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) propeller: "the power-induced flow clean up of the wing trailing edge" increases the wing lift coefficient slope (see above). Conversely, a propeller located ahead of the canard (increasing the lift slope of the canard) has a strong destabilising effect. A highly loaded lifting canard may not have sufficient spare lifting capacity to accommodate large movements of the centre of pressure or of the centre of gravity. Trim may be accomplished in similar manner to a tailless craft, by adjustment of trailing-edge surfaces. In particular, the use of landing flaps on the main wing causes a large trim change. The Saab