Testing feather Badminton Shuttlecocks

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.



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