FLIGHT TESTING/PERFORMANCE IMPROVEMENTS THROUGH WING PROFILE CORRECTION

Abstract

Flight test polar measurements were performed with two modern sailplanes, a Ventus A/16.6 and a Nimbus 3/24.5, to compare their polars when measured in original factory delivered condition to those recently measured after their wing surfaces had been carefully profiled to within about +/- 0.5 mm. Significant drag reductions in the Nimbus 3 and Ventus A polars can be achieved through carefully profiling of the wing sections to match more closely those of the airfoil wind tunnel test models. Factory production accuracy of the wing profiles are now much better than they used to be where distortions of up to about 8 mm have been measured by DGA in the past. However, even the current 1 to 3 mm production and/or post mold curing accuracies are not sufficiently good to provide sailplanes with their full performance poteniials. That can be remedied by either further improvements in the manufacturing process or by laborious post manufacture profiling.