[1] Schweizer developed a line of gliders starting in World War II.
The 2-31 was not intended to be a motor glider, but rather a light aircraft utilizing some glider and sailplane technologies, common parts with other Schweizer designs and an affordable price as a result of using smaller powerplants.
It was developed from the SA 1-30 on the assumption that there would be more of a market for a two-seat aircraft.
The fuselage was based on that of the 1-30 with strengthened 1-26B wings.
[1] The prototype first flew in July 1960, but the type was not put into production because it was thought that the cost of setting up a production line would be too great to compete with other two-seat aircraft available at the time.