I am really strugle what neutral point represent and what it depends on..
In this link we can see how neutral point is calculated.Thay use wing and tail areas and distance between aerodynamic center (L) to determine neutral point position (D).Calculation is set like tail produce lift..(So calculation is the same like you must find fulcrum at see saw..)
What if tail produce downforce(what is often case).If this tail in my example produce downforce,neutral point will move to the left,completly different position.
Does neutral point dependt at change of aerodynamics forces at wing and tail,for example when you change tail incidence,etc?
If I put aircraft in vertical position to eliminate torque by gravity,connect with joint so he can rotate, now must find place at plane which will not rotate(moment is zero) when is subject to airflow.
Is this place neutral point?