A wind turbine includes a plurality of rotor blades, with each blade having a root portion connected to a rotor hub and an airfoil portion extending radially outward from the rotor hub. The airfoil portion further includes a main foil section and a winglet pivotally connected to the main foil section so as to pivot from an in-line position wherein the rotor blade has a first sweep length to an articulated position wherein the rotor blade has a second sweep length. In the articulated position, the winglet may pivot to not more than 90 degrees relative to a longitudinal axis of the main foil section. A deployable sleeve may be connected to the winglet so as to extend between the winglet and the main foil section in the articulated position of the winglet. The sleeve is stowable within either or both of the main foil section or the winglet in the in-line position of the winglet.