I'm quite a newbie of these systems and I am designing the wing box of a drone. I know where I want my shear centre. However, I have been trying to determine the shear centre of my idealized airfoil. My airfoil is the NACA6412 and it's highly unsymmetrical.

I know this subject have been touched in this forum before and I have read T.H.G Megson a lot, but I think I am missing something. I have been stuck in this problem for 3 months now and if someone can provide some light on it, it would be great. My goal is to implement this determination in a script or in excel for future situations.

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    $\begingroup$ The shear center depends on the structural construction, e.g. where the spar, shear box, etc. are located. $\endgroup$
    – JZYL
    Oct 25, 2021 at 22:12
  • $\begingroup$ This is not enough for a response because I don't know the exact method to find the shear center, but I think assuming a constant thickness shell you could come up with a reasonable numeric approximation by dividing the airfoil shell into a number of short straight segments? $\endgroup$ Feb 22, 2022 at 20:59
  • $\begingroup$ This is actually a not bad question, as shear center can change if ailerons or flaps are applied. The main force on the wing is bending from G forces. As long as AR is not too high and airspeed not excessive, a good strong box spar structure should be adequate. Existing designs may save some time. Reverse engineer them. $\endgroup$ Jun 23, 2022 at 14:21

2 Answers 2


Plot the airfoil on a piece of paper, glue that to a piece of cardboard and cut it out. The shear center is where the center of gravity of that cutout airfoil is when balanced horizontally on a pin.

This is a valid method if the wing skin has the same thickness over the full chord. If you intend to use more material in some corner (say, a torsion box forward of the spar), increase the thickness of the cardboard proportionally to the relative shear stiffness of the corresponding section of the airfoil.

If a section does not contribute to shear stiffness (say, an aileron or a flap), leave this section away.

Background: The resistance to torsion of a hollow structural member is proportional to the circumscribed area and the stiffness of the skin of this structural member.


The best way is to assume the airfoil symmetric (since the location of the shear center in the chord is more important) for a preliminary phase; It will help a lot. Also, don't forget that idealization is a very rough estimate of the stress analysis of a wing structure or fuselage. It helps, however, with initial pre-sizing.


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