Christchurch and District Model Flying Club
 

NEW SCIENTIST—

SOME BETTER FACTS PLEASE!

Corrugated wings help dragonflies cut drag on flying (from New Scientist, June 2008: original grammar and questionable facts retained; there was no diagram to assist understanding!)

The diaphanous wing of the dragonfly is not only a thing of beauty, its pleated profile also makes it a superior airfoil.

The dragonfly Aeschna cyanea can glide for up to 30 seconds without so much as a wing beat, yet its wings look nothing like the supposedly ideal, streamlined cambered wings perfected (perfected? – Ed) in 1901 by flight pioneers Orville and Wilbur Wright and used ever since by the aviation industry (ever since? – Ed).  Instead, the wing surfaces are highly corrugated, with pleats that stiffen them against bending across their span. But until now, no one could say for sure whether those pleats have any aerodynamic function, too.

To find out, aerospace engineers Abel Vargas and colleagues at the George Washington University in Washington DC flew detailed virtual models in a fluid dynamics simulator. They found that the pleats gave much greater than they expected in gliding flight, matching and sometimes bettering that of a similarly sized streamlined wing. This is because air circulates in the cavities between pleats, creating areas of very low drag that aid the lift-generating airflow across the wing.

The researchers suggest that palm-sized reconnaissance aircraft could adopt pleated wings to gain both strength and extra lift.

Call on your nearest and dearest to show you what pleats look like – corrugated cardboard has been used in model aircraft construction, but with the smooth side outermost, as I recall – Ed.

Submitted by Brian Wiseman

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