SHIP HANDLING AND MANOEUVERING BASICS.pptx

Ship Maneuvering
Technical Reference
Panama Canal Gatun Lock

SHIP TERMINOLOGY
• Bow
• Stem
• Forecastle
• Hawsepipe
• Weather
decks
• Draft
• Freeboard
• Superstructure
• Pilothouse
• Mast
• Yardarm
• Truck
• Stack
• Keel
• Shaft
• Propeller
• Rudder
• Stern
• Transom
• Waterline
Shiphandling

Lesson Contents
• Shiphandling Theory
• Laws of Motion
• Controllable Forces
• Uncontrollable Forces
• Shiphandling
• Terminology
• Ground Tackle
• Getting Underway
• Single Screw Characteristics
• Twin Screw Characteristics
• Tug Handling
• Man Overboard Recovery

Shiphandling Theory: Motion
• Various forces acting on the ship create
movement.
• Newton’s Laws of Motion
1.Unless acted upon by an outside force:
• An object in motion tends to stay in motion.
• An object at rest tends to stay at rest.
2.The resulting motion of an object is the
sum of all forces acting on it.
3.Every action has an equal and opposite
reaction.

What is Vessel Handling?
Vessel handling is based on the basic knowledge that a vessel floats
in the water and returns to its original position after a list.
It is maneuvered with the assistance of the rudder, main engine(s)
and other auxiliary equipment, using knowledge of the rolling,
pitching and yawing characteristics of the vessel in waves.
In handling the vessel it is necessary to consider the effects of
environmental conditions while controlling the position of the vessel,
its attitude, and its speed, to move the vessel in the designed
direction in a safe and efficient manner, and to stop at the intended
position.
(Theory and Practice of Ship Handling, Kinzo Inoue, Honorary
Professor, Kobe University).
̎

Ship Handling and Maneuvering
Ship Handling and Maneuvering is defined
as the art of proper control of a ship
while underway, especially in harbors,
around docks and piers. It is one of the skills
that any ship handler finds very
satisfying when well accomplished.
The most basic thing to be understood in
ship handling is to know and anticipate
how a ship behaves under all
circumstances and what orders should be
given in order to make the ship behave and
move exactly the way you want her to. The
difference between the ships’ heading and
the actual direction of movement of the
ship should also be constantly attended to
as this is essentially important at slow
speeds and when there are wind and
current.

Vessel with
Stability
Means
Rudder, main
engine, thrusters,
anchors, mooring
lines, tugs etc.
Vessel
maneuverability
Rolling, Pitching and
Yawing characteristics
in waves
Environmental conditions
*Geography (existence of shallow areas and
water
depth etc.)
* Facilities (port facilities)
* Navigation (buoys, fishing boats, marine traffic
etc.)
* Social (regulations, navigation regulations etc.)
* Nature (wind, tidal flows, visibility, waves etc.)
Ship
Navigator
Control of vessel position, attitude,
and speed for safe and efficient
* movement in the required
direction
* stopping at the required position
Operatevesselas described
̏

Shiphandling Theory: Forces
• Controllable
• Propeller
• Rudder
• Bow Thruster/APU
• Mooring Lines
• Anchors
• Tugs
• Uncontrollable
• Wind
• Current/Tides
• Seas
• Water Depth

Propellers
• Provides the most important source of
force on a ship.
• (Usually) makes ship go forward.
• Most ships have 2 propellers.
• Aircraft carriers / Patrol Craft have 4.
• Frigates have 1.
Controllable Forces

Propellers
• Forces resulting from the use of the
propellers:
• Forward (or reverse) thrust
• Side Force
Controllable Forces

Propeller Thrust
• A result of the propeller spinning on its
shaft.
• Caused by a pressure differential
between the opposite sides of the
propeller blade.
Controllable Forces

Propeller Thrust
Rotation of
propeller blade
Water Flow
Low Pressure
Propeller
Blade
High Pressure
Resulting Thrust
Controllable Forces

Controlling Propeller Thrust
• Depends on type of propellers
• Fixed Pitch Propellers
• Controllable Pitch Propellers
Controllable Forces

Controllable Pitch Propellers
• Found on all gas turbine ships and
some diesel amphibs
• 0 - 12 kts
• shaft rotates at 55 RPM
• thrust (speed) controlled by changing the
pitch of the propeller blade
Controllable Forces

Controllable Pitch Propellers
• >12 kts
• thrust controlled by changing the speed
(RPM) of the shaft.
• The shaft always spins in same
direction whether going forward or
backward.
Controllable Forces

Fixed Pitch Propellers
• Found on steam ships (carriers, subs,
amphibs)
• Cannot change pitch of propeller
• Thrust (speed) controlled by changing
speed of the shaft
• To go backwards, must stop shaft and
spin the shaft in the opposite direction.
Controllable Forces

Side Force
• Causes stern to move sideways in the
direction of propeller rotation.
Propeller
Controllable Forces

Side Force
Astern Ahead
Twin Screw
Side
Force
Bottom
Single Screw
Going Ahead
Side
Force
Side
Force
Controllable Forces

Screw Current
• Consists of two parts
• Suction Current - going into the propeller
• Discharge Current (Prop Wash)- comes out
of the propeller
Suction Current Discharge Current
Acts on Rudder
Propeller
Controllable Forces

Rudders
• Used to control ship’s heading by
moving the stern.
• To have an effect, must have a flow of
water across the rudder.
• Normally this flow of water is the
discharge current of the screw.
Controllable Forces

Rudder
Force
H
Li
o
g
w
h Pres
ss
sure Area H
Lio
gw
h Pres
ss
su
ure Area
• Acts a wing
Rudder
Water
Flow
Rudder
Force
Controllable Forces

Propellers / Rudders
• Primary means of controlling the stern
Thrust
Side Force
Rudder Force
Controllable Forces

Pivot Point
• Imaginary point on the ship’s centerline
about which the ship pivots
Pivot Point
Thrust
Side Force
Rudder Force
Controllable Forces

The ship’s pivot point
• The turning effect of a vessel will take effect about the ship’s ‘pivot point’ and
this position, with the average design vessel, lies at about the ship’s Centre of
Gravity, which is generally nearly amidships (assuming the vessel is on even
keel in calm water conditions).
• As the ship moves forward under engine power
, the pivot point will be caused
to move forward with the momentum on the vessel. If the water does not exert
resistance on the hull the pivot point would assume a position in the bow
region. However
, practically the pivot point moves to a position approximately
0.25 of the ships length (L) from the forward position.
• Similarly, if the vessel is moved astern, the stern motion would cause the Pivot
Point to move aft and adopt a new position approximately 0.25 of the ship’s
length from the right aft position. If the turning motion of the vessel is
considered, with use of the rudder
, while the vessel is moved ahead by engines,
it can be seen that the pivot point will follow the arc of the turn.

• If the turning motion of the vessel is considered, with use of the rudder
, while
the vessel is moved ahead by engines, it can be seen that the pivot point will
follow the arc of the turn.

• The combined forces of water resistance, forward of the pivot point and the
opposing turning forces from the rudder
, aft of the pivot point, cause a ‘couple
effect’ to take place. The resultant turning motion on the vessel sees the pivot
point following the arc of the turn.

Pivot point means the center of any rotational system. It is very vital to know the location of
the pivot point as the ship handling depends greatly on knowing the location of the same.
The pivot point is not a fixed point. It changes the location depending on the below
factors;-
▪ When the vessel is at rest or static, the pivot point is almost the same as that of the center
of Gravity, which is denoted by G.
▪ When the vessel moves forward, the position of pivot point shifts forward. The new pivot
point will be about 1/4th of the Length of the vessel from the forward.

▪ When the vessel moves astern, the position of the pivot point shifts towards the stern. The
new pivot point will be about 1/4th of the Length of the vessel from the stern.
• while the vessel moves astern, the pivot point moves towards the stern. This shift of the
pivot point can be made to advantage. Let's assume that both the tugs are pulling with the
same force. Since the pivot point has shifted more towards the stern, the effect of the
Forward tug will be increased automatically. The reason being that the turning lever for the
Forward tug has been increased, because of the shift of the pivot point. Therefore the action
of the forward tug will be dominant over the stern tug. Therefore the bow will move to
PORT
.

The pivot point at anchor
• It should be noted that when the vessel goes to anchor the pivot
point moves right forward and effectively holds the bow in one
position.
• Any forces acting on the hull, such as from wind or currents, would
cause the vessel to move about the hawse pipe position.
• Use of the rudder can however
, be employed when at anchor
, to
provide a ‘sheer’ to the vessel, which could be a useful action
to angle the length of the vessel away from localized dangers.

Pivot Point
Ship twisting with no way on.
Controllable Forces

Pivot Point
• Usually located 1/3 the length of the
ship from the bow. (Just behind the
bridge.)
• Pivot point is not fixed
Controllable Forces

Forces which affect
location of the Pivot Point
• Headway or Sternway
• Ship’s Speed
• Anchors
• Mooring Lines
• Tugs
Controllable Forces

Wind
• Acts on the sail area of the ship
• Exposed superstructure
• Hull structure
• Ships tend to back into the wind
• 30kts of wind = 1kts of current
Current
• Acts on the underwater part of the ship.
• Creates set and drift.
Uncontrollable Forces

Depth of Water
• Squat - Occurs a high speeds
• bow of a ship rides up onto the bow wave
• stern of a ship tends to sink
• Shallow water effects.
Uncontrollable Forces

• Headway
• moving forward thru the water
• Sternway
• moving backwards thru the water
• Bare Steerageway
• the minimum speed a ship can proceed
and still maintain course using the rudders
Shiphandling: Terms

• Stand by lines
• Take in the slack
• Take a strain
• Heave around
• Avast heaving
• Hold
• Check
• Double up
• Single up
• Take in
• Slack
• Ease
• Take to the capstain
Ground Tackle, Mooring Lines
Sequence:
Commands:
Shiphandling:

Safety
• Battle dress
• Snap back zone
• Tugs
• Pilots ladder
Shiphandling: Ground Tackle, Mooring Lines

Rudder
Force
Hliog wh Pres
ss
sure Area HLiogwh Pressssuure
Area
• Acts a wing Rudder Water
Flow
Rudder
Force
Controllable Forces

Internal and External Factors
Internal Factors/Forces
These are the factors or forces INSIDE the ship that affects how the
vessel behaves or performs during maneuvering, some examples are:
Engine Power, Specification of Propeller and Rudder, Mooring Lines
and Anchor, Thrusters and Vessel Speed.
External Factors/Forces
These are the factors or forces that happens OUTSIDE the ship
that affects the maneuvering of the vessel while underway,
approaching a port or being docked, some examples are:
Tide, A sudden change in wind velocity and direction (gust), Set and
drift, The proximity of other vessels, The depth of harbors.

External Factors/forces
● Tide - At low tide, the water will be
too shallow for the ship to move and
she will hit the bottom of the harbor.
This means that ships need to
schedule their arrival at or departure
from some ports around the high
tides at those ports. Ships' mooring
lines tighten as the tide rises, and
slacken when the tide goes out. High
tides help in navigation. They raise
the water level close to the shores.
This helps the ships to arrive at
harbor more easily.

● A sudden change in wind
velocity and direction (gust) -
The Wind Force will develop a
sideways force on the vessel,
away from the exposed side.
Making Headway with Stern to
Wind, the vessel loses “course
stability” and is difficult to steer,
this effect is greater when there
is also a following Sea or Swell.

● Set and drift - Ignoring set and
drift can cause a mariner to get
off their desired course,
sometimes by hundreds of miles.
A mariner needs to be able to
steer the ship and compensate
for the effects of set and drift
their vessel while
upon
underway. The actual course a
vessel travels is referred to as
the course over the ground.

● The proximity of
other vessels

● The depth of harbors -
Shallow water affects the
maneuverability of ships
limited
considerably. The
water depth will change the
pressure distribution
around the vessel and lead
to an increase in
hydrodynamic forces.

Internal Factors/forces under the control of the
Shiphandler
● Engine power
challenging to
keeping control.
- It can be
slow down while
This is because
reduction in propeller speed reduces
water flow over the rudder and the
rudder becomes less effective. The
conventional approach for halting is
to put engines astern. The ship will
be less responsive to steering when
a propeller is rotating astern because
the water flow across the rudder is
disrupted. In addition, there is the
disruptive effect of transverse thrust.

● Speed - The turning circle will
not increase by any
therefore
considerable margin with an increase
in speed, because the steering effect
is increased over the same period.
Generally speaking, higher speeds
mean more force on the rudder but
also more momentum. So, the head
will turn faster, but the ship will travel
farther along its previous track. The
higher momentum also means more
heeling.

● Effect of the type of propeller -
Propeller affects every phase of
performance - handling, riding,
comfort,
engine
safety.
speed, acceleration,
life, fuel economy and
In boat
are
determining
propellers
performance,
second in importance only to the
power available from the engine
itself. Without the propeller's
thrust, nothing happens.

● Rudder movement and type -
The rudder acts as a hydrofoil.
By itself, it is a passive
instrument and relies on water
passing over it to give it ‘lift’.
Rudders are placed at the stern
of a ship for this reason and to
take advantage of the forward
pivot point, which enhances the
effect.

● Thrusters - The thruster takes
suction from one side and throws
it out at the other side of the
vessel, thus moving the ship in
the opposite direction. This can
be operated in both the
directions, i.e., port to starboard
and starboard to port. The bow
thrusters are placed below the
waterline of the ship.

● Anchors and mooring lines - The
purpose of an anchor is to keep a ship
safe and secure at a desired location or
to help control the ship during bad
weather. However, to accomplish these
vital purposes, just having an anchor is
not enough. The anchor must be solid,
dependable, and used properly at the
right time and place. On the other hand,
an anchor mooring fixes a vessel's
position relative to a point on the bottom
of a waterway without connecting the
vessel to shore. As a verb, mooring refers
to the act of attaching a vessel to a
mooring.

● Tugboats - Tugboats are
small,
capable
powerful boats
large
of steering
ships by pulling or pushing
them. They are used to
assist these ships in places
where they are unable to
maneuver themselves,
such as narrow water
channels and ports.

Three Types of Basic Ship Motion
1. Longitudinal motion (forward or astern).
2. Lateral motion (sideways).
3. Rotational or turning motion.

SHIP FACTORS THAT AFFECT MANUEVERING
● Handling characteristics will vary from ship type to ship
type and from ship to ship. Handling qualities are
determined by ship design, which in turn depends on
the ship’s intended function. Typically, design ratios,
such as a ship’s length to its beam, determine its
willingness to turn.
● However, desirable handling qualities are achieved
only when there is a balance between directional
stability and directional instability.

Other Variable factors affecting ship
handling.
● Human factor – A delay in time
between your given order and the
execution of the order will affect how
you intend to move your ship. This
is caused by human factors
because the individuals you are
ordering may have different
responses depending on their training
and ability to perform the job, or that
orders have to be relayed by an
officer to the helmsman, which is a
bad practice that should be avoided
so that the conning officer should be
able to give his orders directly to the
helmsman.

● Wind and current are usually associated as both being
forces not under control of the shiphandler. The two
forces have, however, a different effect on the ship
because of the difference in nature of the two. When the
ship is affected by wind alone and moves through the
water, the hull meets underwater resistance. When, on the
other hand, the ship’s motion originates from current,
there is practically no resistance of the above-water area
to air. As water is eight hundred times denser than sea
level atmosphere, current must,
than
by nature, have
wind, especially on
considerably stronger effect
loaded ships.

OCEAN CURRENT
Ocean currents are the continuous, predictable, directional
movement of seawater driven by gravity, wind (Coriolis
Effect), and
directions:
movements
water density. Ocean water moves in two
horizontally and vertically. Horizontal
are referred to as currents, while vertical
changes are called upwellings or downwelling.
Ocean currents act much like a conveyor belt, transporting
warm water and precipitation from the equator toward the
poles and cold water from the poles back to the tropics.

● Current has a direct effect on the under-
water part of the ship and an indirect ef-
fect expressed in momentum after the
ship alters course or comes out of a cur-
rent, when the ship will carry momentum
in the direction of the current that the
ship was previously subjected to.

Effect of Wind and Current
● Whereas the effect of wind on the ship has to be
considered with respect to the pivot point, current
affects a freely moving ship as a whole and
consequently its effect is on the center of gravity.
However, when we try to keep the ship stationary relative
to the ground, we must arrest the ship’s movement and
let the ship make speed through the water contrary to
the current, in which case the ship meets underwater
resistance.
● All freely moving ships, not being subjected to wind and
dead in the water, have the same speed as the current,
whether the ships are big or small, loaded or light. Ships
not freely moving, as ships at anchor or moored, are
subjected to pressure exerted by the current, pressure
which is directly proportionate to the exposed underwater
area and to the square of the current velocity.

● In a strong tide we see that ships at
anchor, or moored to a single point, are
heading into the tide; when it is nearly
slack water ballasted ships will be more
affected by wind while the loaded tankers
still remain heading into the tide.
● When we approach the monobuoy with a
ballasted tanker in wind and tide condition,
the direction of the loaded tankers,
moored on single points nearby, gives
us an indication of the direction of the
current. However, the heading of the
ballasted ship, after having been tied up
to the buoy, may be quite different from
the heading of the loaded ship

Wind
Vessels such as Container and Ro-Ro Ships have large
freeboard and are thus more affected by winds. This exposed
area of the ship is also known as windage area as the effect of
wind is more prominent over it.
The wind effect on the same ship will be different at different
places, depending upon the draught condition of the ship. A wind
with force of 3-4 on the Beaufort scale will have similar effect in
light condition as with wind force of 7-8 when the ship is down to
her marks.
When ship is at slow speeds during maneuvering or near to the
coast, wind direction is easy to find; but this is not the case when
out at high sea. The direction of the wind perceived when
standing on deck is its relative direction. This is the resultant of
the true direction of the wind and the course steered by the ship.

EFFECT OF WIND
● Needless to say, with no tug assistance, it is wise to get
this area of ship handling right first time and also
appreciate what the limits are.
Navigators can use the wind:
1. As a good brake
2. As a device for making a tight turn.
3. To maneuver comparatively easily as long as the wind remains
about two to three points on the bow.

Vessel Stopped
● we have a ship on even keel, stopped dead in the
water. It has the familiar all aft accommodation
and we will assume, at this stage, that the wind is
roughly on the beam.
● Whilst the large area of superstructure and
funnel offer a considerable cross-section to the
wind, it is also necessary to take into account the
area of freeboard from forward of the bridge to the
bow. On a VLCC this could be an area as long as
280 x 10 meters.
● The center of effort of the wind (W) is thus
acting upon the combination of these two areas
and is much further forward than is sometimes
expected. This now needs to be compared with the
underwater profile of the ship and the position of
the pivot point (P).
● With the ship initially stopped in the water this
was seen to be close to amidships. The center of
effort of the wind (W) and the pivot point (P) are
thus quite close together and therefore do not create
a turning influence upon the ship. Although it will
vary slightly from ship to ship, generally
speaking, most will lay stopped with the wind just
forward or just abaft the beam.

Vessel Making Headway
● When the same ship is making headway,
the shift of the pivot point upsets the
previous balance attained whilst stopped,
figure 2. With the wind on the beam, the
center of effort of the wind remains where it
is but the pivot point moves forward. This
creates a substantial turning lever between
P and W and, depending on wind strength,
the ship will develop a swing of the bow into
the wind.
● At lower speeds the pivot point shifts even
further forward, thereby improving the wind's
turning lever and effect. When approaching a
berth with the wind upon or abaft the beam
that as speed is reduced the effect of
the wind gets progressively greater and
requires considerable corrective action.
● When approaching a berth or a buoy with
the wind dead ahead and the ship on an
even keel such an approach should be
easily controlled. Even at very low speeds
the ship is stable and will wish to stay with the
wind ahead until stopped.

Vessel Making Sternway
● The effect of the wind on a ship making sternway is
generally more complex and less predictable. In part this
is due to the additional complication of transverse thrust
when associated with single screw ships.
● Figure 3, we have already seen that with sternway the
pivot point moves aft to a position approximately 1/4
L from the stern. Assuming that the centre of effort (W)
remains in the same position, with the wind still on the
beam, the shift of pivot point (P) has now created a totally
different turning lever (WP). This will now cause the stern to
swing into the wind.
● Some caution is necessary, however, as the turning lever
can be quite small and the effect disappointing, particularly
on even keel. In such cases, the stern may only partially
seek the wind, with the ship making sternway 'flopped'
across the wind. This situation is not helped by the
center of effort (W) moving aft as the wind comes round
onto the quarter. This, in turn, tends to reduce the
magnitude of the turning lever WP.
● The other complicating factor is transverse thrust. If the
wind is on the port beam, there is every likelihood that
the transverse thrust and effect of wind will combine and
indeed take the stern smartly into the wind. If, however, the
wind is on the starboard beam, it can be seen that
transverse thrust and effect of wind oppose each other.
Which force wins the day is therefore very much
dependent upon wind strength versus stern power,
unless you know the ship exceptionally well, there may
be no guarantee as to which way the stern will swing when
backing.

Trim and Headway
● So far we have only considered a ship on even
keel. A large trim by the stern may change
the ship's wind handling characteristics quite
substantially.
● Figure 4 shows the same ship, but this time
in ballast and trimmed by the stern. The
increase in freeboard forward has moved W
forward and very close to P. With the
turning lever thus reduced the ship is not so
inclined to run up into the wind with headway,
preferring instead to fall off, or lay across the
wind. Because the ship is difficult to keep
head to wind, some pilots will not accept a
ship that has an excessive trim by the
stern, particularly with regards SBM
operations.

Vessel Head to Wind with
Headway
● The middle diagram in Figure 6 shows a vessel making
Headway through the water, and Heading directly into the
Wind. W is now well forward of amidships, and in fact very
close to P; the wind is exerting no turning moment, or
sideways force, on the vessel. A comparatively small
change in relative wind direction (either by alteration of
course, or wind fluctuation), will place the wind on the
vessel's bow; the whole of one side of the vessel will now
be exposed to the wind, and W will move aft as shown in
the side diagrams of Figure 6. The following effects will now
be experienced:-
● a) The Turning Force will now develop a turning moment
about P, tending to turn the vessel into the wind again.
● b) The Wind Force will also develop a sideways force on
the vessel, away from the exposed side.
● Head to Wind therefore, the vessel is "course stable",
provided that she maintains Headway through the water.
● If the ship has a large Trim by the stern W will be further
forward, with a reduction, or even loss, of "course stability".
This can sometimes result in a rapid and violent loss of
control.

Vessel Head to Wind with
Sternway.
● Consider the situation when our vessel remains Head to
Wind, but now starts to make Sternway through the water.
W remains forward, whilst P has moved aft, as shown in the
middle diagram of figure 7: the wind is exerting no turning
moment or sideways force.
● A comparatively small change in the relative direction of the
wind will move W aft, as shown in the side diagrams of
Figure 7: however P remains aft of W. The following
effects will now be experienced:-
● a) The Wind Force will develop a strong turning moment
about P, tending to turn the vessel's bow further away from
the wind.
● b) The Wind Force will develop a sideways force on the
vessel, away from the exposed side.
● Head to Wind, as soon as the vessel starts to make
Sternway through the water, she loses "course stability"
and the bow will pay off away from the wind, sometimes
quite rapidly.
● If the ship has a large Trim by the stern W may move
further forward, perhaps quickly, and the loss of "courses
stability" is even more pronounced. This can sometimes
result in a rapid and violent loss of control.

Vessel Stern to Wind with
Headway
● The middle diagram of figure 8 shows a vessel making
Headway through the water, and with the Wind directly
Astern. P is forward, a long distance from W, which is well
aft. A comparatively small change in relative wind direction
will move W forwards as shown in the side diagrams of
Figure 8: however W is still some distance abaft P. The
following effects will now be experienced:-
● a) The Wind Force will develop a strong turning moment
about P, tending to turn the vessel's Stern further away
from the Wind.
● b) The Wind Force will develop a sideways force on the
vessel, away from the exposed side.
● Making Headway with Stern to Wind, the vessel loses
"course stability" and is difficult to steer, this effect is greater
when there is also a following Sea or Swell.
● If the ship has a large Trim by the Stern, W may move
further forward, and loss of "course stability" may be
generally less pronounced, but still a potential danger.

Vessel Stern to Wind making Sternway
● The middle diagram of Figure 9 shows a
vessel making Sternway through the water,
and with the Wind directly Astern. P has
moved aft, fairly close to W, which remains
even further aft. A change in relative wind
direction will eventually move W forward of
P, as shown in the side diagrams of Figure
9, with the following effects:-
● a) The Wind Force will develop a turning
moment about P, tending to turn the vessel's
Stern back into the Wind.
● b) The Wind Force will develop a sideways
force on the vessel, away from the exposed
side.
● Making Sternway through the water, with Stern
to Wind, the vessel is again "course stable".
● If the ship has a large Trim by the Stern
W may move further forward, generally
improving "course stability"; however with
such a Trim, there is always the possibility of
an unpredictable loss of control.

Wind force
● Wind force depends on- windage,
wind velocity (wind pressure),
the angle between apparent
wind, and heading. Wind
pressure is proportional to wind
velocity squared.
● The Centre of wind pressure
depends on the distribution of
windage alongside the ship.

Ship in a beam wind
● Ship stopped
● The wind force is large.
● There is no longitudinal component.
● The behavior of the ship depends on
the center of wind pressure, which
could be in front of or behind the point
of application of transverse resistance
force (pivot point). This point is
approximately at midship.
● Ship is drifting and turning either way,
depending on the
relative position of these points.

Ship with headway
● Point of application of wind force is
behind the pivot point.
● Ship has tendency to swing
towards the wind line.

Ship with sternway
● Point of application of wind
force is in front of the pivot
point.
● Ship has tendency to swing
out of the wind line.

Wind from bow quarter
● Ship with headway
● The point of application of wind
force is behind the pivot point.
● The ship has a tendency to swing
towards the wind line.

Ship with sternway
● Point of application of
wind force is behind the
pivot point.
● Ship
swing
line.
has tendency to
towards the wind

QUESTION:
WHAT ARE
THE
FORCES
INA TURN?

104
Turning circle and dynamic
stability

 Course keeping ability is related to dynamic
stability on straight course.
 Ships can be dynamically stable or
dynamically unstable
 Ship is dynamically stable if after small
disturbance will remain on the new straight
course slightly deviated from the previous
one without using rudder.

 Dynamically unstable ship will
make a turning circle with rudder amidships
 Dynamically unstable ships are more difficult to
handle, and if the amount of dynamical instability is
large, they might be dangerous
• There is, however, no force that can bring
the ship to the original course without using
rudder.

ILLUSTRATE DIRECTIONALLY STABLE AND DIRECTIONALLY
UNSTABLE SHIP

ILLUSTRATE DRIFT ANGLE AND STATE IMO CRITERIA FOR
TACTICAL DIAMETER AND ADVANCE

 Initial turning test
 Initial turning ability is a measure of the reaction
of the ship to small angle of rudder; Is defined
by the distance travelled before realizing certain
heading deviation when rudder is
applied.
WHAT IS INITIAL TURNING ABILITY OF A SHIP
AND IMO CRITERIA

• Ship is moving along the curvilinear path with the
centre at point O. The distance between the centre of
curvature and the centre of gravity of the ship is
radius of instantaneous turn.
• Ship’s centreplane deviates from the tangent to the
path of the centre of gravity by the drift angle.
• The line perpendicular to the ship’s centreplane
through the centre of rotation,marks pivot point
(PP).
At this point, there is no transverse velocity in
turning; for people on board it appears that the ship
rotates around this point (Fig. 2.8).
Transverse velocity is greatest at stern.
•
•

question: Compare the turning characteristics wrf length , beam of ships
 Two ships of the same length have nearly the
same Transfer
 Tactical Diameter for both ships is almost the same
 Radius of the steady turning circle is much smaller
for tanker
 Drift angle is much larger for tanker
 Pivot point is closer to the bow in tanker
Comparison of Turning characteristics of
Full and Slender ship

 Effect of ship size on turning performance
 Turning characteristics depend on the
ship size. The tactical diameter is not
proportional to the displacement of the
ship but relative tactical diameter D/L is
equal for ships geometrically similar of
different size as well as for full-scale
ship and its model.

Effect of ship parameters on turning and course keeping
Manoeuvring performance depends on ship form and proportions. Table below
shows
the effect of ship performance on manoeuvring characteristics

Shiphandling: Terms
Turning Circle: The path described by a ship’s pivot
point as it executes a 360° turn.
Tactical Diameter (180°)
Final Diameter (360°)

Kick
Final Diameter
Tactical Diameter
Turning Circle
Shiphandling:
Terms

• Advance
• Distance gained toward the direction of the
original course after the rudder is put over.
• Transfer
• Distance gained perpendicular to the
original course after the rudder is put over.
Shiphandling: Terms
Advance and Transfer

Advance & Transfer 90° Turn
Kick
Advance
Transfer
Shiphandling: Terms

Kick
Advance
Transfer
Shiphandling: Terms

Shiphandling: Terms
Turning Circle: The path described by a ship’s pivot po
it executes a 360° turn.
Tactical Diameter (180°)
Final Diameter (360°)

Turning circle
▪ The turning circle of a vessel is the circle the vessel will describe when her helm is
put, hard over to starboard or hard over to port, usually with her engines full ahead.
▪ The determination of the turning circle of a vessel is normally carried out during
the sea trials of the vessel prior to handover from the builders to the owners.
▪ The turning circle, tighter with stopping distance, are placed on board of the vessel
in the trial papers, so that they can be consulted by the ship’s Master
, the watch
officers and eventually the pilots.
▪ With regard to the turning circle the following statements are usually stated in the
trial papers:-
• The advance of the vessel.
• The transfer of the vessel.
• The tactical diameter that the vessel scribes.
• The final diameter that the vessel has scribed.

Turning circle
• Turning circle information from trials or estimates for various loaded/ballast
conditions; Test condition results reflecting ‘advance’ and ‘transfer’ and the
stated maximum rudder angle employed in the test, together with times and
speeds at 90°, 180°, 270° and 360°; details should be in diagrammatic format
with ship’s outline.
• Turning circle maneuver is the maneuver to be performed to both starboard
and port with 35° rudder angle or the maximum rudder angle permissible at
the test speed, following a steady approach with zero yaw rate.
• A ship’s turning circle is the path followed by the ship’s pivot point when
making a 360° turn without returning to the initial course.
• If the vessel is fitted with a right-hand fixed propeller
, she would benefit from
the transverse thrust effect, and her turning circle, in general, will be quicker
and tighter when turning to port than to starboard.
• A vessel listed will turn more readily towards her high side with smaller
turning circle on that side.

▪ The diameter of the turning circle is equal to about 4
ship’s lengths (4L).
▪ In position 1, the helm is put hard to starboard and
the vessel will first move to port of her initial course.
The vessel also start to turn to starboard. Due to the
position of her turning point ( pivot point) at about
¼ from the bow, the bow will hardly be moving
inside the initial course but the aft of the vessel will
swing to port. Only in position 4, after 4 ship’s
lengths on the initial course, the aft of the vessel will
start to move to the inside of the initial course. In
position 5, the ship’s course will have changed about
90° to starboard.
▪ Conclusion:
If there is an obstacle straight ahead of the vessel at
a distance of less than 4 ship’s lengths, this obstacle
can not be avoided by a helm action only. The port
quarter of the vessel will hit the obstacle.

• Advance - Advance is the distance travelled in the
direction of the original course by the midship point of
a ship from the position at which the rudder order is
given to the position at which the heading has changed
90° from the original course., measured from the point
where the rudder is first put over and should not
exceed 4.5 ship lengths
• Transfer - Transfer is the amount of distance gained
towards the new course (shown here for 90° heading
change).
• Tactical Diameter - Tactical diameter is the distance
travelled by the midship point of a ship from the
position at which the rudder order is given to the
position at which the heading has changed 180°
from the original course. It is measured in a
direction perpendicular to the original heading of
the ship..
• Final Diameter - Final diameter is the distance
perpendicular to the original course measured
from the 180° point through 360° (shown here for
steady turning radius, R).
• Pivot Point - A ship’s pivot point is a point on the
centerline about which the ship turns when the rudder
is put over
.
• Drift Angle - Drift angle is an angle at any point on the
turning circle between the intersection of the tangent
at that point and the ship’s keel line.

Max.
Advance
Advance
Reach
Kick
Transfer
Max. Transfer
Tactical Diameter
Final Diameter
TurningCircle
̓̒
Regarding the method of turning circle, which is measured during a sea trial and displayed in the
bridge, in the event that it is a container ship: Max. Advance or a Max. Transfer etc., the Final
Diameter at the time when rudder is steered to full, is generally 3.5 to 4 times that of the hull
length.
However, this information is based on a vessel carrying ballast (ballast condition) and most of them
navigate at a speed of approximately 15 kts. There is no data available for when a vessel is fully
loaded and at full speed. These specifications are invaluable for the
helmsman in the event of rapid turning at
S/B being necessary (e.g. to prevent a
collision or grounding).
Maneuvering with rudder Hard Over at
Full Speed is not realistic because the
above-described trouble may occur
.
In such a situation, in order to carry out
avoidance maneuvering safely at full speed
and to remain at a safe distance from the
shore, take into account the sea area while
paying careful attention to rate- of-turn
speed.

Advance :
2.1 miles
Final Diameter :
4.2 miles
18 min.
̓̓
Focus on the rate-of-turn speed during the ship's hull turning round moment
Although it will differ depending on a ship's hull construction, speed and stability, the rate-of-
turn speed, which neither causes deceleration or engine harm, is approximately 10 degrees
per minute.
Conditions ɿ Steer at a controlled limit of 22 kts and 10 degrees per minute for rate-of-turn speed.
- Time required for turning
round at 360 degrees
ʹ 36 minutes (0.6 hours)
- Running distance over 36 minutes
ʹ 13.2 nautical miles (22 knots ͇
5VS
O3 BU
F ̍̌ EFHS
FF N J
OVU
FT
4I J
QT TQFFE LU
T
0.6 hours ʣ
For example, in the event of avoiding a
crossing vessel, it is necessary to
consider the sea area and time
required for turning round at 90
degrees.
Otherwise, calculate estimated size of
sea area, required for one turning
round, by drawing and formula and
checking it by drawing it on the nautical
chart.
Total run : 13.2 mile
ʢ ̏̒෼ʣ
Transfer :
2.1 miles
9 min.
27 min.

General remarks
▪ The turning circle conducted in shallow water will be considerably increase
compared with a turning circle conducted in deep water
.
▪ Turning a vessel with her helm hard over will cause the vessel’s speed to
decrease considerably.
▪ A deep laden vessel performing a turning circle (e.g. in case of man
overboard) will experience less effect from the wind or sea condition than in
light ballast condition.
▪ A vessel trimmed by the stern will generally steer more easily but the tactical
diameter of the turn will be expected to increase.
▪ A vessel trimmed by the head will decrease the size of the turn but will be
more difficult to steer
.
▪ A vessel conducting a turning circle with a list could normally be delayed.

▪ Turning towards a list would normally generate a large turning circle.
▪ Turning away from a list would normally generate a smaller turning circle.
▪ A vessel tends to heel towards the direction of turn once helm is applied.
▪ A vessel turning with an existing list and not being in an upright position
could in shallow waters experience an increase in draught.
▪ The type or rudder can have influence on the turning circle of a vessel.
▪ A narrow beam vessel normally make a tighter turning circle then a wide
beam circle.
▪ A vessel equipped with a right hand fixed propeller would normally turn
tighter to port than starboard.

Factors will affect the rate of turn and the size of
turning circle
1. Structural design and length of the vessel.
2. Draught and trim of vessel.
3. Size and motive power of main machinery.
4. Distribution and stowage of cargo.
5. Even keel or carrying a list.
6. Position of turning in relation to the available depth of water
.
7. Amount of rudder angle required to complete the turn.
8. External forces affecting the drift angle.

1. Structural design and length. The longer the ship
generally, the greater the turning circle . The type of
rudder and the resulting steering effect will decide the
final diameter, with the clearance between rudder and
hull having a major influence . The smaller the
clearance between rudder and hull the more effective
the turning action.
2. Draught and trim. The deeper a vessel lies in the water
, the
more sluggish will be her response to the helm. On the other
hand, the superstructure of a vessel in a light condition and
shallow in draught is considerably influenced by the wind.
The trim of a vessel will influence the size of the turning
circle in such a way that it will decrease if the vessel is
trimmed by the head. However
, vessels normally trim by the
stern for better steerage and improved headway and it would
be unusual for a vessel to be trimmed in normal
circumstances by the head.

3. Motive power
. The relation between power and displacement will affect
the turning circle performance of any vessel in the same way that a
light speedboat has greater acceleration than a heavily laden ore
carrier
. It should be remembered that the rudder is only effective when
there is a flow of water past it . The turning circle will therefore not
increase by any considerable margin with an increase in speed,
because the steering effect is increased over the same period. (The
rudder steering effect will increase with the square of the flow of
water past the rudder
.)
4. Distribution and stowage of cargo. Generally this will not affect the
turning circle in any way, but the vessel will respond more readily if
loads are stowed amidships instead of at the extremities. Merchant
ship design tends to distribute weight throughout the vessel’s length .
The reader may be able to imagine a vessel loaded heavily fore and aft
responding slowly and sluggishly to the helm.

5. Even keel or listed over
. A new vessel when engaged on trials will be on
an even keel when carrying out turning circles for recording the ship’s
data. This condition of even keel cannot, however
, always be
guaranteed once the vessel is commissioned and loaded. If a vessel is
carrying a list, it can be expected to make a larger turning circle when
turning towards the list, and vice-versa.
6. Available depth of water
. The majority of vessels, depending on hull
form, will experience greater resistance when navigating in shallow
water
. A form of interaction takes place between the hull and the sea
bed which may result in the vessel yawing and becoming difficult to
steer
. She may take longer to respond to helm movement, probably
increasing the advance of the turning circle, as well as increasing over
the transfer
. The corresponding final diameter will be increased
retrospectively.

7. Rudder angle. Probably the most significant factor affecting the turning
circle is the rudder angle . The optimum is one which will cause
maximum turning effect without causing excessive drag. If a small
rudder angle is employed, a large turning circle will result, with little
loss of speed. However
, when a large rudder angle is employed, then,
although a tighter turning circle may be experienced, this will be
accompanied by a loss of speed.
8. Drift angle and influencing forces. When a vessel responds to helm
movement, it is normal for the stern of the vessel to traverse in
opposing Motion . Although the bow movement is what is desired, the
resultant motion of the vessel is one of crabbing in a sideways
direction, at an angle of drift. When completing a turning circle,
because of this angle of drift, the stern quarters are outside the turning
circle area while the bow area is inside the turning circle. Studies have
shown that the ‘pivot point’ of the vessel in most cases describes the
circumference of the turning circle.

• Headway
• moving forward thru the water
• Sternway
• moving backwards thru the water
• Bare Steerageway
• the minimum speed a ship can proceed
and still maintain course using the rudders
Shiphandling:
Terms

Ship Ahead
Propeller Ahead
Rudder Amidships
Shiphandling: Single Screw Ships

Ship Astern
Propeller Astern
Rudder Amidships
Ship follows the rudder:
Ship will tend into the wind:
Ship will tend to port very easily
Ship does not tend to starboard easily

Ship Ahead
Propeller Astern
Rudder Amidships

Ship Ahead
Both Propellers Ahead
Shiphandling: Twin Screw Ships

Ship Ahead
One Propeller Trailing
Counteract with rudder

Ship Astern
One Propeller Trailing

Ship Ahead
Both Propellers Ahead Different Speeds

Propellers Split

Single Headline
• Simplest Tie-up
• Best to allow tug to
push or pull only
• Not good if complex
tug maneuvers
required.
Shiphandling: Tug Tie-Ups

Double Headline
• Not as simple
• Allows tug to push
or pull and complex
tug maneuvers

Power
• Most versatile tie-up
• Good for general
purpose use
• Holds tug securely
to ship.

Recovery Maneuvers
• Williamson Turn
• Anderson Turn
• Race Track
• Y-Turn
Shiphandling: Man Overboard Recovery

Easiest Method?
• Daylight: Anderson
• Night: Williamson
• Subs: Y backing
• Carriers: Racetrack
• Boat / Helo?

Recovery considerations
• Helicopter
• average time to ready for takeoff is 10-12 mins
• Small boat
• average time to launch 6-8 mins
• Ship
• fastest method

Right Full Rudder
All Engines Ahead Full
Kicks Stern Away
Man Overboard
Starboard Side

Williamson Turn
Shift Rudder
When 60° Off Course

maneuvering
• Williamson
port starboard
- slow
- good for night
or low vis
60 deg

Anderson Turn

maneuvering
• Anderson
port starboard
- fastest
- most skill

Racetrack Turn

maneuvering
• Race track
port starboard
- high speed
- easier approach

Y-Turn

maneuvering
• Y-backing
- poor control
- keeps ship
close to man

maneuvering
• tear drop
port
starboard
- Carriers
modified
racetrack

Stopping distance and
forces for stopping the ship

STOPPING OF SHIPS
CAPT RAJIV K VIG 163

Stopping distance – Stopping time
▪ The stopping distance is the distance that a vessel with her rudder amidships
and her engine full ahead, will run from the moment her engine are put astern
until she comes to a complete rest ( stop) over the ground.
▪ The time taken to complete this is call stopping time.
▪ Stopping distance and stopping time must :-
• Be expressed in ship’s lengths (L) or m. and the stopping time in minute and
second.
• Be clearly expressed on the bridge.
▪ The water resistance, at a constant speed is equal to the power of the engine
and, as a rough estimate, that water resistance is proportional to the square of
the speed ( V²).

Stopping distance – Stopping time
General remarks
▪ Suppose a vessel with a speed of 16 knots with her engines at the average power of 100%.
The water resistance in that case is also equal to 100%. The engines are stopped and the
vessel is continuing to move on her own inertia with her helm at midships.
▪ When the vessel has slow down to 8 knots the water resistance will be equal to 25% of the
inertia water resistance.
▪ The stopping distance depends for a great deal on the proportion between the propeller
power Ahead and Astern.
▪ The power of a turbine steam engine, working astern is about 70% of its power working
ahead.
▪ When applying astern propulsion to stop a ship, the ship may by considered as being
stopped when the wake reaches the middle of the ship.

▪ When the stopping time and the speed of a vessel are known, it is quit easy
to determine the stopping distance.
▪ When considering the stopping distance, take into account the distance ran from
the time the speed Telegraph is put on full astern and that the propeller actually
start to turn astern. The engineer is not always close to the manoeuvring board and
whale minute can elapse before the propeller actually turns in reverse direction.
▪ Elements such as the wind, the state of the sea, the depth of water should be taken
into account when considering the stopping distance and the stopping time.
▪ Keep in mind that when astern power is applied, the vessel will not stay on her
original course but the bow will turn either to starboard or to port depending
on the type of propeller used.
▪ For instance, with a right hand fixed propeller
, the astern will move to port and the
bow to starboard. When the vessel has come to complete rest, the vessel may well
have turned over 90°.

Stopping distance of ships
As we all know, ship like any other transport utility does not have brakes to
make them stop immediately. When the engine is given stop order
, the ship will
continue moving in the same direction due to inertia and will come to stop after
moving for some distance.
• Every ship has three different stopping distances depending on:
a. Inertia Stop.
b. Crash stop.
c. Rudder cycle stop.

Inertia Stop
• When the engine of the ship is stopped, the ship will continue moving in the
same direction for some more distance due to inertia. Here no astern
command is given (used to produce “braking effect” for ships), and hence ship
will travel more distance in the inertia stop method.
• The distance in miles may only be tenth of the initial speed for light ships, but
more than half the speed for deeply loaded ships.
• I.e. if ship speed 10 kts for laden ship the inertia stop will be about 5 N.M. if
ship speed 10 kts for light loaded ship the inertia stop may 1/10 of initial
speed which is one N.M.
• Stopping ability
• The track reach in the full astern stopping test should not exceed 15 ship
lengths.
• However
, this value may be modified by the Administration where ships of
large.
•Displacement make this criterion impracticable, but should in no case exceed
20 ship lengths.

Crash stop
• Crash stop is usually the term used when the ship has to sudden stop in
emergency situation. Here the engine, which is moving in an ahead direction
is given an order for full astern, leaving the rudder in the mid ship position to
stop the ship within minimum distance and shortest possible time. This stops
or reduces the speed of the vessel heading towards the collision course.
• Crash maneuvering is turning the engine in opposite direction to reduce the
heading speed of the ship. After certain time, the ship stops and starts
streaming in astern direction. This is done by supplying starting air at about
30 bars from the air receiver to the engine. The stopping air is known as the
brake air .
• The brake air when sudden injected inside the engine cylinder
, will try to
resist the motion of the piston and the rotation of the crankshaft and
propeller
.

Crash stop procedure
• When there is an emergency like collision, grounding etc. the controls
are transferred immediately in to the Engine room controls.
• The bridge will give astern direction in the telegraph, acknowledge the same.
• When the telegraph is acknowledged only the starting air cam will reverse
its direction but the fuel cam will remain in its running position due to
running direction interlock since engine is still running in the ahead
direction
• The fuel lever in the engine control room is brought to ‘0’
• As soon as the RPM of the engine drops below 40 % of the Maximum
Continuous Rating of the engine, give break air few times in short time frame.
• The break air will inject with astern timing setting inside the ahead moving piston
which will resist the piston motion .Since fuel will not inject until running direction
interlock opens, as soon as the rpm drops near to Zero, give fuel and air kick by
bringing fuel lever to minimum start setting.
• When carrying out Crash Maneuvering, some safeties need to be bypassed to avoid
tripping of engine in mid of emergency.
• When the ship stops and situation is under control, a detailed Main
engine inspection is to be carried out when there is a chance.

Rudder cycle
• A well tried method of using the engine to brake the forward progress of
the vessel is to initially keep the propeller going ahead but reducing the
revolutions and turning the helm from one side to the other to create a
rudder drag.
• When headway has been reduced the propeller can be reversed and
astern revolutions built up as the speed through the water declines.

• A typical Rudder Cycling maneuver for a ship
proceeding with 16 knots was carried out as
follows:
1. Initial speed 16 knots. (Full ahead)
2. Hard over to port 20° and, reducing speed to
(Half ahead)
3. After turning 40° to port, hard over the
wheel to starboard side and reduce to (Slow
ahead)
4. When the ship have passed the
original course hard over to port
5. Reduce to (Dead Slow ahead)
6. Finally when coming back to the original
course hard over to starboard and
engines (Full astern).
7. STOP ENGINE .
• The track reach of this maneuver is reduced
to less than half the crash stop.

Anchoring in emergency.
A vessel is approaching a channel in reduced
visibility, speed 5 knots. The officer of the
watch receives a VHF communication that the
channel has become blocked by a collision at
the main entrance. What would be a
recommended course of action when the
vessel was 1 mile from the obstructed
channel, with a flood tide of approximately 4
knots running astern?
1. Assuming the vessel to have a right-hand
fixed propeller
, put the rudder hard a-
starboard and stop main engines. The vessel
would respond by turning to starboard. The
anchor party should stand by forward to let go
starboard anchor
.

2.Let go starboard anchor
. Full astern on main
engines to reduce head reach. Letting go the
anchor would check the headway of the vessel
and act to snub the vessel round. Stop main
engines.
3.Full ahead on main engines, with rudder hard
to starboard. Ease and check the cable as
weight comes on the anchor
. Once the vessel
has stopped over the ground, go half ahead on
main engines, allowing the vessel to come up
towards the anchor and so relieve the strain on
the cable. Heave away on the cable and bring
the anchor home. Clear the area and investigate
a safe anchorage or alternative port until
channel obstruction is cleared.

• Stopping test
• Stopping test should be performed from the test speed with
maximum astern power.
• As indicated in figure, the ship’s track and heading after
astern order are plotted versus time.
• Head reach and lateral deviation are presented
in terms of the number of ship lengths.
• The time lag between issuing the astern order
and the moment when the propeller stops and
reverses should be measured.
Stopping test

 Test speed :
 VT= CB x VD
 VT : test speed
 VD : design speed
 CB : block coefficient
 IMO standard:
 Track reach < 15L
 QUESTION: IMO CRITERIA FOR STOPPING DISTANCE IN CRASH STOP

RUDDER CYCLING
QUESTION: FACTORS WHICH AFFECT EFFICIENT RUDDER CYCLING: SPEED,AREA OF
RUDDER, RUDDER FORCE,SIDE FORCE,DRAFT/DEPTH RELATIONSHIP

Comparison of different stopping techniques
QUESTION: What is the most effective way of achieving minimum head reach for
stopping a ship

•
•
179
Some other dangers affecting frequently tug’s safety are listed below:
Bulbous bows are not visible when they are underwater and because of their
important
dimensions the stern of the tug may touch the bow when passing or taking a towline.
Short
towlines can also create similar danger for tugs. This situation is especially dangerous
in
the case of excessive forward speed of ships to be assisted.
An inexperienced ship’s crew may not be able to release tug’s towline when needed.
After
slacking off the towline by a tug, when ship’s speed increases, the tension
simultaneously
increases in the towline dragged through the water. The releasing of the towline
becomes
very difficult, if not impossible.
•
•
•
•
•
•
•
DANGERS ASSOCIATED WITH TUG OPERATION

Type of tug co-operating with a ship,
where the main difference results
from the location of tug’s
propulsion and towing point.
The choice is between conventional
single or twin-screw tugs very often
fitted with nozzles and tractor type
tugs. The
ASD (azimuth stern drive) tugs are
the compromise linking some of
the benefits of conventional and
tractor tugs type.
QUESTION: WHAT ARE THE
DIFFERENT TYPES OF TUGS IN USE?
180
• When the bollard pull of assisting tugs is not
sufficient to counteract all external forces
• acting on a ship (underestimation of
wind force, current velocity increases),
tugs can be
• jammed between the ship and the
berth as the result of drifting ship’s
motion.
• When passing or taking a towline, the ship’s
speed and heading must be constant. Any
• change in values of the above parameters
creates additional danger to the tug. If such
a
• situation will occur, the assisting tug must
be immediately informed to anticipate
expected
• manoeuvres.

• Dangers related to ship-tug cooperation
• When assisting a ship, tugs operate in her close proximity in disturbed water pressure
• regions surrounding a ship’s hull. This is the source of interaction phenomenon,
especially
• dangerous for relatively small tugs when comparing with the size of assisted ships.
• Consecutive positions of a tug when approaching a ship to be assisted are shown in fig.
• . When the tug approaches the aft part of the ship (position 1), an increase of her speed
• may occur due the incoming flow velocity. In the close proximity of ship’s hull, a low
• pressure starts to move the tug towards the hull. For ships in ballast condition or for
ships
• having particular overhanging stern, the tug can easily come to position 2, which creates
• danger of damages to the tug’s hull and superstructure.
QUESTION: IDENTIFY DANGERS TO TUGS IN PROXIMITY OF SHIP HULLS; WHAT IS
GIRTING
181
•

•
182
Proceeding further along the hull (position 3), the tug is under important suction
force
oriented towards the ship’s hull and outward turning moment due to tug bow-
cushion. Once
sucked alongside it is very difficult to get off again and to continue the way.
Tug in position 4 enters the high-pressure area. Arising outward turning moment
must
be eliminated by appropriate use of rudder and engine. When arriving to position
5 close to
• the bow, very strong “out force” acting on the stern tries to bring the tug to
position 6
• broadside under the bow with risk of capsizing. Immediate action of rudder and
use of
• available power (full astern) can correct the position. Tractors type tugs are less
vulnerable in
such a situation.
•
•
•
•
•
 The main source of danger for a tug when assisting a ship is ship’s too high
speed.
 Classical tug accidents (so-called “girting”) are presented in next three figures.
In fig., a tug working on a line is assisting a ship making a turn to starboard
(position 1). Ship is suddenly accelerating for example to improve turning abilities
in order to realise the turn correctly. The speed after few moments becomes too
high and the consecutive tug positions are more and more aft with high tension in
the towline (positions 2 and 3). The danger of capsizing is then real.
The above-described situation is less dangerous for tractor tugs because
their towing point lies at the aft. So-called “gob rope” for conventional tugs
can improve much the situation by shifting the towing point more to the
stern, but on hand it limits the manoeuvrability of the towing tug.

SHIP DEAD IN WATER
PLACEMENT OF TUGS
Pivot point at midship.
Two tugs pulling or
pushing
sideways.
Ship is shifting to one
side without swing if
both tugs develop
equal pulling or
pushing forces and
levers are
the same.
CAPT RAJIV K VIG 32

SHIP MAKING HEADWAY
Pivot point shifts forward.
Stern tug working on large
lever is more effective.
Ship has a tendency to swing
to port.
QUESTION: WHICH TUG IS MORE EFFECTIVE I. GOING
AHEAD
II) MOVING ASTERN
CAPT RAJIV K VIG 33

 Pivot point shifts aft.
 Stern tug working on
small Lever (less
effective)
 Bow tug working on
large Lever
 Ship has a tendency to
swing to starboard
Ship making sternway
CAPT RAJIV K VIG 34

Mooring Lines
2 1
3
4
6 5
Bow
Line
Stern
Line
Spring Lines
After Bow
Spring
Forward Bow
Spring
After Quarter
Spring
Forward Quarter
Spring

Mooring Lines
• Lines
• 1-6
• Lines 1 and 6 are thicker than others
• Mooring procedure
• fake out lines
• safety brief
• heaving lines

Mooring Lines
• Terms:
• Heaving Line
• Tattletale
• Fenders
• Capstan (p. 188 Seamanship)
• Rat Guards (p. 175 Seamanship)

Deck and Pier Fittings
Shiphandling: Ground Tackle

Mooring Lines
2 1
3
4
6 5
Bow
Line
Stern
Line
Spring Lines
After Bow
Spring
Forward Bow
Spring
After Quarter
Spring
Forward Quarter
Spring
Shiphandling:
Ground Tackle, Mooring Lines

Anchors
• Most common anchor
• Standard Navy Stockless
• Most ships have two
• Deep water anchor - 14 shots of chain
• Normal anchor - 12 shots of chain
• Shot - 15 fathoms (90 feet)
Shiphandling: Ground Tackle, Anchors

Scope of Chain
15 fathoms
30 fathoms
45 fathoms
60 fathoms
Shiphandling: Ground Tackle, Anchoring

Anchoring
• Approach
• Standby
• Let Go the Anchor
• Reports
• P. 194 (Seamanship)
• Anchor watch
Shiphandling: Ground Tackle, Anchoring

• Concerns:
• Watch the stern/pier
• Watch for other
ships
• Winds / Currents
• Set on or set off pier?
• Using mooring lines
and tugs as
necessary to control
bow / stern
Shiphandling: Getting Underway, Mooring

Getting Underway, Mooring
The Ideal Approach
• Approach on a converging course 10 to
20 degrees from the heading of our
berth.
• When parallel, swing the rudder
opposite the pier, and stop the ship.
• Stop headway by backing outboard
engine.
• “Walk” the ship in by tensioning line 1;
“twist” the stern with the engines.
Shiphandling:

Less than Ideal Conditions
• Being Set On:
• Stop parallel to the pier, with 1/2 a beam
width of open water between you and the
pier.
• Allow the current to push you onto the
pier.
• Being Set Off:
• Make your approach at a larger angle to
the pier at a considerable speed.
• Be careful not to part your bow line.

• Easier than anchoring
• Buoy held securely by several anchors.
• Chance of dragging reduced.
• Two methods
• Ordinary
• Trolley
Requires:
MWB / RHIB with boat crew
Your ship
A buoy

Conning Officer
• Drives the ship’s heading and speed
through standard commands (orders) to
the helm and leehelm
• Helm - controls the rudder
• Leehelm - controls the propellers
Shiphandling: Standard Commands

Basic Format
Conning Officer
Command
Verbatim Repeat back
(Carries out command)
Report
Acknowledges Report
Helm / Leehelm

Standard Commands
HELM CONSOLE
Shiphandling:

ENGINE ORDER TELEGRAPH

Investigation of Environmental Conditions (harbour conditions)
Harbour conditions must be investigated each time a port is entered,
not only just the first time.
For liner services, conditions must also be investigated and verified at
appropriate intervals as well.
Such investigation requires the collection of as much data as possible
and verifying it with the local agent.
Recently it has been possible to find information out via the Internet.
However, many vessels do not have an Internet connection, and it is
therefore desirable that a shore team collects the relevant data and
provides it to the vessel.

̑
1. Investigation of Geographical Conditions and Conditions
Associated with Harbour Facilities
2. Investigation of the Navigation Environment
(e.g. buoys, fishing vessels, fishing reefs,
shipping movements)
3. Investigation of the Social Environment (local regulations and
navigation restrictions)
4. Investigation of the Natural Environment
(e.g. wind, tides, visibility, wave direction)
Tidal Information
through the Internet

Example of Investigation of Geographical Conditions
(1) Maximum Permissible Draft and Under Keel Clearance (UKC)
Maximum permissible draft and Under Keel Clearance (UKC) are
important information in making decisions on safe entry of the
vessel to harbour
.
As shown below, UKC is a value indicating the margin between
the sea bottom and the bottom of the hull. For example, if the
water depth and draft are the same (UKC = 0), there is a
possibility that the vessel may run aground, and entry to harbour
is therefore unsafe.

̓
= Relationship Between Maximum Permissible Draft and UKC =
The relationship between maximum permissible draft and Under
Keel Clearance is as shown by the following calculation.
The maximum permissible draft must consider errors and a safety
factor together with the variables in the calculation. It is also
necessary to investigate the maximum permissible draft for each
harbour (or each berth) to determine problems.

Most harbours set guidelines for UKC, and many harbours throughout
the world manage UKC together with data on weather and sea
conditions to ensure a margin for navigation. many harbours employ
fixed UKC which is a proportion of the draft, or a set value in meters.
The European Maritime Pilots’ Association and the Japanese harbour
technical criteria employ the following guidelines.
̔

On charts, the allowable limit for error in water depth at the international depth
datum is as follows.
Water depth to 20m
Water depth to 100m
Water depth to 100m or more
: Up to 0.3m
: Up to 1.0m
: 10% of water depth
The actual water depth is the depth on the chart, plus or minus the tide level. The
tide level is obtained from the tide table. Since this tide level is a predicted value
which can be calculated from a fixed datum, it must be considered that the actual
tide level may differ
. If the diurnal inequality and abnormal weather conditions etc.
are ignored, the accuracy of the tide table is within 0.3m of the actual value.
̕
= Water Depth and Tide level =

= Vessel’s Sinkage While Underway =
When a vessel begins moving the
distribution of water pressure around it
changes, and the hull lowers slightly in the
water
.
When navigating in harbours, therefore,
the amount of this sinkage of the vessel in
the water must be added to the draft while
at berth.
This amount becomes greater as the
water becomes shallower, and as speed
increases, as shown in the following graph.
Large vessels are operated at low speed
(S/B speed) in harbours, and it is
therefore appropriate to estimate the
sinkage of the vessel as 0.1 – 0.2% of the
length of the vessel.
It is also necessary to consider sinkage of
the vessel due to rolling, pitching and
yawing of the vessel with wind and waves,
and swell.
̍̌

= Example Calculation to Decide Whether or Not to Enter Harbour =
LOA = 200m, draft = 12.00m
• Maximum draft of vessel: Draft at departure (or expected draft at arrival) +
amount of sinkage of vessel (0.2% of LOA)
12m + 200m x 0.2%(0.4m) = 12.40m
• Safety factor for water depth on chart: 0.6m (water depth error + tide level error)
• UKC: 10 – 20% of maximum draft (depending on sailing area),
15% in calculation = 12.40m x 15% = 1.86m
Minimum Required Water depth = 12.40m + 0.60m + 1.86m = 14.86m
̍̍

̍̎
(2) Turning Basins
When entering and leaving most harbours, the vessel will use its
own power, or auxiliary facilities such as tugs or bow thrusters, for
turning. The harbour design criteria guidelines specify as standard a
circle of a diameter three times the length of the vessel when
turning under its own power, and twice the length when turning
with the assistance of tugs.
Many harbours do not provide
sufficient area as shown in the
following diagram. In such cases,
it is necessary to investigate the
relevant points sufficiently in
advance (verifying the number of
tugs required, and determining
the procedure for turning the
vessel., etc.)

(1) Maximum Size of Acceptable Vessel at Pier
= Design Criteria for Harbour Facilities =
Technical criteria for harbour facilities according to Japanese ministerial
ordinances are as follows. Verify that sufficient pier length is available
based on the length of the vessel. The same considerations apply in
other countries.
Example of Investigation of Port Facilities
̍̏

Strength of Mooring Bitts
It is also necessary to verify that the mooring bitts on the pier are able
to withstand mooring of the vessel. Strength of mooring bitts in
accordance with Japanese harbour technical design standards are as
follows.
̍̐

Fenders
Fenders are also an important item of equipment for safe mooring of
the vessel. Particularly when a swell enters the harbour, insufficient
fenders may result in damage to the pier and to the hull of the vessel.
If damaged fenders are discovered after entering harbour, they should
be photographed to guard against claims later on.
̍̑

Tugs
Tugs are an important means of assistance when maneuvering while
entering and leaving harbour
. Verifying the number and power of tugs is
an important part of the investigation of harbour conditions.
= Power and Number of Tugs =
• Size and loading condition of the vessel
• Conditions of main engines, rudders, and anchors of the vessel
• Weather and sea conditions (wind direction, wind force, direction and speed of
tidal flow, waves)
• Method of approaching and leaving the pier (mooring toward the direction of
arrival and departure)
• Water depth in the area (consider effects of shallow water)
• Availability of thrusters
• Area available for maneuvering
̍̒

Guidelines are commonly set for the number of tugs required at each
harbour. Use this information for reference.
When no guidelines have been set, use the following equation to
determine the necessary power in conjunction with the deadweight
of the vessel.
̍̓

It is possible to reduce the number of tugs if they are fitted with
thrusters.
While bow thrusters operate only in the transverse direction, tugs
have a significant difference in that they allow towing and pushing at
an angle.
It is important to increase the number of tugs used when entering
or leaving harbour without hesitation in bad weather and sea
conditions.
Bow thruster Tug (towing and pushing at an angle)
̍̔

Vessel Maneuverability
Approximately 70% of incidents of damage to harbour facilities involve
damage to piers and fenders, however most are due to mistakes in
operation of the vessel.
Such mistakes in confined harbours with limited area available for
maneuvering are due to the following;
(1) Inability to accurately determine the effects of external
forces such as wind and tides.
(2) Mistakes in speed control and turning of the vessel while
using engines and tugs.
The ship navigator gradually reduces speed in
accordance with the distance remaining, and is
required to adjust speed and turn the vessel while
considering its type, size, loading condition,
inertia, maneuverability, and the effects of external
forces.
̍̕

Effects of External Forces (wind)
ᶃ Straight ahead if no external forces are acting
in windless conditions.
C
/ WЌ
/ WB
: WB
Wind
G
ᶄ When the wind is at 45˃ to starboard, the vessel is pressed to
leeward. The point at which the wind acts (C) is ahead of
the vessel’s center of gravity (G), and a turning moment
(N (Vα)) acts to turn the vessel in the leeward direction.
ᶅ When the vessel begins drifting (diagonally) leeward, water
: WЌ
E
Water Resist.
Direction of Ship
Movement
resistance is generated on the leeside of the bow. The point (E)
at which this force acts is ahead of the point at which the wind
pressure acts (C), and a turning moment (N (Vβ)) acts to turn the
vessel in the windward direction.
β
: WМ
/ WМ
ᶆ The vessel turns under the turning moment of the wind or water resistance, whichever
is the greater
. Since water resistance is normally much greater than air resistance,
the vessel begins to turn windward. (N (Vβ) > N (Vα))
ᶇ The rudder acts against the turning moment, i.e. the vessel is controlled with the
moment N (Vσ) generated by the rudder angle (σ).
ᶈ Finally, with turning moment of the wind, water resistance, and rudder in
equilibrium, the vessel maintains a course at the angle β (leeway) to the right
ahead, and proceeds with drifting leeward.
=Transverse Movement and Turning Under
Wind Pressure While Underway=
̎̌

̎̍
The point (C) at which the wind acts approaches the vessel’s center of gravity (G) the
closer the relative wind is to the transverse axis of the vessel. At 90˃ (abeam) it acts
almost entirely on the vessel’s center of gravity. As a result, the turning moment N (Vα)
acting in the leeward direction is reduced (turn), and the force Y (Vα) acting on the vessel
in the leeward direction increases (drift), and the diagonal angle increases, increasing the
turning moment N (Vβ) due to water resistance.
Furthermore, when the relative wind moves from the transverse to the rearward
direction, the point (C) at which the wind acts moves from the vessel’s of gravity
towards the stern, the turning moment N (Vα) rounds up the bow, and acts in the same
direction as the water resistance.

̎̎
The course can be maintained if the moment derived from the wind and water resistance
can be controlled with the rudder
. If such control is not possible, an increase in the turning
moment due to water resistance increases, and the course can no longer be maintained.
This graph shows the ratio of wind speed
(Va) to speed of the vessel (Vs) on the
vertical axis, and the relative wind angle
on the horizontal axis, and indicates the
regions in which the course can and
cannot be maintained with a rudder angle
of 30˃. If the ratio of wind speed to vessel
speed exceeds 3.7, a region occurs in
which the course cannot be maintained
due to the relative wind angle.
At vessel speeds of 6 – 8 knots (3.1 – 4.1m/sec) inside the harbour, a wind
speed of 11 – 15m/sec results in a ratio of wind speed to vessel speed of
3.7, and the course may not be able to be maintained in these conditions
depending on the direction of the relative wind.

̎̏
In the following graph, rudder angle is shown on the vertical axis, and the regions in
which the course can and cannot be maintained for each ratio of wind speed to vessel
speed. When the ratio of wind speed to vessel speed (Va/Vs) reaches 4, depending on the
angle of the relative wind, a region in which the course cannot be maintained occurs,
despite a rudder angle of 30˃.

̎̐
It is important to maneuver the vessel while
considering the rounding up angle leeway (β)
when navigating in a channel without the
assistance of tugs under wind pressure.
In such cases, wind direction and speed,
and vessel speed, must be considered, and
an investigation conducted to determine
whether or not maneuvering is possible in
the region in which the course can be
maintained.
The maximum allowable wind speed for
entering and leaving the harbour is very
often set, however hull shape etc. should be
considered together with the criteria
established for the harbour in question.

Leeway of 3˃ to starboard to ensure passage
under center of bridge. (Incheon Port)
Modern radar with
advanced technology
displays generally
incorporates GPS
information. If this
function is used skillfully
the leeway angle and
direction of drift can be
understood in numerical
terms. This information is
effective in maneuvering
the vessel.
̎̑

Turning the Vessel using 1(one) Tug Boat(Free of External Force)
When turning with one tug pushing at the stern (or bow), the center of the turn is the
pivot point (P), rather than the center of gravity (G). Turning the vessel on the spot in a
circle of radius 1/2L (L being the vessel length) is therefore not possible.
The radius of area required for turning can be found with the following equation.
Turning radius (R) = GP + 1/2L
C
P
G
1/2 L
GC
GP
L: Turning radius of moment of inertia around
vertical axis through center of gravity (G)
˺ 0.35L
P: Pivot point, center of rotation when turning
vessel
G: Center of gravity
C: Point at which tug acts on vessel
̎̒
ː Turning the vessel

G
Пʹ̡̎
10m/sec
Simulator
(Container)
̎̓
Turning within a circle of diameter 1L using 2 tugs under Wind Effect external Force
A simulation was run of turning a container vessel of 246m
in length subject to winds of 10m/sec at 45˃ to starboard
at the beginning of the turn, using two tugs. The tugs were
used solely for turning, and no adjustment was made for
drift.
While dependent on hull shape and vessel
type, a wind speed of 10m/sec is the limit,
even if a 2L circle is available for turning this
vessel. A larger area is required for turning at
wind speeds in excess of 10m/sec.
-PB N
-QQ N
#SFEUI N
%FQUI N
%SBGU N
%JTQ ,5
5SJN N
( QPTJUJPO
8JOE
1SPKFD
U
'SPOU
ᶷʣ
4JEFʢᶷʣ

Speed Control
Incidents of failing to control a ship’s speed while entering harbour, with
the vessel consequently colliding with the pier causing major damage to
the pier, shore cranes, and the vessel itself, never cease.
Ships differ from motor vehicles in that they
are not fitted with a braking mechanism to
reduce speed. Control of speed must
therefore rely on controlling the speed of the
main engine, reversing the main engine, or
the assistance of a tug.
In order to ensure that the vessel stops precisely at the scheduled
point, the ship navigator is required to consider its type, size, loading
condition, inertia, and maneuverability, and the effects of external
forces etc. when adjusting speed.
̎̔

̎̕
These factors are obviously not formally calculated while the vessel is
approaching the pier, and lack of communication between the pilot
and captain is a cause of incidents, as is insufficient advice from the
captain.
Both the captain and pilot are required
to have a quantitative, rather than an
intuitive exchange of information, based
on experience, understanding of the
stopping distance and the time required
to stop.

Basics of Stopping Distance, Vessel Weight, and Acceleration
Hull shape and resistance must be considered when determining details
such as stopping distance and the time required to stop, however
approximate values can be derived with the following equation based on
the principle of conservation of energy.
̏ ̌

̏ ̍
W.: Apparent displacement (displacement + additional mass*) (tons) Vo
: Initial speed (m/sec)
X. : Final speed (m/sec)
F : Forces acting (tug thrust and reverse engine thrust) (tons)
T : Elapsed time (seconds)
S : Forward movement (m)
Α : Acceleration applied to vessel (m/sec
2
)
* Additional mass
When accelerating and decelerating the vessel, the vessel itself moves,
while at the same time, the water in the vicinity also moves as a result of
this movement.
Power is therefore not only required to move the vessel, but to move a
part of the water in the vicinity.
This is, in effect, the same as moving a vessel of increased mass. This
increased mass is referred to as ‘additional mass’.

Speed Reduction Plan for Vessel Approaching Pier in Direction of
Arrival (example)
When approaching parallel to the pier in the direction of arrival it is
necessary to determine in advance when to stop the engine, and to
understand guidelines for evaluating whether or not speed through the
primary waypoints is excessive while approaching the berth.
For example, while moving forward at dead slow ahead as shown in the
following image, when stopping the engine with simultaneous braking
applied by a stern tug, and with a distance to the stop position of 4L and
1L, it is necessary to determine beforehand the speed at which it is
possible to stop at the scheduled point.
While incorporating a safety margin in the distance to the berth noted
above, it is also needed to reduce speed by increasing the braking effect
of the tug or by reversing the engine if the approach to the berth is at a
greater speed.

In practice, rather than maneuvering the vessel to stop at the stop
point, braking is applied while controlling speed so that the vessel
stops at the target at the front of the berth without losing control.
Verify displacement of vessel, power at engine astern,
and power of tug, verify the distance and time
required to stop during maneuvering for approach,
and maneuver the vessel with a safety margin.
̏ ̏

Reference Values for Reducing Speed
The spreadsheet below presents the equation in (4)-1 in a format
ready for data entry. Enter the necessary data to calculate approximate
values for stopping distance and stopping time, and safety margin. It is
important to recognize reference values for the stopping distance of the
vessel using simple spreadsheets. Early braking by tug or reversing the
engine is necessary if the safety margin is 0.3 or less.
̏ ̐

̏ ̑
In addition to this
spreadsheet, it is also
effective to consider the
maneuverability of the
vessel in preparing
speed reduction
guidelines in graphic
format.
The guidelines should
be posted on the bridge,
with copies kept in
storage. The guidelines
can be provided to the
pilot as reference
material for information
exchange upon
boarding to assist in
communication.

Up to 20,000GT
(conventional method)
Conventionally, the vessel approaches at an angle on a face line of
the pier, the bow line is taken, and the stern is pushed to the pier
.
This method is still used with vessels of up to 20,000GT.
However larger vessels generally approach and position parallel to
the pier at a distance of 1.5 – 2 times the beam, and are then pushed
sideways onto the pier by a tug (parallel approach).
Large vessels
exceeding 20,000GT
(parallel approach)
Control of Berthing Velocity When Approaching the Pier
̏ ̒

̏ ̓
= Advantages and disadvantages of the parallel approach =
[Advantages]
• While this depends on the layout of the pier, a mistake in reducing
speed does not result in damage to the pier
. When the pier is of
considerable length, a mistake in speed control simply results in
overrunning the scheduled stop position, and does not result in
damage to the pier
.
• With the conventional method, container ships etc. with large bow
flares sometimes damage cranes etc. overhanging the pier.
This risk is much reduced with the parallel approach.
• The attitude of the vessel is more easily controlled with the parallel
approach, facilitating response to rapid changes in external forces.
[Disadvantages]
• An extra 10 – 20 minutes is required to reach the pier
.

(5) Berthing Velocity Control
The energy of the vessel when contacting
the pier can be calculated with the following
equation, and is proportional to the square
of the speed of contact.
E
W’
G
V
C
: Contact energy (ton-m)
: W (displacement (tons) ʷ transverse additional mass coefficient (1-0 – 2.0)
: Acceleration due to gravity (m/sec2)
: Berthing Velocity (m/sec)
: Energy diminution coefficient due to turning etc.
̏ ̔

Contact
energy
(t-m)
Berthing Velocity (V cm/sec)
Using an additional mass coefficient of
1.8, and C of 0.5 in the above equation, a
container vessel with a displacement of
50,000 tons approaching the pier at a
speed of 10cm/sec has a contact energy
of approximately 23 ton-m.
This is equivalent to a 1 ton motor
vehicle colliding with a wall at 80km/h.
Vessels generally approach at a maximum speed of 10cm/sec, with large
vessels and VLCCs approaching at 5cm/sec.
These speeds allow absorption of the energy of the vessel when
contacting the pier fenders, and prevent damage to the hull and the pier
.
̏ ̕

Preventing Damage to Harbour Facilities
· Grasp External forces
· Control the attitude and speed of the vessel appropriately while
maneuvering.
· It is necessary for the captain to plan the procedure for entry
and exit in advance.
· Bridge Resource Management During Harbour Entry and Exit S/B
When the pilot boards the vessel, present the pilot card, and
explain draft, displacement and other points of special note.
Officers stationed at the bow and stern report repeatedly on
movement of the tugs.
̐̌

· Bridge Resource Management During Arriving and and Departure
S/B in Harbour
Consult with the navigator on the day prior to harbour entry for a briefing
on harbour entry and exit procedures.
When the pilot boards the vessel, present the pilot card , and explain draft,
displacement and other points of special note.
Obtain information from the pilot on where the tug is to be taken up,
whether the pier is to be approached on the ship’s port or starboard side,
and the number of mooring lines etc. to be used. If there is time available,
verify the requirements for maneuvering of the vessel (e.g. turning point).
̐̍

· Ensure that the officer on the bridge reports engine speed (when engines
are operated), and that the helmsman reports rudder status as appropriate.
When the engine is stopped in the final stages of approaching the pier, the
officer may begin tidying up the bridge and he / she may neglect to report
the berthing velocity of the vessel. It is important that the required
information (e.g. ahead/astern speed, berthing velocity) is reported
appropriately until an instruction is received from the captain that it is no
longer necessary.
· Officers stationed at the bow and stern report repeatedly on movement of
the tugs.
In non-English-speaking regions in particular, the pilot and captain of the tug
frequently converse in the local language, and information on movement of
the tug may not reach the captain of the vessel. It is important that officers
stationed at the bow and stern report concisely whether the tugs are
pushing or pulling the vessel, and in which direction etc.
̐̎

· Mooring lines are set in consultation with the pilot or Master. Even after
the lines are tied on the bitts, they are generally left un-tensioned (with no
slack).
It is important to follow the instructions of the ship navigator when winding
in mooring lines to control the attitude of the vessel.
It is always necessary to verify any doubts.
This applies not only the captain, but also to
the crew. The captain is responsible for
creating an atmosphere in which this
behavior is encouraged.
̐̏

A ship’s anchor drags
The impact of external forces
Dragging Anchor
>
The holding power of the anchor
and cable.
Masters and deck officers should be
aware of how various parameters, such as
the scope of cable in relation to the depth
of water and the effects of wind, wave
and tidal forces on the vessel, can in turn
exert excessive forces on the anchor and
cable system leading to break-out of the
anchor from the ground and dragging.
The reason why an anchor drags
̐̐

Empirical or Rule of Thumb Methods for Assessing
the Minimum Required Length of Anchor Chain
d: Water depth(m)
L: Minimum Required Length of Anchor Chain(m)
· Japanese publication Theory of Ship Operation
Fine weather :
Rough weather:
L = 3d+ 90 m
L = 4d+145 m
· United Kingdom publication Theory of Ship Operation
L = 39 x ˽
̳ m
̐̑

Traditional means of detecting a dragging anchor
ᶃ Checking the ship’s position, to confirm whether it is
placed outside of a turning circle.
ᶄ The bow cannot stand against the wind.
ᶅ The ship’s side against the wind hasn’t changed.
ᶆ Checking to see there is no slacking of chains just before a
ship’s side against the wind turns.
ᶇ Checking whether there
are extraordinary vibrations
through the anchor chains.
ᶈ Checking the course recorder in
case it does not indicate a
“figure-of-eight” motion locus.
̐̒

The above methods remain well-tried but,
of course, only confirm that the anchor is
dragging. They do not predict when
dragging is likely to commence.
According to one current study, an analysis of anchor
dragging has shown that there are two associated
phenomena, or stages, to the process which indicate
that dragging may be about to occur before it is detected by
the more usual methods outlined above.
̐̓

· The First Stage : Dragging Anchor with Yaw and Sway
Yaw and sway motion of a vessel when
lying to an anchor is sometimes referred
to as “horsing”. Area [A] in the diagram
shows the situation where the ship is lying
at anchor and yawing in a “figure-of-eight”
motion.
It has been found that as wind pressure
force begins to exceed the anchor’s
holding power, the ship yaws and is
pressed to leeward, as shown by area [B]
in the diagram.
It is suggested that, during this period, it should be
relatively easy to control the maneuverability of a ship in
such a state and to weigh the anchor.
̐̔

· The Second Stage : Anchor Dragging caused by Wind Pressure
Where wind pressure force gradually becomes stronger, one
side of the ship turns against the wind and is then pressed and
moves to leeward at a certain speed, as shown in area [C] in
the diagram.
It is suggested that, during this stage, it is difficult to weigh
anchor and, even if possible, this takes a considerable amount
of time. If weighing the anchor cannot be accomplished, the
ship loses its maneuverability.
Dragging anchor may not be detected by the Traditional
Methods until the vessel has entered the second stage
described above, by which time it may be too late to avoid a
dangerous situation from developing.
̐̕

Early prediction and detection of the dragging of an anchor is
also possible using the ship’s wake indicators in the ECDIS,
RADAR and GPS displays. Therefore, counter measures for the
safety are required to be taken as earlier as possible.
ECDIS
AREA ʮ
̗ʧ
RADAR
AREA ʮ
̗ʧ
GPS
AREA ʮ
̘ ʧ
̑̌

ː 3.2 Wind Pressure Force Calculation
Hughes Formula
В : Wind direction from bow [degree]( Relative Wind Direction )
7B : Headwind speed [m/sec]
ρ : Air density [0.125kg ɾ sec2 /m4 ]
A. : Ship’s projected area from bow above waterline [m2]
B. : Ship’s projected area from side above waterline [m2]
a : Length from bow to wind pressure center [m] (Point of
Action )
RB : Resultant wind pressure force[kg] → divided by
1,000 to be “ton” ( Total Wind Force )
α : Wind pressure force angle[ degree]( Angle of Action )
CRa : Wind pressure force coefficient.
Passenger : 1.142 - 0.142cos2В 0.367cos4В- 0.133cos6В
General Cargo : 1.325 - 0.050cos2В- 0.350cos4В- 0.175cos6В
Tanker & Bulk carrier
: 1.200 - 0.083cos2В- 0.250cos4В- 0.117cos6В
Resultant wind pressure force is proportional to the square of wind speed.
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̑̍

ː 3.3 Holding Power created by Anchor and Anchor Chain
S : Catenary length against the external force (m)
Z : Water depth + Hawsepipe height from sea surface (m)
M : Minimum Required Contacted length of the chain (m)
L : Minimum Required Length of Anchor Chain (m) (= S + M)
5Y: External force (kgf)
H (Holding Power created by Anchor and Anchor Chain)
= Ha + Hc = λa x Wa’ + λc x Wc’ x M
̑̎

H : Holding power created by Anchor and Anchor Chain (kgs)
Ha : Holding power by Anchor (kgs)
Hc : Holding power by Anchor Chain (kgs) ( Resistance of cable)
Wa : Anchor Weight in Air (kgs)
Wc : Anchor Chain Weight per m in Air (kgs)
Wa’ : Anchor Weight in Water (kgs) = 0.87 x Wa (kgs)
Wc’ : Anchor Chain Weight per m in Water (kgs) = 0.87 x Wc (kgs)
M : Minimum Required Length of Anchor Chain (m)
λa : Anchor Holding Factor
λc : Anchor Chain Holding Factor
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Calculating the Catenary Length of an Anchor Chain
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S : Catenary length against the external force (m)
Z : Water Depth + Hawsepipe height from sea surface (m)
Wc’ : Anchor Chain Weight per m in Water (kgs)
= 0.87 x Wc (kgs)
Tx : External force (kgf)
Under the condition that L [Minimum Required Length of Anchor
Chain (S + l ) ] is fixed at a certain level, if Tx [External force (kgf) ]
increases, S [Catenary length against the external force(m) ] will
also increase.
On the contrary, however, l
[Minimum Required Contacted
length of the chain (m) ] decreases
so that H[Holding power created by
Anchor and Anchor Chain (kgs) ]
will be diminished.
̑̐

ᶃ→ᶄ From right to left. Anchor chain is
tight condition
ᶅ Left side position. Anchor chain
become relaxes.
Biggest Impact Force
ᶆ
ᶇ→ᶈ From left to right. Anchor chain is
tight condition
ᶉ Right side position. Anchor chain
become relaxes.
Biggest Impact Force
ᶊ
In this way, the ship’s center of gravity is
moving in a “figure-of-eight” pattern as
illustrated by the green track in the
diagram.
ː 3.5 Horsing (Yawing and Swaying)
Motion and Impact Force
̑̑

̑Ship’s operational safety measures for anchorage and their effects
Counter measures
Increase draught by
taking in ballast water
Effectiveness
Ship’s weight is
increased so that
vessel’s motions
(Horsing) are decreased.
The point of action
shifts afterward and
tends to decrease the
horsing motion.
Increases anchor chain
holding factor
.
Extended catenary
length absorbs more
external force on
anchor
.
Remarks
Consider stability issues.
Trim by the head Consider stability issues.
Maintain propeller
immersion.
Veer more anchor cable Consider that weighing
anchor is difficult in
rough sea conditions
and more time will be
required to weigh the
anchor.

Counter measures
Drop the other anchor
Effectiveness
Can reduce yawing and
horsing motion by half,
and reduce force on
anchor by 30%ʙ 40%.
Remarks
Consider amount of
second cable required is
one and a half times the
depth of water
.
Consider the possibility
of fouling the cables,
particularly when
pitching heavily.
Danger of fouling an
anchor if the vessel is
turned under the
influence of wind
and/or tide.
From the outset of
anchoring, to deploy
both anchors
Riding to two anchors
is said to increase
holding power and to
decrease horsing
motion.
̑̕

Counter measures
Use of bow thrusters
Effectiveness
By stemming the wind,
this can effectively
reduce the horsing
motion and ease cable
tension. If the power of
the bow thruster is 80%
of the wind force on
the bow, it is said that
width of oscillating
motion and impact
force are diminished by
about 40%.
Remarks
The possibility that
extended use of the
bow thrusters may not
be possible for
technical reasons.
Ensure that the bow
thrusters are kept
submerged when the
ship is pitching and
rolling.
̒̌

Counter measures
Use of the main
engine in combination
with steering
Effectiveness
This can be an
effective deterrent to
the horsing motion
and will relieve the
tension on the anchor
and cable system.
Remarks
Do not allow the vessel
to pay-off suddenly
when the tension on
the anchor cable has
been eased as a
sudden increase in
tension may break-out
the anchor. Do not
allow the vessel to
override the anchor,
particularly in shallow
water where the vessel
could impact on the
anchor if pitching.
̒̍

̒̎
=Example calculation of the increase in holding power when cable is veered =
Ship’s type
Anchor Weight in Air (Wa)
: PCC laden with 6,000 units
: 10.5ton ˰ 9.135ton in Water
Water Depth + Hawsepipe height from sea surface (y) : 25.0m
Length of one shackle of anchor cable
Ship’s Projected area from bow above waterline (A)
Wind pressure force Coefficient (CRa)
: 27.5m
: 800sqm
: 0.75
Air density (ρ) : 0.125kg/sec2/m4
The anchor cable is assumed to have formed a catenary with no
cable lying on the ground.
Anchor Holding Factor (λa) : 7.0
Anchor Chain Weight per
meter in Air (Wc) :
0.166ton/m ˰ 0.144ton in Water

Anchor Holding Power = Impact Force (external force) : 63.90tonf
Catenary Length(S’) : 150.90m (5.5shackles)
The critical wind speed can be calculated from the Hughes Formula
: 16.90m/sec.
The average wind speed
11.3m/sec ʙ 13.5m/sec.
The critical wind speed =
Average wind speed x 1.25ʙ 1.50
ˎImpact Force (external force)
The Wind Force from ahead : 10.65tonf
= Wind Force from ahead x 6
̒̏

̒̐
(Situation after one additional shackle(27.5m) of cable is veered)
After a further shackle of cable is veered, the critical wind speed will be
increased.
Only part of the longer cable system will lay along the ground with the
remainder forming part of a new catenary.
Y Z
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S’ : Catenary Length before one shackle is veered
150.90m(5.5 shackles)
M : Contacted length of the chain (laid over the bottom)
23.6m
Additional New Catenary 3.9m
:
The holding power created by the
anchor and cable system = 67.3ton

= 17.3 m/sec.
= 11.5m/sec ʙ 13.8m/sec.
In comparison with the average wind speed before
one shackle of cable is veered, there are increases of
0.2 m/sec ʙ 0.3m/sec to the critical wind speed.
Importantly for those on the bridge, the critical wind
speed is not increased as much as might be expected
even if the anchor cable is veered considerably.
a full length of cable (12shackles) is veered)
The average wind speed = 13.1m/sec ʙ 15.7m/sec.
̒̑
The wind force from ahead = 11.23 tonf.
The critical wind speed
The average wind speed
Increase of 1.8 m/sec ʙ 2.2m/sec

The Critical Wind Speed
While looking into various reference books, there is
no concrete indication.
Reasons
· The holding power of each vessel’s anchor is dependent upon
the condition of the ground in the immediate vicinity.
· The actual holding power may not always conform to the
theoretical value obtained by calculation.
· Continuing changes in the direction of the anchor cable and
the angle of action on the mooring system. The result is that
the anchor cable may be subjected to shock stresses as the
cable sags and then tightens.
· The horsing motion may not be constant and the motion may
even be accelerated.
After taking into consideration all the factors set out above the
safe and prudent decision may well be not to anchor.
̒̒

Emergency measures taken and their effectiveness after
dragging anchor
ᶃ Veering an Additional cable and use of the second anchor
Adding cable to the first anchor is not seen as an effective means
of stopping a ship from being pressed and drifting to leeward.
ᶄ Use of bow thruster
The minimum thruster power must be equal to the wind force on
the bow.
ᶅ Use of the main engine and steering
The required power of the main engine
̒̓
Steering : Hard Over Wind speed : Engine Order
20m/sec : Slow Ahead
25m/sec : Half Ahead
30m/sec : Full Ahead

Difficulty in maintaining maneuverability
It should be remembered that when the propeller is working
the effect of the bow thruster will be decreased by about 20%
per 1knot of ahead speed. In other words, at about 5 knots, the
effect of the bow thruster is negated.
Limitation of maneuvering by rudder
Numbers entered in the vertical axis
are wind speed per ship’s speed and
the wind force angle is entered along
the horizontal axis. The yellow zone
shows the area under the curve in
which the effect of the rudder is lost.
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Wind Speed
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Wind speed of 20m/sec, the ship’s speed would
have to be more than 5knots (2.5m/sec)
̒̔

Preparation for safe anchorage
(1) The following considerations must be taken into account:
To select a sheltered good anchorage
· Land configuration
· The bottom configuration
· Holding grounding condition
· An appropriate depth
· Sufficient room
· Sheltered from such an external force as wind and sea
· Degree of congestion of other ships at anchorage
To prevent an accident in the event that the anchor drags
· Keep a safe distance from other ships
· Keep a safe distance from shallows/other facilities
̒̕

Recently there has been an increase in the number of accidents involving anchor cables becoming entangled or
anchors and cables being lost. These accidents have mostly been caused by mistakes that were made during the
operation of letting go the anchor
. In particular, most accidents have been caused by not controlling the running-out
speed of the anchor cable, that is, without braking when the anchor is let go.
Test results show that the speed of anchor free fall reaches 10m/sec after 50m when an anchor is let go without
braking. That is to say, 12 shackles (=330m) could totally run out in 33 seconds.
According to investigation results, although
most mariners involved in anchor-related
accidents stated that the brake did not work
well, thorough investigations on site have
established that a bent brake shaft and / or
lack of maintenance were the cause. The crew
were unable to properly apply the brake.
To ensure safe anchoring, the veering rate
must be limited to a brake force of 5 to 6
m/sec.
Anchor Operation
̓̌

̓̍
If the depth at an anchorage exceeds 20m, the possibility of damage to or loss of the
anchor and its cable becomes greater due to excessive running out speed if the anchor is
allowed to free fall. To avoid this hazard, the anchor should be lowered by walking back
into the water until the anchor reaches about 5m
above the bottom.
When letting go, the brake should be applied
in order to slow the veering rate until the
length veered is about 2m - 3m more than the
water depth. This should prevent the cable
from piling onto the anchor
.
After the anchor touches the bottom, the ship's sternway should be limited to about
0.5k - 1knot in order to avoid imposing excessive strain on the cable and also to further
avoid piling. The aim is to lay the cable across the ground in an orderly fashion and
without imposing any excessive stress on the system. (Ideally, repeat stretching, little by
little, every time until it becomes taut.)

Anchor Cable Veering RateɾScope of Cable To Be
Paid OutɾBrake Force of Windlass
The Graph on the next page shows the relationship between brake force, scope of cable
and veering rate determined during trials on board a 230,000dwt VLCC when anchor and
cable are paid out using the brake. During the trial, the cable was first released with half
brake applied. The brake was applied 3 seconds after letting go the anchor and was fully
applied again after another 5 seconds in order to stop veering completely. As can be seen,
the length of cable veered this time is about 21m.
If the anchor is let go by free fall and the veering rate exceeds 10m/sec, it becomes
difficult to arrest the cable and the brake lining may be damaged. If, however, the
veering rate is limited to about 5-6m/sec by the timely application of half brake, such
damage will be avoided.
̓̎

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Examples of entangling
̓̏

(1) Technical measures while lying at anchor
· External forces associated with wind speeds and directions
· wave height and period
· Flow direction and velocity
· Ship’s type, Hull dimensions, draught, trim
· Understanding the holding power of the anchor system
· Quantitative assessment of wind pressure forces
· Management of the main propulsion systems
(2) Prediction and early detection of dragging anchor
· Understand fully the relationship between holding power and
external forces
· To detect dragging anchor by observing the horsing motion
· To use track display function of ECDISɾ RADARɾ GPS
ː 3.12 Technical Measures for Anchoring ̓̐

෼ߟ ɿ ߴ෼ધͷFull Speedߤ ෼ Լ ʹ͓͚Δճ෼ӡಈͱ੍‫ޚ‬
Taking into account Turning Motion in the event that a high speed vessel (container
ship or PCC etc.) is operating at full-loaded capacity and at full speed.
Failure as a result of rapid turning during operation at high speed
For example, the following problems may occur when a container ship operating at
22 knots steers its rudder to full (hard-over).
-If the main engine is in over-load (torque rich) and also in MO operation mode,
main engine rpm decreases together with the sounding of the Slow Down alarm.
-Outer heel increases due to centrifugal force. Because GoM of a container ship is
between 1.2 and 1.8 meters at full load, outer heel increases due to rapid rotation,
which may cause a dangerous situation.
So as not to cause the above failure, it is a requirement that the vessel navigate at a
restricted rate-of-turn speed at 5-10 degrees per minute (15 degrees per minute at
max.).
̓̑
Ref. ɿ Vessel Turning Motion and Control for High Speed vessels
under Full Speed conditions

Turning in Circles
A case study of the distaster which started the first
international convention
The Turning Characteristics of the
SS Titanic
Tactical
diameter
90°
Transfer
Final
Diameter
Advance

PRESENTATION OVERVIEW
 What do we already know about Titanic's turning
ability?
 Some turning basics
 Developing the model
 Titanic's turning circle
 14 April 1912 at 11:40 PM ATS
 The classic scenario does not hold up
 A failed port-around maneuver?
 Was there a "hard-a-starboard" call?

What Do We Already Know?
• Titanic turned a full circle of 3850 ft measured diameter at
20.5 knots during her sea trials off Belfast Lough.1
• Forward travel for the hard turn was reported at 2100 feet.1,3
• A hard-a-starboard (left full rudder) order at 21.5 knots
results in a heading change of two points (22.5 degrees)
after 37 seconds.2
• A hard-a-starboard (left full rudder) turn at 22 knots would
result in a forward movement of about 440 yards (1320 ft)
for a heading change of 2 points.3,4
• Small changes of speed do not significantly change the
diameter of the turning circle, just the time it takes to turn a
certain amount.5
References:
1. Eaton & Haas, Titanic - Triumph and Tragedy, Ch. 4, 2nd Ed.
2. Edward Wilding, British Inquiry (BI 25292).
3. Edward Wilding at Ryan Vs. Oceanic Steam Navigation Co.
4. Edward Wilding at the NY Limitation of Liability Hearings.
5. Mr. Roche (Marine Engineer’sAssociation) British Inquiry p. 770.

Some Turning Basics
Turning Circle - Aship’s turning circle is the path
followed by the ship’s pivot point when making a 360
degree turn.
Advance - Advance is the amount of distance run on the
original course until the ship steadies on the new course.
Advance is measured from the point where the rudder is
first put over.
Transfer - Transfer is the amount of distance gained
towards the new course (shown here for 90° heading
change).
Tactical Diameter - Tactical diameter is the distance
gained to the left or right of the original course after a
turn of 180° is completed.
Final Diameter - Final diameter is the distance
perpendicular to the original course measured from the
180° point through 360° (shown here for steady turning
radius, R).
Pivot Point - A ship’s pivot point is a point on the centerline
about which the ship turns when the rudder is put over.
Drift Angle - Drift angle is an angle at any point on the
turning circle between the intersection of the tangent at
that point and the ship’s keel line.
Reference: http://web.nps.navy.mil/~me/tsse/TS4001/support/1-11-1.pdf

Forces Acting on Titanic's Rudder
22 knots Hard Over 40°
Force on rudder  21 x AR V2 R (newtons) *
AR is the rudder area in square meters
R is the rudder angle in degrees
V is velocity of the ship in meters per second
Area of Titanic's rudder by Simpson's rule** = 401.7 ft2 = 37.3 m2
R = 40° hard over
V= 20 knots = 10.3 meters/sec
Force = 3,324,000 newtons = 334 long tons
Rudder pressure = 0.83 tons/sq-ft
* Equation is for a spade shaped rudder. http://www.sname.org/NAME/problem7.pdf
** http://www.encyclopedia-titanica.org/articles/rudder_weeks.pdf
spade
shapped
rudder

The ship turns because of hydrodynamic forces on the hull, not the
force acting on the rudder.
direction of water flow
direction of ship movement
rudder force
developing turn - build-up of hull forces
hull force
rudder force
Drag and propulsive forces not shown.
straight approach
start of turn - helm pushed over

The speed of a ship in a turn will decrease due to increased resistance.
4.53
For Titanic:
CB = 0.684
Turning diameter = 3850 ft Ship length =
850 ft
Approach speed 38 ft/sec (22.5 knots) Turning
diameter-to-length ratio = 4.53
Steady turning speed-to-approach speed ratio = 0.77 from above
Steady turning speed for Titanic = 0.76 X approach speed = 28.9 ft/sec (17.1 knots)
A steady turning rate at 17 knots under hard helm for the final diameter of
turn works out to a steady state turning rate of 0.86 degrees per second.
0.76

What Else Do We Know About How a Ship Turns?
The ship will heel toward the outside of a turn.
G = center of gravity
B = center of bouyancy
GM = metacenter height
Bouyancy force = Weight of ship (W)
W  L = W  GM sin = FC  H
FC = W/g  v2/R
T
aking:
H = 18.6 ft
GM = 2.6 ft *
W = 48,300 tons * v
= 29 ft/sec in turn R
= 1925 ft
 = 5.4° heel angle for
hard-over full
speed turn
G
B'
weight
of ship
W
bouyancy
force
waterline heeling moment arm
H
hydrodynamic hull force
equals
centrepital force FC
righting moment arm L
Looking forward from astern
during a turn to port
(exaggerated view)

M
B
* Bedford & Hackett paper

Angle of Heel Development Over Time
Estimated angle of heel for Titanic in a full-speed maximum turn is 5.4°
typical angle-of-heel development
steady heel angle
Adapted from: http://web.nps.navy.mil/~me/tsse/TS4001/support/1-11-1.pdf

What Else Do We Know About How a Ship Turns?
For Titanic with 40° rudder deflection:
Drift-angle reaches ~8° and the heading changes at 0.86°/sec in 3rd phase.
steady-state = 8°
max = 40°
Phases in a Turn
1. Rudder thrown.
Adapted from: http://web.nps.navy.mil/~me/tsse/TS4001/support/1-11-1.pdf
rsteady-state = 0.86°/second
2. Ship skids and
drifts out while hull
forces build and
starts to turn ship.
3. All forces balance
out and ship stays
in steady turn.

Determining Pivot Points and Drift Angles
The drift angle in degrees can be taken as β = 18 L/R (in degrees).
For Titanic, β = 7.95  8°.
The location of the pivot point is X = R sinβ ahead of the center of
gravity of the ship. For Titanic, X = 266 ft ahead of bulkhead H, or
about 159 feet back from the bow (app. 1/6th shiplength) under the
forward well deck.
Reference:
http://web.nps.navy.mil/~m
e/tsse/TS4001/support/1-
11-1.pdf
Path of CG of ship
in the turn
Drift angle 
Heading angle

Velocity
vector
Center of turn
Direction of ship movement
 =   
Pivot point
Center of Gravity (CG)
Steady turning
radius R
1925 ft
ship length L
850 ft BP
X

Pivot Point and Drift Angle for the Titanic

What Can We Learn From Zig-Zag Maneuvers?
Response curve for
ship studdied shows
a heading change of
20° in 34 seconds
from t=0 before helm
shifted to opposite
side.
Tracks closely a
heading change of 2
points in 37 seconds
seen on Olympic for
a "hard-astarboard"
helm order when
running at 21.5
knots.
Steady turn rate for
this ship is 50° per
minute (0.83° per
second). This is
about the same
turning rate for the
Titanic in the steady
turn phase under full
helm.
We can use the dynamics off these curves to model the turning
characteristics of the Titanic for several types of turning maneuvers.
34 sec
20°
steady turn
rate of 50°
per min
0
°

Spread Sheet Analysis
... ...
...
speed
(knots
)
speed
(ft/sec
)
increment
al
distance
in
7.5 sec
percent
max
22.5 38 285 100% initial
21.3 36 270 95%
19.5 33 248 87%
18.4 31 233 82%
17 29 218 76% in full
turn
Time
(sec)
rudder
angle
(deg)
heading
(deg)
delta
heading
angle
drift angle
(deg)
course angle
(deg)
X position
(ft)
Y position
(ft)
-15 0 0.0 0 0 0 570 0
-7.5 0 0.0 0 0 0 285 0
0 0 0.0 0 0 0 0 0
7.5 -40 -2.0 -2 -2 0 -285 0
15 -40 -5.0 -3 -5 0 -555 0
22.5 -40 -11.0 -6 -6 -5 -802 -22
30 -40 -17.5 -6.47 -8 -9.47 -1032 -60
37.5 -40 -23.9 -6.47 -8 -15.94 -1242 -120
45 -40 -30.4 -6.47 -8 -22.41 -1443 -203
52.5 -40 -36.9 -6.47 -8 -28.88 -1634 -308
60 -40 -43.4 -6.47 -8 -35.35 -1812 -434
67.5 -40 -49.8 -6.47 -8 -41.82 -1974 -580
75 -40 -56.3 -6.47 -8 -48.29 -2119 -742
82.5 -40 -62.8 -6.47 -8 -54.76 -2245 -920
90 -40 -69.2 -6.47 -8 -61.23 -2350 -1112
97.5 -40 -75.7 -6.47 -8 -67.7 -2433 -1313
105 -40 -82.2 -6.47 -8 -74.17 -2492 -1523
112.5 -40 -88.6 -6.47 -8 -80.64 -2528 -1738
120 -40 -95.1 -6.47 -8 -87.11 -2539 -1956
127.5 -40 -101.6 -6.47 -8 -93.58 -2525 -2173
135 -40 -108.1 -6.47 -8 -100.05 -2487 -2388
420 -40 -353.9 -6.47 -8 -345.91 -242 -47
427.5 -40 -360.4 -6.47 -8 -352.38 -458 -18
435 -40 -366.9 -6.47 -8 -358.85 -676 -14

Titanic's Turning Circle
Model Results

Titanic's Turning Circle
With Ship Profiles Overlain
Advance 2540 ft
90°
Transfer 1740
ft
Tactical
diameter
3880 ft
Final
Diameter
3860 ft

11:40 PM on 14 April 1912
What the British Inquiry Said
Report on the Loss of the SS Titanic
30th day of July, 1912
The ship appears to have run on, on the same course, until, at a little before 11.40,
one of the look-outs in the crow’s nest struck three blows on the gong, which was the
accepted warning for something ahead, following this immediately afterwards by a
telephone message to the bridge “Iceberg right ahead.” Almost simultaneously with
the three gong signal Mr. Murdoch, the officer of the watch, gave the order “Hard-a-
starboard,” and immediately telegraphed down to the engine room “Stop. Full speed
astern.” The helm was already “hard over,” and the ship’s head had fallen off about
two points to port, when she collided with an iceberg well forward on her starboard
side.

11:40 PM on 14 April 1912
Conclusion of the British Inquiry
Report on the Loss of the SS Titanic
30th day of July, 1912
From the evidence given it appears that the “Titanic” had turned about two points to
port before the collision occurred. From various experiments subsequently made with
the S.S. “Olympic,” a sister ship to the “Titanic,” it was found that travelling at the
same rate as the “Titanic,” about 37 seconds would be required for the ship to change
her course to this extent after the helm had been put hard-a-starboard. In this time
the ship would travel about 466 yards, and allowing for the few seconds that would be
necessary for the order to be given, it may be assumed that 500 yards was about the
distance at which the iceberg was sighted either from the bridge or crow’s nest.

What About the Engines Stopping or Reversing?
Trimmer Thomas Dillon: "They stopped...about a minute and a half [after the collision]. They
[then] went slow astern ... about a minute and a half [later for] about two minutes."
Greaser Thomas Ranger: "We turned round and looked into the engine room and saw the turbine
engine was stopped...There are two arms [that] come up as the turbine engine stops...
[that was] about two minutes afterwards...[after the jar.]"
1st Class Passenger Henry Stengel: "As I woke up I heard a slight crash. I paid no attention to it
until I heard the engines stop...[They were stopped] I should say two or three minutes, and then
they started again just slightly; just started to move again. I do not know why; whether they were
backing off, or not."
1st Class Passenger George Rheims: "I did not notice that the engines were stopped right away;
they were not stopped right away; of that I am positive.
[I felt a change with reference to the engines] a few minutes after the shock, possibly two or three
minutes; might have been less."
2nd Class Passenger Lawrence Beesley: "There came what seemed to me nothing more than an
extra heave of the engines and a more than usually obvious dancing motion of the mattress... and
presently the same thing repeated with about the same intensity...I continued my reading...But in
a few moments I felt the engines slow and stop."
The engines did not stop nor reverse until some short
amount of time after the ship struck the iceberg.

Applying the Model
The turning model can be used to analyze several
scenarios including:
• The classic "hard-a-starboard" maneuver.
• An attempted "port-around" maneuver.
• A delayed "hard-a-port" maneuver.

We Also Need A Typical Iceberg
Passenger Henry Stengel: "I noticed, a very large one, which looked
something like the Rock of Gibraltar."
AB Seaman Joseph Scarrott: "It resembled the Rock of Gibraltar looking at
it from Europa Point."
QM Olliver: "The iceberg was about the height of the boat deck; if anything,
just a little higher. It was almost alongside of the boat, sir. The top did not
touch the side of the boat, but it was almost alongside of the boat."
250 ft
visible
portion
allowing for
underwater
contour
Model for a 2 dimentional plot

The "Hard-a-Starboard" Scenario
7.5 Second Increments Shown on a 500' X 500' Grid

What Do the Turning Model Results Say?
A turn of "hard-a-starboard" 37 seconds before
collision with no other corrective action would have likely
produce severe damage along the entire starboard side.

Reality and Contradiction
QM HICHENS AT THE AMERICAN INQUIRY
QM Hichens: "The sixth officer repeated the order, "The helm is hard astarboard,
sir." But, during the time, she was crushing the ice, or we could hear the grinding
noise along the ship's bottom. I heard the telegraph ring, sir."
QM HICHENS' FIRST RESPONSE AT THE BRITISH INQUIRY
951. Had you time to get the helm hard a starboard before she struck? - [QM
Hichens] No, she was crashing then.
QM HICHENS' CONTRADICTION
957. Before the vessel struck had you had time to get the wheel right over? - [QM
Hichens] The wheel was over then, hard over.
958. (The Commissioner.) Before she struck? - Oh yes, hard over before she struck.

Some Reality Checks
QM Alfred Olliver: "I know the orders I heard when I was on the bridge was
after we had struck the iceberg. I heard hard aport, and there was the man
at the wheel and the officer. The officer was seeing it was carried out right."
AB Seaman Joseph Scarrott: "Under port helm. Her stern was slewing off the
iceberg. Her starboard quarter was going off the iceberg, and the starboard
bow was going as if to make a circle round it."
Fireman Alfred Shiers: "I saw the berg that was going away...on the
starboard quarter, off the stern."

Some Reality Checks
Was the Iceberg Really Dead Ahead?
This sketch (shown here with inverted
colors) was drawn by Lookout Frederick
Fleet to show how the berg appeared
when first sighting. Notice how he
placed the berg slightly off the
starboard bow of the ship, not dead
ahead of her. Fleet occupied the port
side of crow's nest while Lee had the
starboard side.
Despite what he told Senator Smith,
this view may explain an apparent
delay in getting an immediate response
from the bridge when the 3 bell
warning was given.
Senator SMITH. They swung the
ship's bow away from the object?
Mr. FLEET
. Yes; because we were
making straight for it.

Time From 3-Bell Lookout Warning to Collision
Lookout Fredrick Fleet: "I saw this black thing looming up; I didn’t know what it was. I asked
Lee if he knew what it was. He couldn’t say. I thought I better ring the bell. I rang it three
times." [Interview with Leslie Reade]
QM Robert Hichens: "[The first notice that there was something ahead was] three gongs from the
crow's-nest, Sir...Well, as near as I can tell you, [it was] about half a minute [before the order came
'Hard-astarboard']." [British Inquiry 969-973]
QM Alfred Olliver: "When I was doing this bit of duty I heard three bells rung up in the crow's
nest, which I knew that it was something ahead...When I heard the report, I looked, but could
not see anything, and I left that and came was just entering on the bridge just as the shock
came." [American Inquiry]
IT TAKES ABOUT 45 SECONDS ON AVERAGE TO WALK FROM THE STANDARD
COMPASS PLATFORM TO THE BRIDGE NOT COUNTING REACTION TIME.
Time from 3-bell lookout warning to collision would be about 50-60
seconds based on QM Olliver's reported actions.
Iceberg spotted some short time earlier by Frederick Fleet.
We really don't know what time Murdoch first spotted the iceberg.

Modeling a "Port-around" Maneuver

Modeling a "Port-around" Maneuver
92 ft
882 ft OA
Setting the heading angle. 26.25 -40 -16.0 -5 -7.0 -9 -931 -50
Time
(sec)
rudder
angle
(deg)
heading
(deg)
delta
heading
angle
drift angle
(deg)
course angle
(deg)
X position
(ft)
Y position
(ft)
-15 0 0.0 0 0.0 0 570 0
0 0 0.0 0 0.0 0 0 0
3.75 -13.3 -0.5 -0.5 -0.5 0 -143 0
7.5 -26.7 -2.0 -1.5 -2.0 0 -285 0
11.25 -40 -3.6 -1.6 -3.3 -0.3 -424 -1
15 -40 -5.5 -1.9 -4.5 -1 -559 -3
18.75 -40 -8.0 -2.5 -5.5 -2.5 -689 -9
22.5 -40 -11.0 -3 -6.0 -5 -812 -20
30 -26.7 -19.0 -3 -6.0 -13 -1044 -80
33.75 -13.3 -22.0 -3 -4.5 -17.5 -1152 -139
37.5 0 -22.5 -0.5 -3.0 -19.5 -1254 -175
41.25 13.3 -22.5 0 -2.0 -20.5 -1357 -214
45 26.7 -22.0 0.5 -1.0 -21 -1458 -253
48.75 40 -21.5 0.5 0.0 -21.5 -1560 -293
52.5 40 -19.5 2 1.0 -20.5 -1662 -331
56.25 40 -17.2 2.3 2.0 -19.2 -1765 -367
60 40 -14.5 2.7 3.0 -17.5 -1869 -399
63.75 40 -11.6 2.9 4.5 -16.1 -1973 -430
67.5 40 -8.4 3.25 6.0 -14.35 -2079 -457
71.25 40 -5.1 3.25 7.0 -12.1 -2186 -479
75 40 -1.9 3.25 8.0 -9.85 -2293 -498

"Port-around" Scenario — Did It Happen Like This?
3.75 Second Increments Shown on 250' X 250' grid

SUMMARY AND CONCLUSIONS
 A turning model was developed for SS Titanic based on
reported observations of Titanic and Olympic and generic ship
maneuvering characteristics
 Model applied to a spread sheet for analysis
 model uses realistic parameters such as speed reduction in a turn
and drift angle
 data gives heading angle, course angle, and X-Y coordinates as
function of time
 results allow for animation analysis
 The classic collision where the ship sideswipes an iceberg 37
seconds following a "hard-a-starboard" order does not hold up.
 Several alternative scenarios have been considered
 a port-around type of maneuver
 a delayed hard-a-port only maneuver
 The model can be easily extended to look at other scenarios

SHIP HANDLING AND MANOEUVERING BASICS.pptx

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