Cantilever parasol wings?

Discussion in 'Hangar Flying' started by cluttonfred, Mar 11, 2019.

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  1. May 8, 2019 #121

    Riggerrob

    Riggerrob

    Riggerrob

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    Antonovs - and similar military jet cargo planes - have anhedral to compensate for the excess “dihedral effect” (roll stability) created by wing sweep.
    Too much roll stability can create too much stability .... aka. Dutch Roll. That is why Boeing 727 had such a massive fin .... to compensate for all the stability created by the dihedraled, swept wings.
     
  2. May 10, 2019 #122

    mcrae0104

    mcrae0104

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    Not sure I follow you there--it had too much yaw stability, so they added fin area (another contributor to stability) to compensate?

    Maybe you are thinking of a plane other than the 727, which has little dihedral.
    image.jpg
     
  3. May 10, 2019 #123

    Victor Bravo

    Victor Bravo

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    727 had a massive fin because there was a large air intake duct inside it, and it was also not very far aft of the CG. So I believe they needed a big fin primarily to create adequate tail moment... in addition to anything else related to sweep or dihedral.
     
  4. May 10, 2019 #124

    cluttonfred

    cluttonfred

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    We’re a long way from Fokker-inspired parasols, but perhaps he meant the Boeing 707?

    [​IMG]
     
  5. May 12, 2019 #125

    larr

    larr

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    I think there is a tendency to over estimate that effect of wing sweep at small angles. For example, the 747 has greater sweep than the Antonov and still has dihedral.
    747 vs an.jpg
    Dutch roll is an unfortunate side effect of wing sweep, so that airliners all have yaw dampers.

    Boeing has always used large vertical stabilizers even when there is no sweep - the B 17 is a good example of that.
    And yeah, this is way OT. But I think it's an important discussion to have.
    A V.40 replica would be just fine as it was. Except for the lack of a tail strake.
     

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