rear aileron cable clearance holes

[75Fox]

Hi everyone! I am a new builder who is just starting out on the 4-place Model B...

I am now working on a set of templates for the ribs, and have a question about the center ribs #6 through #10. Looking at the plans, the rear aileron cable passes through these ribs on its way to the bellcrank on the aileron drive linkage. The plans make provisions for the cable in the way of a 1/2" clearance hole in the .032 ribs #1 through #5 (with the special "D" lightening hole), but make no mention of this clearance hole in the .025 ribs. It seems like the cable will pass straight through the flanges of the rear lightening holes of ribs 6 - 10 if I cut them out according to the plans...but is passing a clearance hole through a flange really a good idea, or should I alter the size of these particular lightening holes to accommodate the clearance hole?

Thanks,

Tim

[nichzimmerman]

Hi Tim,
Some have dremmeled out part of the flange of the .025 ribs and also added a fairlead to secure the cable (as shown in Eric Newton's manual and website, http://www.mybearhawk.com/wings/assembly5.html). If you do that, it wouldn't hurt to add a small reinforcement to that lightening hole, but your plane won't fall out of the sky without it. I would suggest you proceed without doing anything further, then figure it out when you assemble the wing. When the aileron drive and bellcrank are installed, you can run a string through the aileron cable path and see what's in the way. I did it this way and in the end, I didn't need to change anything. But I bulit the original wing.

-Nic
4-place #1217
Nine years in and almost reached the point where a kit-builder starts.

[75Fox]

Thank you so much Nic, this explains everything perfectly! I will proceed on course heading...

[johwiltb]

I just was stumbling on this issue when modeling the wings in SolidWorks. I haven’t worked it out yet, but it *currently* looks like the cable won’t quite make the flanges and will go through the webbing. I’m not quite sure what to do yet, either, but am interested in what you find out. I have the Model B as well and wonder if the airfoil change or other changes affect this versus the original wings...

[SimonNicholson]

F7773B02-D426-4C79-AFE7-E64B90542214.jpeg Yesterday I made 10mm holes in the ribs for the aileron cable. They are parallel above the flap push rod in ribs 1-6. In rib 6 there will be a fairlead and the cable will downslope to the aileron bell crank.

[75Fox]

Thank you! This explains a lot. Just wondering, what are you going to use to change the course of the cable downward toward the bell crank from the fairlead at rib 6? Can the fairlead itself guide the direction?

[SimonNicholson]

The fair lead will be used to change the direction. All the other penetrations in the ribs will have snap bushings apart from ribs 1 & 2 which already have fairleads installed

[johwiltb]

Yesterday I made 10mm holes in the ribs for the aileron cable. They are parallel above the flap push rod in ribs 1-6. In rib 6 there will be a fairlead and the cable will downslope to the aileron bell crank.

This totally makes sense now. I just saw another Bearhawk wing up close today at a shop and saw what you mean. He did his a little different (not a huge fan of it), but I was able to play with the cable a bit and get what it actually looks like laid out. Can confirm, that fairlead on rib 6 should perfectly setup a downslope through the lightening holes. Thanks!

[svyolo]

I did mine as described, straight out to pass over the flap arm, and then a slope to the bell crank. If I was going to do it again, I would slope to rib 6 to just barely clear the flap arm, then slope the rest of the way to the bell crank. The angle the cable makes through the fairlead at rib 6 would be shallower. I believe it is a 4 degree turn as it is described.

The aileron loop has lots going on. 6 pulleys, 2 bell cranks, and the stick, not to mention the aileron hinges. Lots of opportunity for friction. Mine has a little more friction than I like.