RCU Forums - Flaperons......huh?

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RE: Flaperons......huh?

Quote:

ORIGINAL: daboosailing

I don't doubt what you folks are saying to be true. However, attempt to explain why an airplane would pitch down with flap deployment. From an aerodynamic standpoint, down flaps, increases the AOA of that portion of the wing adjacent to the flap/flaperon. Increasing AOA should cause a pitch-up, not down. The aircraft's reaction should be the same as up-elevator. Again, I'm not calling you liars! Just interested in this phenomena. My guess is it must have something to do with icreased down-wash from the wings with the flaps deployed.

I disagree. My GreatPlanes Dazzler will pitch down with flaperons. And im talking about +/- 10 degrees only. Ive tested at low speed, high speed, will always pitch down. I had to program my radio to put little elevator up to flight straight.

RE: Flaperons......huh?

Hi Guys
For my 1/2 penny worth
Down flaps increase the undercamber of the airfoil therefore increase lift by causing an greater differential in pressure above and below the airfoil section this would not work at high speed as the laminar flow would be upset at anything above the new airfoil sections correct laminar flow vector, this also moves the Center of Pressure closer to the Center of Gravity and thence makes it easier to stall i.e. c of p gets behind the c of g breakaway of the airflow and stall. The opposite effect by raising the flaps/ailerons up, this effectivly puts washout into the section making it harder to reach an angle of attack that would allow the c of p to get behind the c of g and cause a stall, up flap would effectivly dump lift and allow a much steaper approuch without stalling, ensure you have enough elevator authority, down flap makes the aircraft more prone to float on and on and on and on but does decrease the landing speed, but only up to a point where the stall is violent, don't forgett here we are flying small scale airfoil sections in full size air Renolds numbers be damed.

Mike

RE: Flaperons......huh?

Quote:

ORIGINAL: rkutach

any flaps outside the white arc is NOT good... only an idiot would do this...

I agree fully, but as daboosailing just demonstrated, sometimes idiots do fly planes. :D
Probably had a terrible instructor. [:'(]

RE: Flaperons......huh?

I am still corn-fused about the elevator-flap mix. I am tinkering (note-tinkering=just doing it just to do it) with puting flapperons on my Avistar retro-fitted with a PT-40 wing. I have my flapperons set to switch H on my 9C. Should I have the elevator go up or down ( I am guessing down, but still....)? Also, I noticed I was able to adjust the rate in which the elevator deflected (I beleive it was called elevator delay), what should I set that to, if at all?? Thanks in advance!!

-Shane

RE: Flaperons......huh?

Deploy the flaps at a recoverable altitude and see what you need to hold to keep the nose level.

I have one plane with flaperons (modifed SPAD Debonair). The other day, I was flying for aerial video, and the plane kept pitching up. Turns out, the flap switch had gotten nudged so the flaps were fully up (more like spoilers). When the flaps are down, the plane will practically stand still, but it pitches the nose down.

Brad