Can someone explain the design of glider wing airfoils and the subsequent pressure distribution over them?
I hypothesize that:
The pressure distribution should form a resultant force in the forward, upward direction, since two components of force are required to maintain equilibrium in the flight of a glider: a) lift - in equal opposition to weight, and b) a forward component of the total reaction generated by the airfoil - in opposition to drag.
Thus I conclude that the angle of attack of a glider airfoil relative to flight direction would be negative, in order to achieve a forward component opposing drag; although it would be positive relative to airflow, such as to generate low pressure over the wings. Either that or the camber is designed such that the two mentioned criterias here, (a) and (b), are upheld.
Should there not be any opposition to drag, I would expect to see the glider decelerate in the forward direction, until the airflow stalls over the wings, and the glider loses lift and falls.
I am also curious to know about the various designs of glider airfoils: a) what are the criterias defining them, and b) how do they differ from those of powered aircraft, if there are any differences at all?