Tom Seitz writes:
>I understand that for applications where the wing will be really stressed, it
is better to put the spar at the 1/4 chord point, the reason being
>that this is where all the bending force is applied. If the spar is offset
from this point, the wing will tend to warp.
>Is this correct? Or is the max thickness point close enough to the 1/4 chord on
many airfoils not to be >significant?
The center of lift location as a fraction of chord is x/c = 0.25 - CM/CL.
In a typical winch launch of a typical glider CM = -0.05, CL = 1.0,
and so the center of lift is closer to 30% chord. This is the place to put the
spar if you want to minimize twisting. If the wing is very stiff torsionally
this may not matter.
- Mark Drela
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