Aluminum wing ribs

Discussion in 'Smith Mini Plane' started by mschmitt, Jun 10, 2018.

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  1. Jun 10, 2018 #1

    mschmitt

    mschmitt

    mschmitt

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    Any other Smith's out there have aluminum wing ribs? I am build a few new ones for mine. I measure the old, cracked ones and they were .038" thick. I went with .040 2024 Al, but they are extremely hard to form. The old ones don't seem to be that hard. Wondering if I should be using 6061 instead or go to thinner material. It's only the end rib that I need to replace. Thoughts?
     
  2. Jun 10, 2018 #2

    cwilliamrose

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    If it's 2024-T3 it's not likely possible. I'd try 6061-T6 which can be annealed with a torch, that should give you a good shot at it. Post a photo of a rib, maybe we can make a few suggestions.
     
  3. Jun 10, 2018 #3

    TFF1

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    That's pretty thick. I would think .025-032 would be the ballpark.
     
  4. Jun 10, 2018 #4

    cwilliamrose

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    It could be that the thickness you measured was more than the blank's thickness if you measured it at the flange where the material has gathered (due to shrinking). Try to measure it where no forming has happened.
     
  5. Jun 10, 2018 #5

    planebuilder

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    You should be able to form them from 6061T6 without annealing. Like Bill said...Pics needed.
     
  6. Jun 14, 2018 at 3:17 AM #6

    mschmitt

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    Tried adding a photo but it took forever. Decided to order some 6061-T4 in .025 and.032. I am also going to try a different forming block as well. We'll see how it goes this weekend.
     
  7. Jun 15, 2018 at 12:10 AM #7

    mbourget

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    T-4 is good. Wing Ribs generally are loaded in compression and, in that regard, 2024 and 6061 are so close in that property that 6061 is a good "substitute". It is easy to form a solid flanged rib with proper technique. For best results, you will have to relieve for work hardening while forming. (Note: Anneal is a different goal - "cooking off" soot or sharpie pen is actually taking the material to "W" temper and is not annealing but that's the popular, if inaccurate, term used generally)

    John Thorp authored a series of S/A articles on "Building the T-18" I think the third article described building the wing ribs (not at my usual computer) Read the article and I advise copying his technique of "wiping" the aluminum down the form block with a backer-block it will improve the rib's "compliance" with the form block.
     
  8. Jun 15, 2018 at 2:44 PM #8

    mbourget

    mbourget

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    Attached, please find the article on Wing Ribs referenced in my last . . .

    OH, I just discovered I can "drag and drop" files from another "window" How Nice!
     

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