowling alley is set up correctly--- i.e. proper amount of oil/friction on the lane and ball. On a golf green, the surface is not so finely tuned, and the slopes vary, so the skidding on a slope is much less predictable than a roll (in my opinion of course). I therefore, prefer a putter (and ball combination) that produces less skid.

BBFTX
Single-Axis Golf Forum

Dear BBFTX,

Great questions! Let's get as good a handle on them as we can.

YOU: First, do you think more skidding leads to more bouncing on a putt?

ME: Yes, probably true, but to what real extent and in what sorts of putts on what sorts of greens?

YOU: Second, whatever leads to a putt bouncing, does bouncing affect accuracy or not?

ME: Probably moreso than skidding.

YOU: Third, what are the psychological impacts of skidding and bouncing vs. roll on the golfer's confidence level in putting?

ME: There are two sorts of confidence: real and delusional. real confidence comes from knowing what works in terms of cause and effect and also knowing the present limits of one's capability to manage the causes and effects. Delusional confidence is useful only to the extent it dampens out doubts, anxiety, and second-guessing that comes from NOT knowing what works and how in terms of cause and effect or what one's limits really are. A good putter with real confidence is not likely to see a lot of bouncing, and if he does he knows its either his fault or no ones and he could either have avoided it or not, but he doesn't get a knock in his confidence because he just says "oops" don't do that again. The delusionally confident golfer sees bouncing and doesn't know what causes it or how to avoid it, so he has the "anxiety" and "stress" of people who are not in control of things.

YOU: Also, have you used the GR 2 bar putters and how do they "feel" in comparison to other putters to you?

ME: Yes, I like it quite a lot and always tell people I see using one that I think it is a very good putter.

YOU: I applaud you raising the question of whether skid hurts the line of roll (your response to item #10). It's pretty easy to blindly accept the putter-maker's assertion that skid is bad if one doesn't really think about this! On a level surface, I certainly believe a skidding ball should hold the line as well as a true roll (good analogy is billiards perhaps).

But, greens are rarely level and my experience tells me skidding can have a clear impact on amount and timing of break on the putt (good analogy is pinball perhaps). People who play pinball hate surfaces that allow the ball to skid too much because the ball tends to go in a straight line much longer than they expect.

ME: When you "whack" a ball to "get it there" and "go by the hole 17 inches in case it misses", you inevitably create more skid than necessary and so will quite often hit thru the break, as you observe. Golfers need to learn that the least effort is sufficient, almost always the most accurate, and the best.

YOU: For me, a skidding or bouncing golf ball tends to go straighter than a rolling one on a slanted surface. The more skid that a putter/ball/green produce on anything but a straight putt, the harder it is for me to accurately play the right amount of break. I simply can't predict when the ball is going to stop skidding and thereafter roll and break. Although I haven't seen anyone prove this in a study, I certainly believe this from my own experiments with different putters.

ME: Handling the break is really a question of touch or controlling the pace of the ball "over there" where the break occurs. This is done by "seeing" the break in advance using your standard sense of delivery speed of the ball "over there" and then sticking to this same sense of pace when you execute the putt. Any other "touch" when pulling the trigger will not follow the path you visualized.

YOU: I have a Guerin Rife 2 Bar and before I bought it, I compared it to a couple of other putters that "feel" good to me to see which were more accurate. These experiments are along the lines of "hit twenty 25-foot putts with each putter and see how many you sink and how tight the distribution of misses are." I do this with putts that have some break, on real greens --- not fake, flat putting surfaces in the store or at home. A tightly controlled experiment? No, but probably a step beyond what most players take when buying putters. My little experiments showed the Railgun to be the most accurate putter for me from about 5 ft up to 12 ft or so. With a 20 or 30 ft putt, the Guerin Rife produced better results for me than others I've tried. Inside 5 ft, it seems I can make any putter work equally well once I'm used to it.

ME: Excellent experiment! The better performance of the GR may be due to the smaller "footprint" on the green, as big-head putters tend to make people overly cautious about the bottoming out of the stroke, which is happening with more violence and potential disaster on longer putts.

YOU: Another good analogy to think about is bowling. There, many excellent bowlers that WANT LOTS of skid, in order to delay the roll and the hook on the ball, until the ball is very far down the lane. The bowling ball goes in a fairly straight lane while it is skidding with LOTS of sidespin, then hooks abruptly when it starts rolling. The best bowlers can control this skidding and roll timing very accurately, but only when the very controlled surface of a bowling alley is set up correctly--- i.e. proper amount of oil/friction on the lane and ball. On a golf green, the surface is not so finely tuned, and the slopes vary, so the skidding on a slope is much less predictable than a roll (in my opinion of course). I therefore, prefer a putter (and ball combination) that produces less skid.

ME: The bowling analogy is interesting but also potentially misleading. The surface friction of a green is vastly more oppositional to the bottom of the ball than is a bowling lane. This means that the sort of sidespin given a bowling ball by the fingers in the holes is a) not really possible for a putted ball, and b) in any event gets washed out by the green surface almost immediately. try "bowling" a golf ball onto a green with the same finger action / release used to spin a bowling ball. This from CB Diash:

"5.01.09.05.02., Daish, C.B., The Physics of Ball Games, (London, English Universities Press, Ltd., 1972), , 82: place a ball along the line of a putt; imagine three axes through the ball's center, one parallel to the line of the putt and horizontal (called the horizontal sidespin axis); one horizontal but perpendicular to the first axis and to the line of the putt (called the horizontal forward roll axis); and a vertical axis. A hook or slice action on a putt has to be made by imparting spin around the first horizontal axis, parallel to the line of the putt, so that the ball rolls around like a bullet-pass football as it goes forward. This spin will cause friction at the point of contact with the ground and this friction will tend to make the ball curve to the right if the ball spins from top to bottom rightward over this axis. However, this is not a spin that a putter can impart. in billiards, the cue stick must be angled down at one side of the top of the cue ball so that the blow is partly down and under as well as partly forward: such a ball will curve toward whichever side of the top is struck. A moment's thought will convince the reader that it is impossible to generate such a spin in a shot with a golf putter. The only spin which can be applied in this case is about a vertical axis, produced by drawing the face of the club across the ball at impact. Such a spin imparted in a golf drive will certainly produce a slice or a hook due to the aerodynamic forces generated as the spinning ball flies at high speed through the air. But for a ball rolling relatively slowly over the ground, such [aerodynamic] forces will not arise and the spin will not produce any deviation in the path of the ball. Thus, in spite of all the nonsense talked to the contrary, it is virtually impossible to hook or to slice a putt in golf, either deliberately or by accident."

Cheers!

Geoff Mangum
Putting Coach and Theorist
PuttingZone.com
Golf's most advanced and comprehensive putting instruction.

When struck by the putter, the ball begins to skid or slide because it's energy is high and it overcomes friction. While skidding if it encounters a resistance like an errant blade of grass or a change to a higher surface friction, the ball will suddenly slow down from it's higher energy state and violently pop up and then bounce on the grass and presumably reducing it's energy thus allowing friction to induce rolling. After bouncing, I doubt the ball will resume skidding, but I suppose it could if it's energy was not greatly diminished.

Can a putter head design mitigate such upsetting conditions? I doubt it !

Surely it is indeterminate how far a ball will skid, when and where it will pop up and start it's bounce while skidding, and when it will start to roll, when it is on a randomly chaotic grass surface. To suggest that there is some relationship between putter designs and these events is dubious and perhaps not worthy of such detailed analysis particularily when anecdotal experiences are involved. Of course everybody is free to search for a technological solution to something that may be beyond resolution, and who knows what could be discovered when so many great minds are attacking the perceived problem.

Dear sammy,

A green surface is not quite as troubled with high-definition spots out of the usual pattern as is commonly feared. Mostly, a green surface has a uniform coverage of small-sized detail features -- small in comparison to the ball as a size, shape, and mass in motion across the surface features.

A typical blade of bent grass may be 1/8th inch high and 1/10th inch wide, with the blade structure containing cellulose and water like a water bag. A green of usual size has as many as 16 million of these grass blades uniformly covering the area of the green. If you image a green as a bed of nails with the nails very densely and uniformly spaced, then a ball will have tens of thousands of encounters with specific "nails" along a given putt path. This makes the ball-surface physics more like the behavior of a gas, in which statistical anaylsis of micro-events best describes the macro-behavior. Even if some blades are taller or shorter than others and some blades are stiffer or more bendy than others, the vast number of encounters ensures that the ball's overall path is not grossly un-averaged by any one particular encounter.

What really screws up the line of a putt is ball pitch marks and invasive weeds that grow in clumps taller than the normal grass variety covering the green (e.g., pads of tall poa annua with seed heads). Bouncing and bounding is also inherently bad for the integrity of the line due to the un-average forces involved of the ball meeting the grass and more specifically the turf with grass blades and stems in between ball and truf.The landing of a ball from a given height and on a landing angle is vastly more violent in the encounter with the turf and grass than is the encounter of the bottom of the ball moving sideways across the grass, whether skidding, skidding some and rolling some, or just rolling. The rebounding of a ball out of the somewhat "spongy" turf is on a similar scale of un-average in comparison to a ball traveling level across the grass.

But even so, on a scale of 1 to 10, with rolling have a mere 1 chance of messing up the line, and bouncing / bounding having perhaps three times as much chance or a 3, mis-alignment of the face at impact has an even greater chance of messing up the line, especially when compounded with aiming error to start with. In other words, improving aim and stroke technique is a lot more important for consistently good results than is sweating the variability of the surface (it's called "the rub of the green" as in something that can't be helped) and what "ture roll" technology or technique will gain some measure of control over the -ball-surface physics.

Cheers!

Geoff Mangum
Putting Coach and Theorist
PuttingZone.com
Golf's most advanced and comprehensive putting instruction.

Forgive me for this but i do believe it is possible to apply side spin to a ball with a putt. I have viewed this phenomenum with my own eyes courtesey of high speed filming. This occurs when the clubface is not square to the path at impact or through a non centred strike...basic ball flight laws.

The bowling sidespin that I and CB Daish are referring to is right side over left side, and not right side back around left side. The axis of the former is from back of ball on equator out opposite front of ball, with the line of axial rotation parallel to the ground. A bowling ball and a forward pass both "spiral" on the same axis parallel to the ground when moving level.

The sidespin you are referrring to makes the ball spin on an axis running from top of ball thru bottom of ball, perpendicular to the ground. Two different animals.

Cheers!

Geoff Mangum
Putting Coach and Theorist
PuttingZone.com
Golf's most advanced and comprehensive putting instruction.

i see your point and have overlooked that seperate definitions earlier, however both axis are refered to as side spin in commonly used terminology.

The ball that spins on an axis running from top of ball through bottom of ball, perpendicular to the ground.......do you believe that this action will not have influence on the direction the ball travel in laterally? in otherwise it would not lead to the ball veering off its indended line?

Dear kipling,

Yes, I believe this sort of vertical-axis sidespin can affect the line of roll of a putt. What appears to happen is that the sidespin of the bottom of the ball occurs down in a small "channel" of grass with sidewalls. One sidewall has the spinning surface of the ball rolling at it, whereas the other sidewall has the spinning surface of the ball rolling away from it, as the lateral direction of the ball progresses targetward thru the linear channel of grass. This "offset" or "unequal" friction tends to "grab" the ball on the "at it side" while "opening the wall" on the "away side" of the channel. (This is all a very minor effect since the channel walls are not very high up on the bottom of the ball and also are not very stiff or rigidly pressing against the ball surface.) There are then two simultaneous effects on the line of roll: 1. the channel "at it side" counters the sidespin and reduces it, while 2. the ball trends slightly off line to the "away from it side" of the channel.

Hence, a cut stroke imparts "cut spin" (clockwise looking down on the ball for a right-hander). The "at it side" is on the left of the line or channel, and the "away from it side" is the right wall of the channel. Similar to the aerodynamics sidespin effect on a ball flying thru the air, the left side has added "pressure" (opposition or resistance) and the right side has reduced "pressure" so the ball follows the path of least resistance and trends to the right.

The inertial properties of the ball mass in sidespin rotation tend to preserve this rotational motion despite the opposition of the grass to the bottom of the ball. However, the opposition on the bottom of the ball is a summation of different forces or force "vectors." The sidespin is only one aspect of the forces of ball motion against green surface friction / opposition. The MUCH LARGER force is the oppositional vector in the line of motion of the ball AT THE TARGET rather than the sideways oppositional vector of the sidespin, which runs perpendicular to the target line.

The main opposition of the grass to the target-line direction of the ball is what causes skid to reduce and transform into "forward roll." The mass of the ball in gravity (45 grams) tugs the ball against the surface, and on a level surface this "force" or weight of the ball is what makes the friction of the given surface have the SIZE of force that it does. How big is this force? The "normal force" (force straight down onto a level surface) is described by the equation F = mg, with F being in units of Newtons and mass m in kilograms (a ball if 0.045 kg) and g in meters/second squared (gravity is 9.8 m/sec^2). So the normal F is 0.0046 Newtons (or 460 "dynes" in the CGS units). ("Weight" of mass is the same as "force" in this case -- see Nave. Given this "normal force" or "weight" of the ball's mass onto the green, the "kinetic friction" of oppositional force applied to the laterally skidding ball is known by F(k) = mu(k) * N (weight in Newtons) (see Nave.) According to Werner and Grieg: The Coefficient of sliding fricition depends upon the Stimpmeter speed of the green. Coefficient = .946 -.021*Stimpmeter reading (in feet). There is no unit for this coefficient. So let's take a Stimp 10 green. The sliding / kinetic friction would have a mu(k) of about 0.746, and an oppositional sliding friction force against the 0.0046 Newtons of the ball weight of about 0.0034316 Newtons (343 "dynes"). The grass friction is about 75% of the ball weight.

So there are "four horses" pulling the ball at the target and "three horses" pulling the other way. In comparison, the "force" of the left channel wall against the bottom of the ball tending to shove the ball to the right out of line is meagre indeed. One might imagine a line of itty-bitty squirrels perched along the top of the left wall, all punching the ball to the right with tiny little punches as it speeds past -- not too significant compared to the titanic "tug of war" between the four horses one way and the three horses the other way. the sidespin forces are about on a scale of a ski slalom "inside gate pole" hitting a downhill skier on the left shoulder as he whizzes thru the gate. yeah, there's a force there, but it's not big in comparison to the downhill momentum of the racer. Well, okay, more like hitting a succession of poles with the left shoulder -- a constant "flicking" of the racer leftward a little.

And the BIGGER frictional opposition that stays aiming in the main line of the putt (in the direction opposite to the direction of travel of the ball) basically "occupies" and "replaces" the sidespin with forward roll.

Comparing "bowling" sidespin (axis of rotation level to line of travel / lane) with golfball "cut spin" (vertical axis of rotation, or even to forward rolling and skidding of a golf ball across a green, the WHOLE circumference of the ball comes in opposition to the surface friction due to the spin, whereas in a "cut spin" sort of action, the bottom of the ball ONLY spins clockwise as the ball slides / rolls its whole circumference down the line. Only the opposition of the sidewalls of the channel affect the line of the ball. And because the wall of grass (perhaps it is more of a wedge-shaped V channel rather than a "canal" sort of channel) is only meeting a small section of the ball, it is more like the way a bowling ball rolls out of the ball return onto the holding rack. Sidespin in this sense is not that powerful a factor. (Compare Douglas Weidman's Bowling Spin.)

But I agree that the sidespin doesn't always disappear entirely. If the sidespin persists (the sidespin rotational momentum does not cease or get replaced by forward roll entirely) until the forward roll of the ball slows sufficiently, there is the occasional effect of the sidespin during this SLOW ROLLING part of the putt being large enough to THEN move the ball out of the track sideways. Not much, but a little.

It's necessary to distinguish imparting sidespin to the ball from hitting the ball to the side off line. A "cut stroke" is partly a path from out-to-in plus partly a face angle slightly "open". If the face were not open a bit, the "cut stroke" would really be a dead pull to the inside. It is the "glancing" nature of the open face plus out-to-in path that gives the straight-ahead skidding start plus some rotational sidespin to boot. For example, approximately, the combination of 5 degrees face open with a 30 degree out-to-in path thru impact results in a putt that starts straight (i.e., 0 degrees off the intended path) with a bit of sidespin, depending on how much force or putter head velocity is used in the blow and how much "friction" there is in the putter face-ball contact during this specific impact. Truth be told, there is not usually much ball-face friction in putters for usual sorts of strokes. In the full shot, the forces are very much bigger and the grooves on the face make a difference in the sliding friction of the ball up the face while compressed, but this is generally nothing like what happens in a putt.

Do grooves or soft inserts on a putter face promote sidespin? Probably a little, but it is mostly an unexamined question. Dr Norman Lindsay says grooves add friction in the face-ball physics of impact, but that this friction is "redundant", presumably meaning that the added friction doesn't add enough to make any difference. he writes: "Grooves, pimples or insert materials -- It’s frequently claimed that grooves, ridges, pimples, other surface shapes or even surface chemistry can impart topspin. As it happens, grooves assist backspin in high lofted clubs where additional surface friction is needed. In putters additional friction is redundant. Simple, direct measurements on putters show that grooves or different face materials do not contribute spin in any direction." I'm not sure what this means, really, but I suspect that increasing dwell time, as soft inserts do or using soft-covered balls does, will amplify sidespin.

Cheers!

Geoff Mangum
Putting Coach and Theorist
PuttingZone.com
Golf's most advanced and comprehensive putting instruction.