thinning down from 6061 to 2024

Discussion in 'Sheet Metal' started by Norm Langlois, May 12, 2019.

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  1. May 16, 2019 #81

    Norm Langlois

    Norm Langlois

    Norm Langlois

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    VP1
    I did say I should reverse the spar.

    I have lashed out as well. The problem here is those nay Sayers think they are correct, even, when there are others that are favorable . The balance is no one has the right to demean others because one won't bend to there will, Regardless.
    Your post Victor is extremely demeaning. I did report it I doubt anything will become of it.
     
  2. May 16, 2019 #82

    Dana

    Dana

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    Let's tone it down, guys...
     
  3. May 16, 2019 #83

    Norm Langlois

    Norm Langlois

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    As I mentioned slightly .Long ago there was an individual that has engineering back ground told me The spar might actually be cantilever-able. if reversed. I have been aware of that potential along time.That was back in the threads of Oshkosh 365. Those are all lost.

    Another likely misconception, is what the same Naysayers think of the compound flared lighten holes.
    They be leave they are weakening the web. They do not. how much they strength they add is not known. The destruction of the test spar shows they do not allow deformation of the web and focus the compression on the flat apex. Unfortunately the flat is required to avoid bend fracture, to avoid bending over 30 degrees I adamantly appose some suggestion .
    This spar Idea is not a true triangle it is and enhance geometry using sheet metal and to avoid additional weight, use the unibody technology of automobile chassis. adding structure to the apexes the lightest way possible. Getting to the required compression load structure.

    If you out there are going to just declare with out any real proof that a MODIFIED structure is likened to a shape you personally reject keep, that on your back burner it just an opinion after all isn't it.
     
  4. May 16, 2019 #84

    Norm Langlois

    Norm Langlois

    Norm Langlois

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    As I said in the beginning here I intend to build a spar . how long it takes whether its not garage builder friendly is not important. The kit plane are very good , build one if you like. There are a few who would if they could build war plane look a likes .If I can find a way to build the cantilevered wings they need. ????
    I told you I don't fly any more, I make things. If there no good , The scrap man gets them.
     
  5. May 16, 2019 #85

    mcrae0104

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    It may well be OK, Norm. For the loads BB outlined above, a triangular spar (equilateral) with a height of 12" made of .040 2024-T3 has about the right section modulus for the moment at the wing root. Obviously buckling needs to be dealt with, and inverting the section helps this because it places the compression edge 4" from the neutral axis, where the stresses are lower than the tension edge, which is 8" below the N.A.

    Outboard from the root, where the moment is lower, lightening holes could be OK because you don't need the full I value out there that you do at the root. Alternately, you could start with a smaller triangle that doesn't meet the bending needs at the root, and supplement with caps at the vertices near the root. This may result in a lighter spar than the lightening hole approach because 1) buckling is less of a problem the smaller the faces are, and 2) the caps could be tailored to taper just to provide the section modulus needed.

    Stiffeners inside the tube could also help. Conceptually it might be something like this:
    tri spar.jpg
     
  6. May 16, 2019 #86

    BBerson

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    Need to look at negative flight loads also, for any non-symmetrical section such as this. The lower cap will be in compression in the negative maneuvers (which are unlikely). But negative gusts are likely. I have hit my head on the ceiling a few times (out of the blue) from unexpected gust in cruise. Perhaps negative 2g.
     
  7. May 16, 2019 #87

    BBerson

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    mcrea's drawing is looking good.
    Norm, if you can bend a big radius, I would use 7075-T6 for those root cap lamination angles.
    Up to 70,000 psi.
    Normally 7075 is hard to bend. I bent .040" 7075-T6 on my old 10 foot Whitney brake but sold it in the move.
    Now I have a four foot brake that can't do much.
     
  8. May 16, 2019 #88

    BBerson

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    The Zeppelins were made with light alloy (Dural they invented) triangle lattice frames. Lightest known structure at that time. Some were sheet metal with holes like Norms.
     

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  9. May 16, 2019 #89
  10. May 16, 2019 #90

    BBerson

    BBerson

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    Yes, the Zeppelin girders were not airplane spars. The girders were not loaded as cantilever, and spars are different.
    But triangle beams are often used for things like cranes.
     
  11. May 16, 2019 #91

    BJC

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    Most cranes with built up triangular sections load those sections primarily in compression, not bending. An obvious aircraft exception is the aft fuselage structure of -7 and -8 series Aeroncas / Champions.


    BJC
     
  12. May 16, 2019 #92

    BBerson

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    I don't know what your point is about triangle spars, I guess you think they are not appropriate.
    Page 42 of Aircraft Structures by Peery gives an example of a triangle spar: "similar to that used on some, full cantilever, fabric covered wings."
     
  13. May 16, 2019 #93

    Norm Langlois

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    Maybe a few think its a stand alone spar. true mono. Its not and I should not have presented it that way . Before I finished up the original wing I was advised to put a torque control tube in at the TE some pictures show this short 2 inch tube . near the engine mount. Any wing construction would still need that I expect. Dihedral wing  and plane 002.jpg
     
  14. May 16, 2019 #94

    Norm Langlois

    Norm Langlois

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    This wing works with the flying wire. I agree with inverting and adding to the spar as well. I want to make it only 6 inches deep . Also with only a single row of lightening holes . The hole would not be as much for lightening ,but for coining a pan into the web . Much like these holes but with a larger return to a smaller hole.
    This wing is spliced where it is only because the center section is 8 ft. Any new attempt, would be going for a removable wing . So the center would not carry through.
     
  15. May 16, 2019 #95

    Norm Langlois

    Norm Langlois

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    I want to be clear about this. I am not looking to create the same spar , smaller . Or even invert this one. this has only two side webs. The bottom was left open for warping. I later had to add a web to remove the warp character, and its not the same material thickness.
    The wing in the picture has a USA 5 Modified airfoil its very thick and the spar is 9.8 inches deep with 11.4 webs ( approximate dimensions) Over all its too heavy.
     
    Last edited: May 16, 2019
  16. May 16, 2019 #96

    Norm Langlois

    Norm Langlois

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    The img is a drawing of a 3 piece or 4 piece option this could have many versions . the riveted construction would allow for add ons flats angles mount clips etc.
     

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  17. May 18, 2019 #97

    Norm Langlois

    Norm Langlois

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    Macrae's post is good . It would need to be applied internal and integrated, with the bulkheads. But 3 sided forming is not going to happen. I can do 2 plus 1, or 3 independent sides. Riveting 3 sides together is not that big a deal. provides paired flanges doubling thickness. It also gives you options like Macrae has depicted, to add.
    Large radii is not an option for me at present.
    I posted elsware about the reluctance of industry to do any work to airplane components. I have been refuse . Finding a press brake and dies won't be likely.
    Lining up all your ducks is tough. I have 10 ft limit and its not powered, it's 14 gauge steel capacity .
     
    Last edited: May 18, 2019
  18. May 21, 2019 #98

    oldcrow

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    P1.jpg Been following this post. Norm, I like what you are trying to do, and I saw post#30. Since you have the sheet metal skills and equipment. Try making your doublers bigger and wider at the root ( shown red)and then taper toward the tip. Just a suggestion as I don't have the skills to equate the strength in this matter. ( the holes where put there just so I could align the parts)
    Good luck, Ken
     

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