3, in which the abscissae are the angles of the
heel, and the ordinates the various lengths of the levers, at the end
of which the whole weight of the vessel is acting to right itself.
The curve may be constructed in the following manner: Having found by
calculation the position of the transverse metacenter, M, for a given
displacement--Figs. 1 and 2--the metacentric height, G M, is then
determined either by calculations, or more correctly by experiment, by
varying the position of weights of known magnitude, or by the stability
indicator itself. Suppose, now, the vessel to be listed over to various
angles of heel--say 20 deg., 40 deg., 60 deg., and 80 deg.--the water
lines will then be A C, D E, F K, and H J respectively, and the centers
of buoyancy, which must be found by calculation, will be B1, B2, B3, and
B4. If lines are drawn from these points at right angles to the water
levels at the respective heels, the righting power of the vessel in each
position is found by taking the perpendicular distances between these
lines and the center of gravity, G. This method of construction is shown
to an enlarged scale in Fig. 2, where G is the center of gravity, B1
Z1, B2 Z2, B3 Z3, and B4 Z4 the lines from centers of buoyancy to water
levels; and G N, G O, and G P the distances showing the righting power
at the angles of 20 deg.
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