Quote from: Ken Culbertson on April 29, 2026, 12:34:18 PMIf I were to add fences how tall should they be.

Beats me.  I'd make them tall enough to cover the flap at full deflection each way.  This may be a dumb idea.  I've never tried it, except for keeping the fuselage tall and flat next to the flap root.

Quote from: Howard Rush on April 29, 2026, 12:00:55 PMI worry about aerodynamically funny stuff happening where a moving surface passes a fixed surface.  One might put a vertical fence on the fixed surface.  Remi Beringer did this on, as I recall, his stabilizer next to an elevator balance horn. 

  Maybe that, but I like your mentor's solution - removing any stays on the "fixed" part and taping it to the adjacent flap, so the entire thing moves as one.

  The problem I am discussing is not exactly new. One of David's airplanes (blue and white one, maybe new for the 95 NATs) had a bit of a warp in the fixed part of the wing. He was using the "filler" at the end as a trim tab to get the wings level, and it took a decent angle to do it. It did funny asymmetric things all the time. Straighten the wing, and straighten the tab, it all went away. But of course the warp came back, the tab had to be deflected, and all of it came back. It's exactly as described, as the edge of one flap lines up with the tab, it acts differently than the other, since it is deflected.

  In the cases I have seen lately, there were similar arrangements, but also had feedback electric systems with a decent amount of torque and (hypothetically) high enough jerk to generate a decent reaction angular momentum in the time available. But the ESC doesn't respond fast enough to make that very believable. A next step to rule it out is to changes the ESC setting from "3d" to something much slower, if there is no effect, then, that rules it out.

    Brett

Could the answer simply be that only a slight variation or disturbance in laminar flow over the flaps resulting from a change in the slip stream from the propeller during power and pitch change in conjunction with the outward "centrifugal" directional air flow from tethered flight result in roll or sudden hinging due to an unbalanced lifting effect? If so, would the only correction be adding more tip weight to dampen the moment? Additionally, would a slower lap time (slower airspeed) having more turbulence over the flap surfaces tend to aggravate the problem especially in corners?

Quote from: Steve Dwyer on April 29, 2026, 04:58:07 PMCould the answer simply be that only a slight variation or disturbance in laminar flow over the flaps resulting from a change in the slip stream from the propeller during power and pitch change in conjunction with the outward "centrifugal" directional air flow from tethered flight result in roll or sudden hinging due to an unbalanced lifting effect? If so, would the only correction be adding more tip weight to dampen the moment? Additionally, would a slower lap time (slower airspeed) having more turbulence over the flap surfaces tend to aggravate the problem especially in corners?

I think you have a point about the prop wake varying with speed relative to other aerodynamic stuff. I'd think that during the trimming process we would compensate for the swirly air effect. Wouldn't a thrust boost when the plane slows down cause a right roll due to swirly air?  Brett saw a left roll.

Flow over the low-pressure side of the flaps isn't laminar. I doubt if it is on the other side, but I don't remember.

I know I am outside my pay grade here so this is more in the form of a question, but doesn't a sudden power increase cause a "snap roll" or "rotational jerk" effect opposite the rotation of the propeller?  The difference here should be similar to that in a real airplane with a radial engine vs an inline.  Electric is pure radial. Except for the prop IC is mostly inline even if there is only one in the line.  It makes sense to me that you are going to get some roll (mitigated by the tether) with boost, either electric or pipe driven, BUT it will be greater with electric because of the design of the motor.

Ken

Quote from: Howard Rush on April 29, 2026, 01:11:57 PMBeats me.  I'd make them tall enough to cover the flap at full deflection each way.  This may be a dumb idea.  I've never tried it, except for keeping the fuselage tall and flat next to the flap root.

Here is what I plan to try.  At least they will make a nice conversation piece.

Ken

Quote from: Ken Culbertson on April 30, 2026, 07:16:49 AMI know I am outside my pay grade here so this is more in the form of a question, but doesn't a sudden power increase cause a "snap roll" or "rotational jerk" effect opposite the rotation of the propeller?  The difference here should be similar to that in a real airplane with a radial engine vs an inline.  Electric is pure radial. Except for the prop IC is mostly inline even if there is only one in the line.  It makes sense to me that you are going to get some roll (mitigated by the tether) with boost, either electric or pipe driven, BUT it will be greater with electric because of the design of the motor.

Ken

If you think so, go with reverse pitched props and your "snap roll" is safely(?) outboard from the center of the circle vs inboard! IMHO the dynamics of CL stunt are insanely complex. The articles above about full scale roll-yaw coupling can't really be applied to wing tip tethered flight in a 60' radius hemisphere. Our flight is more governed by wind, linear momentum and gravity with continuously variable vectors relative to flight path.

One of the neat things about the SparkFun Artemis data logger is the Real Time Clock/Calendar. I can have someone film me doing proscribed maneuvers and then go back and overlay the 6 axis data on the flight path to see if it makes any more sense than without it.