An apparatus is disclosed for taking advantage of the Bernoulli Principle for moving an airfoil, the airfoil being mounted on a collar for rotation about an axle when in a moving fluid medium. The axle is slanted at a backward angle in the fluid medium direction in a manner so as to permit the motion of the fluid medium to exert a substantially continuing lift force on the top of the airfoil blade adjacent to its leading edge to take advantage of the Bernoulli Principle for a portion of the blade arc, and, for other portions of the arc of rotation, so as to permit the force of the fluid medium to exert rotational force on the bottom of the airfoil blade.