washout vs inverted tip section
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May 26, 2012
, 11:36 AM
Joined Jan 2007
Airfoils produce lift both ways, no matter what the direction the camber is. An inverted airfoil just isn't very efficient at producing upwards lift - it's drag is higher than an upright cambered section when producing upwards lift, and the stall AoA from the chord line is lower. An airplane with a cambered airfoil can still fly inverted.
I have a little plank flying wing with an upside down Clark Y airfoil that flies pretty well. It doesn't need a reflexed airfoil because the negative Cm of the Clark Y becomes a positive Cm when it is inverted.
The stall behaviour of the airplane would likely not be noticeably different. You would still want to set the relative angles, including the induced angle of attack especially on a swept wing, so that the tips aren't stalled when the centre section stalls to prevent tip drop and incipient spins.
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E205 polars upright and inverted.
Inverted Clark Y plank glider
Last edited by kcaldwel; May 26, 2012 at