 A Design Approach and Selected Wind-Tunnel Results at High Subsonic Speeds for Wing-Tip Mounted Winglets by Richard T. Whitcomb

Originating report, July 1976. NTRS author abstract describes small nearly vertical wing-tip surfaces and wind-tunnel measurements of forces, moments and loads on a representative narrow-body transport wing. Its comparison with a tip extension approximately matches the increment in wing-fuselage-junction bending moment. The article's drag-budget example is original, not a numerical result of this experiment.

Additional exact locators: printed pp. 7–8, Incidence and twist and Cant or dihedral. These distinguish winglet incidence from cant and discuss the tradeoff among induced-drag reduction, skin friction and wing bending moments, including root-flow interference for outward cant. The Winglet cant angle article states its own explicit vertical-reference convention.