The Badminton Characterisation Test (BSC)
comprises three major procedures:
Ocular Inspection
Flight Monitoring
Players Questionnaire
Manufacturer send in 2 tubes of shuttles for test. When they arrive
all shuttles in one tube are weighed and thereafter stored for
3 week in a container at 83 % RH and room temperature. Shuttles
are weighed again and thereafter tested by test stokes to select
two representative shuttles for the Players Questionnaire.
The Ocular Inspection has the objectives, from the design point
of view, to give a fingerprint of the shuttle sent for approval
and also compare design with regulations in BWF statutes.
By Flight Monitoring the aerodynamic and physical aspects of flight
are determined mainly by video recording. Also the weight differences
and changes due to relative humidity are determined in this part
of the test.
In the Players Questionnaire international players test-play without
knowing the brand of the shuttle. A special form grading characteristics
at different types of strokes is completed. Views from the players
are summarised as an over all impression.
Results from these three test are summarised in a report to the
technical committee of IBF which takes the final decision of approval.
Environmental conditions impact on shuttle
characteristics
The distance a shuttle travels after hit,
decrease with decreased temperature and increased pressure. The
reason is that the density of air increase with decreased temperature
and increased pressure. As rule of thumb, if pressure drops 1
mbar the length of flight is increased a little less than 1 cm.
If the temperature increase 1 °C the length of flight increase
about 2,5 cm.
Durability of shuttles (feathers) depend on the amount of water
the feathers contain. Water acts as a softening agent for the
keratin that the feather is made out of. In the feather naturally
occurring oils also act as a softener. As feathers age the get
more brittle due to evaporation of water and oil but also due
to oxidation processes as a part of the degradation.
Shuttle speed is often presented in grains (G), but this is only
the weight of the shuttle. A normal “speed” of 79 G
weights 0,065 gram/grain * 79 grains = 5,13 gram.
Aerodynamic characteristics and influence on play
A non rotating shuttle turns around the
centre of gravity, which is located about 10-20 mm above the base.
A shuttle in flight is influenced by gravimetrical forces and
air forces (centre of pressure, CP). The location of the CP changes
during flight. Since the shuttle after most strokes rotates, the
rotation limits the shuttle from turning, in a similar way as
in a gyro.
Parameters that influence speed of shuttle is weight, feather
angle and form, projected area and diameter that the points of
feathers form. The strongest drag force is formed behind the shuttle
during flight due to turbulence. One part of the turbulence is
formed from the speed of rotation of the shuttle. A high speed
of rotation increase drag forces and reduce speed of shuttle.
A shuttle rotates counter clock vice, which is the reason why
all shuttles deviates to the right (seen from the hitter) during
the last part of the trajectory. Since speed of rotation generates
large drag forces a shuttle that after the stroke rotates less
travels a longer distance and at a higher speed, if impact force
is constant. A left handed player has an advantage over the right
handed when it comes to generate a stroke of high speed, because
the movement of the wrist generates less counter clock vice rotation
of the shuttle.
By hitting the shuttle with a sliced racket the speed of rotation
could be increased or decreased. A clock vice rotation in the
beginning of the trajectory makes it much easier for the shuttle
to turn around the centre of gravity when the rotation stops.
This is used to get a net shot landing close to the net.
A shuttle with a hard cork base travels a longer distance than
the corresponding shuttle with a soft base. The reason for this
is that a larger fraction of the impulse is transferred to the
hard base shuttle.
Even tough the length of the court is the same independent type
of shuttle, the usable length during play is shorter with a shuttle
that rotates less. The reason is that the retardation of a fast
rotating shuttle is higher and a shuttle that you hardly reach
would be to long if the shuttle rotates very slow.
Shuttle that fligh and is hit horizontally backs for a few centimetres
with feathers bent outwards and wanes that easily separates generating
a shuttle looking like a “brush”. This shock impact
generates a shuttle that is slower due to the increased friction
(more turbulence along the feather outside). A shuttle that drops
vertically and is hit is initially pressed together and wobbles
a little before finding the right track. This type of hit does
not generate the same change of speed.
In my work trying to understand and develop
the game from the shuttle horizon I am very interested in comments
and discussions in this field.
Slowmotion captures of feather Badminton Shuttlecocks during gameplay.