The aircraft has plenty of items (area) for the wind to  strike including wing, wires, struts, pilot, carriage, engine,  wheels, tubes, fuel tanks, etc. Parasitic drag can be reduced  by streamlining the items. Round tubes can be streamlined  reducing the drag to one-third, and cowlings can be used  to streamline the pilot and the carriage completely, but not  without the additional expense and additional weight of the  streamlining. Streamlining does make a noticeable difference  in the speed and gas mileage of the WSC, especially for the  faster aircraft.  [Figure 2-16]  With the large speed range of WSC aircraft, weight,  complexity, amount and expense of streamlining, and  resultant drag reduction are determined by the specific  mission for the aircraft and the manufacturers’ make and  model.  [Figure 2-17]  Total drag is the combination of parasite and induced drag.  Total drag = parasitic drag + induced drag To help explain the force of drag, the mathematical equation  D = C$_{D}$  x q x  S is used. The formula for drag is the same as  the formula for lift, except the C$_{D}$ is used instead of the C$_{L}$.  In this equation, drag (D) is the product of the coeffi cient of  drag (C$_{D}$), dynamic pressure ( q ) determined by the velocity  squared times the air density factor, and surface area (S) of  the carriage and wing. The overall drag coefficient is the ratio  of drag pressure to dynamic pressure. Induced and parasitic drag have opposite effects as AOA  decreases and speed increases. Note the total drag in  Figure 2-18 . It is high at the slowest air speeds at high angles  of attack near the stall, decreases to the lowest at the most  efficient airspeed, and then progressively increases as the  speed increases. The WSC wing can fly with a large range  of airspeeds. Generally, the most efficient speed is at the lowest total  drag providing the best rate of climb, glide ratio, and cruise  economy. However, slower speeds provide higher angles  of climb, and faster speeds provide quicker transportation.  [Figure 2-18] Figure 2-16.  Air flow around objects. Figure 2-17.  Fast WSC aircraft with complete streamlining (top) and  slow WSC aircraft with minimum streamlining (bottom). 2-9