Aerodynamic Investigation of Wing Tip Sails

Wing tip sails were investigated to determine potential aerodynamic improvements for a wing having an aspect ratio of 10 and a taper ratio of 0.43. The airfoil section used for the wing was an NLF- 0215 and the wing tip was rounded. Three tip sails were utilized for all investigations with each tip sail having a root chord that was 20 percent tip chord of the wing. The wing sails were mounted at the tip of the wing along the chord line. Looking along the span towards the wing root the orientation of each sail tip was the same as the wing tip. Initial studies used sails constructed from two Wortman airfoils. A generic cambered tip-sail was also investigated. Individual sail angle of attack as well as sail dihedral and anhedral were investigated. PMARC, an aerodynamic paneling code was used to predict lift, induced drag, and viscous drag with the use of a momentum integral analysis. All viscous predictions were calculated for a Re/foot = 2.19 × 10⁶. Lift to induced drag results yield the highest values for the sail geometries that had negative decalage angles between adjoining sails. Sails with positive decalage angles between adjoining sails yielded the lowest lift to induced drag ratios. Sail dihedral and anhedral angle had a marked effect on lift to induced drag ratios. Lift to total drag results are also presented.