What does the pressure distribution over a glider's wing look like? 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?
The pressure distribution over a glider's wing is no different from that of a well-designed aircraft. A glider can maintain flight by flying slightly downwards, so the direction of motion is not straight but slightly down. Doing this in rising air will result in sustained flight.



Look at the sketch above: The flight path angle $\gamma$ is negative and in still air the flight path vector $\text{x}_k$ is parallel to the direction of the airspeed. Due to the inclination of the flight path, the lift vector is tilted forward such that its horizontal component is exactly opposite to the drag force. This is shown on the right where I moved the vectors into a closed sequence which demonstrates that all forces balance.

From the viewpoint of the glider, the lift is pointing straight up and drag directly backwards, but the weight force is slightly tilted forward. In a way, it seems that the thrust of a glider is its weight force.

Now let the whole air packet in which the glider flies move up. The glider will still sink down within this air but relative to the ground it will gain altitude if the upward air velocity is high enough.