Hello,
I'm trying to design an aircraft by using XFLR5 and I've some questions analyzing my results for different weights, 35 and 50 Kg.

I've run some stability analysis and I've noticed that neutral point is the same for different weights. So, neutral point is not influenced by the mass?

I've stimated the center of gravity for CL/CD)max. CL/CD)max is influenced by the geometry of the aircraft, not by the mass.But, is the same for CL^3/2 / CD, the condition for maximum endurance??

The forward center of gravity limit is also influenced by the mass??


Thank you!

Too bad no one has answered. You probably know by now, neutral point is only determined by geometry of the airplane. Neutral point + CG location give static stability coefficient.

From the beginning of my time air the local flying field, if you picked up a 2lb plane or a 15lb plane just at the fat part of the wing (fingertip method) and it hung slightly nose down, it would fly fine.


Most every newly built biplane I picked up was tail heavy, but nobody wants to add weight.


If a plane is nose heavy it has to fly with up elevator trim, which lowers endurance. So max endurance would seem to be at the back of the envelope. When airlines started loading from the back forward, they saved huge amounts of money on fuel. Half empty planes fly better that way.