I'll soon be trimming the TE, final sanding, and cutting out the flaps on the new center-setion of my DR 420. Because I don't need the flaps to go up, it occurred to me that I could bottom-hinge them rather than top-hinge.
My thinking is:
Top-hinged flaps in normal flight would have the advantage that I could drop them a few degrees to increase camber without interrupting the airflow over the upper surface, or drop them 45 degrees to act a bit like airbrakes. But, the disadvantage would be that the under surface airflow would be disrupted nearly all the time.
Bottom-hinged would have the advantage that both the top and bottom airflows would be uninterrupted in normal fight and dropping them 45 degrees would badly disrupt the upper surface airflow but this probably wouldn't matter and might even make them more effective as 'brakes'. But, the disadvantage would be that dropping the flaps a few degrees to increase the camber would interrupt the top-surface airflow which might more than override any extra lift created.
So maybe, If I DO want variable camber top-hinged will be better and, if I DON'T want variable camber, bottom hinged will better because it will give me maximum wing efficiency and better braking effect.
Am I right?
Thanks! And Happy New Year,
David