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When are my ribs "Good Enough" ?

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  • When are my ribs "Good Enough" ?

    I now have a 30 Ton jack on my rubber pad press. That extra push got my lightening hole close enough to 30 degrees that Im
    happy now on that.

    When i am doing the fluting and straightening operation--- I finish the outer flanged lip from about 75 degrees to 90 degrees using the
    RV overbending tool. then I alternate between that tool and fluting until the edge of the flange perfectly touches the table all way round
    and the flange is 90 degrees with no bumps sticking up high. When I get to that stage-- i still have some front-to-back potato chip
    bend. I flip it over on its back onto a rubber pad and hit the flat areas with my small dead blow to bend the bowed area back the other way.
    The rubber pad underneath is intended to give the work a little room to move..... and to facilitate the un-bending.

    After I do this several times--- and then continue to adjust fluting and so forth---- I end up with the end-to-end bend better but not
    completely gone. When I am all done- the cut edge of the flange touches the table all way round-- flange is 90 degrees with no
    bumps....... and when I flip it over down flat---- if I put my finger in the flat area between the two lightening holes- I still have a gap
    of between 3/32 and 1/8 between the metal and the table. I have not added any of the stiffener angles yet (but I expect they will have no
    effect because that bend is 90 degrees to them)

    My question is ---- when those ribs are mounted into the wing---- will that slight curve have any effect as long as the outer flange
    is square and flat (in a single plane in space) ? Do I need to work harder and get rid of ALL that bowing ? Or-- is a little OK if
    the flange is 90 degrees and flat on the table ?

    I have done the first 15 nose ribs for one side. Hope I havnt wasted a bunch of expensive material. !

    ( I have noticed when I have tried more agressively to un-bend that bow - it can induce a wrinkle in the edge of the lightening hole.
    I have to go back and try to un-do it with the bob-tool. even being as careful as I can be- after working it out- it is never quite as
    smooth and even as before------- hence I want to know If what I have done so far is good enough.)

    Thanks ahead of time -
    Tim

  • #2
    If it takes just a wee bit of pressure to flatten them out, then when you rivet the stiffening angles to them, they’ll be perfect. Mine were similar.
    Christopher Owens
    Bearhawk 4-Place Scratch Built, Plans 991
    Bearhawk Patrol Scratch Built, Plans P313
    Germantown, Wisconsin, USA

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    • #3
      I agree with Chris. you can upload a photo but they sound pretty good to me.
      John Snapp (Started build in Denver, CO) Now KAWO -Arlington Washington Bearhawk Patrol - Plans #255 Scratch built wing and Quickbuild Fuselage as of 11/2021. Working on skinning the left wing! -Ribs : DONE -Spars: DONE, Left wing assembly's: DONE., Top skins : DONE YouTube Videos on my building of patrol :https://m.youtube.com/user/n3uw

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      • #4
        Here are 3 views--- one face up - one face down and a 3-rd with a maple strip across it as a visual straightedge.
        This is some of the new sheet that didnt have film and I added my own film. The gap under the straightedge appears
        to be about 3/32........ It appears on this one that most of the bend is in the front half. Thinking maybe I could take a 1 inch wood dowel
        and glue a rubber disk on the end and use it to hit with around the front hole (afraid I might miss with my little rubber hammer.)
        You do not have permission to view this gallery.
        This gallery has 3 photos.

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        • #5
          Looks perfect to me. Again, the rib stiffener angle will take that out.
          Last edited by Chris In Milwaukee; 04-25-2018, 11:06 AM.
          Christopher Owens
          Bearhawk 4-Place Scratch Built, Plans 991
          Bearhawk Patrol Scratch Built, Plans P313
          Germantown, Wisconsin, USA

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          • #6
            Your rib looks amazingly good. Remember that "perfect" is the enemy of "completion." You want it good enough, but you're already there! As Chris said, take one rib and add the stiffener angle to it, and see how good it looks!
            Jim Parker
            Farmersville, TX (NE of Dallas)
            RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)

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            • #7
              THANKS CHRIS an JIM !!!!!!!!
              Some of my nose ribs have that little curve and some came out much flatter. I might try some more tweaking but If the ones with a slight curve
              resist my straightening attempts- i will just pretend they are perfect. :-)
              If its just a little - AND the cut edge lays flat on the table (so the rivet line is straight on the centerline of the flange) I didnt see how it
              could hurt much- other than just cosmetic.

              I have 2 plastic tubs now-- I think I will get ready to clean and prep them for acid wash and the chromic acid (alodyne) treatment and
              then eco-poxy prime. After that I can move on to making the stiffener angles (a whole BUNCH of them-) - and the 15 for the other side
              Kind of neat how quickly I can make them considering that they are a fairly complicated shape. (thanks Bob and N3N JS there-)

              Thanks for the look-see----- I feel much better now ------ just wanted to make sure I wasnt making a mistake and ruining lots of expensive
              sheet metal. (im NOT beyond that... ) BTW---- the carpet protective film I applied to the sheet did a good job of keeping the surface nice during forming.

              Thanks again !
              Tim in Orlando

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