Flaperon travel

[Allen Sutphin 705]

Anybody have any info on the up and down flaperon travel with the stick side to side? I can't find the # of degrees up and down in any of my manuals.

[1avidflyer 1983]

I can't answer your question right now, but whatever the travel is, it should be the same amount up and down on both sides.   It does help to tightly fasten 2 sticks 18-24" long to the flaperons, pointing back near the fuselage.  Mark an exact same distance back on those sticks, and measure to the floor from those marks, on both sides with the joy stick all the way to the right, and all the way to the left.  The closer your dimentions come to each other, the better it is.  The longer the sticks, the greater the dimentions will amplify and be easier to see the difference.  Hope that was understandable..... JImChuk

[Allen Sutphin 705]

Yeah, that makes sense. I have looked at a couple of Foxes and all seem to have more degrees down than up and I found that odd. Could be an optical delusion because of the detached flaperons. I studied the control system and didn't see but a few ways to increase the up travel without increasing the down also. But also the detached flaperon might increase the up ability due to the front dropping down into the airflow under the wing and the down side decreasing the gap between the wing. Whatever the reason, it must work ok and would think all the 1, 2, and 3's are the same. Not a lot of ways to mess up the travel with the factory made rods. Flying the plane is really the only way to find out.

[CoClimber 33]

It is my understanding that the 1, 2, and 3s had a small amount of reverse differential which aggregated adverse yaw.  The 4 fixed that.

[Allen Sutphin 705]

Never heard the term "reverse differential" before?

[CoClimber 33]

I guess I made the phrase up.  As you know aircraft designers will often make the aileron mixers such that the aileron goes up more than down to counter adverse yaw.  In the case of the model 4 onward the aileron goes up twice as far as it goes down.  You noticed correctly that the earlier models do have more down than up which, when you include the smaller rudder, makes the pilot have to work to keep the plane coordinated.  Or so I'm told.  I have yet to fly a KF.  I have a pile of tubing in my shop to convert my KF2 mixer to a KF4 for this reason.  I'm also converting the wings and flaperons because, apparently I want to drag this project out rather than go flying.  

[dholly 718]

Sorry, forgot which model KF you have there. This will help for pre model 4.

 http://www.avidfoxflyers.com/index.php?/topic/595-kf-iii-rigging/&do=findComment&comment=3413

[akflyer 1427]

the normal mixer system gave more down than up, this is where the adverse yaw and potential for control reversal at high flap settings comes from.  The updated F7A arms fixed this and gave you more up travel than down as it should have been to begin with.

Edited 7 Nov 2019 by akflyer

[Allen Sutphin 705]

The correct term the engineers use is differential ailerons. Usually engineers and pilots talk about the same thing in different terms. At least we know what we are meaning! Most pilots talk about stall speed, where as the engineer talks "angle of attack". Once I understood the AOA principal then it was clear how one stalls at any airspeed. Usually in a turn or steep pull up. I would like to have a AOA indicator, just too tight and can't figure out how to mount it on the wing.

[CoClimber 33]

You can make a reserve lift indicator for less than $100. Uses a differential pressure gauge and a second pitot tube mounted at ~45 degrees below the main pitot tube.  If I ever get my plane flying, I can shoot a video of it.

[Allen Sutphin 705]

I have experimented with a manual one on my challenger coming off the jury strut with a 18" tube in clean air. Mounted approx. 10" below the leading edge. A small graph with degrees marked and a piece of yarn that moves up the graph as AOA increases. Worked or seemed to work OK. Light rain, cold temps and gusty conditions give errors so removed it. Store bought ones are a little pricy.