When
it comes to improving your golf game, you can spend thousands of
dollars buying the latest titanium-induced, Tiger-promoted golf clubs;
taking private lessons from the local "I used to be on the Tour" pro;
or trying every slice-correcting, swing-speed-estimating,
GPS-distance-guessing gadget. But, in the end, it’s about getting that
little white sphere to go where you intended it to go. Don't worry,
there are many very smart people trying to help you by designing the
ultimate golf ball. Of course, they are also after a slice of this
billion dollar industry, as any technological advancement that can grab
a few more market share points is worth the investment.
In
fact, the golf ball wars can get nasty. Earlier this month, Callaway
Golf won a court order permanently halting sales of the industry's
leading ball, Titleist's Pro V1, arguing patent infringements involving
its solid core technology which Callaway acquired when it bought
Spaulding/Top Flite in 2003. Titleist disagrees with the decision and
will appeal, but in the meantime has altered its manufacturing process
so that the patents in question are not used.
The
challenge for golf ball manufacturers is to design a better performing
ball within the constraints set by United States Golf Association. The
USGA enforces limits on the size, weight and initial performance
characteristics in an attempt to keep the playing field somewhat level.
Every "sanctioned" golf ball must weigh less than 1.62 ounces with a
diameter smaller than 1.68 inches. It also must have a similar initial
velocity when hit with a metal striker, and rebound at the same angle
and speed when hit against a metal block. So, what is left to tinker
with? Manufacturers have focused on the internal materials in the ball
and its cover design.
Today's
balls have 2, 3 or 4 layers of different internal polymer materials to
be able to respond differently when hit with a driver versus, say, a
wedge. When hit with a driver at much higher swing speed, the energy
transfer goes all the way to the core by compressing ball, reducing
backspin. During a slower swing with a club that has more angle loft,
the energy stays closer to the surface of the ball and allows the
grooves of the club to grab onto the ball's cover producing more spin.
When driving the ball off of the tee, the preference is more distance
and less loft, so a lower backspin is required. For closer shots, more
backspin and control are needed.
The Science of Dimples
Which
brings us to the cover of the ball and all of the design possibilities.
Two forces affect the flight and distance of flying spheres, gravity
and aerodynamics. Eventually, gravity wins once the momentum of the
ball is slowed by the aerodynamic drag. Since all golf clubs have some
angular loft to their clubface, the struck ball will have backspin. As
explained by the Magnus Force effect, the air pressure will be lower on
the top of the ball since that side is moving slower relative to the
air around it. This creates lift as the ball will go in the direction
of the lower air pressure. Counteracting this lift is the friction or
drag the ball experiences while flying through the air.Think about a boat moving through water. At the front of the boat, the water moves smoothly around the sides of the boat, but eventually separates from the boat on the back side. This leaves behind a turbulent wake where the water is agitated and creates a lower pressure area. The larger the wake, the more drag is created. A ball in flight has the same properties.
The
secret then is how to reduce this wake behind the ball. Enter the
infamous golf ball dimples. Dimples on a golf ball create a thin
turbulent boundary layer of air molecules that sticks to the ball's
contour longer than on a smooth ball. This allows the flowing air to
follow the ball's surface farther around the back of the ball, which
decreases the size of the wake. In fact, research has shown that a
dimpled ball travels about twice as far as a smooth ball.
So,
the design competition comes down to perfecting the dimple, since not
all dimples are created equal! The number, size and shape can have a
dramatic impact on performance. Typically, today's balls have 300-500
spherically shaped dimples, each with a depth of about .010 inch.
However, varying just the depth by .001 inch can have dramatic effects
on the ball's flight.
Regarding shape, these traditional round dimple patterns cover up to 86
percent of the surface of the golf ball. To create better coverage,
Callaway Golf's HX ball uses hexagon shaped dimples that can create a
denser lattice of dimples leaving fewer flat spots. Creating just the
right design has traditionally been a trial-and-error process of
creating a prototype then testing in a wind tunnel. This time-consuming
process does not allow for the extreme fine-tuning of the variables.
Simulation Solution
At
the 61st Meeting of the American Physical Society's Division of Fluid
Dynamics last month in San Antonio, a team of researchers from Arizona
State University and the University of Maryland is reporting new
findings that may soon give golf ball manufacturers a more efficient
method of testing their designs. Their research takes a different
approach, using mathematical equations that model the physics of a golf
ball in flight. ASU's Clinton Smith, a Ph.D. student and his advisor
Kyle Squires collaborated with Nikolaos Beratlis and Elias Balaras at
the University of Maryland and Masaya Tsunoda of Sumitomo Rubber
Industries, Ltd. The team has been developing highly efficient
algorithms and software to solve these equations on parallel
supercomputers, which can reduce the simulation time from years to
hours.
Now
that the model and process is in place, the next step is to begin the
quest for the ultimate dimple. In the meantime, when someone asks you,
"What's your handicap?" you can confidently tell them, "Well, my golf
ball's design does not optimize its drag coefficient which results in a
lower loft and spin rate from its poor aerodynamics."
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Comments
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Rob Robson
Co-founder, iStadia.com