Help? Home wing load testing

Discussion in 'Workshop Tips and Secrets / Tools' started by wingtesting, Feb 5, 2009.

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  1. Feb 5, 2009 #1

    wingtesting

    wingtesting

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    We've got a Q2 rear wing that we need to test to 12Gs/~4200lbs.

    We're probably going to go with the sandbag method of testing.

    Any tips on how to go about doing this?

    (I know this is pretty broad. I just wanted to drop a line and see what I get back. I'll be able to provide more details later. For now, any kind of information or direction would be helpful.)

    Thanks!

    Alaina
     
  2. Feb 6, 2009 #2

    Norman

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    Would the negative G test look something like this?:silly: Seriously though notice that the load roughly corresponds to the lift distribution i. e. more guys in the center
     

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  3. Feb 6, 2009 #3

    Mac790

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  4. Feb 6, 2009 #4

    Norman

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    Bags of shot, bags of sand, bags of organic chemicals (guys). They're all bulky. At some point it will be cheaper and/or more convenient to build a whiffltree
     
  5. Feb 6, 2009 #5

    Mac790

    Mac790

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    Norman thanks for the link to that thread I've haven't seen it before. I did some research and I found few pictures (pic1,2) but it doesn't look more convenient or cheaper than bags method to me. Besides always you can borrow some bags from your local "building material dealer" (guys who sell bricks, cement etc), for fraction of costs, many guys doing it.(pic3)

    btw Do you have more links with better description of whiffletree method?

    Seb
     

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  6. Feb 6, 2009 #6

    BBerson

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    I started to fill several sand bags with sand and decided that was a lot of work. Then I moved the wing closer to the hay shed and used 90lb hay bales to load the wing.
    BB
     
  7. Feb 6, 2009 #7

    Rom

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    Here is a March 1992 EAA article that describes structural load testing: members.eaa.org/home/saarchive/eaa_articles/012334.pdf
    I don't know if you have to be logged into the site to retrieve it.
     
  8. Feb 6, 2009 #8

    Mac790

    Mac790

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    Unfortunately you have to be logged, btw is it possible for the guy from Europe to become EAA member. I've heard they have a lot of useful materials on their webpage.

    Seb
     
  9. Feb 6, 2009 #9

    pwood66889

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    "is it possible for the guy from Europe to become EAA member?"

    Yes, it is. There are even chapters in Western Europe. Look on EAA - The Spirit of Aviation - Oshkosh, WI.

    And in the current (February 2009) issue of the EAA publication Sport Pilot & Light-sport Aircraft (TM) there is an article on wing loading; "Loading an Eagle Wing," by L. Milholland, page 56.

    Percy in NM, USA
     
    Last edited: Feb 6, 2009
  10. Feb 6, 2009 #10

    Rom

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    Geography does not matter to be a member. There are European EAA chapters out there also.
     
  11. Feb 6, 2009 #11

    Mac790

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    Thanks I'll try it, I thought that you have to be US citizen or something my mistake.
    Thanks again

    Seb
     
  12. Feb 6, 2009 #12

    Norman

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    Those pictures are as good as any I've seen, Seb. It's not a complex mechanism. There's an article on Wikipedia that goes into the history of it with a schematic drawing but it doesn't really show anything that you don't already know.
     
  13. Feb 7, 2009 #13

    wsimpso1

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    There is video of a wing test done at Boeing on a full scale jetliner.
    Simply amazing. All you have to do is go a little smaller...


    Billski
     
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  14. Feb 7, 2009 #14

    Topaz

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    Geeez... Within 4% of predicted strength! That's really pretty remarkable.

    Always neat to see one of these. Thanks, Bill!
     
  15. Feb 8, 2009 #15

    Mac790

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    Thanks for response, I know it's not a complex mechanism, couple beams, overhead crane, etc but still I think it will be hard for average home builder to build one in his garage, I would rather stay with bags.


    Billski thanks for movie it was impresive.

    Seb

    btw Does anyone have pictures of "home made" whiffletree?
     
    Last edited: Feb 8, 2009
  16. Feb 8, 2009 #16

    Rom

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    In the case of the 777 all of the load was applied at the wing tips. With sand bags, the weight is distributed as per the actual lift distrution that the wing would see during flight. I wonder if the 777 was tested with sandbags, the result would have been somewhat different, perhaps possitive?
     
  17. Feb 8, 2009 #17

    Mac790

    Mac790

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    Rom stop movie at 2.36 and 2.50, you will see plenty of cables along whole wing not only at the wing tips. In my opinion it would be pointless to aplly all load only at the wing tips. (but I'm not a professionalist so maybe I'm wrong)

    Seb
     

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    Last edited: Feb 9, 2009
  18. Feb 9, 2009 #18

    wsimpso1

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    Despite voice over that indicated cables at the wing tips, the whiffle trees are there, putting load over the whole wing, and in approximately the distribution that the aero load is spread. You really see them jump as the wing skin breaks free of the spars. On higher resolution video, the whiffletree and cables are apparent. I worked for Ford until recently, and the video got around, what with Mullaly heading up Ford and ex of Boeing.

    Putting the load in only one place can only apply loads correctly to one spot in wing. The whole point in a test like this is to apply correct laods over the whole structure and find out not only what it will actually carry, but if it will give up in the way forecast...

    Billski
     
  19. Feb 9, 2009 #19

    PTAirco

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    One problem with using the whiffle tree method for testing a homebuilt wing is attaching the individual cables properly to the structure. Easy enough with an open, fabric covered wing, but how do you attach them to a skinned wing? You can loop chorwise straps around the whole, but I am guessing that would induce unintended local loads and possibly buckle leading and trailing edges so you need spreader bars etc. Gets quite complicated if you look at in detail.

    Ideally, of course the airloads should be applied both as suction on the upper surface and pressure on the lower, but few if any structural tests I have seen do this.
    The sandbag method does seem a little simpler, if more tedious.
     
  20. Feb 9, 2009 #20

    Rom

    Rom

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    Guess I missed the rest of the cables with my low rez video.
     

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