You wrote:
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Does this then say that if I wish to design a model of a WWI aircraft, if I
replace the undercambered scale airfoil with one of say a Clark-Y
configuration I will get a better flying aircraft with less need for power.
That will also be more tolerant of gusty wind conditions?
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The short answer is NO.
A Clark Y section is a highly camber section. It just has
sufficient thickness to give it a flat bottom. The camber line
lies halfway between the upper and lower surfaces.
Paul