9th April 2010
‘Hailstorm of doom!’ at least that is what Miriam Sullivan my colleague in the office calls the freak hail storm that hit Perth two weeks ago – battering the city with hail stones the size of golf balls. It is still the hot topic of conversation as people have now moved from swapping horrific hail stories to comparing outrageous insurance claims for property and vehicles. But hold off before you give up your car, the dimpling effect could improve your car’s fuel efficiency, well at least according to the Mythbusters.
Golf balls were not always dimpled but golfers noticed that the more dented a golf ball was the further it flew. It was then later discovered that the beaten in groves on golf balls act as “turbulators” – they cause turbulence in the layer of air next to the ball (the “boundary layer”), “turbulating” this boundary layer reduces drag. Dimpling can also enhance backspin and lift. A backspinning ball experiences an upward lift force which makes it fly higher and longer than a ball without spin. Hence dimples have two profound effects – reducing drag and improving lift that causes golf balls to fly further.
Using these principles, the Mythbusters team compared the miles per gallon (mpg) in a Ford Taurus before and after dimpling the car with 1082 dimples made from modelers clay, they found that dimpling improved fuel efficiency from 26mpg to 29 mpg at a constant speed of 65 mph. But before you go off and start denting up your car – these “results” do not automatically apply to hail damaged cars as size, shape, depth, symmetry of dimples may all affect fuel efficiency and need I say aesthetics of the car but who knows, it may not be too long before we start seeing “The Dimple Car” by Porsche!
But I would really like to know, what I would really like to understand is what produced the largest hail in Perth and caused Australian $100 million worth of damage. Has climate change scored again? Are these warning signs of ends of days? According to Australian Bureau of Meteorology (BOM)- ” The storms resulted as a combination of low level convergence associated with a surface trough; surface temperatures in the low to mid 30s; surface dewpoints 17-19C; and strong instability assisted by a deep mid-level low off the west coast. This low caused the steering wind for the storms to be northerly [which is unusual], ensuring that storms forming near the coast well north of Perth remained close to the coast and affected the metropolitan area.” I guess BOM have not heard of plain English summaries!