The groundwork of practical naval gunnery; a study of the principles and practice of exterior ballistics, as applied to naval gunnery, and of the computation and use of ballistic and range tables - Softcover

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...lateral wind component in foot-seconds, positive when it blows from right to left across the line of fire, and negative when it blows in the reverse direction; let V and f be the initial velocity and angle of departure relative to still air or to the ground, and X be the corresponding range, that is, the range when there is no wind. Then if we draw the triangle of forces for this case, we may obtain the initial velocity and direction of flight relative to the moving air. Thus referring to Figure 21(a), which represents the case of a negative wind, the resultant of OA = V with OC=--Wz is OB=V, which is very slightly greater than V; the angle BOD = f', which V makes with the horizontal, is very slightly less than AOE = f; and V is inclined to the left so as to make with V the small angle BOA. Z 244. Now since V and 4' differ so little from V and f, and since the effect of the increase in V is offset by that of the decrease in f, we may take the range A" corresponding to V, £', to be practically the same as the range X corresponding to V, f. Therefore the only essential difference between the trajectory relative to the moving air and that relative to the ground or still air is that the plane of the former makes the angle DOE = y with the plane of the latter. Referring now to Figure 21(b), in which 0 represents the gun and M0 the target at the range OM0 = X, we Wm see that tan y =; and OM' is the horizontal trace of the trajectory relative V cos f to the moving air. But while the projectile moves through the air from 0 to M', the air itself has moved VeT to the right, and so the projectile really strikes to the right of the target by the distance Thus the lateral deviation caused by the wind component Wz normal to the line of fire is given by the expr...

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