Page 216 - NAVAL SCIENCE 3 TEXTBOOK

222 NAVAL SKILLS

SCALES MANEUVERING BOARD
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The U.S. Navy maneuvering board.

appropriate bearing on the perimeter corresponding to your ves- knots. Now, using a straight-edge or parallel ruler, a line is drawn
sel's heading_ Finally, using the dividers, layoff the scaled length of from the pole toward the 12S-degree mark on the perimeter of the
the vector representing your vessel's speed from the pole, and place outer circle. One point of the divider is placed at the pole, and the
an arrowhead on the end of the line. Customarily, the base or tail other pricks a small point on the line in order to layoff the scaled
of the vector at the pole is labeled with a lowercase e, and the head IS-knot distance. To complete the plot, an arrowhead is drawn at
defined by the arrowhead is labeled with a lowercase r, so that the the head of the vector, and labeled with a lowercase r. The foot or
vector er represents the reference ship's course and speed, tail of the vector at the pole is labeled with a lowercase e (see the
As an example, suppose your vessel is on course 125 degrees illustration on page 223).
at a speed of 15 knots. If the 3:1 scale is selected to represent the Once your m'l-'n ship has been plotted at the pole or center
magnitude of the speed, the dividers are set for this value by plac- of the maneuvering board, and the vector representing its course
ing one point at 0 at the bottom of the 3:1 scale and opening them and speed has been plotted, you are ready to solve any of the basic
until the other point is over the mark representing 15 on the scale. kinds of maneuvering board problenls.
The spread of the dividers now represents a magnitude of 15