Aileron Cable install

[Bcone1381]

I am studying Mark Goldberg's wing assembly manual, and have questions about the routing of the Aileron Control Cable. A little background, the Ailerons are controlled by a giant cable loop that runs up one strut to the bellcrank, then from the one bellcrank to the other bell crank passing over the top of the rear seat, then down the other strut back to the stick.

The cable that runs from bellcrank to bellcrank passes through 10 ribs in one wing, thru the fuselage then 10 ribs in the other wing while also passing over Flap Dive Linkages and Support Frames in both wings. Does everyone run the cable straight and level out past the Flap Drive Linkage, then use a fairlead at Rib #10 to slope the cable to target the aileron bellcrank arm? I am thinking that keeping the aileron cable elevated will give the outboard Flap Arms and Flap Push-rod room to move.

Brooks Cone
Patrol #303
Making plans for a Kit.

[Mark Goldberg]

Hi Brooks. I have to hand it to you for preparation above and beyond most as well as understanding what is needed. The one thing not everyone picks up on is when running that cable in the aft part of the wing - that indeed the flap pushrod comes UP as you lower the flaps and the height of the cable run has to take that into consideration. There have been a couple builders who ran that cable too low so when the flaps went down the pushrod hits the cable. Not really too hard a problem to fix but better to get it right the first time.

I use the plastic snap bushings where the cable goes through ribs where needed. We give you with the kit a fairlead tube welded to a piece of plate so that it can be riveted to a rib web so the builder can place the cable where it is happy. Usually that welded piece is used on one side or the other of the bay where the flap support frame is. Mark

[Bcone1381]

Thanks for the nice complement Mark. You confirmed my thoughts with your usage of Plastic Snap Bushings between fairleads.

Reading your post forced me to ask "How much clearance will a parallel Aileron Cable have as it crosses the Flap Push-rod. So, I just took measurements off the plans and it will give 7/8" clearance above the the max height of the Outboard Flap Arms. It seems like the best method to drill these holes in a straight line from the wing root to Rib 6 is to....

1) Make a template that captures the exact position of the Aileron Cable Fairlead at Rib #1. (Support Tube Fairlead... plans p15.)
2) Use Template to position the Fairlead at Rib 6.
4) Rivet the kit provided Fairlead Tube-Plate to Rib Web 6.
5) Use Template to position Cable penetrations in Ribs 2,3,4,and 5.
6) Install Fairleads inserts and Snap Rings where appropriate.

After Rib 6, the cable will leave the parallel track, and take a slight descent for a straight path towards bellcrank. We can call this the Bellcrank Approach...We have the Wing Root Initial Fit, the Rib 6 Locator Outer Marker and the Bellcrank Final Approach Fix.

Brooks Cone
Patrol #303
Planning for a Kit.

[Mark Goldberg]

You are much more methodical than me Brooks. Your plan is certainly good and would work. I just moved the flap mechanism to see how high the pushrod would go in the area where the cable passes over it - and drilled the rib hole accordingly. Mark

[svyolo]

Mark, per your method of using the fairlead tubes, I am a little confused. The plans show the cable going through holes drilled in the ribs. After our discussion, I thought you meant to use the fairlead to angle the cable to run through the large lightening holes, and not drill through every rib.

[Mark Goldberg]

No. I did not mean for you to run the cables through the big lightening holes. Some of the kits have the holes already drilled in the upper part of the ribs for the aileron carry through cables. If not, then you need to drill them. The parts I sent you are for you to make one of the holes (with a fairlead) through the rib closest to the flap pushrod. This hole needs to be high so the flap pushrod does not rub on the cable when you lower the flaps.

Sighting from the aileron bellcrank to that weldment/fairlead in the wing root will give you straight line. But the cable needs to be higher right there near the flap pushrod. Not a straight line if you are looking from the rear. But it is a straight line looking at it from above. Hope this makes sense. Mark

[Mark Goldberg]

You can use snap bushings on the other ribs if you want. MG

[svyolo]

Thanks. Thats kind of what the plans show, so I was confused. The plans show a straight line horizontally, but it needs to stay a little higher to stay above the flap pushrod, and then angle slightly lower at each rib on the run to the aileron bell crank.

[Bcone1381]

When I started this thread in 2017, I was planning the build before the kit purchase was made. Today I am applying these steps. This post has two purposes....1) report on how things went, 2) Ask one question.

Here is a photo that is taken looking thru Rib 6 looking inboard. The holes for the rear aileron cable have been drilled, and are ready for their snap bushings.


IMG_6246.JPG
I installed a fairlead in Rib 6, (Seen in the upper left corner of the photo) just outboard of the flap drive linkage. A wood dowel placed in the cable run holes simulates the aileron cable. The Cable penetrates each rib from 1 to 6 in exactly the same location. As you can see in the photo the cable passes over the flap arm with significant clearance. For the photo, I positioned the Flap Arms at their highest postion, and held the push rod up as far as it will go. This exceeds the real life flap arm hieght. We still have 5/8" clearance. So I like the cable run from rib 1 to 6.

From Rib 6, the cable descends gently in a straight line to another fairlead rib 10 just before reaching its final destination at the Aileron Bell Crank. I am real happy how this turned out. But.....I have still have a question.

How close can a cable penetration hole be to a lightening hole before the rib needs to be reinforced?
IMG_6242.jpg
It should be clear in the photo above that that Rib 10 requires a doubler, because there is only about .2" of rib material remaining between the lightening hole and the fairlead. Other Aileron Cable Passage holes have .8" like what you see in the first photo at Rib #5. Others have .4" Do they all get reinforced? And what should a reinforcement look like?

I am thinking something like this in the photo below. Feedback?
IMG_6233 (1).jpg
Brooks

[Mark Goldberg]

Brooks - I have put in doublers where the holes for that cable run got too close to the edge of the big lightening holes in the ribs. Probably not needed, but awfully easy to do before you close up your wings. For future peace of mind. Mark

[svyolo]

Both of my wings have a notch cut into the lightening hole of the first short rib. That actually made me initially think that the aileron cable was angled into the lightening hole. But I only have 3/16" from that notch to the hole for the aileron cable in both wings. I am still not sure what those notches are for.

[SimonNicholson]

683E863C-080A-4698-A06B-BE3748358D0E.jpeg I have just installed my aileron carry through cable and hit a snag. It looks as though I will need to open up the number 10 rib a lot to allow the cable thimble eye to pass through. How much throw does the bell crank need?

[svyolo]

The cable definitely cuts into the hole. If not, there is so little material left you probably need a doubler anyway.

[Paul Johnston]

No fair lead so close to the bell crank- too much drag. For that one I wold open the lightening hole to include the cable. Tin snips& die grinder.look how close the hole is to rib stiffener on the right.Your structure would be uniform

[Bcone1381]

Thats not set up right. The aileron cable should pass thru rib #10, then over the frame, then attach to the bellcrank. Your bellcrank is inboard of its support frame, but it should be outboard of the of its support frame. I wonder if its installed upside down or the left side was installed on the right wing.

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[SimonNicholson]

It is a Bravo wing so it is upside down. It caused me some initial confusion as the support frames were in the opposite wing. In my photo we are looking through the bottom skin.

[Collin Campbell]

The 4-place and the Patrol aileron bellcranks are significantly different. Brooks' picture is a Patrol setup and the picture Simon posted is a 4-place. Atthough the Bravo uses the same airfoil as the Patrol the aileron bellcranks are the same as the "A" model due to the cable pulling from the bottom of the stick vs. the top on the Patrol. There will need to be more clearance though for the cable. From the picture it looks like enlarging the lightening hole somewhat would solve the problem...Collin

[svyolo]

As that bell crank rotates, the aileron cables translates fore and aft. It translates the most at the bell crank, and triangulates down to nothing at the fairlead at rib #6. So all the holes in the ribs have to allow some fore and aft movement of the cable. On mine I had to add doublers to the 3 ribs inboard of the bell crank, and had some minor clearance issues on a couple of ribs on one wing as well.

When you are doing your measuring, there is no tension on the "system". When you rig it all up, the tension causes some flexing in the direction of the tension around the entire system. A few places I thought the cable ran free, it had some interference when I tensioned the cable for the first time.

[SimonNicholson]

Did you end up going with 1/2 inch holes? I have mostly 10mm (1/4”) but think I will have to go out to 22mm.