Improving Hang-Glider Maneuverability using multiple winglets:a numerical and experimental investigation

The main aim of the present paper is to investigate the influence of multiple winglets on hang-glider climbing performance. The study aims to optimize the CL3/2/CD parameter. The investigation was performed both numerically and experimentally starting from airfoils and winglet shape design. Given the shape of a real hang-glider wing under aerodynamic load the first phase of the work concerned the main geometric characteristics of winglet design : number of winglets, airfoils, planform shape, twist. A 3D wing model was built and using the indications obtained from the design, different sets of winglets were built. The wing model was built to enable winglets to be applied to the wing tip without changing the wing span and aspect ratio. The tests carried out on the hang glider model showed an improvement in wing performance of about 15%. However, the model reproduced a full scale wing flying under aerodynamic load and, according to the model builders, it showed a positive twist angle (leading edge up). This could mean that the winglets were more efficient because the original wing showed a strong tip vortex, A new model wing with an elliptical planform was therefore built to verify this further. The test results on the elliptical wing did not show the same improvement in performance obtained with the hang glider model. Nevertheless, compared to the original elliptical wing an improvement was still found.