This question is actually about any design with twin rudders mounted on the wing tips, with only outward deflection permitted. The Long EZ family obviously comes to mind; I don't think there's anything that would make it unique for this.
To allow crosswind landings, an 11.5° slip must be possible. At this slip, both vertical stabilizers in the Long EZ are acting (with some force based on their area) to reduce the yaw. The undeflected rudder is also acting to reduce the yaw. The only forces keeping the yaw locked in (ignoring aileron yaw effects) is the deflected rudder, both via lift and drag. Assuming that for sane deflections rudder drag is not the dominant force (is this fair? they're awfully far from the centerline) this would seem to suggest that much less than half the vertical stabilizer+rudder area is holding in the yaw and much more than half is trying to knock it out. But assuming the lift slope of each unit area is very approximately comparable, how is this feasible with rudder deflection limited to 20° (is this a fair assumption? 30°?) or so.
To allow crosswind landings, an 11.5° slip must be possible. At this slip, both vertical stabilizers in the Long EZ are acting (with some force based on their area) to reduce the yaw. The undeflected rudder is also acting to reduce the yaw. The only forces keeping the yaw locked in (ignoring aileron yaw effects) is the deflected rudder, both via lift and drag. Assuming that for sane deflections rudder drag is not the dominant force (is this fair? they're awfully far from the centerline) this would seem to suggest that much less than half the vertical stabilizer+rudder area is holding in the yaw and much more than half is trying to knock it out. But assuming the lift slope of each unit area is very approximately comparable, how is this feasible with rudder deflection limited to 20° (is this a fair assumption? 30°?) or so.
