What is the nature and extent to the benefit of covering up the bottom of an airfoil?
It seems like all the early airplanes just had ribs and spars that were wrapped only on top, but then pretty soon wings started getting wrapped underneath too.
Despite the added weight of covered wing bottoms, I'm assuming that the planes flew much better this way.
Are there any resources about experiments on covered vs exposed wing bottoms? How much less aerodynamic is it to leave them exposed?