green. A little boy was standing by bemused as we took perhaps 6 or 8 boxes of floaty things to the cashier. The funniest bit is that they actually worked. Arnie could see the bright orange dragon and the giant pink doughnut. Mikey McBryan from Buffalo Airways (who owns the plane) was with me beside the dam waiting for Arnie to fly in with the spinning bomb. We were both very nervous. Then a call came in on the radio with a fair few expletives that they couldn’t spin up the bomb because it was out of balance. Hilary and I had spent days (and several nights) balancing these bombs, and even rebalancing after they’d been painted on one side with yellow paint (Richmond colours again) and the paint was really rather heavy. My laptop still has spatters of yellow paint on it because we did the balancing before the paint was properly dry. We didn’t have time to balance all the bombs and – dammit – the one that Chuck Adams (Buffalo Airways engineer) chose was the only one that was unbalanced. The plane was shuddering and shaking. Arnie had to return to the hangar and a new bomb was loaded. Chuck and Arnie were pretty cross.
The most beautiful discovery for me was the proof that the 1954 film footage used spinning bombs. I don’t think anyone has noticed this before. Take a look at the trail of disturbed water behind our bomb just before it bounces. This is due to the Magnus ‘downwash’. If the bomb is spinning then it generates lift, and Newton’s third law says ‘every action has an equal and opposite reaction’. This means that air must be being pushed downwards. This down-moving air, or ‘downwash’, disturbs the water surface. A bomb that isn’t spinning produces no disturbed water. You can see it with the cricket balls on Jesus Green, and the gas-launched cylinders in the Cotswolds. You can see it in the 1954 film too. Proof that Wallis was using spinning bombs during the early tests he did with the Wellington bombers. There is nothing documented about this as far as I know.
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Feat u r es
The final run then. Mikey and I are even more nervous. The dam is still leaking – perhaps it will collapse before we get a chance to blow it up? But no, we hear the sound of engines and Arnie appears – lines up on Jungle Jim, and releases the bomb. Three bounces and … whack! I’m not sure what got into Arnie, but he flew way too low (around 30ft instead of 60ft) and he released late. Moreover the fast-spinning bomb at 1000rpm was always going to bounce well. We were meant to get close to the dam, but we just about knocked it over! You can see in the photographs that we displaced a couple of those 500kg concrete blocks. It was quite an impact.