2014 World Cup, Brazuca: The Physics of Adidas’ New World Cup Ball.
Since 1970, every World Cup football has been made by Adidas, an ideal opportunity to showcase their latest developments in ball design and technology. (Disclosure: I work at the Centre for Sports Engineering Research at Sheffield Hallam University, which has worked on some projects with Adidas. No one at the Centre for Sports Engineering Research has worked on Adidas’ World Cup ball.) In 2006, they took a radical departure from the norm with the Teamgeist. Traditionally, a football is constructed from 32 panels stitched together by hand. The Teamgeist had 14 panels that were glued together with heat (thermally bonded), resulting in a ball that was more “marble-like” than previous generations.
The change was not only aesthetic. Players using the ball complained of erratic behavior in flight. For the next World Cup (South Africa, 2010) Adidas considerably redesigned the ball, the Jabulani, which had only eight thermally bonded panels. Unfortunately, criticism of the ball was, if anything, louder than it had been four years earlier. Many coaches and players compared the Jabulani to a beach ball that swerves unpredictably.
Their radical design is different from a standard stitched football in two ways. First, fewer panels mean shorter seams. By my own measurements, a 32-panel football has a seam length of around 405 centimeters, compared to 345 cm on the Teamgeist and 203 cm on the Jabulani. Second, thermal bonding created a much lower seam profile. A laser scan of the surface of the Jabulani and a stitched football shows the stitched seam is more than twice as deep as the Jabulani’s. The floating, beach-ball-like behavior of these footballs isn’t because they are light, but because they are smooth.