Aileron rigging

[Nev]

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]

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.

[svyolo]

Another issue is clearance of the pushrod, etc. Bob takes everything to tight limits. Maybe something interferes with more than 23 degrees up. Bob will know.

[AZBearhawk272]

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]

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

[Nev]

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]

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 ?

E312DED8-AAF0-4AAC-9EED-786EC8457D8B.jpeg

[Nev]

Yes only on the Bravo is my understanding, due to the size of the rib hole needed and being very close to the lightening hole.

[Bcone1381]

My issue is I'm too cheap to go buy that awesome tool that will swage those balls onto the cable.

[AKKen07]

Brooks- I just bought the cables (for flaps) made up with the ball from Spruce. Just doubled the length plus margin and had them put a ball on each end. Will cut in half and Nicopress the other ends just to the length I need for each side.

[Bcone1381]

Nev,

With respect to the photo and your post on differential rigging.
Yes, I have done this on at least 4 Bearhawk riggings. It works best in conjunction with raising the trailing edge of the aileron up a bit as previously noted.

That said, the amount of offset in your bench setup photo is way much, my experience is that if the distance from the rear spar to the point of stick cable attachment is CLOSER to the spar by
.125 of an inch than the center of the pivot to the spar. ( which is approx 4.5 in ) This means that the cross connect cable will be SHORTER than that illustrated in your bench top setup.
I like the setup and see the little marks of measurement. All good there. Try rigging so the cross connect cable is shorter than Nominal Squared Up and see what happens with your marks.......
And is everything moving the correct direction?

The objective here is, in a right turn for example, right aileron goes up more, a bit sooner that the left aileron goes down.......
I see differential angle at the aileron of Upward going at 25 Deg and the Downward going aileron at 20 deg at full stick travel. Not all of this comes from the bell crank offset rigging.
This is not a problem for cable tensions and slacking as long as the cable is reasonable tensioned 25 - 40 lbs.

Kevin D
#272
KCHD

I rigged my aileron drive system today and wondering this technique that Kevin performs is the best practice is for the Riblet airfoil wing, or if its only to be applied to the Original Modle A airfoil.

[Nev]

I rigged my aileron drive system today and wondering this technique that Kevin performs is the best practice is for the Riblet airfoil wing, or if its only to be applied to the Original Modle A airfoil.

Can't answer your question specifically sorry Brooks, but what I can say is that adverse yaw is fairly noticeable on my 4-place, and if I was able to increase the aileron differential a small amount, I would. A combination of the adverse yaw characteristics and high rudder sensitivity make for steep initial learning curve for those of us that didn't have a background on similar types, and were numb from the waist down after years of yaw dampers. (You should see me on the dance floor )

In my case the length of the aileron pass through cable ended up being slightly longer than I had planned (they were made for me in a different city), so I wasn't able to shorten it enough to increase the differential. However I do plan to order a slightly shorter one in the future to do this.

[Nev]

I should add that for me it's a case of finding the right balance. The Bearhawk does have the ability to hold its own in a fairly strong cross-wind, and I suspect this comes partly from the down-going aileron's ability to increase drag on the down-wind side, which provides a correcting tendency and assists directional control.

[Bcone1381]

An important data point. After posting #22 and upon return to the hangar I looked up at my rigging and thought it best to call Bob. My interpretation from that brief talk: Bob seemed familiar with Kevins rigging on the Alpha model said the Patrol rigging is a different design and so I rigged it to match the Patrol plans.

[African Bear]

I had an issue , always fling with a heavy right wing. I assumed it was my lack of experience, but after discussions and advice from the group, I measured up my flap deflections and found my right flap to be slightly reflexed compared to the left. I set too and adjusted the angles to as close as I could with an inclinometer and that largely put paid to my heavy wing. I then adressed the ailerons which were slightly drooped, I was advised that they should be 3/8 inch reflexed. I found that was a lot of adjustment, so chickened out and made them align with the wing tips. The plane behaves so totally differently now. She turns nicely without having to use a lot of top rudder , added about 5 or 6 mph TAS on the cruise speed and she will fly hands off for a reasonable distance now. Never possible before. Totally get Battsons findings at the top of the thread.

[Bcone1381]

Rigging!! Wow! Speed increase impressive.