Common myths debunked
we're in a
position to think about some of the things I see all the time in
articles and forum discussion -- things said with the ring of truth
that are not true at all. For instance...
harder clubface gives more distance.
This has been
advertised so often that many people seem to believe it and repeat it
as the truth. It simply isn't! I have written a whole article
this one. But here's the short form of the real story.
Almost all the loss of energy at impact occurs in the ball.
material, when compressed as much as it is, will give up energy to its
own internal friction. The ball manufacturers are not in a position to
improve things here, because USGA rules insist that a certain amount of
energy is dissipated by the ball.
But what about the other participant in impact, the clubface?
If we let
the clubface flex a little, that's a little compression that the ball
does not have to do. And springy metals like steel and titanium can
flex a little and spring back with almost no loss of energy; they have
very little internal friction. That suggests that you get better energy
transfer (less loss) if you let the face flex.
And in fact it works that way! You often hear the terms
and "trampoline effect" to describe the hot-face drivers available
today. This refers to increasing
the coefficient of restitution (COR) of a driver by using a flexible
face. In practice, it is indeed possible to absorb
some of the flex in the low-loss clubface and relieve it from the
higher-loss ball -- with distinctly measurable gains in distance.
Bottom line: Rigid, hard faces don't give more distance, flexible
a full shot you want to hit the ball as hard as you can ... with both
hands. This is advice from Ben Hogan's classic
book, "Five Lessons: The Modern Fundamentals of Golf".
I agree with almost everything in the book. But not this. And now we
know the problem with this particular piece of advice. Any addition
of hit with the hands has to be timed exactly right in order
help more than it hurts. I have done
a study on this and found that, no matter how you try to hit
the ball hard at impact, you can't. At least you can't if you have held
the lag instead of "casting". If you have a decent golf swing, the
clubhead is already moving so fast through the impact zone, you can't
move your hands fast enough to even keep up with it -- much less exceed
it enough to further accelerate the head.
That does not mean Hogan's advice is bad instruction, just bad physics.
There can be other benefits to the move, if it acts as a
"trigger" to hold the lag until the impact zone. If it serves
that purpose, then any later attempt at forcing a release is pretty
harmless. But that is psycho-biological reasoning, not physics.
club accelerating through impact for more power.
Like the previous point, this is good instruction but bad physics.
There are lots of things that will go wrong with your swing if you
don't accelerate into the ball, but loss of potential
distance is not among them. Let's do the math.
So you're not going to get any measurable additional ball
speed during impact by accelerating through the ball. And that means
that you won't get any measurable additional distance.
consider a typical strong adult male with a 100mph clubhead speed and a
downswing that takes 0.3 seconds from transition to impact.
- So the clubhead accelerates from 0 to 100mph in 0.3
an average of 333mph per second. (Yes, "miles per hour per second" is a
legitimate unit of acceleration. You won't see it often in physics
texts, but you'll hear it a lot in auto sports. "Zero to sixty in five
seconds." The implied unit of acceleration is miles per hour per
- Suppose you could keep that average acceleration going
right through impact. (We all know you can't, but suppose you could.
Let's be really optimistic here!) Let's compute how much of an increase
in clubhead speed that would give from the beginning to the end of
impact. We compute that number, because it is the absolute maximum
additional contribution to clubhead speed you could use when you figure
ball speed and distance. In fact, it would be no more than half of that.
per second times 0.0005 seconds (the duration of impact) gives 0.17mph.
That's only one sixth of a mile per hour. Good for less than half a
yard of distance, and that is probably not even measurable among the
effects of normal shot-to-shot variation.
So why don't I dismiss the advice as bunk. Instead, I follow it myself.
It's because golfers are brain and muscle as well as a source of
momentum transfer. If the brain tells the muscles it's OK to ease off
at impact, all sorts of other things go wrong. The muscles relax a bit
too early, and you lose a lot of speed before impact.
Or you stop turning, resulting in wrist cupping, and the ball goes dead
left. As I have said before and undoubtedly will say again, just
because it's bad physics doesn't mean it's bad instruction.
ball starts in the direction of the
clubhead path and spins in the direction the clubface is pointing.
This is often presented as a recipe for hitting an intentional hook or
slice. "Line up with your swing path (shoulders, hips, feet) pointing
where you want the ball to take off, and the clubface pointing where
you want the ball to end up."
Now we know that the ball starts out between the clubface
the swing path -- and considerably closer to the clubface direction
than the swing path. So this recipe, simple though it is, has no
validity in fact. It will produce a hook or slice as advertised, but
taking off much closer to where the clubface is pointing than to the
come many pros still win tournaments while giving this advice in
televised tips? It's because they themselves are not doing what they
think they are doing. They practice the shot enough that they know what
it feels like and how to do it. If you actually took enough slow-motion
video, you would see that the clubhead is coming into impact
differently from the way they visualize it -- but exactly as they have
learned to do it in practice.
is caused by the clubface
rotating closed/open during impact.
Another recipe I've seen espoused for an intentional hook or slice.
"Rotate the hands closed at impact for a hook; rotate them open for a
My opinion is that these instructions may actually be
some golfers -- but not because the ball's spin is affected by the
clubhead's rotation. It isn't! But the golfer focusing on rotating the
face closed is likely to come into the ball with the face already
closed. And that will produce a hook.
Another way to look at it is to see just how much rotation
you can accomplish during impact. Numbers!!!
Basically, any value from this recipe has to do with the
trying to rotate the club, and nothing to do with the actual rotation
- In a good swing, the wrists stay cocked until
about 50 millisec before impact. So the club "lag" goes from 90° to
in 50 milliseconds. This is an average of 1.8°
- Without even trying
to rotate the club, the structure of the body rotates the
clubface in synch with the uncocking wrists. So the clubface angle goes
from 90° to 0° in 50 milliseconds.
impact lasts only 0.4 milliseconds, the clubface rotates 1.8°
0.4 = 0.72°, during impact. That's less than three quarters of
- It is very unlikely that deliberately
rotating the club (with
hands or forearms) will more than double the rotational speed at
let's be generous and say that it could add another 3/4° of
rotation at impact. How much hook do you think this tiny rotation will
grooves work because the sharp
edges dig into the ball.
I'm amazed how widely this is believed. It makes a lot of intuitive
sense if you assume that the force between ball and clubface is a
couple of pounds; the sharp grooves will increase the friction. But now
we realize the ball is compressed on the clubface by a couple of thousand
pounds, and clubface roughness really isn't needed at all to create
In case you still have any doubt, consider the great square groove war
of the late 1980s. It was precipitated when Ping (the only club
manufacturer using square grooves at the time) rounded the edges of the
grooves a bit so they wouldn't shred ball covers. It accomplished that
goal (therefore, it must have radically reduced the "dig" effect of the
edges) without affecting the spin performance at all. So something else
must be at work here. And now we know that it's the volume of the
grooves, and the ability of that volume to channel away the slime that
builds in grassy contact.
effect is caused by
This is repeated by people who should know better -- folks who write
instruction about clubmaking. Most of them are no longer making this
mistake any more, but I still see it in some places. It is true
that gear effect
and face bulge are intimately related -- but this myth
gets cause and effect mixed up. In an important sense, face bulge is
caused by gear
Face bulge is the horizontal curvature of the clubface. You see it in
woods, especially drivers, but never in irons. That's because it is
intended to compensate for the gear effect on a
shot. If there
were no gear effect, then face bulge would not be necessary nor
helpful. In that sense, bulge is caused by gear effect.
Look at the diagrams. The one on the left has a flat-faced driver with
three shots: center-face impact,
toe impact, and heel impact.
We know now that the toe-impact shot will hook and the heel-impact shot
will slice. This is a result of gear effect, and has nothing to do with
The picture on the left is not pretty. Depending on where on the
clubface you strike the ball, you may hook into the left rough or slice
into the woods on the right. But there is a way to make the driver a
little more forgiving: curve the face like the
driver on the right. In the right-hand picture, the hook from the toe starts out to
the right because of face curvature -- bulge. The hook takes the ball
back to the center. Similarly with the heel
slice; bulge starts it left, and it slices back to the
The shaft is
a string at impact. This one is true!
This is not a myth at all, but a very reasonable metaphor. What it
means is, "If you think you can affect ball flight by force you are
exerting on the handle at impact, think again. You have no more control
on the head during impact than if the club were on
This is seriously counter-intuitive, so let's take a good
look. We've already
from the point of view of frequency and time. The time constant of the
shaft is orders of magnitude longer than the half millisecond of
impact. But now we're ready to look at the forces involved rather than
the more abstract time considerations.
Bottom line: The shaft won't exert any usable force on the
impact. If your strength and weight don't get the job done
the clubhead is accelerating toward the ball, anything you do at impact
won't have any more effect than if the shaft were a string.
- Clamp a shaft horizontally by its butt, and hang
a one-pound weight from the
tip. How much did the tip deflect when you added the weight? Even if
you used a stiff shaft, the deflection was close to half an inch. So
the shaft deflects at least an inch for every 2 pounds.
how much force does the head exert on the ball during impact?
We figured it out in this section, and it's about 2000 pounds.
how much would the shaft have to deflect for the force it
exerts to make a significant difference in what happens to the ball.
Well, a one percent change in force is just about at the threshold of a
detectable change in performance. That is, if the force change is less
than one percent, any difference in the result is going to be too small
to notice and very difficult to even measure. One percent of 2000
pounds is 20
finish the story, how much would the shaft have to bend for you to
apply at least 20 pounds to the clubhead by something you do at the
grip? If one pound bends the shaft a half inch, it will take ten
inches of shaft bend to exert a force of 20 pounds. So the shaft would
have to bend at least ten inches
during impact to make a detectable difference in the ball flight. You
know that's not going to happen.
rolls more than a fade because it has topspin.
It's amazing how often I hear this. But it's obviously not true. If it
had topspin, it wouldn't carry 100 yards. That describes a duck
hook, which may indeed have topspin, but not a desirable draw.
did this myth start, and how close to true is it? Well, some
reduce the backspin and some fades increase it. So, although a draw
doesn't have topspin, it may have less backspin
than a fade -- thus it will roll farther.
should this be? And why don't I say it's true for all draws and fades?
Draws and fades can be caused by changing the swing path while keeping
the clubface pointing at the target, or they can be
opening/closing the clubface. Only really good golfers have enough
control of their swing path to determine ball flight via swing path;
most golfers will try to open or close the face. This can take many
forms: rolling the forearms through impact to close the face, using a
stronger or weaker grip, setting up with face open or closed, etc. But
they all have one thing in common; they involve closing the face by rotating the shaft
around its axis.
Consider the figure at the right.
shows a perfectly upright 90º lie. If clubs were actually
like that, then rotating the shaft would open or close the clubface, and
real clubs are built more like diagram (b), with a lie in the vicinity
of 60º. Rotation around the shaft's axis occurs at an angle.
does not simply open or close the face.
you would expect a draw created this way to fly lower and have less
backspin, because it was struck with less loft.
the shaft to close the face also hoods the face, reducing the loft.
the shaft to lay the face open also increases the loft.
goes farther at high altitude because of the thinner air.
This is sometimes true, but sometimes not. The prevalence of this
belief is undoubtedly due to television announcers saying it repeatedly
during coverage of The International, a tournament that takes place at
Castle Pines, CO, almost 7000 feet above sea level.
closer look at why it isn't true in all cases. It is plausible that the
ball goes farther in thinner air, because there will be less drag. But
there has to be a limit where thinner air means the ball does not go as
far. That's because distance depends on lift, not just on reduced drag,
and thinner air means less lift. If we hit a ball in a vacuum (the
ultimate in thinner air), we lose a lot of distance from what we're use
to at sea level; as we have seen, lift makes a big difference.
|But 7000 feet
is far from a complete vacuum, and the pros do indeed hit
their shots farther at The International. So is the "myth" true for all
practical purposes? No, but we have to look at a variety of golfers to
see why. By now, we are used to seeing ball speed, launch angle, and
spin make a difference in distance. Let's
look at three golfers with very different ball speeds, and
loft of their drivers (thus varying launch angle and spin).
we'll look at the typical Tour pro, with a clubhead
speed of 115mph.
(The big hitters have a higher clubhead speed; 115mph is modest for a
Tour pro.) This golfer does get more distance at altitude. If we look
at the graph, we see that his usual driver (assumed to be optimized for
sea level performance) has a 10º loft. Even at this loft, 7000
feet gives him an extra 7 yards of carry.
But he has
opportunity. The reduced drag and lift suggest that a higher launch
angle should help, and the additional spin wouldn't hurt. By going to a
14º driver for The International, he can get better than a
advantage over his normal driver performing at sea level, and about 15
yards more than his normal driver at 7000 feet. Given the prize money
at this tournament, it would be very reasonable for him to have a
special driver just for this week (especially since he probably gets
the clubs he endorses for free).
Now let's turn to the typical
male golfer you'll find on US courses. His clubhead speed is
probably around 85mph.
(No, he won't say so -- and he'll tell you he typically hits his driver
270 yards. He is most likely delusional, and this is a very common
delusion.) At sea level, his ideal
driver is lofted at 16º-17º. At 7000 feet, he can get
same carry distance from the same driver. If he adds on a degree or
two, he can wring out an additional 3 yards at 7000 feet -- not a lot,
Reality check time! How many typical
do you know who play with a 16º driver? He is much more likely
have a 10.5º driver, but let's give him credit for going to
loft -- say 12º or maybe even 14º. At these lofts, he
still getting noticeably more distance at sea level than at altitude.
we turn our attention to the typical senior female golfer,
with a clubhead speed of about 60mph.
As we see from the graph, she gets more distance at sea level than at
altitude for any loft. That's because, at that clubhead speed, she
needs all the lift she can get.
The moral of the
TV announcers tell the truth for the touring pros they are covering.
Those guys get significant increases in distance at Castle Pines.
you're a typical male golfer (not a genuine big hitter), you'll
probably get better performance at sea level, unless you get a really
high-loft driver (in the vicinity of 18º).
you're a slow-swinging senior, altitude isn't going to get you any
good driver design has a high launch angle and low spin.
That's a qualified "yes", but heavily qualified. True, a properly
fitted driver has more loft than you probably would have guessed. But
it doesn't have to be anywhere near the mathematical optimum, which is
generally much higher launch and lower spin than you can readily build
into a driver.
If all you do is get the loft right
so that you
are on the "ridge" of maximum distance for your golfer's ball
then you are fairly close to the maximum distance that can be
theoretically attained. Admittedly, that driver will have considerably
lower launch angle and higher spin than the optimum driver. But you
would have to make large differences in launch angle and spin to get
even small differences in distance.
But wait! It's even worse than that. Suppose your driver is designed to
be "on the ridge", and you are tinkering with it to get higher launch
and/or lower spin. You must be very careful what you tweak; you are
more likely to make things worse than better. Consider:
The only reliable ways to increase launch angle at the same time as
decreasing spin are to increase your angle of attack and catch the ball
high on the clubface. And the way to do that is practice, not
purchases. The only ways you can accomplish that through equipment is
longer tees (and the skill to catch the ball sitting way up off the
ground) and a lower CG in the clubhead.
- Most things you can change about the club itself will
change launch angle in the
same way as spin. That is, almost anything you can do to
increase the launch angle will also increase the spin. This is
guaranteed to reduce your distance.
- If you manage to increase the launch angle by itself,
without decreasing spin, you will not help distance at all. If you do
very much of this, you will hurt your distance.
- Same goes for decreasing spin without increasing launch
angle. Doesn't help, and enough of it can hurt.
modified Jan 23, 2011