tescoapp:
Any chance northsouth you can speed tape some string onto the fin top middel bottom. just U it around the fin and tape so it can't escape. And tell us what it does while yawing.
Naaah I'm gonna get stude to take control, climb out the door, sit astride the rear fuselage and stick me hands in the airflow.
Seriously, what I've got so far is:
1) yaw left, "span"wise flow on right side of fin/rudder reduces (negative) AoA of tailplane/elevator, causing reduced downforce, causing nose drop.
Meanwhile....
2) left tailplane is blanked, causing loss of (negative) lift, causing reduced downforce therefore nose drop
The flaw seems to me to be that:
a) "span"wise flow should also occur in a conventionally tailplaned aeroplane - but perhaps it's ineffective due to being in the slipstream as you suggest tescoapp?
b) does blanking only have a significant effect when it's the low pressure side of the tailplane that's blanked - as it would be in the Tomahawk? In low-set tailplane aircraft it'll be the high pressure (upper) side that's blanked. But maybe the effects are balanced out by the slipstream. Must try yawing with closed throttle next time I fly PA38 to see what diff that makes.
NS