flicka5,

Well, you're right, the term is in broad use, which is unfortunate. The reason that I specifically brought it up in this context is that japan's question was asking about drag as a function of lower surface shape, and that is not the primary factor that affects drag. Camber ( of the mean line ) and thickness have fundamental affects on airfoil performance, and for that reason, it makes sense to discuss airfoils in those terms. Lower surface concavity per se is not as useful in this regard, and the use of the term 'under camber' instead of lower surface concavity leads to some confusing ambiguity. The term 'semi symmetric' has the same problems. It's especially unfortunate that Andy Lennon uses the term inappropriately. This is a case of someone's expertise in one area spilling over to lend him credence in an area in which he does not have any.

banktoturn