Steve,

Actually, in the general case, there's no way to know that filling in the concavity on the lower surface will result in about half the camber. Whether this is true depends on the chordwise thickness distribution. The original question was about the lift and drag differences between flat bottomed and 'undercambered' wings. Because the bottom surface shape per se does not have a strong, well understood, effect on lift and drag, it makes more sense to introduce the conventional, correct, definition of camber in answering the question.

When I go to an auto mechanic, he does not refer to a brake caliper, for example, as a 'doohickey', just because I am not familiar with the correct names of the parts of a car. He explains to me that the problem with my car is related to the brake caliper, explains what a brake caliper is, and proceeds to use the correct term for the rest of the conversation. Can an auto mechanic only help other auto mechanics? I think the situation is the same here. I avoid jumping in every time a post refers to 'undercamber', and correcting the poster just because I am picky, which I guess I am. In this case, to correctly answer the question requires a better understanding of the concepts and terms. As you say, the term 'undercamber' means something to most people. Unfortunately, the amount of 'undercamber' is not the correct characteristic of the wing to consider, so it doesn't make sense to use the term just because it is more intuitive.

banktoturn