[stephen f. polyak]

Simply, if I understand your question…. The wing's operating range of angles of attack from initial lift to stall is greater than 3 degrees. Having the washout run from the root to the aileron junction does not prevent the full wing (all airfoil sections) from producing lift when sufficient speed is reached to takeoff. Because of washout, when the plane is flying, the relative angle that the wing operates at decreases from wing root to wing tip. Thus, the inboard region of the wing will reach its stall angle before the outboard region. As the inboard region looses lift due to a stall, the aileron, being part of the outboard region which is not at stall, continues to deliver roll control. Without washout, on reaching the stall angle, the entire wing would loose lift and aileron effectiveness would be seriously degraded.