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) than otherwise necessary, reducing or even reversing the reduction in size enabled by the canard lift. With a lifting-canard type, the main wing must be located further aft of the center of gravity than a conventional wing, and this increases the downward pitching moment caused by the deflection of trailing-edge flaps. Highly loaded canards do not have sufficient extra lift available to balance this moment, so lifting-canard aircraft cannot readily be designed with powerful trailing-edge flaps. Pitch control in a canard type may be achieved either by the canard surface, as on the control-canard or in the same way as