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**Nev** · 09-14-2021, 05:57 AM

This means that the cross connect cable will be SHORTER than that illustrated in your bench top setup.

Kevin this is all very good to know thanks.
So if I’m understanding correctly, the short arms of both bellcranks should be closer together, not further apart ?
I deliberately exaggerated the angles in the bench test in order to be able to measure the travel, but interesting to note that only a small amount of offset from normal will result in additional differential.

**svyolo** · 09-14-2021, 11:52 AM

Thinking about it NEV, I think the easiest fix is to extend, further out, the aileron horns. I thought about that a couple of years ago. Measuring off the plans, which are small in scale so more prone to measuring errors, I get about 16 degrees of offset. By that I mean I measure vertically from the bottom of the aileron/wing (not the angle of the aileron spar) to the arc created by the sweep of the pushrod hole. Then measure from the hole to the vertical line, and then calculate with Trig. For some weird reason I seem to remember a general rule of thumb with flat bottom airfoils that 2 to 1 is about the right amount of differential and you got that somewhere around 30 degrees of offset. I can't offer any reference for this other than my memories of RC gliders.
I would run it by Bob before you started modifying anything, But simply drilling another 3/16 hold farther inboard, then using that hole and the existing one for the pushrod as a mount for a "horn extension". Weld it on if that works out. Or just make new horns.

The other is to modify, or make new ones, bell cranks where the pushrod is set maybe 105 or 110 degrees, leaving the cables at 90 degrees. With a cable loop I think the cable connections probably need to be at 90 degrees, but I could be wrong about that.

The B model plans show 23/17 differential already. If I was going to do it I might shoot for 27/13 to start out with. You can get the function of a little more than that with Marks method of reflexing the trailing edge a bit.

I would definitely run it by Bob.

For me I have also thought about how to make the ailerons droop with flap deployment, but the cable loop makes how i would do it very difficult or impossible. The only way I can think of doing it with the existing setup is to have a linear actuator in the pushrod. I probably would never try it.

**AZBearhawk272** · 09-15-2021, 12:06 AM

Nev,

Yes, the short arms should be closer together.

All, just realized that my aileron rigging commentary and experience is on all the Original Bearhawk Wing and not the Ribblet Model B.
The situation is not that Bob did not have differential in the Ailerons rigging which there is, it is the following.
On the original wing when initiating a very slight aileron input the nose would make a pronounced movement away from the direction of the stick deflection.
Changing the rigging so the upward going aileron moved a bit more caused the counterbalanced portion of the aileron to drop below the bottom wing surface sooner and created more drag than on the other wing keeping the nose from moving opposite of the turn.

This was a situation that had to be corrected to have autopilot interface working.

Not sure what the Model 5 or Bravo wing will behave like due to the difference in aileron configuration.

Kevin

#272

KCHD

**Nev** · 09-15-2021, 01:20 AM

Thanks Kevin, all understood. Good to know the background on this too.

**Nev** · 09-16-2021, 05:58 AM

I guess a side effect of raising the ailerons slightly is to add some washout, which on an aircraft with slow approach speeds is an added safety factor.

**Nev** · 09-16-2021, 03:20 PM

Has anyone used fork ends to attach to the bellcranks instead of nicopress on the aft cable ? They would provide more clearance and require smaller holes in the ribs. Any issues with doing it this way ?

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