Getting negative CDi from VSPAero analysis

[Mike Kelly]

I am analyzing the attached vsp3 file in VSPAero using thick components. The set I am analyzing does not include the landing gear or propellers. I am sweeping alpha from -5 to +15 degrees and running separate analyses for elevator deflection angles ranging from -15 to +15 degrees. When I look at CDi for the Drone_elev-15.polar file, it looks reasonable. However, when I run it for -10 degrees CDi turns negative for the negative alpha iterations. The vsp3 file shows how everything was configured for the VSPAero run with elevators at -10 degrees. Can you please take a look and let me know if I need to modify my model or change the VSPAero parameters to get the expected result? ~Thanks

[Mike Kelly]

It looks like this is coming down to panel resolution. I already have CDi in the positive by increasing the Num U on the wing and tail to 50 and 30 respectively. I'll iterate on a single value of alpha to find the sweet spot between processing time and convergence.