i use it to steer the aircraft when taxiing or takeoff, in aerobatic maneuvors and to line it up for landing.

my dads Flair cub tends to need rudder when starting a turn or when the airspeed drops to a point where the ailerons loose alot of their control authority

the Rudder is a great tool to have for aerobatics, if you want to orientate the aircraft a particular way in a short space of time, give it a flick with the rudder