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]

No Title

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.



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?

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?

Brooks

 

[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.

 

[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

 

[SimonNicholson]

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.

 

[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.

 

[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.

 

[svyolo]

If there is no translating of the cable, I used 1/2" and snap bushings. After I tensioned it the first time I had some interference, and had to move, and open up a couple of the holes.

 

[James]

Hi Everyone (and especially Brooks and Mark if they can help out),


I printed off this thread in full, and compared it to the existing installation in my wings (uninstalled), to see if I'd inherited any problems, and I think I have a "BIG" one...

Namely, the previous builder passed the aileron cable between the flap drive support tube and the flap pushrod.

The cable route is pretty much as follows (QB 4-Place Wing):

Rib 1 - through aileron cable support and exits wing root.
Rib 2 - similar position, through hole cut in rib
Rib 3 - now goes through the oval-shaped lightening hole (this runs counter to what Mark has said above)
Rib 5 - through the welded fairlead support plate, which has been located aft of the lightening hole (it's a small, round hole on this rib).
Then it angles slightly up, and passes BETWEEN the flap drive support and the flap pushrod.
Ribs 6,7,8 - passes gently upwards towards the aileron bellcrank.

Compared with Brooks' routing solution, the angle the aileron cable makes, sloping down to avoid the flap drive support and then up again to the aileron bellcrank, is less brutal.
But when you fully action the flap swing arm (=the pushrod fouls the cutout in the drive support), it hits the cable and deflects it about 1/8th inch... (photo)

1) I don't know whether the actual flap action asks for the swingarm to move this far. But the plans on Drawing 14, top left corner, shows an arc of movement for the root arm of about 80 degrees, which is similar to what I'm seeing on the flap drive swing arm. Can anyone with a completed plane tell me how much this swingarm moves when you lay out full flap?

2) If this is no good, I'll reroute the cable as per Brooks' suggestion. Can anyone tell me the recommended minimum clearance between the cable and the rib, so I can make my holes as small as possible? (there are some pretty big holes in the aft ribs already... and I'll be installing doublers through the trailing edge spar, as the wing has already been closed up... :-(

Another (possible) fix is to fabricate a box-shaped fairlead and weld it to the flap drive arm, to hold it 1/2 inch aft, so it clears the swing arm... any thoughts?

Ok, any and all information greatly appreciated, I'll put a resume of all the best ideas together, and add them to Jared's comments page for the bearhawk tips.

Thanks guys,

James

EDIT - so, after spending a few hours de-stressing, I've gone back to look at the builders manual - the photo clearly shows the cable passing between the support tube and the pushrod, just as my plane has it... maybe I'm all good, and all my concerns are because Brooks is working on a Patrol wing?? I'd still like a second opinion on whether the flap swing arm will foul the cable at full travel.

 

[PaulSA]

I spent MANY hours trying to sort this out on my Bravo wings - so here goes .....

The QB wings came with the ribs configured as per the A. The position of the aileron bellcrank has changed on the B so this is now wrong - I've been in touch with Mark and hopefully this is now sorted as I had one of the first B sets. With the A, the cable angled forward from the rib whereas the B starts running parallel to the aft spar.

The B routing is as follows - and bear in mind you are doing this with the wing upside down.

There should be a 1/4' hole in the root rib. I enlarged this slightly to take a plastic grommet. The next rib by the fuel tank bay should have a fairlead in the same position. I had to move mine and add doublers. The cable should then travel parallel through the next few ribs and pass under the flap mechanism ("over" when you flip the wing). The notched rib is now redundant. You then need a second fairlead in the same position as the first to guide it. This can be either on the rib inboard or outboard. The inboard rib is 032 so this may be preferable but I used the outboard and doubled it as the routing seemed more logical this way. From there the geometry is quite complicated as (with the wing upsidedown) the cable has to travel up and slightly forward to the rib inboard of the bellcrank - you just have to work it out. Drill the holes where you think they should be and then enlarge as necessary to get the clearance. You may have to use doublers if you don't get it quite right. The rib inboard of the bellcrank will need a large oval (fore/aft) hole as the double cable inboard of the swage needs to be able to pass through - and that's not something you want to end up binding or catching. I also taped and heat-shrunk the cable ends to keep everything tidy

Measuring and drilling is a bit problematic so you may end up with enlarged holes. Get the clearances you need and then add a doubler with a smaller hole in the right place and use a plastic grommet.

James - the cable should not pass through the flap mechanism. If your wing is upsidedown (and I think it is from the photo), then the cable should run parallel to the rear spar and bottom skin until it is outboard of the flap actuator.

As I said, I spent many, many hours sorting this one out .......

Hope this helps.

 

[svyolo]

I spent a lot more time that I thought as well. 2 other gotchas are you are doing this upside down, so if you use cable to measure things the cable will have a bit of "billow" in it the wrong direction. I would use string or fishing line. I used a calculator because I can. The other is the fact that when you fully apply tension to the cable loop, everything contracts a little, so the cable will move slightly toward the center of the wing with tension.

 

[James]

Yeah, thanks for that Paul - I note that 9/10ths of my confusion comes from the fact that I mistakenly posted this question relative to an original Model A 4place QB wing, on a thread that belongs to the "Patrol" part of the forums, and now there seems to be yet another variation for the Model B wing... that's why I hope someone with knowledge of all the differences of three types can give me an authoritative answer.

I note that the photos in my build manual show the cable passing between the rod and the support tube, and then later on in the text, it says make sure the cable passes over the tube by at least 1/4". (I know the wings are currently upside down. I'm still above the tube . Jarred says the old PDF manuals have been superseded by the beartracks tips online, but the relevant section (#3649) just says make sure the cable clears the pushrod when the flaps are extended. It doesn't say which side it has to be, but seems to imply that it's above the pushrod.

Ok, the question is: If you have an original Model A wing, does your aileron cable pass between the flap pushrod and the support tube?

Thanks guys for your patience on this one, I definitely hope we can help out the next guy who finds himself in this position
,
James

 

[jaredyates]

Sorry about this being a case where the manual is coming up short. Please let me know when you get it sorted and we'll add clarification.

 

[PaulSA]

Do you have the A or B wings?

 

[James]

Yep, my wings are maybe 10 years old, so it's a Model A. Serial Numbers 179/180.

No criticism of the manuals or the beartracks info you help provide, Jared - it's helped me a ton so far, and it's a great resource. I've followed it so far without any problems
I think the confusion is the variation between Model A / Model B / Patrol wing layouts.

James

 

[PaulSA]

Got it - therefore ignore all my comments above!!

If you have the old build manual that was available on the Bearhawk site for download, look at the first Wing manual page 7 talking about flap install. It clearly shows the aileron cable passing between the support frame and the actuator . Page 10 then talks about the clearance of the cable from the flap support frame. Bear in mind that the A QB wing was built the right side up as it was the TOP skin that was left un-riveted. Hence these pictures are top skin up.........

So it looks like you are good to go.

 

[jaredyates]

The culture I'm hoping to build around the manuals is that criticism is not bad. It's the only way we know that something needs to be clarified or updated. It sounds like in this case we need to have three different sections, one for the Model A, one for the Model B, and one for the others. Does someone want to put it together?

 

[James]

Best news I've had all day, Paul - the sections you cite in the pubs are exactly the ones I was referring to.

Thanks everyone for their input! I really felt like I was asking a dumb question.
I never thought about "up" meaning different things, depending on the build orientation of each model of the wing, because generally when you use those adjectives to describe aircraft parts, you assume the wing installed on the plane, and that the wheels are (hopefully) pointing towards the ground

I wonder how many other up/down pairs are out there in the manual Jared, which might need changing to "upper / lower"

Ok, time to keep plugging away. I'm on to hanging the ailerons to get the hinges aligned

Thanks again,

James

 

[nborer]

Man I love this forum. I learn a ton from searching. I’m scratchbuilding but want to make sure I understand. I have a 4-place B model. I need an aileron clearance hole in the .032 ribs (main and short) but NOT in the .025 ribs because the cable angles down through the larger lightening hole after rib 5, correct? I ask because I’m about to form my .032 ribs and like cutting holes that I can jig better in the flat blanks rather than in the wing - if it’s practical. I can always leave the holes for later, but if it makes sense to cut them now when it’s easier, I’d like to do it. I’ve already drilled the pilot holes for the flap drive linkages, which I plan to enlarge with a unibit. I did note that the dimensions aren’t called out in the drawing, which means I either need to scale the location or drill to fit the cable...

 

[Bcone1381]

The hole location you are asking about coincides with a steel part that on the Patrol is labeled “Support Assembly at Wing Root.” That piece is welded steel, is located on p.15 of the Patrol Plans, and secures two fittings on it, the inboard support for the flap torque tube and the fairlead for the aileron cable. You want your holes drilled to match that fairlead

 

[nborer]

Thanks! It’s also in drawing 15 of the model B plans. I see it now. I think I’ll drill the flap torque tube in my blanks now but will wait to drill the cable clearance hole until I get everything jigged up.

 

[Pbruce]

I have a suggestion regarding the placement of the aileron carry-through cable holes: Would the designer and/or factory consider providing a paper template of the aft part of the affected ribs showing the hole center location at each rib? My Patrol plans don’t seem to have it. Ideally, this would be on the plans or in the Bearhawk book. I spent way too much time with this and I notice that others have too.

I would also suggest guidance be provided regarding how to provide clearance for the cable at the bellcrank location, since the required hole impinges on the lightening hole in the rib. A builder needs to know if a doubler is required, or if the lightening hole can simply be enlarged to accommodate the cable as the aileron bellcrank moves through its arc.

If the rearmost lightening hole in each rib was about 3/8” smaller at the back, the doubler issue would resolve itself, leaving only the matter of hole placement, which I believe should be undertaken by the designer or factory in the interest of repeatability. The afformentioned template would suffice.

 

[Bcone1381]

Thats a good idea. FYI, I made a template to set the placement of the carry-through cable holes that was specific for my wing. One end of the template was where the cable attaches to the bellcrank, the other was at the rib/fairlead where the cable starts its decent. Each template was layed out on a grid with an X-Y axis. I then measured the distance between the two ends. As the cable penetrates the ribs between the two end templates, it moved a certain percentage, like maybe 12% of the total distance. So I move the penetration on that ribs grid 12%. I hope that makes sense. The cable penetration from start to finish is 100% movement, and each intervening rib is a percentage of the total movement.

 

[Pbruce]

Makes good sense. I ended up doing something similar, but without the template, and I had some accuracy issues. I managed them, and the only place i have contact is a at extreme Aileron deflection at the second rib over from the bellcrank. The cable touches the front of the bushing in this location but does not visibly deflect. I may not even have that much aileron travel anyway. I won’t know until I put the aileron back on.

I wonder why Bob Barrows does not specify rigging the ailerons up with some differential throw to minimize yaw from aileron drag? It seems like there is enough aileron throw available to that.

 

[svyolo]

There is a bit of differential, just not enough. Marks' method of rigging the ailerons both slightly up sort of jury rigs some additional differential that also supposedly helps.

One more thing about the aileron cable, it is a tensioned loop, and gravity has an effect. So when you finally apply tension, the cable, and everything it is attached to will pull (and flex) a little towards the middle of the wing, and the longer cable runs will have a little "billow" because of gravity. If you make your holes to small they won't be able to take these into account. I ended up having to enlarge a few holes.

 

[Nev]

I want to double check that I’ve got this clear in my mind.

Regarding the routing of the aileron cable between the flap support tube and the flap linkage arm, is this picture from the standard manuals the same on the Model B ?



Also, on my first rib closest to the fuselage there is a fairlead mount welded to the steel bar. And on the second rib there is another fairlead mount riveted to the rib. Is it intended to remove this fairlead mount and rivet it to the rib nearest the flap support bar ?

 

[N942VT]

No change in the cable routing for the B model. As for the fairleads these are not intended to be moved but can be if needed. Some kits have come through without this second mount riveted and you mount it yourself. You can use snap bushings at the other ribs or oval out the lightening hole if it's close to it. You can use a piece of string to line up where the holes will be drilled, they do not stay the same distance from the skin from one end to the other.

 

[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

 

[Dpearson]

Hi all, for my A-model 4-place QB wings, I'm wondering how much rotation the aileron bellcrank needs? The rear-facing arm interferes with the rib (photo below) when rotated in the "aileron up" direction.

The build manual mentions "In a few early kits there was a little interference..." and mine was an early kit. It seems I would need to make a pretty big cut to enable the arm + shackle to pass through the rib - is this what others have done? Conceptual CAD (Cardboard Aided Design):

 

[TimTall]

My serial number is #111. It needed a little trim like that to make it work. That bellcrank rotates through but I can't remember how much.

 

[rodsmith]

I had to make the same cut in my early quick build wings.

 

[Dpearson]

That’s great to know. Thanks rodsmith!

 

[Chewie]

I figured this is a good thread to pick up for describing where I'm at on the aileron cable routing in the wing. Here's my setup so far, looking at the top of the right wing facing outboard.
​

I mocked up some paracord with a bungee so I could rotate the bellcrank through it's range and see the travel of the cable.
Here are close-ups of the infamous flap actuator bay.
​​

​

​

You can see the cable just grazes rib 6 and barely misses the pushrod. This is with the pushrod and bellcrank at their most extreme possible positions.​
​

I was initially thinking to notch the rib but that would allow the cable to run even closer to the pushrod, so I'm leaning more to this solution.
​

​

​​ ​Just putting this out there for visuals, and to solicit any comments before I cut or drill metal. I'm all ears!

Happy Thanksgiving everyone!

 

[Bcone1381]

You have installed the Big Hole fairlead. The second fairlead is the Small Hole fairlead. Its more precise positioning your cabel. I think it will lift your cable up 1/4 inch . Will that make a difference?

 

[Chewie]

On Rib 5? I don't think a smaller fairlead would help, the slight shift in location would only increase the interference on Rib 6. I ended up installing the fairlead on Rib 6 instead of notching.

 

[spinningwrench]

On the Patrol only two fairlead bushings are required, one at the flap drive and the other at the wing root. You will spend a lot of time figuring out where to enlarge or punch clearance holes. I followed Brook's method and it worked out pretty well. I did give a lot of thought to how I would service the interior wing fairlead if I ever had to remove it. Getting that snap ring out deep inside the wing would be painful so I fabricated a little removable mount that I could easily access with a socket wrench.

 

[Chewie]

I'm not sure what you mean. Which rib are you showing in that picture?

 

[Nev]

Getting that snap ring out deep inside the wing would be painful

I used lock wire on those similarly located fairleads - a bit easier to install and remove than the rings.

 

[Bcone1381]

On the Patrol only two fairlead bushings are required, one at the aileron bellcrank and the other at the wing root. You will spend a lot of time figuring out where to enlarge or punch clearance holes. I followed Brook's method and it worked out pretty well. I did give a lot of thought to how I would service the interior wing fairlead if I ever had to remove it. Getting that snap ring out deep inside the wing would be painful so I fabricated a little removable mount that I could easily access with a socket wrench.

I used two fairleads, but the outboard fairlead is at rib 5 near the flap drive linkage where the aileron cable changes direction at rib. The cable runs horizontal from the root until it hits that rib, then it starts a descent towards the aileron bell crank. I don't have a fairlead at rib 10.

 

[Chewie]

My arrangement is similar.
It's sounding like you guys had factory ribs that required you to bore additional holes in each rib outboard the flap drive until you reach the bellcrank. On my scratch built ribs, I simply followed the plans and the larger lightening hole negated any need to calculate pass thru locations. Am I interpreting that right?

 

[Bcone1381]

You are correct. The Ribs for the factory build wings are all the same. Some cable holes passed close to the lightening hole and have to be beefed up with some additional aluminum.

 

[Lucasdenes]

Hello friends, it's my turn to ask, what if the cable goes between the flap control? Could that be a problem?