When Winnie the Pooh accidentally dropped a pine cone over the side of a bridge he did more than invent a game that has enthralled generations of children. He also created an engineering conundrum.
Now a leading engineer has come up with the formula for the perfect poohstick. It is not as simple as a bear of little brain might imagine.
The game of poohsticks first featured in The House at Pooh Corner written by AA Milne in 1928. Milne had played the game with his young son Christopher Robin near their home in the Ashdown Forest in East Sussex. Each dropped a twig into a stream on one side of a footbridge and the first to emerge on the other side was declared the winner.
Poohsticks was voted one of the nation’s most popular traditional games in a poll of 2,000 parents, with a quarter naming it as their favourite behind hide-and-seek and “it”.
Almost 60 per cent of poohstick players regard it as a game of chance, according to the survey conducted to mark the publication of The Poohsticks Handbook: A Poohstickopedia by Mark Evans. But luck, it appears, has little to do with it. Rhys Morgan, of the Royal Academy of Engineering, has devised a formula for the perfect poohstick.
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Dr Morgan, who describes himself as an “avid poohsticker”, says that the main variables are cross-sectional area, density/buoyancy, and drag coefficient.
His formula for the Perfect Poohstick is PP = A x ? x Cd.
A is the cross-sectional area (length multiplied by width). The more the flow of water is able push the stick, the faster it will accelerate, so tubby is good.
? is density. As the fastest flow is below the surface, a stick that sinks a bit will go faster than one floating on the surface, where it could be slowed by wind.
Cd is the drag coefficient. This describes the shape of stick and roughness of its surface. A rough stick will create more drag than a smooth stick, so bark is good.
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Dr Morgan identified two other factors for optimum poohstickery: “The ideal stretch of river would be rectangular, and the flow of water smooth, so the poohstick would not have to contend with turbulence or whirlpools,” he said.
Mark Evans, author of The Poohsticks Handbook, said: “Poohsticks is a game of sticks and rivers and bridges and friends and fun. The book is full of hints, tips and general poohsticky advice. It also goes into the history of the game and, most importantly, the rules, so that young players everywhere can make sure their elders and supposedly betters remain Poohsticks legal and un-cheaty.”
VisitEngland has come up with the top 12 poohstick-friendly bridges in the UK, in addition to the original Poohsticks Bridge in Ashdown Forest. They are: Sheepwash bridge, Derbyshire; Morden Hall Park, south London; Heale Gardens, Wiltshire; Packhorse Bridge, Cumbria; Mottisfont, Hampshire; Little Wittenham Bridge, Oxfordshire; Mathematical Bridge, Cambridge; New Lower Bridge, Boscastle, Cornwall; Bridge over Bourne Eau, Lincolnshire; Cantlop Bridge, Shropshire; Essex Bridge, Staffordshire; and Hutton-le-Hole, North Yorkshire.