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Revisiting the 8-foot brake discussion

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  • Revisiting the 8-foot brake discussion

    Obviously there has been a lot of past discussion regarding the need for an 8-foot brake to bend the spar flanges for scratch build wings. The realty is that 8-feet is not enough for the Patrol or Model B wings because of the longer flap spars (8.8 feet).

    I am considering having a precision metal fabrication shop in Spokane bend my spar blanks for me (waiting for the quote...). They have a CNC brake but it turns out it maxes out at 8-feet. However the ends of the brake are not confined.

    I met with the shop yesterday to get the quote and one ideas they suggested was to bend the longer flap spars flanges in two separate segments. They indicated that they could make a small perpendicular cut across the 'flange to-be' before bending, then bend the two split segments separately, to then be following by a small TIG weld repair of the cut!!!

    When I first heard this I said "ABSOLUTELY NOT!!" But maybe this is not such a bad idea!?!? Done correctly the weld should be just fine! The cut could be strategically placed and staggered from one side to the next.

    If this approach could be acceptable... perhaps it could be used on the other spars if an 8-foot brake is not readily available...???

    Thoughts? ...let the discussion begin....
    Karl
    Bearhawk Bravo #1508B - Scratch Build (wings)
    Northern Idaho

  • #2
    No welding allowed on the heat treated 2024... But it sounds like you have a good shop willing to help get the job done.

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    • #3
      A splice done in accordance with AC43.13 is the first solution that comes to my mind.
      Brooks Cone
      Southeast Michigan
      Patrol #303, Kit build

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      • #4
        Buy them from Mark, starting with factory webs is like starting with a really good foundation for a house. However if you have built your ribs, the factory webs might not fit. If so, keep looking for a 10' brake. I'm over in Seattle and we have lots of resourses. You might try over here.
        Gerry
        Patrol #30 tandem

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        • Bcone1381
          Bcone1381 commented
          Editing a comment
          Gerry is right.

      • #5
        it's only .032" aluminum, you don't need a brake, can just do it with seaming pliers.....

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        • Bcone1381
          Bcone1381 commented
          Editing a comment
          As I try to envision this, I see some stock clamped to the blank to position the pliers, something to ensure uniform force and angle for each individual application of the tooling force. But I am just dreaming. I'd love to see an industry best practice of bending a spar with seaming pliers. Can you give us a tutorial?

      • #6
        the sheet metal pros will show you, guys can do miracles with just seaming pliers. I've got two vices setup on my bench ( I used them to hold the form for banging over the flanges too) I just put the spar stock in the vice between two pieces of wood and start bending to the line. As long as you're close it will be good enough, the strength comes from the cap stock etc anyway, not a bend in some .032 thick aluminum. Can definitely get away without having to find an 8' brake, besides it's going to be tough to get a shop to bend for you exactly the way you want it and they'll give you a hard time about using a boot and putting the proper radius on it.

        practice on some shorter lengths first to gain confidence, you'd be surprised how uniform you can make things if you're patient.

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        • svyolo
          svyolo commented
          Editing a comment
          I would love to see the youtube on that. There are some real artists out there in a lot of fields, although that doesn't mean we can all do it.

      • #7
        Originally posted by steve1428 View Post
        the sheet metal pros will show you, guys can do miracles with just seaming pliers. I've got two vices setup on my bench ( I used them to hold the form for banging over the flanges too) I just put the spar stock in the vice between two pieces of wood and start bending to the line. As long as you're close it will be good enough, the strength comes from the cap stock etc anyway, not a bend in some .032 thick aluminum. Can definitely get away without having to find an 8' brake, besides it's going to be tough to get a shop to bend for you exactly the way you want it and they'll give you a hard time about using a boot and putting the proper radius on it.

        practice on some shorter lengths first to gain confidence, you'd be surprised how uniform you can make things if you're patient.
        just to clarify..youre saying you can bend a spar and the spar will be straight?....i agree you can put a bend in any metal...but the un-even application of the bend usually leads to a part that ends up bent like a banana...if you have a link to a video showing this technique ...I`m all ears..ill watch it and learn something new today...

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        • #8
          just draw a straight line where you want to make the bend, put a straight piece of wood along it (you can put your knees on the wood and do it on the floor) and start bending at one end with the seaming pliers, work your way along to the other side. Practice with scrap first.

          lots of youtube videos showing sheet metal work. malco and freund have good tools

          I just got the malco circle cutter, it works great:

          https://www.malcoproducts.com/produc...-hole-cutters/


          https://www.rapidmaterials.com/produ...nching-pliers/

          https://www.youtube.com/watch?v=blLqpf-mXOE
          Last edited by steve1428; 02-24-2021, 08:34 AM.

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          • #9
            Originally posted by steve1428 View Post
            it's only .032" aluminum, you don't need a brake, can just do it with seaming pliers.....
            Uh.... no. That won't work. This isn't .032 aluminum, this is .032 of 2024-T3. It's not the same.

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            • #10
              AC 43.13 pg4-13 par 4-54 b.
              Reheating at Temperatures Above Boiling Water. Reheating of 2017 and 2024 alloys above 212 °F tend to impair the original heat treatment. Therefore, reheating above 212 °F, including the baking of primers, is not acceptable without subsequent complete and correct heat treatment.

              The wording "heat treatment" in AC 43 is also incorrect. 2024-T3 is a tempered aluminum alloy. 2024-T3 alloy is considered un-weldable due to copper content.
              Last edited by Sir Newton; 02-27-2021, 12:59 AM.

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