In 2010 the South African World Cup had a terrible football, the Jabulani
It was too smooth resulting in serious problems. The football had a lot less seam which the technology at the time was not ready for
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| Jabulani: eight thermally bonded panels, unusually short/shallow seams |
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| The 2010 ball had shallow thin seams |
When you kick a football really fast a layer of air develops around it that reduces the drag. This is why golf balls have dimples. An amount of surface roughness can actually reduce drag.
At a certain point the air buffer leaves the football and it gets full drag. This is the critical speed.
The Jabulani had a really high critical speed which means as soon as it got to 24 meters per second it started to slow down quickly. The Trionda's, this year's ball, seams are deeper allowing it to 'catch' air and avoid the critical speed of drag for longer. Also the surface of the ball itself is slightly bumpy in a way the Jabulani's were not.
At a certain point the air buffer leaves the football and it gets full drag. This is the critical speed.
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| Trionda: four panels, deeper seams and textured icons. |
The Jabulani had a really high critical speed which means as soon as it got to 24 meters per second it started to slow down quickly. The Trionda's, this year's ball, seams are deeper allowing it to 'catch' air and avoid the critical speed of drag for longer. Also the surface of the ball itself is slightly bumpy in a way the Jabulani's were not.
Goalkeepers did not like this as they said it made the ball seem like a beach ball that did not have a predictable movement. But the number of goals at the World Cup were really low. So the goalkeeper discomfort at the weird ball paths were probably made up for by the ball going slower in a way that reduced goals.
This book on the mathematics of the football and this article lead to this post