Fun with an old canard: Bumblebees shouldn't fly

Occasional Machine Design contributor James Finkel has an observation about today's xkcd.com comic which portrays a bumblebee piloting an airliner, as a takeoff on the old canard that aerodynamically, bumblebees shouldn't be able to fly. Here's Jim's take:

"The urban legend has its roots in a few bad aerodynamic and physical models.

The initial studies on the supposed inability to fly were based on just looking at the area of the bumblebee wing. When the Scanning Electron Microscope was invented, people discovered that the wings of bumblebees were covered in very fine hairs.

Part two of the explanation is that the rules governing the behavior of air are governed by the Reynolds Number, a dimensionless parameter that tells how air behaves, based on the speed and scale of the air movement.

In the case of the bumblebee, the air at the microscopic level (air around the hairs) behaves like honey, sticking to the hairs.

Finally, the wings do not strictly "flap," rather they move in a figure 8 pattern. Combining the three obscure facts (hairs, Reynolds Number, flapping motion), with the swept VOLUME, the wings are indeed "big enough" to allow the bee to fly.

I would venture to say that few folks have seen the SEM images of the wings, fewer still know what a Reynolds Number is, and bumblebee wing movements are not that popular on utube.

This batch of information is still not widely known (and in total is way less believable) than the urban legend. Although in this case Ockham's razor is wrong, it is still easier."

Thanks for that, Jim!

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