Ship Maneuvering
Technical Reference

Panama Canal Gatun LockＩＮＤＥＸ
Ｐ． １ ……………………………..
INDEX
Ｐ． ２ ……………………………..
§１ What is Vessel Handling ?
Ｐ． ４ ……………………………..
§１. １ Investigation of Environmental Condition(harbour condition)
Ｐ． ６ ……………………………..
§１． ２ Example of Investigation of Geographical Condition§１． ３ Example of Investigation of Port Facilities
Ｐ．１３ ……………………………..
Ｐ．１９ ……………………………..
§２ Vessel Maneuverability
Ｐ．２０ ……………………………..
§２． １ Effects of External Force(wind)
Ｐ．２６ ……………………………..
§２． ２ Turning the vessel
Ｐ．２８ ……………………………..
§２． ３ Speed Control
Ｐ．４０ ……………………………..
§２． ４ Preventing Damage to Harbour Facilities
Ｐ．４４ ……………………………..
§３ Dragging Anchor
Ｐ．４４ ……………………………..
§３. １ The reason why an anchor drags
Ｐ．５１ ……………………………..
§３. ２ Wind Pressure Force Calculation
Ｐ．５２ ……………………………..
§３. ３ Holding Power created by Anchor and Anchor Chain§３. ４ Calculating the Catenary Length of an Anchor Chain
Ｐ．５４ ……………………………..
§３. ５ Horsing(Yawing and Swaying) Motion and Impact Force
Ｐ．５５ ……………………………..
§３. ６ Ship's operational safety measures for anchorage and their effects
Ｐ．５８ ……………………………..
§３. ７ The Critical Wind Speed
Ｐ．６６ ……………………………..
§３. ８ Emergency measures taken and their effectiveness after dragging anchor
Ｐ．６７ ……………………………..
§３. ９ Difficulty in maintaining maneuverability
Ｐ．６８ ……………………………..
§３.１０ Preparation for safe anchorage
Ｐ．６９ ……………………………..
§３.１１ Anchor Operation
Ｐ．７０ ……………………………..
§３.１２ Technical Measures for Anchoring
Ｐ．７４ ……………………………..
Ref. : Vessel Turning Motion and Control for High Speed vessels under Full Speed condition
Ｐ．７５ ……………………………..
Author and Contact address
Ｐ．７８ ……………………………..

１

２§1 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 ofenvironmental 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).

３

Vessel with
Stability

Means
Rudder, main
engine, thrusters,
anchors, mooringlines, tugs etc.

Rolling, Pitching andYawing characteristics
in waves

Vesselmaneuverability

Environmental conditions* Geography (existence of shallow areas andwater
depth etc.)* Facilities (port facilities)* Navigation (buoys, fishing boats, marine trafficetc.)* Social (regulations, navigation regulations etc.)* Nature (wind, tidal flows, visibility, waves etc.)

Control of vessel position, attitude,
and speed for safe and efficient

Ship
Navigator* movement in the required
direction* stopping at the required position

Operate vesselas described４§1.1 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 istherefore desirable that a shore team collects the relevant data andprovides it to the vessel.

５

1.1.1 Investigation of Geographical Conditions and Conditions
Associated with Harbour Facilities
1.1.2 Investigation of the Navigation Environment(e.g. buoys, fishing vessels, fishing reefs,
shipping movements)
1.1.3 Investigation of the Social Environment (local regulations andnavigation restrictions)1.1.4 Investigation of the Natural Environment(e.g. wind, tides, visibility, wave direction)

Tidal Information
through the Internet

６§1.2 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 thevessel 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 thewater depth and draft are the same (UKC = 0), there is apossibility that the vessel may run aground, and entry to harbouris therefore unsafe.

７= 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 eachharbour (or each berth) to determine problems.

８＝ ＵＫＣ ＝Most harbours set guidelines for UKC, and many harbours
throughout the world manage UKC together with data on weather andsea conditions to ensure a margin for navigation.
In Japan, 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.

= Water Depth and Tide level =On charts, the allowable limit for error in water depth at the international depth
datum is as follows.
Water depth to 20m: Up to 0.3m
Water depth to 100m
: Up to 1.0m
Water depth to 100m or more
: 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.

９１０= Vessel’s Sinkage While Underway =When a vessel begins moving the
distribution of water pressure around itchanges, and the hull lowers slightly in thewater.
When navigating in harbours, therefore,
the amount of this sinkage of the vessel inthe water must be added to the draft whileat berth.
This amount becomes greater as thewater 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 istherefore appropriate to estimate thesinkage of the vessel as 0.1 – 0.2% of thelength of the vessel.
It is also necessary to consider sinkage ofthe vessel due to rolling, pitching andyawing of the vessel with wind and waves,and swell.

１１= 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

１２(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, forturning. The Japanese 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 whenturning with the assistance of tugs.
Many harbours do not provide
sufficient area as shown in thefollowing diagram. In such cases,
it is necessary to investigate therelevant points sufficiently inadvance (verifying the number oftugs required, and determining
the procedure for turning thevessel., etc.)

１３§1.3 Example of Investigation of Port Facilities(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 inother countries.

１４(2) 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 inaccordance with Japanese harbour technical design standards are as
follows.

１５(3) Fenders
Fenders are also an important item of equipment for safe mooring of
the vessel. Particularly when a swell enters the harbour, insufficientfenders may result in damage to the pier and to the hull of the vessel.
If damaged fenders are discovered after entering harbour, theyshould be photographed to guard against claims later on.

１６(4) 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 oftidal flow, waves)• Method of approaching and leaving the pier (mooring toward the direction ofarrival and departure)• Water depth in the area (consider effects of shallow water)• Availability of thrusters• Area available for maneuvering１７

Guidelines are commonly set for the number of tugs required at eachharbour. Use this information for reference.
When no guidelines have been set, use the following equation todetermine the necessary power in conjunction with the deadweightof the vessel.

１８

It is possible to reduce the number of tugs if they are fitted withthrusters.
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 enteringor leaving harbour without hesitation in bad weather and sea
conditions.
Bow thruster

Tug (towing and pushing at an angle)

１９§２ Vessel Maneuverability
Approximately 70% of incidents of damage to harbour facilities involve
damage to piers and fenders, however most are due to mistakes inoperation of the vessel.
Such mistakes in confined harbours with limited area available formaneuvering 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 inaccordance with the distance remaining, and isrequired to adjust speed and turn the vessel whileconsidering its type, size, loading condition,
inertia, maneuverability, and the effects ofexternal forces.

２０§2.1 Effects of External Forces (wind)=Transverse Movement and Turning Under
Wind Pressure While Underway=① Straight ahead if no external forces are acting
in windless conditions.

N(vβ)
Water Resist.

② When the wind is at 45° to starboard, the vessel is pressed Direction of Ship
to leeward. The point at which the wind acts (C) is ahead of Movement
the vessel’s center of gravity (G), and a turning moment(N (Vα)) acts to turn the vessel in the leeward direction.
③ When the vessel begins drifting (diagonally) leeward, water
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 windpressure acts (C), and a turning moment (N (Vβ)) acts to turn thevessel in the windward direction.

N(va)
Wind

β

Y(va)

④ The vessel turns under the turning moment of the wind or water resistance, whicheveris the greater. Since water resistance is normally much greater than air resistance,
the vessel begins to turn windward. (N (Vβ) > N (Vα))

E
C
G⑤ The rudder acts against the turning moment, i.e. the vessel is controlled with themoment N (Vσ) generated by the rudder angle (σ).
⑥ 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 rightahead, and proceeds with drifting leeward.

Y(vβ)

Y(vσ)

N(vσ)

２１
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 vesselin the leeward direction increases (drift), and the diagonal angle increases, increasing theturning 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.

２２
The course can be maintained if the moment derived from the wind and water resistancecan 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 thevertical axis, and the relative wind angle
on the horizontal axis, and indicates theregions in which the course can andcannot be maintained with a rudder angleof 30°. If the ratio of wind speed tovessel 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 windspeed 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.

２３
In the following graph, rudder angle is shown on the vertical axis, and the regions inwhich 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°.

２４

It is important to maneuver the vessel whileconsidering the rounding up angle leeway (β)
when navigating in a channel without theassistance of tugs under wind pressure.
In such cases, wind direction and speed,
and vessel speed, must be considered, andan 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 forentering and leaving the harbour is very
often set, however hull shape etc. should beconsidered together with the criteria
established for the harbour in question.

２５

Leeway of 3° to starboard to ensure passage
under center of bridge. (Incheon Port)

Modern radar withadvanced technology
displays generally
incorporates GPS
information. If thisfunction is used skillfully
the leeway angle anddirection of drift can beunderstood in numericalterms. This information iseffective in maneuvering
the vessel.

２６§2.2 Turning the vessel(1)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 thepivot point (P), rather than the center of gravity (G). Turning the vessel on the spot in acircle 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

k: Turning radius of moment of inertia aroundvertical 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

P

GP
G

GC
C

1/2 L

２７
(2) 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 wereused solely for turning, and no adjustment was made fordrift.
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 thisvessel. A larger area is required for turning at
wind speeds in excess of 10m/sec.

10m/sec

φ＝２Ｌ

G

Loa(m)
246.27Lpp(m)
230.00
Bredth(m)32.24
Depth(m)21.20
Draft(m)11.50
Disp.(KT)53,875Trim(m)0.00
G position
-5.5
Wind
Front(㎡）850
Project. Side（㎡） 6,090

Simulator(Container)

２８§2.3 Speed Control
Incidents of failing to control a ship’s speed while entering harbour, withthe vessel consequently colliding with the pier causing major damage tothe 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 themain engine, reversing the main engine, orthe 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.

２９These 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 thecaptain.
Both the captain and pilot are required
to have a quantitative, rather than an
intuitive exchange of information, basedon experience, understanding of the
stopping distance and the time required
to stop.

３０(1) 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.

３１

W
Vo
V
F
T
S
Α

: Apparent displacement (displacement + additional mass*) (tons): Initial speed (m/sec): Final speed (m/sec): Forces acting (tug thrust and reverse engine thrust) (tons): Elapsed time (seconds): Forward movement (m): Acceleration applied to vessel (m/ sec2)* 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 apart 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’.

３２(2) Speed Reduction Plan for Vessel Approaching Pier in Direction of
Arrival (example)
When approaching parallel to the pier in the direction of arrival it isnecessary to determine in advance when to stop the engine, and tounderstand guidelines for evaluating whether or not speed through theprimary waypoints is excessive while approaching the berth.
For example, while moving forward at dead slow ahead as shown in thefollowing 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 ispossible 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 effectof the tug or by reversing the engine if the approach to the berth is at agreater speed.

３３

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 timerequired to stop during maneuvering for approach,and maneuver the vessel with a safety margin.

３４(3) 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 thevessel using simple spreadsheets. Early braking by tug or reversing theengine is necessary if the safety margin is 0.3 or less.

３５
In addition to thisspreadsheet, it is also
effective to consider the
maneuverability of thevessel in preparing
speed reduction
guidelines in graphic
format.
The guidelines should
be posted on the bridge,
with copies kept instorage. The guidelines
can be provided to thepilot as referencematerial for informationexchange uponboarding to assist incommunication.

(4) Control of Berthing Velocity When Approaching the Pier

３６

Conventionally, the vessel approaches at an angle on a face line ofthe 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 tothe pier at a distance of 1.5 – 2 times the beam, and are then pushedsideways onto the pier by a tug (parallel approach).
Up to 20,000GT(conventional method)

Large vessels
exceeding 20,000GT(parallel approach)３７= 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 inoverrunning the scheduled stop position, and does not result indamage to the pier.
• With the conventional method, container ships etc. with large bowflares 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.

３８(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 squareof the speed of contact.

E
W’
G
V
C

: Contact energy (ton-m): W (displacement (tons) × transverse additional mass coefficient (1-0 – 2.0)
: Acceleration due to gravity (m/sec 2): Berthing Velocity (m/sec): Energy diminution coefficient due to turning etc.

Using an additional mass coefficient of
1.8, and C of 0.5 in the above equation, acontainer 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.

Contact energy (t-m)

３９Berthing Velocity (V cm/sec)

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 whencontacting the pier fenders, and prevent damage to the hull and the pier.

４０§2.4 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/BWhen the pilot boards the vessel, present the pilot card, andexplain draft, displacement and other points of special note.
Officers stationed at the bow and stern report repeatedly on
movement of the tugs.

４１・ Bridge Resource Management During Arriving and and DepartureS/B in Harbour
Consult with the navigator on the day prior to harbour entry for a briefingon 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).

４２・ 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, theofficer 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 nolonger 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 arepushing or pulling the vessel, and in which direction etc.

４３・ 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 noslack).
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 forcreating an atmosphere in which thisbehavior is encouraged.

４４§３ Dragging Anchor§3.1 The reason why an anchor drags
A ship’s anchor drags
The impact of external forces>

The holding power of the anchor
and cable.

Masters and deck officers should beaware of how various parameters, such as
the scope of cable in relation to the depthof water and the effects of wind, wave
and tidal forces on the vessel, can in turnexert excessive forces on the anchor andcable system leading to break-out of theanchor from the ground and dragging.

４５

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 √ｄ m

４６

Traditional means of detecting a dragging anchor① Checking the ship’s position, to confirm whether it isplaced outside of a turning circle.
② The bow cannot stand against the wind.
③ The ship’s side against the wind hasn’t changed.
④ Checking to see there is no slacking of chains just before aship’s side against the wind turns.
⑤ Checking whether there
are extraordinary vibrations
through the anchor chains.
⑥ Checking the course recorder incase it does not indicate a“figure-of-eight” motion locus.

４７

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

４８・ The First Stage : Dragging Anchor with Yaw and Sway
Yaw and sway motion of a vessel whenlying to an anchor is sometimes referred
to as “horsing”. Area [A] in the diagramshows 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 ispressed 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 insuch a state and to weigh the anchor.

４９・ The Second Stage : Anchor Dragging caused by Wind Pressure
Where wind pressure force gradually becomes stronger, oneside of the ship turns against the wind and is then pressed andmoves to leeward at a certain speed, as shown in area [C] inthe diagram.
It is suggested that, during this stage, it is difficult to weighanchor and, even if possible, this takes a considerable amountof time. If weighing the anchor cannot be accomplished, theship 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 adangerous situation from developing.

５０

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

ECDIS

RADAR

GPS

AREA 「Ｂ］

AREA 「Ｂ］

AREA 「Ｃ］

§3.2 Wind Pressure Force Calculation

５１

Hughes Formula
Ra =

θ
Va

1
ｘρｘC Ra xVa 2 x(A cos 2 θ＋Ｂ sin 2 θ）/1000 (ton)2ρ: Wind direction from bow [degree]( Relative Wind Direction ): Headwind speed [m/sec]: Air density [0.125kg ・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 ): Resultant wind pressure force[kg] → divided by
1,000 to be “ton” ( Total Wind Force ): Wind pressure force angle[ degree]( Angle of Action )

Ra
α

CRa
: Wind pressure force coefficient.
Passenger: 1.142 - 0.142cos2θ- 0.367cos4θ- 0.133cos6θ
General Cargo : 1.325 - 0.050cos2θ- 0.350cos4θ- 0.175cos6θ
Tanker & Bulk carrier: 1.200 - 0.083cos2θ- 0.250cos4θ- 0.117cos6θ

Resultant wind pressure force is proportional to the square of wind speed.

５２§3.3 Holding Power created by Anchor and Anchor Chain
S : Catenary length against the external force (m)y : Water depth + Hawsepipe height from sea surface (m)l : Minimum Required Contacted length of the chain (m)L : Minimum Required Length of Anchor Chain (m) (= S + l )Tx : External force (kgf)

H (Holding Power created by Anchor and Anchor Chain)= Ha + Hc = λa x Wa’ + λc x Wc’ x l

５３

H
Ha
Hc

: Holding power created by Anchor and Anchor Chain (kgs): Holding power by Anchor (kgs): 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)l: Minimum Required Length of Anchor Chain (m)λaλc: Anchor Holding Factor: Anchor Chain Holding Factor

λa : Anchor Holding Factor

Type
ＪＩＳ
AC14

Sand
3.5
7.0

Mud
3.2
10.6

Dragging

1.5
2.0

λc : Anchor Chain Holding Factor
Dragging
Holding

0.75〜1.0

Sand
0.75

Mud
0.60

JIS

AC14

５４

§3.4 Calculating the Catenary Length of an Anchor Chain
Ｓ

＝

2

ｙ ＋2

Tx
Wc'

y

S

: Catenary length against the external force (m)y: 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 createdby Anchor and Anchor Chain (kgs) ]will be diminished.

５５§3.5 Horsing (Yawing and Swaying)
Motion and Impact Force①→② From right to left. Anchor chain istight condition
Left side position. Anchor chain③
become relaxes.
④

Biggest Impact Force⑤→⑥ From left to right. Anchor chain istight condition⑦⑧

Right side position. Anchor chain
become relaxes.
Biggest Impact ForceIn 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.

５６

風圧力計算 参考値(Wind Pressure Force Cal.：Just Reference)
相対風向角（ θ）
Relative Wind

1 本船が受ける風圧力を風向別に自動計算する表です。
This formula calculate the wind force of your vessel at the wind speed.

風速： Wind Speed

2 船種別の風圧係数は 自動的に計算されます。
The wind force coefficient in each kind of ship is calculated automatically.

θ
風圧力角（α）
Wind Press. ForceAngle

船首から風圧
中心まで の距離

3 下記を入力して ください。（Input followin g data）

α

2 00

a

正面投影面積(Pr o jected ar ea (Fro n t )) (m2 ) (A )8 00

Le n gth from Bo w

側面投影面積(Pr o jected ar ea (S id e)) (m2 ) (B)5,5 00

風速(Wind Sp eed )(m /s)

30.0

Loa(m)

船種（Kind of ship） 下記から選ぶ(Ge n l, P CC, Ct n r : 1 P asse n ge r : 2

Trans(RT)
Long(RL)(Ave.Wind Speed x 1.25 or 1.50)

1風圧合力 RaTan ke r , Bu lke r : 3 )Re sultant＊ 風速は 以下を目安にして入力し てください。(Inpu t Wind S peed b y below r ef. data)
平穏時(Less than 8 m/s)
： 平均風速（Ave. Wind Speed）
強風対策（Strong Wind:8〜13m/sec)： 平均風速（Ave. Wind Speed) x 1.25
暴風対策(Storm Wind: More than 13m/sec)： 平均風速（Ave. Wind Speed) x 1.50
計算結果(RES ULTS)
風向角(θ)
Wind dire c tionfrom bow ( de g )

0
10
20
30
40
50
60
70
80
90
衝撃力(I mp act )

風圧係数（Ｃ R ａ）

風圧力合計( Ra ) 船首尾方向( RL ) 正横方向( RT )作用点( a )作用角(α)係数(C R a)

T otal wind forc e( t)Point ofac tion(m)Ang le ofac tion( de g )Fac tor

1

2

3

0.75
0.92
1.31
1.65
1.73
1.58
1.35
1.22
1.19
1.20

0.750000
0.922400
1.313421
1.650000
1.732710
1.575075
1.350000
1.215025
1.191369
1.200000

0.500000
0.660925
1.035993
1.387500
1.528709
1.445025
1.263500
1.120549
1.060798
1.050000

0.750000
0.871994
1.151506
1.400500
1.479010
1.390836
1.249500
1.161670
1.144983
1.150000

33.75
48.86
99.72
183.30267.24315.24328.43338.32359.08371.25202.50Long itudinal( t)T ransv e rse ( t)

33.75
0.00
58.20
0.00
43.37
22.51
62.80
27.43
69.74
71.28
67.40
45.62
92.57
158.21
72.00
59.67
90.73
251.37
76.60
70.15
67.27
307.98
81.20
77.68
40.97
325.86
85.80
82.83
22.36
337.58
90.40
86.21
10.02
358.94
95.00
88.40
0.00
371.2599.60
90.00
正面風圧抵抗（上記表のθ＝０ の値の６倍, Tanker/Bulkerは４倍）
Wind Force on Front(θ＝０） ｘ ６, Tanker/Bulker x 4))

衝撃力 ： PCC/CTNR船の場合、正面風圧力の５〜６倍、その他の船では ３〜４倍
Impact For ce : Wind For ce on Fr on t x 5〜6 for PCC/CTNR/Passenger ship , x 3〜4 for Tan ker/Bu lker

５７錨・錨鎖による把駐力計算 参考値(Anchor Holding Power Calculation：Just Reference)1

予想される外力に対し係止出来る必要最低限の錨鎖長さを計算します。
The formula in this page are to calculate the holding power of your vessel's anchor and anchor chain.

2

但し、予想外力が錨の把駐力(Wa' x λa)より小さい場合は、下記計算式による繰り出し錨鎖量としています。
In case of External Force<Anchor Holding Power(Wa' x λa),required length of chain is to calculate by following formula.

Req uir ed Length o f Ch ai n = 3 x d + 9 0 m ( Only Exter nal For ce < Wa
3

x λa)

予想最大外力の入力(Expected total external force)
予想最大外力は 、衝撃力の大きさを使用すること 。PCC/CTNR船の場合、正面風圧力の５〜６倍、その他の船では ３〜４倍
Expected total external force should be input by Maximu m Imp act fo rce.
Other type of ship : Wind Pressure on front x 3〜4＊

For PCC/CTNR Ship : Wind Pressure on front x 5〜6,

例： 風圧外力計算で相対風向０度の場合の風圧力が１５トン ： 予想最大衝撃外力 １５ｘ ５〜６＝ ７５〜９０トン( PCC/CTNR)IE) As per Wind force Cal., Relative Wind Directionθ=0 : 15ton : Max Impact Force 15 x 5〜6 for PCC/CTNR= 75〜90 tons

情報入力(Input Data)
予想される最大外力（トン） ： Ｔｘ （衝撃力）
Expected total external Max. force (MT)：(Ｔｘ Imp act Fo rce)

錨の空中自重（ トン） ： （Ｗａ）
Anchor weight (MT) in Air ： （ Ｗａ）

錨鎖1mあたりの空中における重さ（トン）： ( Wc)
Anchor chain weight in Air (MT/m) ： （ Ｗｃ）

計算結果（Result of Calculation)
8 5.6
1 0.5
0 .1 66 ton

ｱﾝｶｰの種類(JIS型. .. 1、AC1 4. ..2)
使用する側の錨鎖保有長さ（シ ャックル）Total Length(Shackles) of using Chain on board

水深(m ) ： ｄ
Water depth (m) ： ｄ

水面からﾎｰｽﾊﾟｲﾌﾟまでの高さ(m) ： ｈ
Hawsepipe height from the sea surface (m) ： ｈ

錨の把駐係数： （λa）
Anchor Holding Factor:（ λa）

錨鎖の把駐係数： （λc)
Anchor Chain Holding Factor： (λc)

外力に対応するｶﾃ ﾅﾘｰ長さ：（ Ｓ）

20 .0 m

1 74 m錨鎖による把駐部の最小要求長さ：ｌ

1 50 mMinimum Required Contacted length of the chain ： ｌ
Minimum Required Length of Anchor Chain ： Ｌ＝Ｓ＋ｌ

1 2 ss

25 m

Catenary length against the external force ： （ Ｓ）

計算上必要な錨鎖繰り出し長さ： L＝Ｓ＋ｌ

2

Kind of Ancher (1: JIS, 2: AC14)

海底から錨鎖孔までの高さ： ( y)Total height (Bottom to Hawsepipe): (y)3 24 m

12 ss

Notice守錨直を励行し てください。
Keep Anch or Watch Strictly

5 .0 m
AC14
1.0

7 .0

錨の把駐係数（λa）は 、計算式を使用するか、マニュアル入力すること。
Anchor Holding Factor（λa）：Use Calculation Formula or Input by mannual.

錨鎖の把駐係数（ λc）は ０．７５〜１．０
Anchor Chain Holding Factor(λc) ： 0.75〜1.0

５８§3.6 Ship’s operational safety measures for anchorage and their effects
Counter measures
Increase draught bytaking in ballast water

Remarks
EffectivenessShip’s weight is
Consider stability issues.
increased so thatvessel’s motions(Horsing) are decreased.

Trim by the head

The point of action
shifts afterward andtends to decrease thehorsing motion.

Consider stability issues.
Maintain propeller
immersion.

Veer more anchor cable Increases anchor chain
holding factor.
Extended catenary
length absorbs more
external force onanchor.

Consider that weighing
anchor is difficult inrough sea conditions
and more time will be
required to weigh theanchor.

５９Counter measures

Effectiveness

Remarks

Drop the other anchor

Can reduce yawing andhorsing motion by half,
and reduce force onanchor by 30%〜40%.

Consider amount of
second cable required is
one and a half times thedepth of water.
Consider the possibilityof fouling the cables,
particularly when
pitching heavily.

From the outset ofanchoring, to deploy
both anchors

Riding to two anchors
is said to increase
holding power and to
decrease horsing
motion.

Danger of fouling ananchor if the vessel isturned under the
influence of wind
and/or tide.

６０Counter measures
Use of bow thrusters

Effectiveness

Remarks

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

６１Counter measures

Effectiveness

Remarks

Use of the main
engine in combination
with steering

This can be aneffective deterrent to
the horsing motion
and will relieve thetension on the anchor
and cable system.

Do not allow the vessel
to pay-off suddenly
when the tension on
the anchor cable has
been eased as asudden increase intension may break-out
the anchor. Do notallow the vessel tooverride the anchor,
particularly in shallow
water where the vessel
could impact on theanchor if pitching.

６２=Example calculation of the increase in holding power when cable is veered =Ship’s type
: PCC laden with 6,000 units
Anchor Weight in Air (Wa) : 10.5ton ⇒ 9.135ton in Water
Anchor Holding Factor (λa) : 7.0
Anchor Chain Weight permeter in Air (Wc)
: 0.166ton/m ⇒ 0.144ton in Water
Water Depth + Hawsepipe height from sea surface (y) : 25.0m
Length of one shackle of anchor cable: 27.5m

Ship’s Projected area from bow above waterline (A): 800sqm

Wind pressure force Coefficient (CRa)
Air density (ρ): 0.125kg/sec2/m4: 0.75The anchor cable is assumed to have formed a catenary with nocable lying on the ground.

６３

Anchor Holding Power = Impact Force (external force) : 63.90tonf＊Impact Force (external force) = Wind Force from ahead x 6
The Wind Force from ahead
Catenary Length(S’):: 10.65tonf
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 〜 13.5m/sec.
The critical wind speed =Average wind speed x 1.25〜1.50

６４(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 theremainder forming part of a new catenary.
2Ｓ'+（27.5ｍ−ｌ）＝ ｙ + 2 x

Wa'x λa + Wc'xλc x l
Wc'

S’ : Catenary Length before one shackle is veered
150.90m(5.5 shackles)
l : Contacted length of the chain (laid over the bottom)
23.6m
Additional New Catenary 3.9m

The holding power created by theanchor and cable system = 67.3ton

:

xy

６５

The wind force from ahead = 11.23 tonf.
The critical wind speed= 17.3 m/sec.
The average wind speed= 11.5m/sec 〜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 〜0.3m/sec to the critical wind speed.
Importantly for those on the bridge, the critical windspeed is not increased as much as might be expectedeven if the anchor cable is veered considerably.
a full length of cable (12shackles) is veered)
The average wind speed= 13.1m/sec 〜15.7m/sec.

Increase of 1.8 m/sec 〜2.2m/sec

§3.7 The Critical Wind Speed
While looking into various reference books, there is
Reasons

no concrete indication.

・ 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 thetheoretical value obtained by calculation.
・ Continuing changes in the direction of the anchor cable andthe angle of action on the mooring system. The result is thatthe anchor cable may be subjected to shock stresses as thecable 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 thesafe and prudent decision may well be not to anchor.

６６

６７

§3.8 Emergency measures taken and their effectivenessafter dragging anchor① Veering an Additional cable and use of the second anchor
Adding cable to the first anchor is not seen as an effective meansof stopping a ship from being pressed and drifting to leeward.
② Use of bow thruster
The minimum thruster power must be equal to the wind force on
the bow.
③ Use of the main engine and steering
The required power of the main engine
Steering : Hard OverWind speed
20m/sec
25m/sec
30m/sec: Engine Order: Slow Ahead: Half Ahead: Full Ahead

６８§3.9 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, theeffect of the bow thruster is negated.
変針操船の限界
Limitation of maneuvering by rudder
Numbers entered in the vertical axis
are wind speed per ship’s speed andthe wind force angle is entered along
the horizontal axis. The yellow zoneshows the area under the curve inwhich the effect of the rudder is lost.

12
風
速
/
船
速
比

10

Limitation of Maneuvering by Rudder

変針不可能域
Unable Maneuvering Area

8
6
変針可能域

4

Wind Speed/Ship's Speed

Maneuvering Area

20Wind speed of 20m/sec, the ship’s speed would
have to be more than 5knots (2.5m/sec)

30

60

90 120 150 180

相対風向角（度）Relative Wind directin(deg)4,500 units ＰＣＣ、
h/d = 1.3
h : 水深(Water Depth)

６９§3.10 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

７０§3.11 Anchor Operation
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 theoperation 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, althoughmost mariners involved in anchor-related
accidents stated that the brake did not work
well, thorough investigations on site haveestablished that a bent brake shaft and / orlack 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.

７１

If the depth at an anchorage exceeds 20m, the possibility of damage to or loss of theanchor and its cable becomes greater due to excessive running out speed if the anchor isallowed to free fall. To avoid this hazard, the anchor should be lowered by walking backinto the water until the anchor reaches about 5m
above the bottom.
When letting go, the brake should be appliedin order to slow the veering rate until thelength veered is about 2m - 3m more than thewater depth. This should prevent the cablefrom 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 andwithout imposing any excessive stress on the system. (Ideally, repeat stretching, little bylittle, every time until it becomes taut.)Anchor Cable Veering Rate・Scope of Cable To Be
Paid Out・Brake Force of Windlass

７２

The Graph on the next page shows the relationship between brake force, scope of cableand veering rate determined during trials on board a 230,000dwt VLCC when anchor andcable are paid out using the brake. During the trial, the cable was first released with halfbrake 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 beseen, 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 becomesdifficult to arrest the cable and the brake lining may be damaged. If, however, theveering rate is limited to about 5-6m/sec by the timely application of half brake, suchdamage will be avoided.

７３
Result of VLCC Anchoring

Examples of entangling§3.12 Technical Measures for Anchoring(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 andexternal forces
・ To detect dragging anchor by observing the horsing motion
・ To use track display function of ECDIS・RADAR・GPS

７４

７５

Ref. ： Vessel Turning Motion and Control for High Speed vessels
Speed航走下における回頭運動と制御
参考 ： under
高速船のFullFull Speed
conditions
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 atmax.).

７６
Regarding the method of turning circle, which is measured during a sea trial and displayed in thebridge, 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 themnavigate 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 theTurning Circle
TransferMax. Transfer

Kick

Reach

AdvanceMax. Advance

Tactical Diameter

Final Diameter

helmsman in the event of rapid turning at
S/B being necessary (e.g. to prevent acollision or grounding).
Maneuvering with rudder Hard Over atFull Speed is not realistic because theabove-described trouble may occur.

In such a situation, in order to carry out
avoidance maneuvering safely at fullspeed and to remain at a safe distancefrom the shore, take into account the sea
area while paying careful attention to rateof-turn speed.

７７Focus 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-ofturn speed, which neither causes deceleration or engine harm, is approximately 10 degrees
per minute.
Conditions ： 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＝ 36 minutes (0.6 hours)
For example, in the event of avoiding acrossing vessel, it is necessary toconsider the sea area and timerequired for turning round at 90
degrees.
Otherwise, calculate estimated size ofsea area, required for one turning
round, by drawing and formula andchecking it by drawing it on the nauticalchart.

- Running distance over 36 minutes＝ 13.2 nautical miles (22 knots ｘ 0.6 hours ）Turn Rate : １０ degree/minutes
Ship's speed 22 kts

Transfer :2.1 miles

9 min.
Total run : 13.2 mile（３６分）

Advance :2.1 miles

18 min.

Final Diameter :4.2 miles

27 min.

７８AuthorCapt. Takuzo Okada
Master Mariner
General Manager
Loss Prevention and Ship Inspection Dept.

☎： +81-3-3662-7229
E-Mail : okada-takuzo@piclub.or.jp