Cul de canard Cul de canard Cul de canard (CDC) (French for "duck bottom") are the feathers from the back of a duck directly around the preen gland (uropygial gland); they are very buoyant due to preen oil produced by the preen gland. They are used when tying dry flies for fly fishing. They owe their buoyancy to their proximity to the ducks preen gland which secretes an oil distributed by the duck as a cleaning and waterproofing measure. It is unnecessary for the angler to add additional oil by way of floatant. Flies incorporating CDC are easy to dress requiring no floatant
Canard (aeronautics) provide this protection. A canard foreplane may be used as a horizontal stabiliser, whether stability is achieved statically or artificially (fly-by-wire). Being placed ahead of the center of gravity, a canard foreplane acts directly to reduce longitudinal static stability (stability in pitch). The first airplane to achieve controlled, powered flight, the Wright Flyer, was conceived as a control-canard but in effect was also an unstable lifting canard. At that time the Wright brothers did not understand the basics of pitch stability of the canard configuration, and were in any event more concerned with controllability. Nevertheless, a canard stabiliser may be