Using flaps on takeoff is a good idea because their use LOWERS the STALL SPEED. RC pilots fly visually without the aide of an airspeed indicator. As such, they often accelerate the plane on takeoff beyond the speed needed to fly, then apply elevator. The aircraft may be traveling at 1.2 to 1.5 times the stall speed. In hot weather the same visual runway speed may yield an airspeed below that needed to maintain VMC (velocity for minimum control). That is why more stall accidents occur on hot humid days than cool days. Air that is less dense causes the wing to develop less lift, the propeller to be less efficient, and the engine to develop less horsepower. Couple that with no headwind down the runway and it often spells disaster for someone who yanks their plane off the ground because they have passed the point of no return. Now, flap use on takeoff would increase the safety margin by lowering the stall speed so that on the takeoff roll, the aircraft would accelerate past the stall speed sooner and thus would prevent more stalls from occurring, all other things being equal.

In regards to rudder use, most would find it surprising that using the rudder instead of the ailerons on takeoff as well as on the landing flair, helps to prevent stalls. At low airspeeds near the stall speed, as one wing drops, opposite aileron initially creates drag and adverse yaw. The increased drag may stall the wing at that point causing a snap. Using opposite rudder however, will cause the lower wing to accelerate, develop more lift, and level the wing.

Happy flying,

Frank