COMMENTS ONTHE DEVELOPMENT OF AIRFOILS RELATEDTO STANDARD CLASS GLIDER PERFORMANCE

The performance of a glider depends essentially on the aerodynamic properties of the wing section. This is studied. The effect of the drag polar shape of the wing section on the optimum wing area and attainable cross country speed is studied. In the study the significant parameters of the drag polars considered are the minimum drag coefficient and the width and shape of the low drag bucket. The results revealed that the selected wing section has a significant effect on the optimum wing area (or the aspect ratio as the paper dealt with Standard Class gliders only) and that the optimal wing section characteristics depend significantly on the day's weather. The intention of this study was not to deal with aerodlmamic optimization but to find out how the airfoil drag polars have evolved during the last 15 years in some particular gliders. The present study was encouraged mainly by two reasons: the possibility to utilize a relatively easy method to measure the airfoil coordinates directly out of a full scale glider and the promising development of computational methods to calculate the aerodynamic properties of airfoils.