On the dynamics of tail fins and wind vanes

Abstract

This paper describes some investigations of the dynamic yaw behaviour of tail fins and wind vanes employing delta wing planforms. Both single and twin wings were tested, the later were formed from two single wings joined at their apices. Comparisons were made using simple wind tunnel models with aspect ratios from 0.7 to 3.07, and various arm lengths, wind speeds and planform areas. The twin wing was found more highly damped than an equivalent single wing, with damping increasing as the angle between the wings increased. Stall related problems became evident as this angle approached or exceeded that for static stall. A computational model based on unsteady potential slender wing theory was developed to predict yawing motions of both tail fin types and compared with experiments. The computational model was found remarkably accurate for the single wing case even at high initial angles of yaw, but generally inaccurate for the twin wing. Possible reasons for this inaccuracy and the superior twin wing response are given.