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Balls to the World Cup: Brazuca wins in the wind

Robot kicker didn't bend it like Beckham

Adidas Brazuca World Cup ball

In soccer, the ball matters: Japanese boffins say the new six-panel design to be used in the 2014 FIFA World Cup is the most stable and predictable in many a long year.

Of course, the balls used in the World Cup are nothing like what oldsters like this correspondent would recognise. The old-style ball has long been replaced at the elite level with designs that try to get rid of the unpredictable aerodynamics associated with the traditional design that mixes pentagonal and hexagonal sewn panels.

Whether that works in practise is a regular World Cup controversy, so the scientists at Japan's University of Tsukuba, led by Sungchan Hong, set to work with balls of different designs (including this year's Brazuca), a wind tunnel, and a kicking robot to see how they behaved.

Their conclusion is that the Adidas Brazuca, which has just six curved panels and a rough surface, behaves more predictably than predecessors like the 2006 Teamgeist (14 panels, glued rather than stitched) or the 2010 Jabulani eight-panel ball, as well as the 32-panel Cafusa used in last year's Confederations Cup and a conventional ball.

Published at Nature's Scientific Reports, the study finds that the Brazuca has the most predictable drag characteristics in the wind tunnel tests. Drag on other balls, Hong found, is much more dependent on the orientation of the ball (with respect to the wind), with the Jabulani and Teamgeist variants much less predictable even than a conventional ball.

The other test the group conducted tested the trajectory of the ball when struck by a robot kicker, with 20 shots for each ball type in each “panel orientation”, launched at 30 metres per second towards a goal net 25m distant.

Once again, the Brazuca and the “conventional” ball were the most predictable. The Cafusa, Jabulani and Teamgeist “varied substantially with the panel orientation”, they write, with Cafusa and Teamgeist “particularly drastic”.

Of course, as they say in the classics, “it's only a model*”. The tests didn't even try to reflect characteristics like humidity, player skill, or all the myriad factors that occur in real life. However, with a more reliable ball, players will have to go back to complaining about the grass or the intolerable pain they suffered in the last passing tackle. ®

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