Aerowerx
Well-Known Member
I have been playing with XFLR5 with a low wing side-by-side tractor configuration, and every thing looks good as a preliminary design.
But when I try a high wing tandem pusher (something like the challenger II) configuration, I can't get it to 'Trim'.
This is what I have been doing: 1)set up the wing planform and tail feathers with guestimates for their mass 2)analyze the airfoils 3)place poing masses for the pilot, passenger, engine, and fuel 4)analyze over a range of angles of attack. 5)adjust the wing incidence so the maximum CL/CD is at alpha=0 6)adjust the wing forward and back until CM=0 at alpha=0 7)do a stability analysis.
As I said, the low wing side by side tractor configuration works fine, but the tandem pusher highwing says something about "can't trim model" and "negative lift found at alpha=x.xxxx degrees", and then exits with an error.
Seems to me that it would be a simple matter to move the wing back and forth until the engine just balances the pilot, with the passenger at (or near) the CG.
Is there something here I am missing? Or have I discovered one of the limitations of XFLR5?
Anyone else on here done a high wing tandem pusher configuration?
But when I try a high wing tandem pusher (something like the challenger II) configuration, I can't get it to 'Trim'.
This is what I have been doing: 1)set up the wing planform and tail feathers with guestimates for their mass 2)analyze the airfoils 3)place poing masses for the pilot, passenger, engine, and fuel 4)analyze over a range of angles of attack. 5)adjust the wing incidence so the maximum CL/CD is at alpha=0 6)adjust the wing forward and back until CM=0 at alpha=0 7)do a stability analysis.
As I said, the low wing side by side tractor configuration works fine, but the tandem pusher highwing says something about "can't trim model" and "negative lift found at alpha=x.xxxx degrees", and then exits with an error.
Seems to me that it would be a simple matter to move the wing back and forth until the engine just balances the pilot, with the passenger at (or near) the CG.
Is there something here I am missing? Or have I discovered one of the limitations of XFLR5?
Anyone else on here done a high wing tandem pusher configuration?
