Now, if we have assumed that the rear wing, being of the same size as the front one, has a lifting effect of only 0.66, and on this assumption is calculated the proper relative positions of the front and rear wings to cause the CP1 to come directly over the CG1, and upon testing the aerodrome find that it is too heavy in front and, therefore, wish to move the center of pressure forward an amount, say b, without affecting the center of gravity, we can calculate the proper relative positions of the front and rear wings in the following manner. While the aerodrome as a whole is balanced at the point CG1, the weight of the wings is not balanced around this point, for the rear wing, owing to its decreased lifting effect, is proportionately farther from CP1 than the front wing. In order, therefore, to avoid moving the center of gravity of the machine as a whole, any movement of the wings must be made in such a way as to cause the difference between the weight of the rear wing multiplied by its distance from CG1 and the weight of the front multiplied by its distance from CG1 to equal a constant: that is,
w(m + a)−w(0.66m−a) = constant,
and
0.33wm + 2wa = constant.
FIG. 7.
FIG. 8.
FIG. 9.