Page 215 - NAVAL SCIENCE 3 TEXTBOOK

fJ The Maneuvering Board

During your years as an NjROTC cadet, you have occasion to be A I'eclor is a plotted line used to represent an)' quantity that
concerned with maneuvering boats and ships. On training cruises has both magnitude (size) and direction. Since vessels have
or visits to naval bases, you may find yourself on board either a courses (direction) and speeds (magnitude) of travel, and winds
boat or a ship for training purposes. It is to be hoped that you will have directions and speeds at which the}' blow, vessel courses, ves-
have a chance to participate in maneuvers, either as an observer or sel speeds, and winds can be conveniently represented by vectors
possibly as a junior watchstander. drawn on the maneuvering board.
In this chapter we will introduce you to the basic concepts of
the Illnncuvering board and how to use it to construct a rdative
T he Maneuvering Board Plot
Illotion plot to solve problems involving wind and the mnneuver-
ing of ships and boats. The specific problems with which we will be The maneuwring board is a type of plot called in mathematics a
concerned are finding the closest point of approach (the CPA) of polar plot, wherein all quantities are plotted using their magnitudes
other vessels to )'ours, finding their courses and speeds, and deter- and directions, as opposed to their x- and y-coordinates as would
mining the speed and direction of the true wind. Such informa- be the case on a standard x-y rectangular type plot. The maneu-
tion is needed to assist in avoiding collisions in various approach vering board features a reference position in the center called the
situations, and to put the ship on the proper course and speed for pole, a series of concentric circles drawn around the pole at uni-
flight operations with aircraft or unmanned aerial vehicles (UAVs). form intervals, and a 360-degree "bearing circle" printed around
There arc also many more advanced types of problems that can be the outside circle. On the left and right margins are scales that
solved using the maneuvering board. As part of their formal train- call be used to represent lengths of vectors or distances between
ing, enlisted operations specialists and line officers who stand deck the concentric circles, and on the bottom is a logarithmic speed-
watches spend many hours learning to solve all kinds of maneu- time-distance device called a nomogram, the use of which will be
vering problems with the maneuvering board. described later.
The polar plot on the maneuvering board can be used to plot
both Ilectors, representing vessel courses, speeds, and tracks, or
Relative Motion
wind speeds and directions, and POil/lS, representing locations of
You know both from observtltions of the world around you and your own ;'1I1d other vessels.
from math and ph}'sics courses you Illay have taken that there is To usc the maneuvering board, you will need the following
no such thing as absolute rest or absolute motion. Rather, all states plotting instruments: a pencil to draw vectors and plot points; a
of rest or motion tire said to be relative to some reference point in parallel ruler and a triangle to assist in drawing vectors and to pick
space or location on Earth. In driving a car, for example, the refer- off directiolls; and navigator's dividers or a drawing compass to
ence for how fast it is going is the road on Earth's surface (or some- pick off distallces between two points.
times the police officer's radar or laser gun). In a passing situation, In order to construct a maneuvering board plot, it is first nec-
the reference for how fast another car is passing YOli is you in your essary to decide the frame of reference lor the plot you are going
car. And the reference for parallel ptlrking is the car in front and to construct. For most purposes, this will be your own vesse\. So
the car behind the empty space YOll want. the first step is to plot a point on the pole to represent YOllr boat or
At sea, the reference for what other vessels and the wind are ship; it is labeled with a capital R, for referellce vessel.
doing relative to )'our vessel is your boat or ship. 'tb determine Next, your vessel's course and speed need to be represented by
these things, it is helpful to construct a relative motion diagram a vector drawn on the diagram. To do this, first choose a suitable
on a standard plotting sheet called a 111l111ell\Ierillg board. For those scale to represent the magnitude of the speed from among those
who have taken math courses or physics, YOll ma)' recognize the in the left and right margins; lIsually either the 3: I or the 4: I scale
relative Illotion diagram drawn 011 the maneuvering board as is a good choice, as this will produce a nice-sized vector to work
being a kind of vector diagram. with on the plot. Now, using a straight-edge or the parallel ruler,
layoff a line for the vector, using the pole as the origin, toward the

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