16 ([return])
"In effect" because, although there may be actually the greatest proportion of keel-surface in front of the vertical axis, such surface may be much nearer to the axis than is the keel-surface towards the tail. The latter may then be actually less than the surface in front, but, being farther from the axis, it has a greater leverage, and consequently is greater in effect than the surface in front.
17 ([return])
The reason the C.P. of an inclined surface is forward of the centre of the surface is because the front of the surface does most of the work, as explained on [p. 62].
CHAPTER III
RIGGING
In order to rig an aeroplane intelligently, and to maintain it in an efficient and safe condition, it is necessary to possess a knowledge of the stresses it is called upon to endure, and the strains likely to appear.
Stress is the load or burden a body is called upon to bear. It is usually expressed by the result found by dividing the load by the number of superficial square inches contained in the cross-sectional area of the body.