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What’s in a ball outer?
With a variety of balls on the
market for rugby, soccer and
netball, your customers may
select one based on what it
looks like — the colours used
or even the patterns on the ball. You will want
to point out that they should also consider the
many factors — such as materials, seals, linings,
etc. — that affect how a ball performs
during play.
In flight, the air close to the surface of the
ball is affected by any unevenness — like
seams, pimples or panels — that cause an
asymmetric flow of air around the ball, dr
Rabi Mehta, an aerospace engineer at NASA
Ames, demonstrated by testing balls in wind
tunnels. The air around the ball is ‘broken’ by
the seams of the ball, which causes the ball to
swerve (or ‘knuckle’) and move unpredictably.
• When a ball is kicked, the air around it
forms a laminar (smooth) or turbulent (disrupted)
boundary layer. During flight the
pressure in the front half of the ball decreases,
while the pressure in the back half
will separate from the surface and equalise,
resulting in a drag force that reduces the
ball’s speed.
• When a ball is kicked with little force (at
low speed) the boundary layer will be laminar
and air layers flowing around the ball
will be smooth and parallel to one another.
When a ball is kicked with great force (at
high speed) the boundary layer will be turbulent
creating chaotic air flow that withstands
the adverse pressure for longer and
causes the turbulent boundary layer to separate
later than with the laminar layer. This
later separation creates less drag on the ball
and allows it to stay in flight longer.
• Air flowing smoothly around a ball and separating
early, leaves a large drag in its wake.
When the air around the ball is turbulent
(e.g. as a result of panels and stitching), air
clings to the ball for longer, separating later
and leaves less drag in its wake. ‘Tripping’
the laminar boundary layer into action (using
panels) makes ball flight more predictable
and longer.
• In soccer, when a ball (spherical in shape) is
kicked with great force, the air around the
ball is turbulent, causing little drag.
o The ball spins toward the side that has the
least opposing force (following its nose)
— this is known as the Magnus effect —
and as it continues on its flight path, its
Our cut-out-and-keep series to
assist retailers with product
knowledge
Words: Rhianah Fredericks. Compiled
with the help of Du Toit Botes of Super-
Brands, Nick Wiltshire of Pat Wiltshire
Sports, Robyn Frick of Puma SA, and
websites: www.soccerballworld.com,
iweb.tms.org, buet.ac.bd, www.telegraph.co.uk,
www.nasa.gov, illumin.
usc.edu, www.nutsaboutsport.co.uk,
en.wikipedia.org, www.tenfactsabout.
co.uk and netball.com.au
travelling speed will drop - causing the air
around the ball to become laminar and its
drag to increase.
o As the ball slows down, it will move in the
direction with the least opposing force —
or look like it is curving.
o Panels or seams on the ball’s side, may
cause a curve to become even more pronounced.
This is how many soccer players
are able to curve a ball toward the end of
its flight and ‘change’ its trajectory.
The role of panels
Panels make up the outer covering of the ball
and the number of panels (sections) can have
an impact on the flight of the ball, as the
seams “disturb” air during flight. The design
of the panels can also affect the predictability
of the flight.
• If a ball has fewer panels, which results in
large smooth surfaces, it will be more unpredictable
in flight and will not travel as far as
a ball with many seams.
o When a smooth ball is kicked, the air
around the ball is ‘unbroken’ by the ball’s
surface and therefore the ball will slow
down quicker as a result of the pressure of
the air around it.
o When a rough surfaced ball (with many
panels and seams) that is able to ‘break’
the air around the ball is kicked, the ball
will travel further because the pressure of
the air around the ball has been ‘broken’
and allows it to travel further.
• A rougher surfaced ball becomes turbulent
much faster than a smoother one and allows
the ball to curve more.
o Typical soccer balls have 32 panels that
each have seams, ensuring a rougher surface
than a smoother ball without seams.
o The hexagon shape of panels on a soccer
ball also causes turbulence to set in much
faster, enabling the ball to travel further
and maintain predictable flight.
The number of panels
• There are various panel designs used in soccer
balls — 32, 18, 16 — panel constructions,
etc. — but the most common design
is 32-panels. This design, known as the Buckminster,
features twenty hexagon (six-sided)
and twelve pentagon (five-sided) pieces that
cover the ball and give it a sphere shape
once it is inflated. The shape of the ball allows
it to roll and spin evenly and smoothly.
This is also the most popular panel design for
professional match balls.
• Rugby balls are constructed with four-panel
designs that give them an oval shape. They
are oval shaped (rather than round like soccer
balls), because it is easier to catch, hold
and run with the ball than it would be to do
with a rounder ball. The shape of the ball
also does not allow it to roll as far as a soccer
ball, which is ideal for throws and passes
that occur in the game.
• Netball balls, much like soccer balls, can
have various panel constructions: 32, 18, etc.
Pimples and performance
Pimples (also known as dimples) can be described
as little bumps or protrusions on the
surface of a ball.
• These add roughness to the surface and,
like panels, they can affect the To p58
2014 March :: Sports Trader