A dimple-free golf ball

July/August 2023

Q: A golf ball with dimples will fly about twice as far as one without. Why don’t aircraft wings have dimples, but some have flown with corrugated wings (the German Junkers F-13 and Ford Tri-Motor)?

Send a response of up to 250 words that someone in any field could understand to aeropuzzler@aerospaceamerica.org by noon Eastern Aug. 14 for a chance to have it published in the next issue.

FROM THE JUNE ISSUE: Birds of a feather

We asked you to describe the common strategy employed by brown pelicans and the Doolittle Raiders.

WINNER: The principle that the pictured bird, and possibly the Doolittle Raiders, were taking advantage of is sometimes called the “wing-in-ground effect.” When any wing is producing lift, the pressure beneath the wing is greater than the pressure above the wing. It is this pressure difference that results in lift. When a wing is sufficiently close to a boundary surface, be it the ground or a body of water, the air beneath the wing can’t dissipate and expand as much as it would higher above the boundary. This inability of the air beneath the wing to expand results in a further increase in pressure beneath the wing. The result of this increased pressure beneath the wing is a further increase in the lift produced by the wing at no additional “cost” in terms of energy required to propel the wing forward. In other words, a wing can be said to be more efficient when flying close to a boundary surface. Practically, this means that the bird can fly farther having consumed the same amount of food, and a plane can fly farther burning the same amount of fuel when flying sufficiently close to the ground or water.

Moshe Hollander, AIAA Young Professional member

Washington, D.C.

hollander.moshe@aurora.aero

Moshe is a flight test engineer at Aurora Flight Sciences of Virginia, where he largely focuses on testing uncrewed aircraft.