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Aileron Cable install

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  • #16
    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.


    • #17
      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,


      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.
      Attached Files
      Last edited by James; 10-13-2019, 04:25 AM.
      The Barrows Bearhawk: Who knew my wife could get jealous of a plane?


      • #18
        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
          svyolo commented
          Editing a comment
          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.

      • #19
        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 :-)
        The Barrows Bearhawk: Who knew my wife could get jealous of a plane?


        • jaredyates
          jaredyates commented
          Editing a comment
          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
          PaulSA commented
          Editing a comment
          Do you have the A or B wings?

      • #20
        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.

        The Barrows Bearhawk: Who knew my wife could get jealous of a plane?


        • jaredyates
          jaredyates commented
          Editing a comment
          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?

      • #21
        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.


        • #22
          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,

          The Barrows Bearhawk: Who knew my wife could get jealous of a plane?


          • #23
            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...
            Attached Files
            4-Place Model 'B' Serial 1529B (with many years to go...)


            • Bcone1381
              Bcone1381 commented
              Editing a comment
              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
              nborer commented
              Editing a comment
              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.

          • #24
            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.
            Last edited by Pbruce; 08-07-2020, 11:30 PM.