Rugby balls made with hi-tech dimples to improve grip may actually make them harder to hold in wet weather, according to new research.
Scientists have found that the raised rubber studs on modern balls – which are designed to increase friction with players hands – can be a disadvantage in wet conditions. They have discovered that a film of water can form between the dimples, making it harder to hang on to a ball securely.
Dr Roger Lewis and Dr Matt Carré, a mechanical engineer at the University of Sheffield, whose work was published just ahead of the final match of Six Nations Cup between England and Wales, believe their findings could help players in major competitions.
“Manufacturers started putting dimples on rugby balls to help provide extra grip,” said Dr Lewis. “They have a range of different designs with the size of the dimples and their spacing.
“In dry conditions, closely spaced pimples were better for grip, but in wet or muddy conditions, the density of the pimples allowed a film of moisture to form between them, so wider pimple spacing is better.
"Given that a slip at the wrong time could mean the difference between winning and losing a match, it’s important that this potential is explored.”
In a paper published in the journal Tribology International, the researchers tested how different textures on the panels of rugby balls made from different materials interacted with the skin on a persons finger.
They found that balls made with high levels of natural rubber were the best for gripping as they tended not to polish like cheaper balls and those with large spaced dimples performed best in the wet.
They also found that mitts, which are sometimes used by players to help increase their grip, could also be counteractive in the wet, unless the dimples on the mitts are small enough to interlock with those on the ball.
The conditions within the Millennium Stadium in Cardiff, where Wales and England are due to play, present their own particular challenges due to the sliding roof that can keep out the rain.
Although the pitch can then stay relatively dry, the roof can drive up humidity, making the ball even harder to handle. Dr Carré said that it may be possible to design balls in the future that better suited for different weather conditions, much like tyres used on Formula One racing cars.
He said: “A small amount of moisture is useful for grip, a bit like licking your finger when turning a page, but in an extremely wet day during a rugby match it can create a film that makes it much harder to grip.
“You could foresee a situation where it could make for a better game by changing the ball depending on the weather conditions.
“We also want to look at the different ways the ball is handled – when players catch they use their palms and then their fingers come into use and when they throw a ball they hold it differently again.
"Different gripping surfaces on the ball could help with this.”
Read the Telegraph article here