Using the Boundary Layer to Gain Effective Wing & Propeller Blade Area.
During WW I Ludwig Prandtl identified the boundary layer and discovered that wires and struts produce much more drag than would be expected from their small frontal areas, making a strong case for wireless monoplanes (however, with modern materials and wingtip tanks, cantilever biplanes or triplanes without wires or struts can be made very aerodynamic). A small wire produces more drag than expected, because some air adheres to it, increasing the effective diameter (boundary layer), around which the air has to flow. Accordinly, the Fokker D.VII eliminated the wire stays between the wings with welded steel tubing N struts.
Because most current private plane wings are large, the boundary layer has a negligible effect on wing area. However, if a higher wing loading & multiple, narrow, tandem wings are used instead of a single large wing, the greater effect of the boundary layer will result in a larger effective wing area than the actual wing area. Moreover, since in laminar flow the boundary layer is thicker at low speed & sea level than at high speed & 11,000 ft, the plane has a very slightly larger effective wing area during TO than at cruising speed.
By extension, since a propeller blade is just a rotating wing, a prop with 4 fold the number of blades (each blade 1/4 as wide as in the original prop) will have the same total area but a higher effective area, owing to the greater effect of the boundary layer.