3 Spees Triangle

8/12/2019 3 Spees Triangle

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HOMEWORK QUESTIONS

3.1, 3.2, 3.4

3.7, 3.8, 3.10


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Definition of Vector

Diagram/Speed Triangle Means for solving the relationship

between actual and relativemovement in order to determine:

*actual COURSE and SPEED of maneuvering

contact*DRM and SRM of maneuvering contact


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Speed Triangle

each line of the triangle represents is a

vector representing course and speed

COURSE = represents either actual direction orrelative direction of movement

SPEED = length of vector represents actual

speed or relative speed of movement


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Speed Triangle plot labels

e - marks the center of the plot

stands for earth as the reference of actual

movement

all actual course and speed vectors are drawn

from e

er vector - represents actual course andspeed of reference ship

r stands for reference ship


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rm vector - direction of relative

movement of m ship with respect to rship

direction indicated from r to m (rm) = DRM

length of rm vector represents relative speedof m ship with respect to r ship = (SRM)

em vector - represents actual course and

speed of maneuvering ship m stands for maneuvering ship


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Speed Triangle

e

mDRM

SRM

Reference ships

course and speedManeuvering ships

course and speed

rm


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Relationship between relative

plot and vector diagram Direction of relative movement indicated by

both relative movement line (M1.M2)

and rm vectorTHIS IS THE CONNECTING LINK

BETWEEN THE TWO DIAGRAMS

RELATIVE PLOT = indicates bearings anddistances

VECTOR DIAGRAM = indicates courses

and speeds


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Similarities of relative plot vs.

speed triangle

Relative Plot:

true RANGE/BEARING measured from center

relative quantity not measured through center

direction of relative side (M1M2)

two true sides and one relative

Speed Triangle

true COURSE/SPEED measured from center

relative quantity not measured through center

direction of relative side (RM vector)

two true sides and one relative


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Dissimilarities of relative plot vs.

speed triangle

Relative Plot:

labeled with CAPITAL LETTERS (R, M1)

TRUE RANGES/BEARINGS

length of relative movement line (MRM)

Speed Triangle

labeled with UNDERCASE letters (e, r, m)

ACTUAL COURSES/SPEEDS

length of RM vector (SRM)


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Example of relative plot vs.

speed triangle The reference ship is on course 060 T at a

speed of 18 knots. At 1600 the maneuvering

ship bears 140 T, range 7,000 yds from thereference ship. At 1610 the maneuvering

ship bears 192 T, range 3,000 yds from the

reference ship.FIND: (A) DRM, (B) MRM, (C) SRM, (4)

Course of maneuvering ship, (5) Speed of

maneuvering ship


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Find DRM

Draw straight line from M1 to M2 and place

arrow to indicate direction

transfer line to center of plot and mark the

bearing on the azmiuth circle

Answer = 295 T

Transfer the relative movement line to the

er vector and draw the rm vector in the

same direction as the relative movement

line


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Find MRM

Take dividers and measure the distance of

the relative movement line using (1:1) scale

Answer = 5,600 yds


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Find SRM

Using the nomogram on the bottom of the

moboard, draw a straight line through the

MRM (5,600 yds) and time (10 min) to getthe third quantity of speed.

Answer = 17 kts

The SRM (17 kts) is the length of the rmvector so measure off on scale with dividers

and lay amount off from r

POINT m IS NOW LOCATED


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Find Course/Speed of

maneuvering ship Draw a line from e to m to locate the

em vector. Direction of this vector is the

course of the maneuvering ship and thelength is the speed of the maneuvering ship.

Answer = 000 T at 16 kts


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Homework

Do problems 4.1-4.5

Quiz on Wednesday - bearings, relative

plot, CPA (no speed triangle problems) Review checklist of MoBoard work

habits pg. 4-8

Read Chapter 5tracking problems

3 Spees Triangle

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