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  • #16
    Originally posted by Jean Claude View Post
    The relevant reference line should be ]
    Should be? There may be some miscommunication here due to the limitations of data exchange on a an internet forum - and some language translation error.

    This isn't the way any of the rotor stringing procedures I've run across are done. Even if the CG was used as the alignment point it wouldn't make any difference aerodynamically if the aerodynamic axis is not aligned with the mechanical torsion axis.
    Sure there is a tendency for a non ridgid rotor blade to try to us it's own CG during flight, but unlike a free body flying wing with 6 full axis of freedom a semi ridged rotor blade is restrained at the root. The CG of the rotor blade is just one force on the free body diagram. If that force happens to a be on the aerodynamic axis than there will be no aerodynamic twisting force introduced. If the CG of the blade is not aligned with the mechanical torsion axis of the blade then there will be a twisting force introduced. Only when the cg of the blade, the aerodynamic neutral axis and the mechanical torsion axis align will there be no torsional loads on the rotor blade.......other than aero torsion loads due to the variation of AOA along the blade.

    Typed this kind of quick. Brother in law's water heater just sprung a leak and he has 11 thumbs.





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    • #17
      Maybe my bad translation, Leon.
      What I mean is that if you introduce the angle of one degree as you mention, it shifts the profile forward at the same time as the center of gravity of the blade, as I drew.
      So I do not see why you suppose that the torsion axis would stay aligned with the other blade, as you drew

      In add, the unbalance vibrations produced by this misalignment will of course be corrected by the user with the same misalignment on the other blade. So the reference axis to consider for the twisting moment is the one that joins the points that I indicated. Not the line of hub bar
      .
      Click image for larger version  Name:	Sans titre.png Views:	2 Size:	3.2 KB ID:	1143755


      The torsional torque is determined by lift and the opposite component of the centrifugal force. The lift is assumed applied to the Aerodynamic Center and thus of course we must add the torsion due to the Cm0 profile.
      Click image for larger version  Name:	Sans titre.png Views:	2 Size:	6.4 KB ID:	1143758

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      • #18
        Originally posted by Jean Claude View Post
        Maybe my bad translation, Leon.
        And it could be my lack of rotor experience. I was kind of hoping to get your response on this thread. I'm a bit busier today than I expected and I need some time to put my words together properly. Thanks for taking the time to help me learn!

        Sorry to hear about the fire today. It was/is a loss to all of us, not just the French.

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        • #19
          Yes, the destruction of this witness of architectural technics and manners of almost a millennium ago is a great loss for heritage

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          • #20
            Toute l'Alemagne est en deuil avec les Français.
            Cheers,

            Juergen

            ..Il semble que la perfection soit atteinte..
            ....non quand il n'y a plus rien à ajouter,...
            ...mais quand il n'y a plus rien à retrancher...
            - Antoine de Saint-Exupéry -

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            • #21
              It is sad of course but not as much as the total destruction of entire cities by wars as in Syria.

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