"T foils on the tail of planes" are an entirely different subject for totally different reasons compared to T foils or L foils on the wings of aircraft.
Although as I think about it, maybe we should be relating the effects of T foils on rudders more to the “T” foils (elevators) on the tail of aircraft as their effects on the plane are much more closely related to the effects of T foils on a boat than any boat rudder foils are related to any foil(s) on the wings.
The elevators (T foils on the tail) control, primarily the forward angle of the aircraft, both nose up or nose down (and every angle in between) and apart from them being “articulated”, their “effect” works in exactly the same way that the T foils on the rudders of a cat work. The L or T foils on the wing tips of aircraft have only the one primary function of improving the efficiency of the wing mainly through reducing the tip vortex effect dramatically, apart from that it has no other “direct” effect on the stability, direction, or trim of the aircraft.
Has anyone seen L foils on the tail section of an aircraft??