Hi alex7403
Depending on the plane, knife edge may require input from the aileron, rudder, and elevator. The amount of input can vary between planes. Here is what I suggest you do: bank 90 degrees to the left with the ailerons as you have been doing, and immediately give it full right rudder and hold it. Observe the plane carefully and add aileron as needed, + or - to hold the knife edge. The plane may track toward the canopy side or the landing gear side. At first disregard this. As you become more proficient, you can add elevator to hold a track. Generally speaking, if it tracks toward the canopy it may be nose heavy; if it tracks toward the gear it may be tail heavy.