MarlneSafetu\-

-.- Ro-Erdam b.v-

1. COURSE DESCRTP'IION

The shiphandling training course comprises five days of discussing and practising.

Research indicates that human error is the most prominent cause of ship groundings and
collisions. Most of these accidents occur in restricted waters near port entrances and where
traffic converges. It is at these times and in these places that the officer has the greatest
workload. He must effectively use all the equipment and resources available.

After an initial simulator familiarization run, the exercises will begin to increase in complexiry
by varying wind force and direction, amount of tug support as available at the designated port,
and type of operation. It is not expected that all your simulator runs will be successful. The
object of the course is to refresh your shiphandling skills under diffrculr siruations. By
engaging in demanding maneuvers or maneuvers which might be considered too risky for the
real world, it is expected that this simulator course will be both a challenging traiahg program
and a valuable information gathering tool. Some runs during the course consist of mechanical
failures or adverse weather conditions.

We trust that your involvement in this program will be both rewarding and enjoyable. If you
have any observations, questions, or input regarding the course content or simulator
operations, please make them known to the instructors.

The course has been designed for six officers to work with the instructional team over a period
of five days. The course attendees will participate in presentations/discussions, simulator
exercises, and debriefings.

1.1 COIIRSE OBJECTIVES

Officers successfully completing this course should:

1. have refreshed his/her skills in controlling the ships speed for safe and
comfortable nmneuvers;

- getting underway from berth/anchorage,

- moormg,
- entering and leaving a channel,
- using tfuusters, engine and rudder to maintain heading while
slowing down/stopping, especially in a following current;

2. develop an effective rug placement and use strategy to meet various sinrations;

3. handle unexpected s ih-rations ;

4. have enforced their theoretical background for handling large vessels.

The.best lafetJ derice on any lhip is a well truined ctew

Shiphandling Truining
 yf;3fi:?Y,ffi
1.2 coL,RSEREQUIRENIENTS

It is the desire of the shipping companies that attendees gain every possible benefit
from the instructors, the syllabus and the simulation exercises. Full and active
participation in every seminar, simulator exercise, and training activiry is all that is
required for a successful completion of the course.

Attitude on the course is very rmportant. Active participation to achieve a successful

completion depends directly on maintaining a positive attitude ft-roughout the week.
one additional small requirement is that participants fill out the course evaluation form
provided at the end of the week and give it to Marinesafety's instructor or training
manager.

1.3 COURSE SCIIEDWE

The schedule on this and the following pages presents the major elements of the course
and when they will occur.

Plenary sessions meet in classroom 1, located near FMB1. Briefing and planrung
sessions may take place either in the classroom or the (de)briefing room.

The course runs from Monday through Friday from 08.30 to 17.30 hrs each day.
Times are estimates except for the daily starting and ending rime.

MONDAY

Time Team one Team two

08:30 Welcome, stalf inrroductions, rrainee introductions, expectations, administrative details,

course overview, objectives and procedures.

09:30 Familiarization run Mawan Channel Theory lessons gs and shiphandling

l0:30 Theory lessons tugs and shiphafldling Familiarization run Mawan Channel

I l:30 Simulation l: Deparrure Europoorr Theory lessons and lunch

12:30 Theory lessons and lunch Simulation 1: Deparnrre Europoon

l3:30 Simularion 2: Deparnrre Nonhville terminal Lunch and theory lessons

Crenshaw Island

14:30 Theory lessons Simularion 2: Deparrure No(hville terminal

Crenshaw Island

t5:30 Simulation 3: Deparrure Dutch Harbor Theory lessons

terminal Easr

l6:30 Theorv lessons Simularion 3: Deparrure Durch Harbo( terminal

East

17:30 End of day one

The bert rafery device oh any ship is a well uained crew.. .

Shiphand,ling Tni^ine
 MarlneSafety r--
-a Botterdam b.v.

TUESDAY

Time Ieam one &am two

08:30 Simularion 4: Arrival San Pedro 93 A/B Theory lessons

09:30 Theory lessons Simulation 4: Arrival San pedro 93 A,/B

l0:30 Simulation 5: Departure Curagao Theory lessons

I l:30 Theory lessons and lunch Simulation 5: Adval Europom MOT I

13:00 Simulation 6: Arrival Europoorr MOT t Lunch and rheory lessons

14:30 Theory lcsson-s Simularion 6: Departure Curagao

15:30 Simulation 7: Deparhrre San Pedro 93 A/B Theory Iessons and video

16 30 Theory lessons and video Simulation 7: Departure San Pedro 93 A/B

l'7:30 End of day rwo

WEDNESDAY

Time Team one Team two

08:30' Simulation 8: Deparure Durch Harbor Theory lessons

terminal North

09:30 Theory lessons Simularion 8: Departure Dutch Harbor rerminal

Nonh

l0:30 Simulation 9: Arrival Curaeao Theory lessons

lI:30 Theory lessons ard lunch Simulation 9: Arrival Curagao

12:10 Simulation l0: Arrival Durch Harbor rerminal Lunch and theory lessons
Easr

l3:30 Theory lessons Simuladon 10: Arrival dutch Harbor ierminal

East

t4:30 Simulation I [; Anival Nonhville terminal Theory lessons'

Crenshaw

15:30 Theory lessons Simulation I l: Arrival Northville terminal

Crenshaw

l6:30 End of day ttuee

- The beat rafety devica oa an, rhe is a treu truined cru),)

Shipho dliq Truinhe
 Marine_S,Sfpty:^
. Rotterdam b.v.

TUGS

AND

SHIPHANDLING
 gf;:ft:",Y"ffi
INTRODUCTION

This document is intended to help shipboard personnel betrer understand and employ tugs to
insure their safe use when required for assist or escort service. More specifically, it will
attempt to describe Jhe primary safery concerns of tug operations so rhat stripboard personnel
will not expect, or ask, attending hrgs to attempt an unsafe act. To do so, not only risks
losing the tug and crew but also places the ship in danger. With a better understanding of a
ilg's abilities and limitations, the overall safety of ESC operations should be enhanced.

DEFINTTIONS

For this document, the foliowing terms will be used to generally describe hrgs based on their
assigned duties.
* Assist tug: A tug made up alongside or astern of the ship with at least one
line.
* Escort tug: A hrg runninq free. in close proximity in order to minimize
response time in an emergency.
x Towing tug: A hrg made up ahead of the ship via the tue's hawser. with the
tug towing the ship.

TUG DESIGNS - GENERAL

A tug, simply stated, is designed to float as large an engine in as small a hull as possible.
In order to accoraplish this task, 60% or more of the hull may be taken up by the engine
room with the balance usually fuel, water, and ballast tanks. The tug rnay also be equipped
with unusually large rudders which allows optimum application of power while assisting a
barge or ship. In order to be as maneuverable as possible, nrgs designed specifically for ship
work will usually be very short and stubby. Such a design creates built in hazards that must
be controlled by tug personnel. Because of the size of the main engines and auxiliary
equipment, it is impossible to subdivide the engine room making the tug susceptible to
sinking if the engine room takes on water in an emergency. Furthermore, because of the low
freeboard, water ingress into the engine room can quickly create a hazardous condition. To
qddress the danger of sinking, hrgs assisting a ship or barge should have all of their main
deck doors closed. Further, the watch officer will be cautious not to let the tug heel over to
a point where the main deck and bulwarks start to dip under the water.

Several other generic design features will improve a h:g's ability to work around a ship
efficiently. First, fendering all around the nrg's hull is extremely important to prevent
damage to the ship. Second, the setback of the main house and wheelhouse will allow the tug
to get back under the ship's counter or under the flair of the bow where pushing can be more
effective. Finally, having a wheelhouse from which the fug operaror can see every corner of
the nrg without leaving the maneuvering station will allow the tug to operate in tight quarters.

"Kort Nozzles" are another feature found on newer or rebuilt tugs. These nozzles (or
propeller shrouds) are designed to direct the thrust of the propeller and can give a nig up to
a 40% (in general 20%) increase in effective horsepower when working at a dead push
(pushing on an object while making no way). The nozzles may be steerable or fixed. In the
latter case rudders are required, such as normal rudders, fishtail mdders, towmaster system,
etc.

The belt safery device on any ship Ls a well taiied cre'v.

 MarineSafety.---
--,^ Botterdam b.u

SINGLE SCREW TUGS

Older tuss will usually be single screw. Many have been rebuilt over the years to
dramatically increase their horsepower (at the expense of freeboard), but all suffer from the
same limitations, namely their relative lack of maneuverability. Because older designs were
usually long and narrow, they do not spin well and the nrg operator rhust usually back and
fill when maneuvering in tight quarters. This makes them generally slower to respond to
commands.

iurther, with oniy one large w.heet, the tug will have a marked tendency to back around
(usually with the stern to port) when operating astem for extended periods. To control this
swing, these tugs usually will run a line (called a lazy lne) from the stern or quarter of the
tug up to the ship. This will allow the tug to back for an extended period but given the
concern for tripping the tug, the ship must be operated at very slow, speed when in this
ionfiguration [under two knots] .
A critical danger when using h.rgs with lazy lines occurs when undoiking a ship with the
wind on her beam. Once off the berth, the ship must gain some speed to counteract the wind.
The h:gs must then get their lazy line in quickly to avoid being dragged along sideways and
tripped. This requires careful maneuvering of the ship, control of speed, and good
communication with the tug regarding when to let go. Another variation of this undocking
maneuver is to use a hawser from the stern of the tug to pull the ship off of the berth. Before
picking up too much speed, it is similarly important to give the tug personnel sufficient time
to release the hawser.

The key to safely using a single screw hrg is to understand their limitations and keep the
ship's manerivers withih that envelope.
 MarineSafety...-
.--. Rotterdam b.v.

TWIN SCREW

Later hlg designs usually have a twin screw layout which greatly improves maneuverability
by allowing them to "twist" or "rwin screw" into position. Further, to accommodate the main
engines positioned side by side these tugs are generally wider (and shorter) than their single
screw counterparts which also increases their maneuverability when working ships in and
around piers.

Twin screw ruqs can, by backing or y one engine, crab along sideways and stay in position
while backing as long as the ship is moving relatively, slowly. Another trick used by some
tug crews to allow them to back along with a ship, is to dip the ship line under their forward
quarter bitts on the side they want to back towards. This changes rhe towing point enough
to effectively offset the engine thmst allowing them to crab sideways faster. If the ship
handler anticipates the need for this type of tug to use full power astern for an extended
period while the ship is moving tfuough the water, a lazy line may be required to insure that
the tug can remain in position.

To obtain more maneuverability when operating in the astern mode, some tugs have been
designed with "Flarking Rudders'' which are rudders mounted ahead of the propellers. Tugs
so equipped are vFry maneuverable. Further, as they have directional cortrol while backing,
they can back hard on their head line while at the same time crabbing sideways to stay in
position with a moving ship.

The best safety device on bny ship ir a well troined cte\,'). ...
TRACTOR TUG DESIGNS
,'Z'' DRN'ES

A tractor tug is equipped with a propulsion system located under the forward part of the hull
that provides thrust through 360" giving the tug handler increased flexibility for
maneuvering. There are two basic rypes of tractor hlg propulsion systems, the first,
(illustrated above and often referred to as "Z'' drive) are produced by several companies
(Aquamaster, Niigata Z-Peller and Schottel), look and operate like the lower unit of an
outboard motor..These designs can be equipped with nozzles to increase their effective
horsepower.
The second type of tractor nrg, produced by Voith-Schneider is called a cycloidal propeller.
In this design, the propeller blades are mounted vertically and look somewhat like an
eggbeater. This design loses some efficiency in a dead push, but is very well maneuverable.
In general tractor tugs push"/pull with their stern towards the ship's hull, otherwise the tug's
propellers are too close to the ship's hull, decreasing the tug's propeller efficiency.
In doing so they can also push better at right angles to the ship's hull when the ship has some
speed.
Another design fean:re of this type of tug is that with a relatively rounded hull shape there
is less concern for tripping while baiking against a head line when the ship has way on.
Adjustment of thrust allows the nrg to crab along sideways with the ship.

Due to its specific design, a tractor type hlg can, when operating in the " indirect towing
mode " , apply tensioir on a tow line in excess of the measured bollard pull. The tug itself will
be placed at an angle to the tow line (much like a water skier) so that the tug's hull becomes
a rudder for the ship greatly increasing the steering forces that can be applied to the stem of
a ship versus a conventional tug. Because tractor tugs are designed for maximum stability
(shoit and wide with a round bottom) these tugs can operate in this " indirect mode'i without
risk of tripping. (see below)

INDIRECT TOWING MODE

'
The be safery device on any shtp Ls a welL trainecl crew . . - . .
 Y;H?Y"ffi
Because tractor tugs are only available at a limited number of ports
within the United States
(Puget Sound and Los Angeles for ESC vessels), and are generally safer to operare,
subsequent information will focus on the safety aspects of conventional tugs.

TRIPPING

Besides the normal safery concerns of working aboard a vessel with heavy lines, wires, and
machinery, the tug watch officer has an additional safery concern, that of tripping or girding
the tug. As described, hlgs are designed to produce large amounts of horsepower; however,
full thrust can only be safely applied, without qualification, along the fore and aft centerline
of the hull. If the thrust vectors are applied off of this fore and aft centeriine the rug will
begin to list and, in extreme cases, the tug will trip and capsize. For example, as a tug is
towed through the water on a headline, the tug's hull will usually be at an angle to the ship
and the water flowing under the tug's hull will create one of these off centerline vectors and
the trlg will begin to list. Because of the limited freeboard available on most tugs, coupled
with the very large engine room, this capsizing and sinking usually happens very quickly,
with the probable loss of life.

The specifics of these operations that may create extreme off centerline vectors will be
discussed later in this article but for the ship handler, it is critical to understand that if this
situation is reached in the mind of the nrg operator all thoughts of the job at hand then
becomes secondary. When the nrg is in extremis, quick action by the watch officer is
necessary to save the tug. Therefore tugs are equipped with quick release towing hooks or
quick release toWing winches. So tugs should be used very carefully because when forced
into an extremis situation, the nrg must abandon the ship which, ' if during a critical
maneuver, couid also place the ship in danger.

OPERATIONS-ASSIST TUG

Application of extreme off-centerline forces occurs most often during two operations. First,
and most often observed, is when an assist tug is used to push on a ship which is underway.
When maneuvering to get out perpendicular to push, some of the tug's thrust will be applied
Io the ship, but some is also required to hold the h:g up, bodily pushing her through the
water sideways. It should be understood that as the ship moves faster through the water more
and more of the tug's thrust is being used to hold the nrg up against the water flow. The
force of the water flowing under the nrg will tend to cause a list which will be directly
proportional to the speed of the ship and the amount of power requested from the tug by
whoever has the con.

Once the tug's main deck begins to dip under the water, the tug is getting into an extremis
situation, and some immediate action needs to be taken to avoid capsizing. Usually, the
normal reaction to save the tug is to cut the ship line.

For safery reasons, conventional nrgs should not be made up alongside a vessel while
underway at a speed above six knots. Additionally, before requiring a tug to push, the ship's
speed should be further reduced to below four knots. If there is any question as to the rug's
ability to remain alongside at a certain speed ship's personnel should discuss this point with
the tug operatoq. Further tests have demonstrated that a conventional tug camot effectively
apply lateral forces to a ship at speeds above approximately three to four knots (depending
on the size of the tug) while creating a hazardous condition for the tug in attempting to do
 y;8fii?Y"ffi
so. For the person conning the ship, it is important to be aware that if a tug does not get to
90', because of the forward speed of the ship or the current, the nrg wili actually be shoving
the ship forward as well as sideways.

From a pqll perspeative, a nrg can assist maneuvering the ship by backing against its headline
as soon as it is safe to put up a headline (about six knots). Another point to consider is that
a tug will be able to push harder than it can pull (because of water flow against the hull of
the tug, propeller design, etc.).

Another method of using an assist n]g is to make the hrg up to the stern of the ship. On a
conventional type hrg two lines may be used in an "X'' pattern (from port bow of the tug to
the starboard bitt of the ship an vice-versa). A nrg made up in this fashion can act as a very
effective rudder for the ship by either coming ahead and pushing against the stern (most
effective on a vessel with a square stern) or by backing against one or the other head lines.
Additionally, a h:g made up astern can be used to provide retardation forces.

There are, however, a few restrictions that the ship's personnel should be aware of so as not
to endanger the conventional hrg. First, the tug astem should never be towed through the
water faster than the tug's hull speed. Second, it is not recommended to require the tug to
push against the stern to steer the ship at speeds over approximately four to six knots
(depending on the size of the tug) as the tr:g could heel over dangerously. Further, depending
on the ship's draft, full bells on the ship may subject the tug to excessive rurbulence and
forces which may part the nlg's lines or make it difficult for the tug to maintain position.
Filally, if a backirlg order is given to the tug a gradual increase is desirable in order to aliow
the rug to get into her line.

A tractor tug when used on the stern will operate somewhat differently. Fhst, because of its
maneuverabiliry only a single line is used. Second, instead of pushing on the ship, maximum
steering conffol forces will be developed by operating in what is called the "indirect towing
mode" as illustrated on page 7.

One last cautionary note, when tugs are alongside and working in the area of the anchors it
is a good practice to place the anchor riding pawl down to prevent it's release.

Against such a background, it is recommended that shipboard

personnel discuss speed
through the water and intended use of the tug(s) with the tug watch officers involved before
passing any lines to ensure that everyone understands what is expected and that the required
assistance can be provided safely.

OPERATIONS - ESCORT TUGS

Escort tugs of proper design (tractor hrgs, azimuth stern drive (ASD) rugs) may make fast
to the stern of a proceeding vessel, optimizing response time to an onboard emergency.
Escort hrgs may also run free at a distance from the ship which enlarges response time to an
onboard emergency. However, when the free running escort tugs are required to respond to
a shipboard loss ofpower or steering failure, also these escort rugs then become "assist tugs"
as sooh as a line is made fast.
The abiliry to provide steering or retardation forces is influenced by vessel speed and hrg
design as described in the previous section. The environmental conditions or regulatory
requirements should be taken into account.

The best safery device on an! ship is a well nained crew . ..

 g;ffi?Y"ffi
Another advantage of having an escort nrg mnning with a sh.ip at night is that the hrg can use
her searchlights to detect unlit buoys or bridge abutments for the person conning the ship
making the SHIPHANDLING easier and safer. Further they can be senr on ahead to look for
ice or to alert pleasure craft of the approach of the ship.

OPERATIONS - TOWING TUG

In the United States, hrgs are not usually employed on of a ship. Exceptions
a hawser ahead
are: when transiting th-rough narrow bridges or channels (Long Beach Channel #2) where the
assist tugs camot remain alongside and when towing a dead ship.

When passing through bridges, the towing rug can provide steering control for the bow of
the ship. Once the tug has cleared the bridge, the tug is then free to pull in any direction.
Generally, this method of operation is used when maneuvering room is restricted and speeds
are, by necessity, maintained at minimum steerage way. This minimum speed is extremely
important to insure that the ship does not overrun the hlg.

A tug towing a dead ship, must insure that control is maintained over the ship at all times.
The main difficulty with this rype of operation is that a loaded ship or barge will generally
be unstable and will tend to swing back and forth on the tow line. This tendency to shear
from side to side will usually become more pronounced as the speed of the tow increases.
Depending on the severity of these swings and the tonnage of the towed vessel, the tug can
very quickly becpme overpowered by her charge. In confined waters, on a short hawser with
a large tow, this shearing can be dangerous at speeds as low as three knots.

If the towed vessel takes a shear, the rug must work to brilg her back onto the base course
and in doing so the towing forces now become angled off of the centerline of the n:g. In
extreme cases where the towed vessel has been allowed to gain too much speed, the tug will
find that she carmot break the shear and the hawser will move further aiong the bulwarks.
At this point, the nrg's list will become severe as the h.rg maneuvers to get back in front of
the tow, forgetting for the moment where it is headed. Once this point has been reached, the
hlg and tow are in extremis. The tug's watch officer must decide if it is possible to safely
get back in front of the tow and regain control possibly slacking the tow wire to ease the
strain on the hrg to do this or; if &at is not possible, get the hawser back over the stern
(eliminating the capsizing theat) and let the fiig flop alongside the tow. In either case the tug
has lost all control of the tow until speed has been reduced and hawser control stabilized.

Dead ships moving within a harbor are normally provided with multiple assist boats made
up alongside in addition to the towing tug. The number one safety factor to remember in
towing a dead ship on a short hawser is to keep the transit speed to an absolute minimum.
Shipboard personnel and the nrg's watch officer must watch very carefully how the. ship is
handling because when operating on a short hawser as there is very liftle time to react if the
ship takes a shear.

Another important consideration when towing a dead ship is the location of the person in
charge. Usually, when shifting in a harbor, the person with the con will be on board the ship
and positioned to see al1 of the tugs. Familiariry with the towing tug's capabilities, as well
as having an understanding witir the hrg's watch officers on how the rugs will be used and
orders given (course changes [versus conecting shears], stopping, maximum speed etc.), is
necessary to best insure the success of the operation.

The best tafery device on any ship is a well ttoined crcw. ...
 gf;8#Y,ffi
Normally at sea, with increased amounts of hawser paid out, the hawser itself will act to
stabilize the tow, but the hrg should work up to full speed very carefully to insure that the
tow is indeed stable. Course changes at sea should be gradual (5" to 10' at a time depending
on the size of the tow) always allowing the tow to stabilize behind the towing tug before
hrrning further. Similarly, speed reductions hould be very gradual to keep the hawser off of
the bottom and to allow the tow to maintain position behind the tug (the tug may have to
shorten her hawser). Consideration should be given to the weather and sea conditions when
slowing down also as the tow will be influenced by these factors to a larger degree.

OFFSHORE RESCUE TOWING

ESC tankers in dedicated trade to Valdez are equipped with a forward emergency towing
package for use when tug assistance is required in the event of loss of propulsion or steering.
The use of this package is demonstrated in an onboard training video. All ship's personnel
should review this tape to gain familiarity with deploying the equipment. For safety reasons,
when releasing the towline, all crew members should stay well clear.

The difficult part of tliis operation, is picking up and making the towline fast on boardthe
tug. Prior to attempting the maneuver, the nrg Captain and Ship's Master need to discuss the
intended operation to insure that each understands their role. This discussion should also
address the timing of the hookup. If the weather is bad with the tug taking seas on deck, it
would be dangerous for the tug's crew to be on deck attempting to make up. If time permits,
it may be desirable to wait for better weather or daylight before attempting to pass the tow
wire. There may be an occasion when expeditious connection is necessary due to the
proximiry of danger, however, the safery of personnel must always be considered.

As demonstrated in the video, once the towing package is deployed, the tug will approach
the buoy and pick it up using a boat hook. Using the attached messenger, the tug will then
pull in the towing wire using its capstan. Once the bitter end of the wire is on deck this will
be shackled into the rug's hawser and the hawser streamed slowly as the tug moves away
from the ship.

On ESC ships that are not equipped with this towing package, all of the towing gear will be
provided by the tug. If the ship.has power on deck, the ship's windlass will be used to heave
the tug's towing gear aboard.

The n:g, when all of the towing gear is ready for deployment, will position itself close
aboard the lee side of the ship's bow. Using a line throwing gun the ship can pass the first
light messenger, then use it to haul in the tug's heavy messenger and then the towing wire.
The tow wire should be run through the bull nose (or a forward chock) and the secured at
one of the forward bins. How to rig the heavy messenger to this tow wire to easily bring it
through your chock is illustrated on the next page.

If the ship does not have power on deck, the tow wire can still be passed using a snatch
block on the foredeck of the ship. The messenger is passed tfuough the snatch block (or
around a bitt if unavailable) and then back to the tug. The tug will then use its own power
to heave the messenger and tow cable up onto the deck of the ship where it can be stopped
off and secured.

l0
The point where tle tow wire passes through the bull nose or chock on the ship needs to be
heavily greased to prevent excessive wear on the towing gear.

When towing another vessel at sea, the tug captain must insure that the two vessels can move
independently in the seaway or else the tow wire might part. To provide this elasticity
between the tug and ship, an intermediate piece of towirg equipment will be used. On the
East and Gulf Coasts where the water depth is relatively shallow, the nrg will generally use
a length of very ela'stic synthetic line (usually braided nylon) called a "shock line". On the
West Coast, with the heavy swells to contend with, the nrg will use one or two shots of chain
to provide a very deep catenary and elasticiry.

pnce the tow wire has been streamed to its required length, the first prioriry is to stabilize
the ship and stop her drift toward shore. As the ship comes around under the control of the
tug and is headed away from the nearest shoreline, the n-rg can add more power and move
the tow around to its intended heading watching very carefully how the ship is handling
(shearing), how the tug is riding (is the tow cable over the stem or dangerously riding up
the bulwarks?) and how much set and drift the tow is experiencing to make good its intended
course. Speed should not be a factor on the first day of the tow; the primary consideration
is to gain control oyer the ship, and establish a safe operation.

Another method that can be used by a nrg to make up to a ship at sea is by using an "Orville
Hook". This hook has a slot similar to a devil's ciaw cut into it to catch chain. In use, the
hook is attached to the main tow wire and then dragged about 200' astern of the h.rg with its
depth regulated by a buoy. To make fast to a ship, the ship's anchor is payed out to below
the surface of the water, and the tug drags the hook around the bow of the ship snagging the
anchor chain. Once the anchor chain is captured, the ship will be required to back out a
certain amount gf chain as surge protection for the tow wire. The tow will then proceed
towing on this hook.

The besi solery device on ony ship is d \lell tained ctew. t1

 MarineSafety.-.--
'.... Rotterdam b.v.

ORVILLE HOOK

COMMIJNICATIONS

In order for the tug to be truly responsive to a ship's commands it is very helpful to
set up
a good communication system. This is very important when tugs are assisting in the docking
maneuver. The peison who has the con of the ship should irxure that each tug knows what
frequencies.are to be worked, how each boat will be identified ("Empire", "Bow boats", etc.)
and what kind of response, if any, is desired. Tug captains should repeat the orders while
mentioning the tug's name or other identification. So, pilot and tug captain will know that
the order is well understood. Finally, while most harbor Brgs will know what the maneuvers
will entail, it is good practice -to review with them these maneuvers and what each tug's
assignment will be to insure that everyone understands the intended plan.

Giving advance notice to a tug is required when a change from all stop to either pushing or
pulling would be required. This allows the tug operator to work the n:g into positing for
optimum response. This is especially true if a tug is working at or near the stern where the
propeller wash will get the tug out of position if it is not prepared. Further, it is better to
ease into any order by initially going to slow, half and then increase up to fuIl, if necessary.
This procedure minimizes the risk of parting the nrgs line when going from stopped to full
astem.

Generally, it is considered more effective and controlled when giving h:g orders during a
docking maneuver, to increase or decrease power requirements in small ilcrements rather
than going from half ahead, stop, half ahead, stop, etc. in rapid succession. Further, if the
orders are too.rapid the tug cannot respond before the next order is given, effectively
accomplishing nothing.

The best safery device dn ony ship is a well truined cte\' ....
 y;:fi:?Y"ffi
Tugs do not record engine commands or push/pull instructions, therefore; it is always good
practice to assign a member of the Bridge Team to monitor the pilot's orders to the tugs.
Having the nrgs respond with whistle signals will aid in catching this type of error.

SLMMARY OF TUG HIGHLIGHTS

Ship's personnel should consider several design factors on the nrg before assigning them to
a particular position to optimally use her capabilities without exposing the tug to danger.
They are:

* Bollard pull, a measure of a tug's thrust in a dead pull as demonstmted by pulling

against a pressure pad, is an accurate measure of a tug's ability to push on a ship.
However, test results are not always available nor determined on a consistent basis.
x Kort nozzles give rp to a 20% increase in effective dead push horsepower.
t Length to beam ratio is important as a long narrow tug will be less maneuverable and
more susceptible to rolling over when working alongside. Depending on the particular
maneuver planned for the ship a longer tug may have difficulry responding quickly
to some orders (to change position for example).
, * Cycloidal propellers, Z-drives, twin screws, flanking rudders or controllable pitch
propellers will make the tug more maneuverable around the ship.
* Draft of the tug will allow her wheel to get a better bite and therefore push harder,
conversely a deep draft nrg will be less maneuverable and may have some difficulty
holding up' agaiast a current.
* Fendering on the nrg is very iinportant to prevent damage to the ship.
* Visibility from the tug's wheelhouse (can they see the corners of the n:g from their
maneuvering position) will be a great advantage to a hrg working closely between a
ship and a pier.
* The substantial setback of the tug's house will allow operation under the flair of the
bow or stern and more effective use of horsepower by pushing right at the stem or
stern of ship (better leverage).
* Clutch time response is very important in close maneuvering siruations. Usually tugs
, designed for ship work will have very quick clutches (5 seconds) where an offshore
boat pressed into ship work will be much slower, sometimes up to 15 seconds or
more.
* Tractor hrgs and ASD nrgs can exceed their design bollard pull when operating in the
" indirect mode".
* Conventional tugs can usually assist at speeds up to about six knots, however, at the
higher speeds they primarily apply backing forces rather than pushing forces.

t3
 y;ffi?Y"ff*
TUG PLACEMENT

In planaing nrg placement, always allow for the unexpected to happen. If the current is
different than planned, if a tug pans a head line, if a tug suddenly loses power, if the ship
loses power; what are the action steps to maintain control? At every phase of handling a ship,
knowing the options for maximizing safery should be included in the overall plan.

Keeping the above in mind, and considering the assisting tug's characteristics, a decision can
be made on how to place them around the ship to optimize response to the particular
maneuver. Generally, the reported horsepower (bollard pull) should be balanced at each end
of the ship but not to the exclusion of tug maneuverabiliry. For example, given equal
horsepower, a tug having twin screws, Kort nozzles, and flanking mdders has more
flexibility in responding to a command than a twin screw, Kort nozzle design. If a tractor
is assigned along with a conventional design, then consideration should be given to making
the tractor fast astern while the ship is moving faster than conventional tugs can safely assist
given that retardation and rotation forces can be applied by the tractor at speeds up to 12
knots.

If when pushing a ship bodily into a berth, there is available two tugs [one of 2,000 H. P.
and the other 4,000 H. P.l, one is used at the bow and the bigger nrg just forward of the
after house, each can push or pull at near maximum power to provide bodily movement to
the vessel. If however, the 4,000 H. P. was placed at the extreme end of the ship, only half
power could be used in order to avoid spinning the ship around the smaller horsepower tug.

Each maneuver is different and there may be several separate maneuvers involved when
moving a ship. Think each maneuver through carefully, step by step before deciding on the
placement of available horsepower. Remember, that given time, the hrgs can very easily be
sent from one poiition to another as each phase of ship movement changes.

TUG LIIIE HANDLING

Establish communication with the nrg's crew before you attempt to heave in the tug's line.
If there is a wire pendant on the end, make sure that gloves are worn to protect against
fishhooks.

Use a messenger of sufficient size and strength to lift the rug's line on deck. If possible,
request the hlg crew to tie off the messenger toward the end of the ship line eye to facilitate
placing the eye over a bitt as well as messenger removal should that be necessary once made
fast. Always slide the messenger Iine back on the eye to prevent it from pinching at the bitt.
Insure that personnel are clear of the line before notifying the tug the line is secure.
Mechanical assist should be used whenever possible to avoid back injury when line handling.

While the nrg is working alongside, there is always the possibility that the line could part
under heavy strain. As a general rule, any point about a l0' cone around the line from any
point at which the line may break is a danger zone. Further, a broken line will snap back
beyond the point at which it is secured. Finally, where the line passes through the chock and
then off at sorne angle to the tug, you cannot count on the line snapping back in the direction
from the chock to the bitt. Because of this potential, personnel should always be kept well
clear of tug lines and consider them to be under tension at all times.

me best lafery device on ant ship is a well trainel crew .. .

 yfi:#??"ffi
Always consider the ship's chock as a potential failure point for a tug's line which is under
heavy tension. Keep the deck crew clear at all times while a tug line is used regardless of
applied load.

After the job is firtiShed, re-establish communication with the tug and then wait until the ship
line has been slacked before allowing the crew to reattach the messenger or remove the eye
from the bift. Before lowering away, insure that the hrg's crew is ready to receive it, and
while lowering, keep it under control using a few hlrns on a bitt or warping end of a winch
to avoid striking persomel on the rug's deck and to keep the line clear of the rug's wheel..
When releasing begins, all ship personnel must be safely out of the way. Lowering should
be done either with the attached line or with a messenger long enough to ensure the towing
line is under control until on the deck of the tug.

When releasing a tug line, the supervisor should insure that all personnel in the area are not
standing near the line or in a bight. He or she should be in a position to observe the actions
of tr:g personnel until the line is safely landed on the rug's deck.

If releasing a lazy line when the hrg cannot get alongside, a messenger should be attached
of sufficient length to insure control of the line (regardless of size) is maintained until the eye
has been brought aboard the nlg. All personnel must stand behind the controlpoint i.e.:
behind the mooring bitt or warping end of the winch. This is especially important if the n:g
is using mechanical assist to retrieve their line.

F'IIRTIIER READING

SHIPHANDLING WITH TUGS - George H. Read

TUGS, TOWBOATS, AND TOWING - Edward M. Brady
MODERN TOWING - John S. Blank 3rd
SHIPHANDLING FOR THE MARINER - Daniel H. MacElrevy
SHIPHANDLING IN NARROW CHANNELS - Carlyle J. Plummer
HARBOUR TUGS. TYPES AND ASSISTING METHODS - Henk Hensen

Thc be$ safery device on any ship is o well trained crev.

 CONTENTS
1. lntroduction.

2. Controllableforces.

2.1 Introduction.
2.2 Engines.
2.3 Propellers.
2.4 Rudders.
2.5 Propeller and rudder combination.
2.6 Bow and stern thrusters.
2.7 Anchors.
2.8 Tugs.

3. S em i-contro lla b le forces.

3.1 Shallow water effect.

3.2 Bow Cushion and Bank Suction.
3.3 lnteraction between shils.

4. Uncontrollableforces.

4.1 lntroduction.
4.2 Wind and Current.
4.3 Required bollard pull to compensate wind and current forces.

5. River/canai navigation and port manoeuvring.

5.1 General.
5.2 Conning.
5.3 River/canal navigation.
5.4 Port manoeuvring.

6. Ship's speed.

\- 7. Emergency.

7 .1 General.
7 .2 Emergency shiphandling.

8. Pilot/C.O. Relationship.

Appendix: A. Explanation Shallow Water Effect and Ship - Ship lnteraction.

B. Use of tugs in pilotage operations.
C. Effectiveness and use of bow- and ste rn-th rusters.
E, M iscellaneous
\- 1 . lntroduction.

Good shiphandling is based on experience. lt is sometimes called an art. That is

true to certain degree. But unknown of the basic principles of manoeuvring and
unknown of the experience of others, one will only learn the hard way. An exact
prediction how the ship will behave in certain circumstances can not be given.
Being aware of what might be expected gives the opportunity to anticipate. A
ship is under influence of several forces. The forces acting on a ship can be
divided in three categories:

A. Controllable fo rces.
The forces controlled by the ship handlers's own actions by:
* engine;
- * P ro Pe ller;
* rudder;
\!- * bow thruster:
* anchors;
* moorings;
* tuis.

B. ntrollable forces.
Sem i-co
Hydronamic Iorces created by:
* shallow waters;
* narrow waters;
* inte raction between vessels.

C. Uncontrollableforces.
Forces of:

* wind;
* current;
* wavgs.

Shiphandling is:

"To use forces under control to master forces not being under control".

It will be clear that a shiphandler has to make an assessment of the passage

3
 and arrival/departure with respect to the external forces that might affect the
. vessel, the semi-controllable and uncontrollable forces. On the other hand he
has to know how to deal with these forces by using the controllable forces.

So the ship handl'er has to know:

how external forces will affect the ship;

how to use the controllable forces in the most effective and safe way and
to compensate and/or minimize the influence of the external forces by
use of the controllable forces.

This Shiphandling Manual will discuss these forces. ln addition this manual will
give recommendations with respect to passage planning.

4
2. Controllable forces.

2.1 lntroduction.

Controllable forces are the forces exerted by the manoeuvring devices,

which are under direct control of the ship handler. These basic
manoeuvring devices are:

the engine;
the propelleris);
the rudder(s);
the bow thruster.

ln addition, the ship can be controlled, depending on the situation, by:

B. the anchors;
moorings;
tugs.

The basic manoeuvring devices together with ship's dimensions and

ship's hull form determine the manoeuvring characteristics of the ship.

These manoeuvring characteristics can be determined at sea trials by

following tests and has to meet certain minimum IMO standards (see IMO
Resolution A. 751(18) of 4 november 1993):
* turning circle tests (see fig. 1);
* zig zag tests;
+ full astern stopping tests.

Pivot ooint.

A most important aspect with respect to manoeuvring is the location of

the pivot point as shown in fig. 1. This pivot point is an imaginary point
where a mariner will find himself moving parallel with the ship's middle
line when the ship is in a turn. The ship is turning around a vertical axis
through this point. lt is not a fixed point. A ship stopped in the water: and
starting the propeller on ahead will have the pivot near the bow. A ship
having speed ahead will have the pivot point somewhere between the
bow and the midships, depending on the L/B ratio. A ship having
sternway will have the pivot point somewhere near behind the midships
and the stern.

The different manoeuvring devices will shortly be discussed.

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6
2.2 Engines.

The most common engines are:

- diesel engines;
- steam turbines.

ln addition one can find diesel electric propulsion, gas turbine engines,
etc.

Diesel enoines.

Diesel engines are most common. The main characteristics of diesel

engines are as follows, assuming a fixed propeller:
* Fast stop and start of propeller.
* Engine can be quickly reversed.
* Difficult to reverse engine at high ship's speed.
* Good astern power \7O - 90% of ahead).
* Minimum rpm can be rather high.
* Starting air lim itations.

Steam turbines.

Steam turbines have been frequently used in large vessels. The percenta-
ge of steam turbines is decreasing and are now rare. Characteristics of
manoeuvring with a steam turbine are as follows:
* Slow response on engine orders.
* Stepless variation of rpm f rom very low till maximum rpm.
* Poor astern power (35 - 4Oo/" of ahead).

Diesel electric engines.

+ Very fast response on engine orders.

* No starting air limitations.

Gas turbine.

* Highly responsive.

7
2.3 Propellers.

Ships can be single screw, twin screw or even be equipped with three
propellers, such as some large Scandinavian container vessels. The
propellers Can be:

- Fixed pitch ProPellers '

- Controlla ble Pitch ProPellers.
- Adiustable Pitch Pro Pellers.

First a short explanation will be given of an important phenomena of

propellers: the paddle wheel-ef f ect.

Paddle-wheel effe ct.

To know the paddle-wheel effect is so important because a shiphandler

witl plan the manoeuvres taking into account this effect. When fitted with
fix propellers, single screw ships are normally equipped with right handed
propellers: Propellers that turn clockwise when steaming ahead.

When a right handed propeller is set for astern, the stern Vvill move to
port. This means that the bow will swing to starboard. ln case of a left
handed propeller the bow will move the opposite way, s.o to port.
Therefore, when a ship does not have a right handed propeller the pilot
should be informed in time, otherwise he might plan a wrong approach
manoeuvre!

The explanation of the paddle-wheel affect lies in the asymmetry of the

water flow through the propeller disc, caused by the proximity of the
ship's hull. With a right hand propeller turning astern, so anti-clock wise,
the water stream at the top of the disc will hit the stern plating with a
strong forward and some portward velocity, exerting a portward force on
the hull. There is a cbrresponding starboard velocity at the bottom, but
the lines here are finer and some of the flow passes under the keel.

When the propeller is turning for ahead there is also a paddle-wheel

ef f ect, but this is much less noticeable.

Sinoleicrew vessels with fixed orooellers.

Right-handed propeller: Ship's bow will swing to starboard when

propeller is turning for astern.
Left-handed propeller: Ship's bow will swing to port when propeller
is turning for astern.
Propeller effectivity on astern is normally good.
Ship's speed at lowest rpm can be rather high. -
Controllable pitch propellers (cpp) are normally turning anti-clockwise to
give the same paddle-wheel effect on astern as with a fixed pitch propel-
Ier. Pilots should be informed when the ship has a clockwise turning
propeller! CPP's may have f ollowing characteristics (see f ig. 2):

Minimum manoeuvring speed can be very low.

* Paddle-wheel eff ect unpredictable.
+ Low propeller efficiency on astern.
Speed can be stePless regulated.
Very fast manoeuvring.
No shortage of starting air.
Propeller is continuous rotating: Beware of mooring lines near the
p rope ller.

Adjustable oitch prooellers.

New type of propellers where pitch can be regulated to a certain extent

regulated only in the ahead position. Depending on the weather situation
the blades can be set in the most effective way during an ocean passage.
With respect to manoeuvring these propellers have following advantage in
addition to f ixed propellers:

Minimum speed can regulated and can be less than with fixed
propellers.

Twin screw vessels,

Twin screw vessels with either fixed or controllable pitch propellers.

Fixed pitch twin screws usually turn outwards when going ahead: the
starboard propeller is 'right handed and the port propeller left handed.
When one propeller is put for astern the turning moment on the ship is in
the same direction as the transverse thrust of that propeller.

ln case of controllable pitch propellers the propellers will usually turn

inwards with the turning moment and transverse effect of the propeller in
the same direction, although the paddle-wheel effect will often be less
and also the astern thrust.
 Ship steaming lull spoed. Ship having stsmway.
Ship is stegrablo doso Propoll€r pitdr is brought Order for sh€ad pitcfi.
towards tho berth with down too quicldy. Ship will might not bo stop-
minimum so 63sifu-

Ship is spproadling berth.

Propoller pitdr is s€t for
Ev6n rathor large ships
astem. Uncedain whidr can stsam uP in tho
direction the bow will go. realizs, that zoro pitch
spring line while moo.-
Possibly poor enem etfoct is not z€ro sp€od, this
ring or unmoodng.
can be dangerous whon
mooring doso to an
oiher ship or when
stardng the cpp when
lin6s ar6 slack

Figure 2 CPP st6rt6d. Ship's lin€s slad(

Dus to transveGe etl€ct ot propollsr
ship's slem might go off tho b€rh.
Copyright H. Hensen.

10
2.4 Rudders.

Ships can be equipped with different types of rudders. The most common
type for modern merchant ships is the semi-spade rudder (see f ig. 3).
High efficiency rudders can be found more and more on modern container
ships, such as Becker (see fig. 4), Barke or Ulstein rudders (having
moveable flaps at the end of the rudder blade), Schilling rudders having
no movable parts are constructed in that way, that they give very high lift
forces.

These high efficiency rudders have special effects:

Steering perf ormance is excellent.

When the ship is dead in the water and the rudder is laid at maxi-
mum angle the rudders wlll exert high side forces when engine
power is set for ahead. ln combination with the bow thruster the
ship can manoeuvred crosswise, without getting headway.
Some type of rudders (Monovec) have their maximum rudder angle
at 70 degrees (maximum side forces for manoeuvring near the
berth are obtained at 40 degrees angle). Highest steering forces at
30 degrees angle.

2.5 Propeller and rudder combination.

It will be clear that rudders, irrespective the type of rudder, are

most effective when located directly abaft the propeller and the
engirie is going ahead.
Twin screw ships may be equipped with one rudder. Steering at
low speed is dif f icult.
Single screw ships are sometimes equipped with two rudders.
Steering at low speed can be difficult, depending on the type of
rudder.
Propellers can be equipped with nozzles, giving better steering
forces.

2.6 Bow and stern thrusters.(see appendix B)

Bow thruster effectivity will decrease when ship,s speed increases.

Bow thruster effectivity will be lost at a speed of 4 - 5 knots. (See
diagram. Fig. 5).
Bow thrusters are most effective when the ship has stern way. The
pivot point lying near the stern, resulting in a long lever of the bow
thruster forces. Besides, the counter-acting forces created by the
inflow of water towards the thruster inlet are less.
8o.w thruster is a good aid while departing without tugs.(see fig 6).
First push the bow to the berth by bow thruster: ship,s stern will

11
5EIF5PAOE f,Uco€P

Modern conoenlional rudder Qpzs.

Figure 3

BECKER-Rudders

Figure 4-
 swing off and turn around the shoulder. Then push the bow off the
berth, ship will swing round the pivot point near the stern and ship
will swing and move away from the berth.
Stern thrusters are much less effective as bow thruster.
Care must be taken with strong bow thrusters near berths. Berth
construction underwater may be damaged by strong waterflow.

2.7 Anch ors.

Anchors can be used for different purposes:

_ anchoring on anchorages awaiting berth;
as an aid while manoeuvring in port areas;
_ in case of emergency e.g. engine breakdown.
While using the anchors care should be taken of:
- Current/wind. Steam up into the current and/or wind while
anchoring.
- Other ships and other ship's anchors.
- Cables.
- Tugs/mooring boats. They may be under the bow while
shiphandler is intending to drop an anchor.
Holding force of the anchors depends on anchor construction and
type of bottom assuming that the anchor chain near the anchor is
horizontal. Ordinary stockless anchors, such as US Navy Stockless,
Beyers SS, Baldt, Union, etc. have a holding power:
_ in sand and fast clay: 4 - 6 times the weight of the anchor;
_ in mud and mean clay:3 - 5 times the weight;
in soft clay and soft mud: 2 - 3 times the weight.
HHP-anchors, such as the AC-14, have a holding power of at least
twice as high.
lf the force exerted on the anchor is in a not-horizontal direction,
the holding power of the anchor will decrease with + 25o/o if the
angle is 5 degrees with the horizontal plane and with + 50% if the
angle is 15 degrees with the horizontal plane.
Care should be taken not to have a too high speed when using the
anchors. Too many anchors are lost due to too high speeds while
anchoring. See Table 1 showing estimated bottom speed in order
not to exceed the breaking strength of the anchor chain.
Extreme care should be taken to apply sufficient chain length
depending on ship's particulars (windage, draft, etc.), waterdepth,
holding ground, wind, current, squalls, weather forecast.
The anchor is also a good aid while manoeuvring. With a dragging
anchor (length of chain approximately 1 .5 times the distance
between the hawspipe to the bottom) the ship can be steered very
well, using a low engine speed (Dead Slow Ahead). One can
relatively easy control wind and current forces or manoeuvre the
sh ip without tug assistance.
Anchors can be used to stop the ship in Emergency. See Par.6.

12
 Percenc of Thrust verus vesset Forsard Speed of Adv.nce
5 Typical: Jel verus ?\rnneI Thruster Svslem
'ig.
, r00x

90r

B0c
TSFUSA
70x Tunnel Thruster

50r

50r

40r

l0r

201

r0!

0t
2.
Speed of Advance ( Knols )

Tunnel Type Thruscers produce maxiFuh a61lard Thrus E al zero

speed and degrade raPidly uith vpssPl foreard speed -

Jet TyPe Eou Thruscers retain cdnstant l',hrust(5with f o r'ra rd

+ Knors) Bilt
sDeed of advance. Onlv when suc!ron is tosr
Tirust be lost- rnEake desiiil for Fam ef fect eill extend this
ran9e -

Figure 5

B \/\i/

Figure 6
13
 positioning

breasting, departing

Japanese towing style

Figure 7a
 approaching berth

European towing style

Figure 7b
positioning

breasting
i Damen Tractor Tug Damen Azimuth
and Stan Voiths Stern Drive Tugs
push-pull. berth ng. flrefrghtrnq and
oush oull berihr.g, {irefrghr ng
sarvage and po uron conrrol
Operatrng areas : harbours and coastalwaters
Ooerar.q a/eas harbours, coastal waters and degp-sea
Propulsron : n,rn rudder proPellers lwrn r!dder propellers
twin voirh Schneider ProPellers

Lenglh o a 29 tO 22 8A Damen
Damen 995 tsear. o r 794
Eeam o a A.S.D. Tug 2208
Tractor Tug 2910 Depth at srdes 400 Deprh at srdes 375
t51 30 48 60
r 160
Powor rang€ {total) 1152-2160
123a9 - 2A91 bhP) r555 bhol
113 - 123 Soeed ra.ge 112
Speed ranqe
Eolla.d puilrange 270- 350 Solard oL lra.ge ra 0

'- Damen Lenqth o a, 29 65

995
LenEth o a
Beam o a
28 7A
r0 60
Damen
Eeam o a A.S.D, Tug 2810
Stan Voith 291 Deplh at srdes 400 Depth al srdes 4,10
110 70 rn6 60
Power ranqe ltotal) 24AO - 241A 22AA 29aO
(32r8.3312 bhpl 12950'3889 bhp)
Speed ranqe - 9
11.8 So€ed ra.ge 1r 8 12 3
Soliard pullrange 342.360 Bollard pui range 350,500

Steerrng System:

- Single plate rudder, single plate llanking rudder

Nozzle and Rudder Arrangemenl 'Caplain ,ou,r"

,. rrl -

Propeller and Rudder Arrangemenl "Coos Bay"

Figure 8
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$.
C

14
2.8 Tugs.
(See appendix C)

* Around the world various methods of tug assistance are in use.

Sometimes combination of these methods are in use. (see fig. 7)
* The type of tug used depends to a large degree on the assisting
method. There are various types of tugs (see fig. B) with all there
own c h a ra cte ristics:
- Tractor tugs with Voith Schneider propulsion.
- Tractor tugs with azimuth propellers forward.
- Conventional tugs with propulsion aft: single screw, twin
screw, screws (fpp or cpp) in (steerable) nozzles. Different
kinds of rudders: normal rudders, fishtail rudders, towmaster
system, f lan king rudders, etc.
- ASD tugs: tugs with azimuth propellers at the stern, which
can operate over the bow and over the stern.
- Pusher tugs with azimuth propellers under the stern which
mainly work over the bow.
The first ones can be found all over the world. The last ones, the
pusher tugs, mainly in the Far East, Australia and New Zealand.
* While making fast tugs, while assisted by tugs and while releasing
tugs, ship's speed should be low:
- Dangerous ship-ship interaction between tug and attended
ship will be Iowest when ship's speed is low.(fig.9).
- Depending on the type of tug the effectivity of tugs will in
general decrease when ship's speed increases.
- Conventional tugs assisting on a tow line may capsize due to
.a too high ship's speed.
ln addition:
- Tugs can be hindered by ship's propeller wash.
+ The effectivity of tugs operating at the ship's side will be low when
pulling, due to the propeller wash hitting the ship's side.
ln addition, when conventional tugs are used at the ship's side the
effectivity is already low when pulling due to the lower effectivity
on astern.
* lf ship's lines are used as tug lines a good quality should be used.
* A good communication and co-operation between ship handler and
tug captain is necessa ry.
* Tug orders should be clear and understandable. No misunderstand
ing of orders and orders repeated by tug captains.

15
Figure 9

16
.- 3. Semi-controllable forces. (see Appendix A)

3.1 Shallow Water Effect.

+ Shallow water causes squat. This rs a decrease in ship's under keel
clearance.
* The effect of shallow water is encountered when waterdepth is
Iess than approximately 2.5 times ship's draft.
The effect is directly proportional to ship's speed squared and, in
addition, to the ship's block co-efficient, the relation between
ship's draft and waterdepth (HiT) and the relation between ship's
midship underwater section and channel cross section.
Squat can roughly be calculated by following formula for HII
between 1.1 - 1.4:
Open waters Squat = Co/100 x V' (Squat in metres, V in knots)
Confined waters = 2xCrl1OO xV2
* Full f orm vessels. Cb greater then 0.70, will squat by the bow.
Fine form vessels, Cb less then 0.70, will squat by the stern.
This is when the ship is at even keel when dead in the water.
When the ship has trim by the head then the squat will increase the
trim by the head. lf the ship has trim by the stern.then the squat
will increase the trim by the stern.
* ln addition, shallow water:
- decreases the ship's speed;
- increases the stopping distance;
- increases paddle-wheel effect;
- decreases rudder effe ct;
- increases the turning circle radius (see fig. 1O);
the ship handler will have in shallow water the idea that the
ship turns as fast as in deep water, because while turning
the ship's speed will not decrease so fast as in deep water;
- decreases swepth path (see f ig. 1 1 );
- increases the influence of currents (see fig. 12);
- increases ship - ship interaction effects (see 3.3);
- increases bow cushion and bank suction effects (see 3.2);
- decreases effectivity of tugs.
* The effect of shallow water is largely dependent on ship's speed.
So, to minimize the effects ship's speed should be low.

3.2 Bow Cushion and Bank Suction.

* Bow cushion and bank suction effects are largely dependent on
sh ip's speed.

17
 * These effects can be encountered in narrow channels and canals.
* Bow cushion and bank suction effects are found in conjunction
with one another.
* Bow. cushion is caused by increased water pressure between
channel bank and ship's bow caused by ship's bow wave.
* Bank suction is caused by decreased water pressure between
nearest channel bank and ship's hull or ship's stern.
* Bow cushion causes the bow to sheer away from nearest bank and
bank cushion causes the ship's stern to stick to nearest bank or
causes the ship to sheer across the channel.
+ These effects are difficult to handle and should be avoided as much
as possible by keeping good clear of banks and/or ship's speed
low.
When ship is taking a sheer the first action to take is to apply hard
counter rudder; if this is insufficient to stop the swing, engines
revolutions must be increased as much as possible until the sheer is
under control; in addition to the extra thrust on the rudder, increas-
ing engine speed in excess of ship's speed moves the pivot point
ahead and the ship turns better; once the sheer is under control
engine revolutions can be reduced and then the wheel eased. To
counter a sheer, it is preferable to take drastic steps first and then
ease those ste ps.
Experienced pilots sometimes use these effects in taking bend in
channel and rivers or when meeting ships in very narrow channels.

3.3 Ship - ship interaction.

* Ship - ship interaction will take place when meeting and overtaking
ships and when passing moored ships at a too close distance,
* Ship - ship interaction increases in shallow water and narrow rivers
and chan nels.
* Meeting ships:
- Bow waves will force the bows apart.
- When abreast, ships will be drawn towards each other.
- When nearly passed sterns might be sucked towards each
other.
* Overta king ships:
- Stern of the ship that is overtaken is pushed away by the
bow wave of the ship that overtakes.
- When abreast, ships are sucked towards each other and
bows are pushed apart and sterns are sucked together.
- When passed, bow of the overtaken ship is sucked towards
the stern of the ship that has overtaken.
* Passing moored ships:
- Ships will tend to move alongside the berth caused by bow
wave and suction of passing ships.

18
 WATER OEPTHIORAUGHT RATIO

r?O

l.vo
L'so

KEY

R: TURNTNG RAOTUS (OVER FrRSi 9Oo HEAOTNG CHANGE)

LENGTH OF OESIGN SHIP
..-
IU 20 30
RUooER ANGLE (deg)

IURNING RADIUS AS A FUNCTION OF RUDDER ANGLI

AND WATER DEPTH

(BASED 0N STNGLE SCREW/STNGLE RUDDER CONTATNER SH|P)

Figure 10
19
 ./-.u WATER OEPIH/DRAUGHT RATIO -\_____--
@

=
1.8

(o
\'":t.
l.b

\19
1.4
/.
{9
il1q
1') ../

1.0

KEY

0.8 WIDTH OF SWEPT TRACK

B= BEAM OF DESIGN SHIP

0.6

o.4

o.z

\-.

10 20 50
RUODER ANGLE (deq)

WIDTH OF SWEPT TRACK IN A TURN AS A FUNCTION

OF RUDDTR ANGLE AND WATER DEPTF.I

(3^SED 0N. SINGLE SCREW/SINGLE RUDDER CONTAINER SHIP)

Figure 11 '
20
 N
(o
io
X
rlt N
O 0)
O
o o
o
N
lJ-
P
!F c
(o
!-
o
r-
E l-
f
X O
LO C
o
O
0)
o
C
(o
o
{J o N
(o
l.- O o
! '0) E')

X c,)
lr
N L
0)
']c
c
l
$--
NE
(tr P
!- C)
-o
c.)
t{-
X \F
uJ
LO

P
o
IJli-
D

-Y.

=
F
Z
LLJ
CC
c.
l
c-)

21
4. Uncontrollable forces.

4.1 lntroduction.

Uncontrollable forces are wind and current. These forces are not always an
disadvantage. Sometimes they are an advantage. ln such sltuations one can
make use of these f orces f or instance while mooring or unmooring. Mostly,
these forces are compensated by steering a drift angle and/or keeping a relative
high speed. ln port areas tug assistance will be required to assist in handling the
vessel in a safe and efficient way. Although wind is called an uncontrollable
force, the effect of wind can be decreased by ballasting the ship.

4.2 Wind and cu rrent.

Wind speed increases with height above sea level. For example, a
wind of 60 knots at 10 metres will be more than 75 knots at 30
metres, but only 30 knots at 2 metres (just above sea level).
Wind effect rs larger on ships with a shallow draft then on ship's
with a large d raft.
A high superstructure andlot a high deck cargo e.g.. containers, will
have a large influence on the wind drift.
The ship may be leewardly or windwardly depending on the ship's
form above the water and stowage of deck cargo and ship's trim.
A ship normally backs into the wind when going astern.
Wind never blows at constant speed, but varies; the same applies
to the wind direction; this is especially of importance in port areas,
where wind may come from unexpected directions with unex-
pected forces.
Current affects Ioaded as well as light ships.
Current pattern
'in port areas is seldom uniform. lt often gives
turning moments to the vessel.
Effect of current increases by decreasing keel clearance.

4.3 Required bollard pull to compensate wind and current forces.

Windforce on a vessel is determined by wind velocity squared, the

windage, the ship's form above the water and the specific gravity
of air. On the basis of the outcome the required bollard pull can be
determined approximately, taking into account a safety margin.
Roughly the required bollard pull can be determined by fable 2.
The forces exerted by currents can be determined by the current
force squared, the underwater form of the vessel, the underwater

22
 lateral area, the under keel clearance and the specific gravity of
water.
An indication of the required bollard pull for a certain current
veloeity is given in Table 2. Difterent keel clearances are taken into
acco u nt.
* The bollard pulls grven in Table 2 are for crosswise winds and
include a sa f ety margin.

23
 .Vea above the Warer ()12)
ql 3 l
</,
*
30

10
Wind-
force 9
25
'.I
20
I
7 15 ,.f
6

5 10 201,

4
5 ,,V,
2
1
,w 50 100 150 200 250 300 350 400 450 500
Bollard pull (Tons)

Necessary bollarul pull to heep the uesset up

Undenvater crossrvise area ()I2)
against a crosstuise vind,.
1000 2000 3000 4000
1.0

I
0.8

0.6
o
0.4

o.2

50

>3
100
2.0
150
1.6

200 1.4
l.
250 1.3
!=oePtt'
300
T Draft

12
350
1.1

Necessary bolbrd prll lo heeP lhe vessel

crossuise up ogainsl the cufienl.

Table 2
24
5. River/canal navigation and port
manoeuvnng

5,1 General.

Before entering pilotage waters, check engine on astern, rudder,

remote controls, cpp, communication between bridge and local
cpp/engine control, between bridge and stations at forecastle and
poo p.
Keep anchors ready.
lnform the pilot accurately about manoeuvring particulars of the
vessel and of all other relevant particulars.
Let the pilot inform the master about any particulars in the fairway,
the port and at the berth with respect to traffic, waterdepths,
currents, weather, berth location, tug assistance, moored vessels,
etc.

5.2 Conning.

Give, or repeat in case a pilot is navigating or'manoeuvring, all

orders to engine and helm in a loud, clear and authoritative voice.
Move occasionally on bridge so that obstructions on deck do not
hide. objects in water f rom view; don't move so often that helms-
man and other control stations can't keep track of you.
Use rudder commands in accordance with the IMO "Standard
Marine Vocabulary"; for turns, use rudder commands followed by
courses to steer; become comfortable with flexibility of rudder
control through "increase your rudder", "ease your rudder", "meet
her", and "steady as you go".
Use seaman's eye in conjunction with other information sources to
check contact bearings, positions, and other ship's tracks.

5.3 River/canal navigation.

Channel transit.

Collect data on ship's manoeuvring characteristics from diagrams

Iocated on the bridge prior to start or transit, Be informed about
ship's draft. Take into account ship's squat for different ship's
speeds.
Determine all pertinent data on the geographic area with respect to
aids to navrgation, waterdepths, currents and weather.

25
 + Approach to channel entrance should commence well to seaward
or entrance; its allows the shiphandler to determine forces which
are acting on his ship and to correct for them early.
+ Transits should be made at moderate speed; fast enough to handle
the ship comfortably and slow enough to minimize the semi-con-
trollable forces; be aware of banking and bow cushion effects; take
care of moored vessels; save power for emergencies.
* Judgements of speed, distance, direction of travel and heading can
be made by determining ranges both ahead and abeam.
+ Ship's track should follow the center of travel and heading can be
made by determining ranges both ahead and abeam.
* Ship's track should follow the center of the channel when in
straight reaches, unless meeting or passing other ships.
* Prior to approaching sharp bends, reduce speed if possible; use
rudder completely before adding power; when power is used, it
should be used in spurts to minimize headway and to maximize
turning moment.
* Generally speaking when rounding a point in a river against the tide
it is advisable to keep as far away from the point (inside bend) as it
is practicable.
Generally speaking when rounding a point with the tide it is advis-
able to keep as close as practicable to the point.
* lf the ship has to swrng on the river, if possible make use of the
current which is less near the banks and of .the paddle-wheel
effect.
* Attempt to determine if, and when, traffic will be met; information
can be obtained from pilot boat, ships met in transit, VHF broad-
casts, port control, and ship traffic systems where available.
+ To determine if the ship is turning with the right rate of turn in a
bend, following formula can be used: ROT = V/R. (ROT in
degrees/min, V in knots and R is the turning circle radius in miles).

Meetino. Overtakino and Passino Situations.

* Agree on overtaking as soon as possible so that only small adjust-
ments of speed and track are necessary, as opposed to radical
adjustments at the last minute.
Overtaking to be carried out with a large speed difference between
ships, so reducing time of overtaking and consequently of interac-
tion effects.
+ Adjust speed if possible so that the meetings and overtakings occur
at widest points of straight reaches, in order to minimize interaction
effects.
* Be alert for natural or ship induced sheers.
* Pass moored ships not too close and at low speed, otherwise
moorings may brea k.

26
5.4 Port manoeuvring.
* Collect all possible date with respect to the berth, berth construction
(fig, 13), fendering (fig. 14), restrictions for the berth with regard to
current/wind/water depth/max. draft, manoeuvring and berthing space,
water depth at the approach to the berth and at the berth, tidal
rise/fall, currents/wind velocity and direction with regard to berth
directio n, etc.
" Determine early on what forces will be affecting the ship while entering
the harbour basin, approaching the berth, while mooring, moored or
while leaving the berth/harbour basin (e.9. wrnds, cur-rents, water-
depth), and how to use or eliminate them (by bow thruster, propel-
lerlengines, anchors, tugs) .
* Determine manoeuvring and docking/undocking plan well in advance -
with respect to approa c h/d eparture toifrom the harbour basin/berth,
taking into account the available manoeuvring space,the influence of
wind and current, the available tug assistance, bow thruster, rudder
and engine manoeuvres.
Formulate mooring plan. Discuss the plans with the pilot.
* Make tugs fast where and when needed, as soon as practical, with due
regard to own ship's headway; have line-handlers ready at all times to
shift or cast off tug lines, with communications to bridge.
* Have mooring men and mooring boats (if any) ready at the berth.
* Check radio communication between ship and/or pilot and tugs,
mooring man and berth operator.
When entering a harbour basin from the river or when leaving the
harbour basin, be aware the ship may take a sheer due to a not uni-
form current flow near the entrance.
Entering a harbour with a cross current, either flood or ebb tide, should
be carefully planned.
* Reduce ship's initial headway upon approaching berth; apply engine,
rudder and bow thruster forces as necessary to dock ship.
* When the ship has to swing before mooring or after departure the
required turning space should be at least 1.5 x length o.a. of the ship
when tug assist€nce is available.
The required turning space will increase when a current is running. The
turning space will increase in the current flow direction with the
distance the current runs during the time needed for swinging.
* lt possible make use of the paddle-wheel effect when swinging, so,
with a right handed propeller turn over starboard when possible.
* lf there is any current near the berth, approach the berth against the
current. When steering a little towards the berth the current witl push
the ship towards the berth. When steering a little off the berth the
current will push the ship away from the berth.
Mooring with the current should be avoided, unless the current velocity
is very low (less then 0.5 knots). No or only a little current vector
towards or away from the berth is acceptable.
" Come parallel alongside the berth with a low approach speed; don't
touch the berth under a large angle or with headway or sternway, it
uirill damage the berth and/or fendering.

27
,3t14

Auoy Slob

Erosion protection
Columns ( piles )

OPEN BERTH

Figure 13

Size s
fuoclio,1 €nergy
Fendershope D/L.Hb,HL Per formotEe curve
Type

tg/tM 80 3 Er I
Cylindrical I I {
51ffi
&l
28@A@ 6 600 norea
"ffisa
t @/550 52 I
Cell
I t I
3mn250 58@ 6m
250/1M 150 t5

I I I
1Mr2@ 2 290 910
V- lype
2@/t@ t50 10

I I I
tffi/35@ i )0 tw
tN./5@ 22
I I
H- type I I t
2stu.@ 69@ 7m
50 4

Pneumolic I I
I500 7M

Different types of rubber fendeo

Figure 14

2A
6. Ship's
_Speed
Several times attention has been paid to ship's speed. Once more it will be
done, because of the importance of keeping ship's speed under control in port
areas. Why is a low ship's speed so important in confined water:

lf an accident happens by engine failure, rudder failure or human

failure the consequences of such an accident will be much less
than with a high speed. Keep in mind: ship's energy is 112 mv2.
The consequences of an accident will rise with the speed squared!
The stopping distance is approximately proportional to the square
of the ship's speed.
lf ship's speed is kept under control, there is more time and power
left to take the right action in case it will be necessary.
lf ship's speed is low:
- tug's efficiency is highest;
- it is safer for the tugs;
- bow thruster efficiency is high;
- shallow water effects, banking effects, interaction effects
will be less.

On certain ships Dead Slow Ahead can be a rather high speed. This does not
mean that one has to sail always with Dead Slow Ahead. Many ships with a
fixed pitch propeller will steer with a stopped engine, if ship's speed is brought
down gradually. Ships with cpp can steer with a very low minimum speed.

Rem em ber: FULL SPEED = FOOL SPEED

29
7 - Emergency.

7.1 General.

* Emergency situations may occur at any time.

* Have anchors ready for immediate letting go: Brake on, cap-
stan/wildcat disengaged, and. if necessary, anchors backed out of
hawse P iP es.
* Discuss contingency plans for reacting to failures with the Sea
DetailiNavigation team.

Z
7 4 Emetgency shiphandling.

Emergency stoppin g:
* Use Maximum Engine Power And Both Anchors To
Prevent Collision - Even At Risk Of Damage Machinery
And Anchors lf Necessary.
* lf Collision Unavoidable Consider Area Or Angle Of
lmpact That Will Cause Least Damage.
* lf Power Lost And Drifting On Lee Shore Walk Out Both
Anchors ln Hopes Of Catching Bottom Before Ship
Grounds.
* Rudder Cycling:
- Most Effective At Higher Speeds.
- Rudder Speed Brake Effect.
- Broadside Effect Of Ship.
* ln case of an engine breakdown in channels, rivers, port areas ship
can be stopped either by tugs or by anchors.
Whether stopping by tugs is possible depends on the type of tugs
and the way they are fastened.
Stopping by anchors can be done according Table 3.

30
 USE OF ANCHOBS IN AN EMERGENCY

STANDBY ANCHOBS. ENSURE ANCHOR PARTY HAVE

CLEAR INSTHUCTIONS BEFORE LETTING GO ANCHORS

IF NATUFE OF EMERGENCY PERMITS OR IF TIfuIE,

REDUCE SPEED TO l!4lNll\i'lUM

IS THEBE SUFFICIENT UNDER KEEL CLEARANCE?

lE 200lo VESSELS MAXIMUM LOADED DFAFT

IS THE SEA BED CLEAR OF OBSTRUCTIONS DO NOT

USE ANCHOFS
EXCEPT TO
AVOIO MORE
SERIOUS
DAMAGE

UNDEH 3O,OOO DWT 30,000/60,000 DWT OVEH 60,000 DWT

MAX SPEED 8 fiS I,4AX SPEED 6 KTS MAX SPEED 3 KIS

LET GO BOTH ANCHOFS, CHECK AT 2 x DEPTH. DEAG UNTIL STOPPED

ONLY PUT OUT II1OFE CHAIN IF UNABLE TO PREVENT GROUNDING

,.. ' ..- .'. Anbhoring checklist

Table 3
 8. Pilot/C.O. RelationshiP.
Why are pilots engaged:
* For their ability to anticipate accurately the effects of currents and
tidal inf luences.
* For their expertise in navigating on close proximity to land and
narrow chan nels.
* For their understanding of local traffic.
* For their ability to work effectively with the local VTS.
* For their proficiency in shiphandling.
* For their expertise in handling tugs and Iinesmen.
' * To support the master and to relieve fatigue.
* To provide an extra person or persons on the bridge to assist with
navigating the shiP

Fact - 90% of all ships casualties occur in restricted or pilot waters.

The C.O. or master should understand the difference between:

- Command.
- Navigation command.
- Conn.

The C.O./master.is "in command" at all times except in Panama Canal.

The pilot is in an "advisor" capacity and is normally used at "conn" and navi-
gates and manoeuvres the vessel, directs the tug boats and mooring men'

The bridge team is to monitor the pilot as per the passage plan checking
position/co u rse/s peed/e n gine, rudder response, tug and line handling'

Do not follow pilot instructions blindly - A good pilot will welcome monitoring
but does not like interfering. A good co-operation between the pilot and the
' bridge team is essential.

31
APPENDIX

32
the area through which the water can pass is narrow, the water's speed will be
high, the pressure low and, so to speak, the ship will sucked towards the
bottom. This is called squat.
Due to differences jn the ship's shape and therefore in the water flow pattern
an full form vessel will have more squat effect at the bow, while a more slender
ship, like a container vessel, will have more squat effect at the stern.
Ships coming close to banks will experience a similar effect, called bank effect.
The more vertical and smooth the bank is the larger the effect. The pressure of
the bow wave will give the bow of the ship a tendency to move away from the
bank. The suction near the stern will give the stern the tendency to "glue" to
the bank. This could result in the stern hitting the bank or the ship being sent
into the opposite bank. (see f igure 1 5).

Vessel proceeding in chennel Bow gets too close to bank

Bow presstrre weve shears Stern suction accentuetes

olf bank

,rrr"O
(

SHALLOW WATER AND BANK EFFECTS INCREASE WITH SPEED

34
 EXPLANATION INTERACTION BETWEEN SHIPS
WHILE
,,IV]EETING OR OVERTAKING CLOSE ABOARD

lntroduction.

The ship - ship interaction is largely dependant on the wave pattern around the
ships. The wave pattern differs by ship.
The actual wave pattern generated by a ship is a matter of some complexity.
The pattern contains four elements: the bow transverse system, the bow
divergent system, and the corresponding two systems at the stern. The two
transverse systems interact. lf we consider a ship starting from rest, while she
is moving at slow speed the bow transverse system, necessarily moving at the
same speed, will have quite a short wave length, giving several crests evenly
spaced along the ship's side from bow to stern.

The bow system starts with a crest near the bow. The similar stern system
starts with a trough near the stern. As speed increases, so does the wavelength
of the two systems. Eventually the first following crest of the bow system
coincides with the initial trough of the stern system; the two systems to some
extent cancel one another out, so reducing the amplitude. of the combined
transverse system following astern of the ship. This is a favourable situation,
making for reduced wavemakinq resistance.

Ships Meeting and Overtaking.

a. Meeting Situation (figure 'l 6)

1,2 Water pressure increases between bows forcing them apart.

3,4 Water pressure decreases between ships when abeam causing
them to move laterally towards each other, especially just before
the stern (stern suction).

b. Overtaking Situation (figure 17)

1,2 As bow nears stern overtaken ship, your bow pressure and the
other ship's stern pressure forces its stern away, and hence the
overtaken ship is forced across your bow.
J As the ships draw abreast, they move laterally toward each other.
4 As stern nears bow of overtaken ship, bows are forced apart and
sterns attract each other. Sufficient speed differential or lateral
dista nce will counteract this.

35
 Although high speeds increase the pressure effects a higher differential speed
\-- also shortens the time the ships' bow and stern pressures effect each other.
Therefore always try to gain co-operation from the other ship. lf it keeps its
speed low the overtaking manoeuvre becomes much safer. And keep the mutual
distance as large as possible (at least 25-30 m).

MEETING SHIP EFFECTS

Bow pressute waves cause

Vessels approaching shear

Abaem ships move towards Stern suction accentuates

each oiher shear

Figure ,16
iI
OVERTAKING SHIPS EFFECTS

vessels approaching Danger of other ship

bow, stern pressure interaction forced across the bow

Abeam ships mov6 towards Dan€er ot storn moving towards

eech olher other ship at braeking away

Figure 17
'rs

36
Appendix B

USE OF TUGS IN PILOTAGE OPERATIONS

Captain H. Hensen, MNI

"An expression freguently heard during the days of sail was:"Different ships,
different long-splices". So today: ln different channels-or harbours-there is
enough dissimilarity in conditions to bring about different customs, or practices
with regard to the use of tugs. "

This is what an American pilot has written in a booklet about manoeuvring in

narrow channels and it is exactly true.
ln fact it takes quite a lot of research and knowledge of tugs to be able to give
a basic answer to the question which type of tug or which working method is
the best for a certain poft. The requirements to which the tugs and assisting
methods must conform are determined by the following factors:

the sort of port, the future developments and the geographical environ-
mental conditions;
the type of ships calling at the port;
the required services in and around the port.

Types of tugs.
At present the following types are mainly in use:

- single-screw tugs;
- twin-screw tugs;
- tractor-type tugs;
- tugs with Z-pellers aft.

The single-screw tug is generally well known. To increase towing power, many
of them are fitted with a nozzie. They may be equipped with a fixed- or variable-
pitch propeller. ln certain situations the lesser manoeuvrability of these tugs
may be compensated for by installing a normal bow propeller or a 360-degree
steerable bow-thruster, which also increases the towing force.
Twin-screw tugs have a far better manoeuvrability than single-screw tugs. With
the tractor-type, the propellers are fixed under the fore end of the tug. These
propellers may be Voith-Schneider propellers or Z-pellers (aZimuth-pToPELLERS
= 360-degree steerable propellers). There are also tugs with Z-pellers aft. These
resemble the twin-screw tugs. However, because of the 360-degree steerable
thrusters, they have manoeuvrability and are suitable for towing on a line and
also for the push-pull method. The method of tug assistance depends on the
type of tug.

37
There are mainly the following methods of tug assistance:

towing on the hook, bitt or winch;

PUShing;
push-pull;
towing alongside.

Every type of tug has its specific capabilities, but also its limitations, however
great the manoeuvrabilitY maY be.

Capabilities and limitations of harbour tugs.

It is important to understand the capabilities and limitations of the various
types, if possible of each tug individually. Knowing about the possibilities and
the limitations of the tug for the daily routine is of particularly of importance for:

the tugboat captain and his crew;

the pilot.

As for the tugboat captain and his crew this knowledge is essential for their
own safety. But above all, in the teamwork between pilot and tugboat captain
whilst manoeuvring big vessels, it is important to know what one's capabilities
are. This is especially so because the margins within which the work is done,
are becoming smaller and smaller, as a result of the scaling up in size of
shipping. lt is also as a result of economic pressure on the shipping companies,
because of which.a minimum of tug power is often used.

This chapter concerns the possibilities and Iimitations of tugs on the following
basis:

tug assistance as it is mainly employed in West-European ports - namely,

towing on a line;
the push-pull method.

Speeds up to about six knots as is customary in port areas will be taken into
account. Specific mooring and unmooring manoeuvres will not be considered.

Manoeuvring characteristics.
lrrespective of type, the following points are generally of importance with regard
to the manoeuvring capacities of tugs:
- sta bility;
- weighU
- engine power;
- type of propellers;

38
 But most characteristrc is:

location of the propellers with regard to

the point of application of the towing force.

Figure 1. Tug with propulsioa Jorward oJ midships, Figure 2 Tug with propukion aJt, as uilh conaenlional l1tpe.
ltactor-tlpc.

Naturally, one expects the stability to be good, for that is of extreme import-
ance for any tug. The dangers of a poor stability are sufficiently well known,
most certainly with regard to tugs. weight, engine power and type of propeller
are closely related. Engine power has increased throughout the years and a
variety of types of propellers has been developed, such as fixed propellers,
variable pitch-propellers, propellers with nozzles, Z-pellers, Voith-Schneider (VS)
Propellers, etc.
The towing force of the tug depends on its engine power and on the type of
propeller as well, as becomes evident in the table below:

Type of propeller: Bp in tons/100 bhp:

Fixed propeller 1.3

Fixed/variable propeller/Z-pellers with nozzle 1.5
Voith-Schneider propeller 1.0
e ll
BHP = Brake Horse Power, i.e. the power delivered by the engine.

The above table applies, with some reservation, to bhps between about 2,000
and 3,500.
ln addition the relation between engine power and towing force {bhp/bp) varies
considerably with the extent of the engine power and in such a way that for a

39
 tug with, f or example, 700 bhp and a fixed propeller, 2 tons/l00 bhp can be
attained, whilst for tugs with about 6,000 bhp with nozzles the towing force
may even be less than 1.3 tons/100 bhp.

As it has already been stated, the most characteristic difference between the
various types is the location of the propellers with regard to the point of
application of the towing force. ln the main the type of tugs can be categorised:

propellers aft - e.9., fixed or variable- pitch propellers or Z-pellers AND

point of application of the towing force amidships. More Iike the conven-
tional type of tugs (fig.4).
propellers foreward the mid section of the tug - e.9., V.S. propellers or Z-
pellers AND the point of application aft. This is the so-called tractor-type
(f ig. 3) .

fig. 3 tig L
Figure 3. Tractor-Upe, propukion Jorunrd, point oJ 4
Fi.gurc Tug with propukion aJt and point of application of
application oJ the towingJorce aJt the towing Jorce amids hips.

There are intermediary types such as:

new tugs with Z-pellers aft, but with a towing winch foreward as well as
aft - some of them are equipped with a bow thruster as well;
older types of tugs, the manoeuvrability of which is improved by installing
a 360o steerable bow-thruster. This bow-thruster, depending on its
working direction, can also increase the towing force. Furthermore, on
some of these tugs the point of application of the towing force can, if
required, be shifted more to the aft.

40
Use and effectiveness.
However, we will stick to the main divisrons. The tractor-type pulls itself ahead
by its propellers but is held aft by its towline, causing the tug practically to lie in
line with the towline, in contrast to the other type, which can turn around the
point of application with the help of the rudder andior the propellers, whilst still
applying force on the line. What consequences this has will be shown in the
f ig ures 5 and 6.

fis.5 f ig.6

It
./,
/' t+

tig 7

Figure 5. afld a ttuclo ward.

Flgure 6. with a conrt tug Jorwarrl
Figurc 7. a shiP moui
Figurc L withashiP

ln fig. 5 and 6 the ship moves ahead. The tug fastened to the fore end has been
ordered to pull to starboard. Now the result is an effect athwartshrps on to the
assisted ship. As it also becomes evident from the figures, the effect athwart-
ships with the conventional type of tug of Figure 6 (this is the tug with the
propulsion aft and the point of application of the towing force somewhere

41
amidships) is relatively much bigger than that of the tractor-type of Figure 5, as:
* The conventional type with its movement ahead has to overcome much less resistance
through the water than the tractor type, which lies in line with the towline, and besides
that the tractor type has to overcome much more resistance under water than the
conventional tug because of the high blades (V.S. tugs) and the skeg (see Figures 'l and
3).

* The conventional type profits by a sheering-out ef{ect. giving extra force on the towline.

* The maximum pulling angle of the tractor type is smaller than that of the conventional
type,

As for the latter, the size of angle'a'is dependent on the ship's speed, the
engine power and the underwater resistance of the tug and is determined by the
insight of the tugboat captain. with an angle that is too big with regard to the
ship's speed, the tug will swing around into a non-contributing position. At
speeds above 4 to 5 knots the angle with VS tugs will not be bigger than about
30 degrees, by which little power athwarthships on the ship to be assisted can
be exercised. Due to the different characteristics of the conventional type, the
angle concerned (see angle 'b') can under the same circumstances be much
bigger. However, this is also dependent on the tug's stability.

Now this difference in effect, and subsequently in effective pulling force,

between both types will not be very noticeable at a low forward speed - e.9., a
speed not more than two knots. However, at higher speeds the difference will
soon become noticeable, as the underwater resistance increases with the speed
squared, by which the tractor type fairly soon has relatively little power left to
exercise any ath.wartships force on the ship being assisted. Consequently at
speeds of over 4 to 5 knots the effect athwardships is relatively very small with
tractor tugs, especially with VS tugs.

Bollard pulls compared-

lf we now have another look at the table mentioned previously and compare:

-a conventional tug of 1,800 bhp with variable-pitch propellers and

-a VS tug of 3,000 bhp,

then we can see that the bollard pull of:

- the conventional tug is 1,800 x 1 .5 27 tons

and of:
- the V.S. tug is 3,000 x 1,0 30 tons

According to this, it becomes quickly clear that with a speed of over two knots
the conventional type in the above mentioned situation will soon be superior, in
spite of the mLch lesser power.

42
For tractor tugs with Z-pellers, the difference with the so-called conventional
type is less, through the greater effectiveness of the propellers. By increasing
the installed power of the tug, the disadvantages will be less, but only because
of the higher bollard pull. The conclusion is, that the conventional type of tug,
made fast forward, is relatively much more effective than the tractor type
forward.

Now the situation aft will be considered, again with the same ship that steams
ahead and has to go to starboard. The discussion above, with regard to the
difference in effectiveness and maximum pulling angle of both types of tugs,
also applies to this situation, when they are made fast aft and are assisting in
the way as it is shown in the situations 1 of Figure 7 and 8.

Here the great difference between the manoeuvring capacities of both types of
tugs can be seen. During the further process of the manoeuvre the conventional
type of tug cannot, if this should be necessary, at a speed over about two knots
swing around to a position behind the vessel (Figure I position 1 to position 2)
in order to, for example, reduce the speed of the assisted vessel. The reason is
mainly that the point of application of the towing force lies too far forward.
Such a manoeuvre with a conventional tug is asking for trouble. At what speed
this manoeuvre could be possible depends on the tug's stability and also
depends on the insight of the tugboat captain. For the tractor type, however,
such a manoeuvre is no problem. This type is very flexible and can easily drop
astern of the vessel and take the speed off the vessel effectiv.ely, assisted by
the underwater resistance of the tug.

However, in that situation (Figure 7, position 2) the VS tug is inclined to sheer

from one side to the other, caused by its skeg. And the greater the force on the
tug, the greater this tendency becomes - in other words, the greater the
vessel's speed, the more wash from the propeller of the assisted ship, the
greater this effect. One thing and another can be neutralized by the tug's
paptain by keeping the tug on its course by a lot of helm by means of the vs
propellers, but this costs engine power and consequently towing force.

Concluding, one may say that it depends totally on the ship's manoeuvre what
is required from the tug aft. This could be to help as effectively as possible to
make a turn (as indicated above), to take the speed off the vessel as effectively
as possible, or to control the speed of the vessel, etc. For the first-mentioned
situation - namely, in assisting a ship under speed to make a turn - the conven-
tional type is relatively the most suitable; for the other situations the tractor
type is better.

Push-pull method.

Commencing from the situation where two tugs are used, it will be seen that
both tugs in Figure t have been fastened with one or two lines to the side of

43
 the ship. lf the vessel, which has a little forward speed, has to go to starboard,
tug No. 1 will pull astern, by which a turning moment will develop in combina_
tion with the assist-ed ship's rudder and the propeller turning ahead. The ship,s
speed will not inprease appreciably. Tug No.2 can assist by pushing on the
vessel at right angles as much as possible, by which this tug also acts as a kind
of rudder for starboard movement by its resistance.

fig. fi9.

lgure t htuotugs.
Figurc 1 ith tuo tugs.
Figure 1

44
Now it is already quite clear that both tugs are in a good positions for a turn to
starboard, but not for a turn to port. ln that case tug No.1 would have to push,
which will, however, have little effect, as this tug finds itself close to the pivot
point of the vessel. Furthermore, this tug may increase the ship's speed, if it
cannot push at right angles, and thirdly the tug's resistance will also counteract
the turn. Neither does the tug aft lie in a good position to be ef f lcient. lt has to
pull, preferably at right angles to the vessel, by which it also counteracts the
turn by its own resistance. For a good turn to port both tugs should be fastened
to the other side of the ship. Alternative turns to starboard and port can be
p ro b lem atic.

Moving astern.
ln Figure 10 the ship is moving astern. The forward tug can assist in steering
the ship in the right direction. At any speed it has to see to it that it can keep
on pushing at right angles which explains the line athwartships from the tug to
the ship's side. Here the resistance of the tug can also either accelerate or
counteract the turn, depending on the turning direction. The effect of the tug
aft is less. lt can be hindered by the propeller wash of the ship's engine going
astern. That is why it can often not work properly at a right angle, also because
of the ship's speed astern.
During the mooring manoeuvTes of Figure 11 both tugs can easily change from
pushing or pulling or the other way round. To obvrate cert;in disadvantages,
this method is often applied in combination with one or two tugs towing on a
lin e.

It will be clear that only tugs which have the same towing force ahead as well
as astern are particularly suitable for the push-pull method. At the same time it
is desirable that they can keep on operating as much as possible at right angles
with the ship. This means that tugs with Voith-Schneider propulsion and tugs
with Z-pellers are suitable for this method of assistance. Naturally, the tugs
must be equipped with good fendering and arrangements to be able to make
fast in the right way to the ship's side.

A great disadvantage is the loss of the tug's effectiveness with this method. For
if the tugs are pulling at right angles, the tug's propeller wash will hit the ship's
hull with force and therefore has an opposite effect. That is why the tug's
propellers must be away from the ship's hull as far as possible so as to minimize
this effect.
As opposed to towing on a line, this method has the great advantage when
moor-ing, in that the vessel can be pushed straight on to the berth. Moreover,
the tugs can, if required, change over quickly from pushing to pulling, or the
other way round.

45
Less space.
Many a time it has been said that for the push-pull method less manoeuvring
space is required..However, that is not quite true and in certain situations even
quite untrue. For example, a ship having tugs towing on a line, which have to
pull athwartships to keep the ship up into the wind or current, does indeed
require a lot of space. On the other hand, tugs should not be made fast along-
side if space is very limited, as in situations of passing through a bridge,
entering locks, drydocks, etc. ln such circumstances tugs alongside require too
much space and a tug on a short towline or a with two cross-lines needs less
sp ace.

lf the ship affected by severe forces athwartships, be it by wind, current or

both, then the loss of effectiveness of tugs made fast to the ship's side may
play a very big role. For example, if a ship has to moor with a very strong
onshore wind the tugs' propeller wash hits the ship, resulting in a great loss of
effectiveness. ln such situations it is better that the tugs tow on a line, so that
this loss of effectiveness is prevented.

The push-pull method is especially effective at low speeds, trom zero to about
two knots, for the more speed the ship makes, the less the tugs will be able to
work at right angles, becoming less effective when manoeuvring.

Ship's speed
The principal conQlusion is that every type of tug has its own characteristics
and as such they will have a totally different influence on the manoeuvres or the
feasibility of them. The ship's speed is the most important factor for the tug's
effectiveness and safety and that speed has, as far as circumstances permit, to
be adapted to the possibilities and the limitations of the type used. And so that
is why it is very important to know, when manoeuvring, especially during
marginal circumstances, which type or types of tugs and which assisting
method will be used and what the possibilities and limitations are. With the
distribution of the available tugs over the vessel and the planned manoeuvres,
such as:

taking a critical bend in the fairway with a big vessel;

steaming in or out of a harbour basin with or against the current;
passing through a bridge with a lot of wind;
taking the speed off the vessel in time,

they can be taken into account, so that one is not taken by surprise regarding
the expectations about the tugs.
For ports with much variation in the kind of harbour basins, berths, entrances to
harbours, tug assistance by towing on a line is the obvious method on account
of its greater and more general applicability. The push-pull method, if necessary

46
 in combination with other methods, is an excellent method for arrival and
!, departure procedures at certain reserved berths, if the circumstances, tugs and
ship comply with the required conditions.

(Printed in ''THE TVNUTICNI- INSTITUTE ON PILOTAGE AND SHIPHANDLING")

47
Appendix C

EFFECTIVENESS AND USE OF BOW- AND

STERN-THRUSTERS.
Captain H. Hensen.

Many ships are equipped with one or more laterai thrusters. Some of these ships
have a bow- and a stern-thruster; most of them only have a bow-thruster. But
lateral thrusters are often used by pilots in harbour areas while manoeuvring.
That is why some knowledge about the working and effectiveness of lateral
thrusters and their influence on the ship's manoeuvres is recommmendable. This
knowledge about the possibilities and limitations of lateral thrusters may be of
importance when using them during the manoeuvring; moreover because of the
fact that bow- and stern-thrusters are often considerable underpowered.

Starting from a bow-thruster of sufficient power, the question mostly asked is:
Why is a bow-thruster working so badly with speed ahead? Which factors play
a role in this? Has it something to do with the construction of the bow-thruster,
or with the location of the pivot point? And, if so, are there possibilities to
improve the working of a bow-thruster?
These kind of questions will be answered in this chapter. An eye llruill be kept
upon the realationship with daily practice.

Different kinds of lateral thrusters.

There are different kinds of lateral thrusters, viz,:

* lnboard lateral thrusters with fixed- or variable-pitch propellers.
* lnboard Iateral thrusters, working with propellers or waterjets, steerable in
more than two directions.
* lnboard lateral thrusters, working with waterjets, 360-degree steerable.
* Outboard lateral thrusters, sometimes retrectable, 360-degree steerable,
equipped with fixed- or variable-pitch propellers.
* Lateral thrusters, working with cycloidal propellers.

The first group of lateral thrusters are mostly seen on ocean-going vessels: the
usual bow- and stern-thrusters. The other ones can be seen on inland craft, tug-
boats, drilling platforms, dredgers, etc.

48-
 Effectiveness of bow- and ste r n-thrusters.

It is indeed true, that effectiveness of a bow- and stern-thruster strongly

depends on the way it is constructed in the ship. But also of importance is the
shape of the ship near thruster. To get a tunnel thruster as effective as possible,
then the following is essential:
* The effectiveness of the propeller of lateral thruster must be as great as
possible.
+ Unwanted vortices near the tunnel inlet, outlet and in the thruster tunnel
itself nust be prevented as much as possible.

This means also that the waterflow while entering, passing and leaving the
tunnel must be as homogeneous as possible. The waterflow while entering and
leaving the tunnel must cause the least possible counteracting forces.

To get the effectiveness of an appropriate constructed propeller of a tunnel

. thruster as great as possible, then in theory the following basic principles should
be applied:
* The tunnel diameter should be as large as possible.
* The iet velocity should be as small as possible.

However, this is not quite practicable at conventional installations (although

succesful applications of this theory have been realized in modern wind energy
planrs).

Avoidance of vortices.

It will be clear, that in a bow-thruster tunnel constructed as the one shown in

Figure 1A, there will be much loss of effectiveness due to vortices outside and
in the tunnel and an unequal waterflow through the tunnel. Besides that, the
propeller of this thruster is not situated in the middle of the tunnel, through
-- which the thruster will be more effective to one side as to the other. To improve
the working of this bow-thruster, construction must be otherwise, whereby
attention has to be paid to the following aspects:
* The tunnel length.
* The construction of the entrance/exit of the tunnel.
* The location of the propeller in the tunnel.

Moreover, following points has to be taken into account: also in ballast condi-
tion the tunnel has to be deep enough under water, that is to say the top of the
tunnel has to be at least the diameter of the tunnel underwater; and the protec-
tion grids outside the entrance of the tunnel must have the smallest affect on
the effectiveness of the bow-thruster.

49
Tunnel construction requirements.

Now, looking at what is stated above, then the construction of bow- and stern-
thruster tunnels should meet the following requrrements to avoid as much as
possible unwanted vortices etc. which influence on the effectiveness:
* The ship's sides near the entrance and exit of the tunnel must be, seen verti-
cally, parallel - not a V-shape as in Figure 1A, but like the tunnel of Figure 18.
* The ship's sides should also be parallel longitudinally, but this is a result of the
above mentioned requirement.
* The tunnel length should be about two to three times the diameter of the tunnel.
Often the lenth oI the tunnel lies between 1.5 and two times the diameter, due
to the width of the ship near the location of the tunnel. The tunnel length should
even be Iarger than the above mentioned two to three times the diameter; if the
tunnel is placed in a V-shape part of the ship, then the tunnel length should be
three to five times the diameter of the tunnel.
* The thruster propeller should be located in the middle of the tunnel, otherwise it
works better to one side than to the other, as alreday mentioned before.
* The entrance of the tunnel should be well rounded to prevent as much as
possible vortices at that place. These vortices can cause a loss of effectivity up
lo 20 o/o, according to model tests.
* Protection grids before the tunnel entrance should be constructed so that they
will reduce the resistance of the tunnel entrances when the ship is under way
and not disturb the water supply of the tunnel too much when the thruster is
used.

However, the possibilities to meet all these requirements depends on the ship's
construction and the ship's shape. And although this differs for every type of
ship, a compromise between these requirements and the ship's construction
always have to be sought.

prss tvt lri

Figure 1

50

C
Counteracting forces near the tunnel.

Regarding the counteracting forces near the bow-thruster tunnel there is a

difference betwee.n:
* A ship with no speed through the water,
* A ship with speed ahead.
* A ship with sPeed astern.

ln a ship with no speed trough the water, the effect of the bow-thruster will be
greatest. But, in a ship with speed ahead and where the bow-thruster is working
to one side, all kinds of pressure fields will develop near the entrance and exit of
the tunnel, as indicated in Figure 1C. A positive pressure field will develop at B
and at C. The last one is caused by relaxation of flow ahead of the emergent jet.
The negative pressure at D is created by the accelaration of the inflow. How-
ever, the one with the greatest influence is the negative pressure at A caused
by the emergent jet. ln Figure 1C the bow-thruster is working to starboard, but
the resultant force of the pressure fields is working in the opposite way,
because of the great influence of that negative pressure field at A. This counter-
acting force is increasing strongly with the ship's speed ahead.

The explanation for this lies in the behaviour of the emergent.iet. With a ship
stopped in the water the jet is squirting straight out from the ship's side. When
the ship gathers headway, the jet is bent back, and when a ceitain ship's speed
is reached it attaches itself to the ship's hull, flowing aft in contact with the
plating. The result of this is that the water pressure on the hull plating is sharply
reduced and will exert a suction thereon. And it will be clear that the suction,
acting over an aiea of plating, creates a force which is opposing the bow-
thruster. This can reduce the effectiviness of the bow-thruster by even as much
as 50 per cent at a ship's speed of 2 knots. For example, a bow-thruster which
delivers 10 tons of force for manoeuvring with a ship stopped in the water, may
only be good for 5 tons or even less when the ship has some speed ahead.

Anti-suction tunnel.

To solve this problem of the counter acting pressure fields as much as possible,
an extra tunnel is sometimes constructed behind the bow-thruster tunnel (see
Figure 1D) to connect the negative and positive pressure fields. This is the 'anti-
suction-tunnel'(A.S.T.-tunnel). These disadvantages, due to the counteracting
pressure fields, do not exist at lateral thruster which are not built in a tunnel,
but stick out underneath the ship. The effectiveness of a bow-thruster also
decreases when the ship has speed astern, but not in the same way as with
speed ahead, because the influence of the negative pressure field created by the
emergent jet is much smaller.

The power of the stern-thruster is mostly two-thirds of the power of the bow-

51
thruster. And what has been said about the influence of the pressure fields near
the bow-thruster tunnel- but then in reversed way regarding the influence of
speed ahead and speed astern- naturally also applies to the stern-thruster.
However, to meet the construction requirements for a stern-thruster is much
more difficult than for a bow-thruster and, moreover, the water flow at the stern
is much more complicated. So it is f or several reasons that the eff ectiveness of
a stern-thruster is in general much less than that of a bow thruster.

Conclusions,

The effectiveness of bow- and stern-thrusters depends on:

+ The construction of the bow- and stern-thruster and of the tunnel.
* The ship's shape.
* The ship's speed.

As far as the ship's construction permits, appropriate construction of the bow-

and stern-thruster and eventually an A.S.T.-tunnel will improve the effective-
ness. lt will now also be clear that bow-thrusters of equal power may have a
total different effect with the same kind of ships and under the same circum-
stances, only because of a different construction of the bow-thruster.

Manoevring with a ship equipped with a bow-thruster is . more difficult and

totally different from manoeuvring with a ship equipped with a bow- and stern-
thruster. However, it will be seen that the influence of bow-thrusters on
manoeuvres will apply in many cases to stern-thrusters as well, but in reverse
regarding speed ahead and astern. However, attention has to be paid to the
fact, that the effectiveness of a stern-thruster is mostly much less in relation to
bow-thruster (as previously mentioned).

lnfluence of a bow-thruster on the manoeuvres.

With regard to the influence of a bow-thruster on the manoeuvres, two aspects

are of importance:

+ The location of the pivot point.

+ The point of application of force exerted by the bow-thruster.

A good explanation of the location of the pivot point under different circum-
stances takes a too long time, so hereafter only the place of the pivot point is
given approximately, without any further explanation.
Again three different situations are looked at: a ship with no speed through the
water, a ship with speed ahead, and a ship with speed astern.

Although thg effectiveness of the bow-thruster is highest in a ship with no

speed through the water, for a moment consider the location of the pivot point

52
 and the effect of that locatron on the manoevres.
when the bow-thruster is started in a ship with no speed through the water, the
ship will pivot about a point that jies approximately at one ship's beam distance
f rom the stern. Bit, when the bow thruster is started in a ship alongside, in
the
direction towards the quay, the ship will start turning about a point where the
ship's shoulder will rest on the quay. This can be very handy in departure
manoeuvres.

l:=r, 2
--Figure
For example, in Figure 2A {situation 1) the bow-thruster is started towards the
quay. The ship's stern will swing out because of the fact that the ship is turning
about the point where the ship's shoulder is resting on the quay (see a). All the
after lines are gone, of cour-se. When the stern is far enough from the quay
(situation 2) and the forward lines are gone, the bow-thruster can be started to
starboard. The ship will then pivot about a point close to the stern (see b). And
because of that, as soon as the ship lies more or less parallel with the berth, she
will be quite a distance free from the berth and ready to leave (situation 3). Of
course, starting from a situation with not too much wind onto the berth and no
current.

Combination use.

Many small container ships, the so-called feeder ships often use the bow-
thruster together with the rudder and the propeller and this in combination with
the forward spring, as shown in Figure 28. When only the ship's propeller and
rudder are used.the ship will turn about a point where the spring is situated. But
if at the same time the bow-thruster is working to starboard; then the ship will

53
come parallel off the berth and ready lo Ieave.
Now, let us look at a ship with speed ahead trough the water. This can be
because of the ship's own speed, but also because of a counter-current at a
ship with no bottom speed. Starting with a turn to starboard, two dif f erent
situations have to be looked at:

The bow-thruster only will be used for the starboard turn.

A combination of rudderi propeller and bow-thruster will be used for the
starboard turn.

When using only the bow-thruster for the starboard turn, then, as soon as the
ship starts turning, the pivot point will be situated somewhere between the
stern and the midships. Although the lever of the turning moment is large, the
effect will be very low, because the effectiveness of the bow thruster is very
small and decreasing rapidly with the ship's forward speed, as already men-
tioned, and there is a high water pressure at the bow and consequently the
lateral resistance of the ship is highest near the fore ship and it is increasing
with the ship's speed. The bow-thruster has to push the bow against this high
lateral resistance, against the bow wave. The consequence is, that at a forward
speed of about 4 knots, the bow thruster is too weak to overcome the lateral
resistance and to push the bow to starboard.

Pivot point.

When using the rudder and propeller for the starboard turn, then the pivot point
is situated between the bow and the midships. The exact Iocation depends on
the ratio of the'ship's length to beam (L/B). The high lateral resistance at the
bow, the bow wave, will now have a favourable influence on the turn. When in
this situation the bow-thruster is also started to starboard, then it will mostly
increase the rate of turn, in spite of a shorter lever. For the same reason,
stopping this turn only by the bow-thruster is hardly possible. The bow wave is
then opposing the bow-thruster again.

As alraedy mentioned above, the position of the pivot point depends on the ratio
ship's lenth/ship's beam. This has to do with the strenght of the lateral resis-
tance at the bow. Wide beam ships and ships down by the head have a relative-
ly strong resistance at the bow and consequently the pivot point lies further aft
and closer to the midships when turning under rudder. The handling charateris-
tics of these ships are as follows:

A slow steering response, due to the shorter steering lever.

* A small turning circle, due to the stronger lateral resistance at the bow.
A fast rate of turn.
A swing is difficult to stop, because of the large turning moment of the
strong lateral resistance at the bow in combination with the shorter
steering lever.

54
The consequence is, that on thjs kind of ships with headway, the bow-thrusrer
will be of less influence for making a turn or stopping a swing than on slender
ships and ships yyhich are not down by the head. Attention has to be paid also
to situations with lesser keel clearance. Lesser keel clearance will cause a larger
turning circle and a higher influence of the current. Therefore, in such situations
the eff ect of the bow-thruster is relatively much less.

A ship which has speed astern is in a more favourable situation, because the
effectiveness of the bow-thruster is not decreasing that much compared with
speed ahead, the lever of the bow-thruster force is large because of the fact,
that the pivot point is now situated between the midships and the stern, and the
higher Iateral resistance at the stern is now assisting the bow-thruster in making
a turn.
The consequence is, that on a ship having sternway, the bow-thruster is very
effective in steering the ship, so the manoeuvring can go easier. Also because
of the fact, that with a ship moving astern, the speed can easily be taken off the
ship or the stern be brought into the right direction by means of the propeller
and/or the ship's rudder. But, when manoeuvring in this way, attention has to
be paid to the transverse force of the propeller. This transverse force can be
upto 10 per cent of the applied stern power.

Small ship eample.

For example, in Figure 2C, thete is a small ship of 1O0 meter in length, with a
right handed propeller, engine power 5,000 hp, bow-thruster 500 hp; no tugs.
The ship has to enter a harbour basin going astern. The engine is going slow
astern with 2,000 hp. The transverse force of the propeller may be 10 per cent
of 2,000 = 200 hp. That is a force of about 2 tons. To compensate for the
transverse force of the propeller the bow-thruster will be put to port - this is in
the same direction as the transverse force of the propeller. So there are now
two forces working to the p^ort side - 2 tons of the propeller and 5 tons of the
bow-thruster. This means a total transverse force on the ship of 2 + 5 = 7
tons in the same direction .
lf there is also a little wind from the starboard side, then the ship has to steer
with a very large drift angle to compensate for all the forces and with a little bit
more wind such a manoeuvre might even be impossible without the assistance
of a tug.
So, special care has to be taken in situations where the bow-thruster, the
transverse force of the propeller and the wind are all working in the same
direction. A comparable situatuation can come into being when this ship is
entering the harbour basin with headway and has to moor port side alongside
and the wind direction is towards the berth!

55
More effective astern.

The influence of a bow-thruster on the manoeuvres is very small for ships

having headway,- because of the fact that the effectiveness of the bow-thruster
is decreasing rapidly with the ship's speed and the bow-thruster has to over-
come the lateral resistance at the bow, which is increasing with the ship's
speed. For speeds of over 4 knots the effect of the bow-thruster is not notice-
able anymore.
For ships having sternway the influence of the bow thruster on the manoeuvres
is much better, mainly because of the fact that the effectiveness of the bow
thruster is less decreasing with the ship's speed and moreover the high lateral
resistance at the stern is assisting the bow thruster for making a turn.
ln this field improvements are hardly possible unless the capacity of the bow
thruster will increase.

(Printed in 'NAUTICAL INSTITUE ON PILOTAGE AND SHIPHANDLING')

56
Appendix D

CPP
Ship Maneuvering Safety Studiesl
Haruzo Eda-2 Member.
Robert Falls,3 Visitor, and David
A. Walden,a Associate Member

l, tac ruoolr

FlC. 3 Etract ot walar d6pth on lurning p.rro.rianc. FIg. 4 Tumlng traloctory

lSo.ooo o.Jt Tl{r(r. a!!o ollu

llr(L.l-O O (O[Or IlOn

l5-otc ruoDtr

FIg. 5 Ellect ol water_depth on lurntng perrorrnanco

(Es5o
results in de6p and sllaltow wate/)
Osjla Elal
FIg. 5 E,t6cl ol toadlng on turning perlormance
Ship Maneuvering Saiety Studies
TIIINNG INAJEDII]W, EFECT OF BUtt FONU
hof . Eda
TAMEI versus C0MAI]IEB S]11?
Rltt- & UIIIE-F0E, versus FII,IE- & StENnEB-F0Bll

BIDBEB AN, deg = -35.0

7
A
E

E
 WAVES, SHIP MOVEMENTS

Yow
,+
-r
I

:lot
TI
I StfiY

Fig. 2. l. 7.A Types of ship's movements

'
Ship movements due to waves car be up to 2,/9 of the significant wave height
for smaller ships. VLCC and large ore carriE-rs, due to their huge sizq are only
susceptible to waves with a period of more than l0 seconds. Waves with a
shorter period will scarcely result in vertical motions for these ships.

$r
fi)
t

Fig. 2. 1. 7.B lUave directions

long periodic
woves

' t' .- n .
Wove leneth ,, Wove_E1glL
Ship length Ship tength "''
Fig. 2. 1.7.C Combination of waves
!-6
\-_ lU
J
zCI
\/
a
tr
o
I
o
z
\,
 I

(5
z
CI
o
CT
o
a
TE
o
o
z
 STOPPING SHIPS AN EMERGENCY
Captain P. J. D. Russell, FNI
PLA Pi|ot 'ru
Vice-Chairman, U KPA(M ) Tec hn i ca I Co m m ittee

WHEREVER sHIpS MovE in narrow waters, critical vessel's hardling capabilities or equipment or
situations will arise, whether it be an error of mannrng weakness-knowledge which it is essential
judgement, a mistaken response to a helm or engine for the pilot to have before it beiomes evident too late.
order, a sudden breakdown of the main or auxiliary
machinery of the shipr or possibly a collision or
obstruction in the fairway ahead, It may be due to a
paned tow line, to avoid imminent collision with
anotler vessel or dock, or possibly the failure of a
bridge or lock gate to open. Whatever causes the continual awareness of wind arrd weather, wiII all
crisis. the reaction of rhe pilot must be rapid and have direct influence on the type ofemergency action
correct. to be taken.

Speed and momentum

prepared and will have, over the years, given some

thought while conducring routine manoeuvres as to
possible remedies in the event of a crisis requiring an
ability to stop, and particularly those forces direcdy
emergency stoP-
under his conrrol. The most obvious of rlese are speed
Some pilo nough to complere artd consequental stored momenrum,a kno,^,i as
tlreir entire c y being involved in kinetic energy.
a situation w pur to the ultimate
test. Others rheir fair share of
The greater ttre displacement of a vessel, the
greater her inenia and momcntum- Unforrunately
mechanical defects, whi.le a few of rhe Iess prudent will
through the use ofexcessive speed or as the result ofan
engine power is based on the amount required to
overcome underwater resistance at a desired speed,
over-optimistic manoeuvre find themselves in an while .inertia and momentum increase at a higher
emergency srruanon.
ratio than underwater rcsistancc. The result is that,
whiie sea speeds can be kept approximarely the same
without proportional increase in powcr, the accelera-
tion and more imponaatly tie deceleration is reduced
and therefore such ships require handling at much
lower speeds in order to be stoppcd.

Displacemcnt Speed Mooentum

to a ccrtain extent self-inflicted or che rcmedies
r to have 10,000 tons 10 ft-lscc - 100,000 ft rons/
authori- 100,000 rons I ftlscc - 100,000 ft tons/
hich it is Figutc 15.
From the above it can be seen tiat ifbotl vessels are
Th-e reader shou.ld, however,. realise thar ship-
.handling is neither an exact science or a mysterious
an.' 1t rnvolves combinations of variables so

trim or draught, arrd when acting equally on tlre

whole lengh of the ship as would be lhe case when'thc
tide is direcdy astern or ahead.

Displaccrocnt Currcnt/Tidc Moocaruo

10,000 rons 2 knots following - 20,000 knor/

100,000 tons I knors following - 200,000
rtguft z-.
320 THE NAUTICAL INSTITUTE
 Whrlc the pilot in narrow warers or in the final especial.ly how much c-hain ro slack out, before he goes
approaches to a berrh will need to control his speed lorward ro sra-nd byrl. The imponance of hariie a
.- .ricdy to that which a.llows fu.[ manoeuvring capabi- man forward who can haadle rhe archor artd bc relied
lities, the writer is well aware rhat there are esruaria.l upon to put ouc thc correcr amount of chain-no
porrs in rhe world, used by VLCCs and large ships, mor€, no less-can not be oversrressed.
where the passage has to be carefully planned. The effective way to use anchors to stop in an
Somctimes such plals allow a very small rida-l wrndow emergency is to let gojust sufficienr chain to ilow the
and speeds on pa;sage possibiy in excess of rhose anchor ro Frrsr grab and then break loose ald drag.
compatible with emergency stopping. Port aufiori- The anchor musr not dig in and holdrs. Should th--e
ties and pilots need to bc continually aware of these alchor hang up or too much chain be allowed ro mn,
situations and make maximum use of loca.l mles the mome nrum of dre moving mass of the ship on rhe
allowing such vessels priority. I:r addition rhere relativeiy small bra-ke on the windlass wil either burn
should be a number of specially reserved 'escape out *re brale or part rhc cable in all but a smal.l or
alchorages' into which vessels cart be brought in an moderate size ship. It is vital that Lhe anchor breaks
emergency. It must be said, however, rhat in the evenr out of rhe ground and relieves the srrain on the bra-ke
of a main engine failure or steering gear defect, the or chain.
oprions open to the pilot may be somewhat limited. To use rhe anchors, the vessel's un_derkeel clear-
ance should be at leasr 20 per cent of the vessel's
Anchors maximum loaded draught, in order ro prevent under-
'Never do damage wirh an archor at your bo-. if water damage ro the ship. The amounr of chain used
you are able to use it",8. For most ships rhe use of should be twice the deprh of waterr6 or t j D, where D
mchors rema.in the pilots' most effective tool for is the disrance from the hawsepipe to the bottomlT.
'venting groundings or berthing accidencs- There Provided the aachor is correcdy worked, and the
lY however, wirh the building of very large displace- deprh of wacer does not exceed 120 ft or 1f shackJes of
rt vessels considerable doubt in the minds of cable, ttre ship will continue along her track slowiy
rirariners about the use of alchors on such vessels in Iosing headway, arrd can be brought to a conrrolled
an emergency, such advice as: stop. This is panicularly useful after a loss of main
'Today thc anchol cablc aad wiadlass oJa WCC or engine or steering gear.
largc buk caricr mul bc rcgarded ar an extrtmc!1 Naturally, many mariners will be concerned that it
Jtagih atangcmcnL As ships haoc incrcased in sizc, might be dilficult to srop the chain running after
anchors haac b€conu propon;oaatcj lightcr, cables Ietting go because of the ship's speed over rhe bortom
ptopottionatcQ shoicr, a;ndl4tseJ morc uulnerablc or the depth of water. This concern is especially
to shock!oads.. Ia couzqutnce, thc aachoing process prevalent when handling larger ships. It is pardy due
mttt ba cond.uctcd with atrcmc caution lest tht gear bc to lack ofconfidence, for, as stated earlier, emergency
caried awa2'9 . situations are forrunately rare and until experienced
'Thc anchors of a 542,000-dwt iankr arr propor' rhe abrhry of the brake to cope with the demaads put
liondkly ottly onc-ffth ds fuaay as those of an upon it are naturally suspect. There has in fact been
18,000-dut ucsscl, and thc cables proponionatell some improvement in the bral<ing mechanisms on
only half as long. ' VLCC windlasses, induding the use of retrof-rt disc
brakes and the installation of combination disc and
'Thcrc is no nargia Jor mor and in conscquencc th,
barrd brakesrT". It should, however, be remembercd
noliot lhst lfu anchms (or such ships) caa be that static friction is t-hree times greater than dynamic
dcphlcd in ancrgcncl situztioas, i no hnger friction for an asbestos bra-ke barrd on the windlass's
lcnablc.'
-7lon,.ur, dnrmr8. The bral<e has three times as much holding
in the extreme to the standard advice of power when rhe gypsy is stopped, as when it is
'). .o both anchors on rhe runro,rl until they get.an turning. The secret is to screw up the brake as soon
ellEctive grip and then alternate.ly checking arrd as tlle anchor touches bottom and the weight has
veering them as the vessel's way is reduced.' momentarily come offthe cable. The anchor digs in as
Uncertainty as to use has meant that far too often the chain comes tight arrd is chen pulled free from the
pilots fail to use an anchor ii,hen they could do so quite bortom before the staric friction is overcome,
safely, for fear of losirg it or for a not-unfounded fear draggirg along the bottom as the flukes ball up with
of sitting on it with a loaded tanker. While, of course , mud.
in many ports in tlc world pi.lots daily use aachors The arbitrary maximum depth of lI shackles is
with great skill, still for too marly the anchor does not based upon the most I chink one could expect to drop
exist. Lack of familiarity ofuse by pilots often breeds an anchor in an ernergency, in a large ship and still bc
similar qualities among those on the ships responsible able to retain control of tIe weight of anchor and
for working the anchors, wirl the result tiat arr cable. It should, therefore, be treated wich caution
unexpectcd order to 'let go' will mean the alchor and where possible the anchors should be walked back
being a.llowed to run out to the bittcr end in a cloud of
dirt and rust. Once the order is given, the noise on the
forecastle hcad is such that beldted orders to 'hold on
at one shackle' are rareiy heard.
.and screw up
'n pilotage waters whcre the anchor is regulariy
..--d and manned. the oilot should ensure that tie
deck officerund..tt-d. what is required and
PILOTAGE 321
 I SHACKLES = 810'

9 SHACKLES = 810'

ll SHACKLES = 990'

13 SHACKLES = 1170'

Figure 3: Comparative cable lengths

out ready ro help pull rhe ship back offle. The timing underkeel cleara-nce of 5m or less-the rurning cirdc
of this action will depend on the rario ship's of a loaded VLCC2o has been found ro be 60 per cent
length/length of anchor cable (see Figure 3). greater thar in deep water. The swept advalcc, a
more significalt mcasuremen(, increased by only 13
Emergency solutions per cent. Therc is a.lso a reduction in speed )oss in
proposed ro examine a number shallow water.
rhe pilot may need to rake If the vessel is already proceeding at less than ful.l
nd suggest possible solutions. specd when ir becomcs necessary to tale action, tle
for every possible contingency, englnes
small a
diamete
increase
rpm is reduced.
The 'hard turn' is not tic only metlrod of stopping
a ship in open waters; the pilot may have sulficicnt
Open sea-collision avoidance
When space allows, a hard rurn to pon or star-
board, mainraining engine speed unril almosr
completely round, will rum even the largest ship on a
tactical swept diameter ofaround three ship's lengths
in deep watcr. Speed t-hlough rhe warer rapidly drops
with the rate of turn and with t}e engines pur ro fulJ
astern in thc final stages of tIc turn, the ship can be unccrtain.
broughr to a stop less thalr onc ship's length from the lRudder cycline'is less effective than the 'hard
stan of the turn. In shallow wate r-i.e., with an rurn' but under l?"knors. wirh limired spaces on botl
322 THE NAUTICAL INSTITUTE
 SIANDBY ANCHORS. ENSUHE ANCHOFI PASTY HAVE
CLEAR INSTFIUCTIONS BEFOFE LETTING GO ANCHOFS

IS THEHE SUFFICIENT UNDER KEEL CLEAHANCE?

lE 200lo VESSELS ivlAXlMUM LOADEO DHAFT

IS THE SEA BED CLEAH OF OBSTRUCTIONS DO NOT

USE ANCHOFS
EXCEPT IO
AVOIO MOBE
IS THE NATUHE OF SEA BED L]KELY TO SNAG OH SEHIOUS
HANG UP ANCHORS? DAMAGE

v
FFYESI

SHIPS UNDEFI3O,OOO DWT 30,000/60,000 D\/1rI: OVEFT 60,000 DWT

, LET GO BOTH +,S ON ONLY USE ANCHORS ONLY USE ANCHORS

THE RUN, CHECKING & IF SPEED BELOW IF SPEED BELOW
VEEFIING UNTILVESSEL 4 KNOTS 2 KNOTS
gTOPS
rHY DHAGGING WITH TRY DMGGING
BOTH s'S2 x DEPTH BOTH $'S2 x DEPTH
IF UNABLE TO HOLD
IF UNABLE TO HOLD
VEER & CHECK
VEER CABLE
CABLE IF POSIBLE

SOME FIISK OF PFOBABLE LOSS

LOSING ANCHORS OF BOTH ANCHORS
ONLY USE TO DANGER TO $
PFEVENT SEHIOUS PAFTY, USETO
DAMAGE BE AVOIDEO

MAX SPEED 8 KTS

LET GO BOTH ANCHOHS, CHECK AT 2 x DEPTH, DRAG UNTIL STOPPED

ONLY PUT OUT MORE CHAIN IF UNAELE TO PREVENT GFOUNDING

Figure 4: Anchoring checklist

PILOTAGE 323
 BUDDER
CYCLING
- -N CRASHASTEHN
LJ MoDEFNVARIABLE
16 KNOTS
PITCH PHOPELLOR

I t HARD TURN
I r-iTO STARBOARD
/,DEEPWATER
-- { HARD TURN
CRASH ASTERN
SHALLOW WATER CONVENTIONAL
RIGHT HANDED

-L-) RUDDER
cycltr.rc
12 KNOTS -
CRASH ASTERN

tlJ
o
(r
l OISTANCE
o ALONG
BUDDER CYCLING O
IL COURSE
LL
6 KNOTS o
CRASH ASTEHN

'----'/ TUBN

Figure 5: Schematic comparison of searoom for emergency manoeuvers

of large tankers
I SrARr

lNtTtAL COURSE _ 20"

HARD rc) STARBOAHD
-
INITIRICOURSE -
- \-\J 4oo

n MAXIMUM
\J OVERSWING
HARD TO PORT INITIAL
a COUBSE
DEAO SLOW AHEAD
fi
V
MAXTMUM
OVEBSWING
HARDIO STARBOARD
FULL ASTERN n rNrrrAL
U COUHSE

STOP ENGINES _J. DEAD IN THE

WATER
1.2 SLU
FINISH

Figure 6: Rudder cycling

324 THE NAUTICAL INSTITUTE

 sides or possiblv in a traffic roureing sysrem, where Stopplng in narrow channels
use of rhe 'hard turn' may cause conlusion ro other
shipping and involve possible legal implicarions,
'rudder cyding' is ro be recomme nded. Under 6 knors
it can be scen the end results are much doser, but it
should be remembered rhar only under rhe 'crash
stop' is conrrol of rhe ship largely lost.

Stopping with restricted searoom

The principle of rudder cycling (see Figure 6) is to again. reducing speed rhrough the
reduce speed by introducing underwater resisrance warer y enough to use che anchors
while retaining conrrol of the steerage up ro the last as des Figure 4). Thc slower the
moment. This is done by 'fish tailing' with the rudder vessel deeper the water, the more
hard over on either side and by 'yaws' with a grear srern power you will be able to use wirhout transverse
rate of tum22. In orde! to mainta-in a good rare ofturn rhrust effecr lrom rhe propeller.
rhe engine speed is reduced step by step and kept ciose
ro the ship's speed. In shallow watefJ wich 20 per
cent underkeel clearance, trials have indicared rhat
while a vessel mainrained a rruer track and sreering
was good, she took longer to srop than in deep warer
(320 per cenr UKC) where rhe steering was also
effecrive. In medium deprh water (50 per ienr UKC)
the steering was less effective whi.le rhe sropping stern ro ride . This assumes thar furrherprogress in the
distance was good. channel is prohibiced.
With fie Ioss of the main engine , a vessel can be
'coasted' to a stop using rudder cycling, bur in rhis '[o lay a ship on the starboard side of a channel2+
case crialsll indicare the reverse reacrion to char of bring her ro rhar side wich speed reduced ro bare
powered rudder cycling. In shallow water rhe vessel sreerage way. Drop the port anchor and slack the
srops quicker, while steering was found to be less chain until the vessel is allowed co dredge slowly
effective. In medium depth warer sreering abiliry is alongside rhe bank. Do not put out so much chain thar
soon losr, while sropping is less effe*ive. In. deep the vessel srops before she is alongside the balk. If the
warer steering is more effecrive but a vessel carries anchor flerches up too soon, rhe tide wlll take charse
waY. from astern and cause rhe ship to lie across tie

(2)

BACKING
STERN
COME
AHEAD LINE

STERN TUG AHEAD / -2,TUG AHEAD

LINE TO LEFT .Z TO BIGHT
(rF FEOUTRED) 0) sHrFt srERN (1) SHIFE STERN
MOVES LEFT MOVES RIGHT
(2)SHrP TURNS (2) SHIP TUHNS
TO FIIGHT LEFT

TUG FULL
ASTERN
SHIPS HEADWAY
REDUCED
BOTH TUGS
FULL ASTEHN
HEADWAY ,/
REDUCED
r',/'

Figure 7: The American method

PILOTAGE 325
 3\

COU NTEBS
SHEER:..t

D E'\I I"EQ
COUNTERS
HEADWAY
ure 8: The Eu an method TBANSVEBSE THHUST

channe.l. Ease the ship ahead against rhe anchor The European method
putting tle helm to pon as rhe ship nears the bark. (I )
Three convenriona.l rugs on long hawsers witJr only
GraduaJIy reduce rhe rpm unril the vessel lays wirh nr.r mber 3 ru g sccurcd with a backin g headlinc to
rhe
her stern against the bank while the anchor holds the reduce headway. Securcd on pon sidc it counters
bow off as the tide or currenr from afi runs along the lransvcrse thrust effecr going astern.
porr side of the ship. (2) Onlv in dire emcriency and at spccds oflcss thal 3
knors, might thc tugs bc pcrsuaded to Iav back for
Stopping ships with tugs fear of girding.
(3&4) Alternarivcly providing vcsscl has minimurn spced,
Probably most accidenrs ta-ke place during berthing the vessel mav be swung inro the tidc to assist
sroPprng.
(5) The increasing usc of Shottel and Voitl Schncidcr
rugs in Er-rropcan watcrs has lcd to grcady incrcascd
safer;- in the evcnt of an emergcncy dcveloping.
Whcn supplied wirh a combinarion of convenrional
rugs and Voith Schncidcr, always position the VS
rug on rhe centre lead afi. From this position rhe tug
nor onJy assisrs with rcducing hcadway ofvour ship
but can bc uscd ro maintain a straight coursc by
progress in the event of an emergenc\'. countcracring transversc thrust cffect or that of a
shecr ro porr. The European method of sccuring
tugs, docs allor.'for usc ofthe ship's anchors in most
cascs, cxcepr perhaps as in (2).
It is not inrended ro suggest remcdies here for thc
infinitc number oflikely benhing accidents, suffice to
sav, think carefully beforc you deploy your tugs,
control vour speed and be prepared.
working. There are advanrages in aJJ systems; ir is up
to us to recognise those advantages and ma-ke rhe bcst Using bank eflecl under power
use we can of she rugs artd pracrices we inherit. it is assumed the rcader will havc srudied 'bank
effect' elsewhere2s and chercfore no explanarion is
given here. How iucky we are that our forebears had
the sense to mal<e rrles that aliowed for a vessel to kecp
to the starboard side of a channcl, for whi.le it is
possible to lay a ship aJongside eirher bank, it is
certainl,y easier to do so ro the starboard bank. In
artempting tlese manoeuvrcs the shiphandlcr should
be fuiiy aware that thc uromentum of alarge ship may
well overcome dre 'bow cushion,' while the 'stern
sucrion' will usua.llv be slrongcr thar the 'bow
sccuring tugs can somewhat limir tl-re use of anchors cushion ' Thar the giearer the speed of rhe ship, the
326 THE NAUTICAL INSTITUTE
 faster the warcr will rravel down the on shore side, 600 OFF COUFSE
causing rhe hull to move bodily towards rhe bank ar (40" vLcc)
FULL HELM
grearer speed (venturi effccr). 2 TO STAFBOAFO
Starboard baal<-Stcer co bank using helm arrd
engines until bow cushion and srern suction is felt- Put
engincs astern as vessel comes parallel to bank. Keep
ship balanced and a.llow to come gendy alongside.
Port bauk-Approach bank wirh engines going STEADY ON HECIPFOCAL
astem, as vessel comes parallel ro bank. Stop engines COUFSE
and kick ahead with port helm. Keep balanced and Figure 10: The Williamson turn
drop aJongside.
It is hoped rhar this chapter offers sound advice to
will
rhose about to embark on a career in pilorage and
stimulate rhoughr and discussion among my col-
Ieagr.res wherever rhey may be practising their skills
and hopelully may cven result in a scrious accident
being avoided.
The views expressed are rhose of rhe aurhor, witlr
grareful acknowledgemenc to rhe authorities referred
ro below and withouc tnrhom rhis paper could not have
been written. They do not necessarily reflecr the views
ol rhe United Kingdom Pilors Associacion (Vlarine)
ENG IN E Technical Commitree or the author's employers, the
ASTERN Port oI London Authoriry-
Emergency situations are thankfully rare, but
when they do happen, rhey do so in a hurrv. Some
mental preparation is essenrial for the correcr
response. Training on simulators artd manned
models would give confrdence to rhe pilot and
substance ro his rheories.!
ENGIN E
ASTERN ENG IN E
AHEAD References
I R. A. B. Ard)ey Harbour Pilotagc Page 118.
2 ivlacElrcvcy S,trp handliag Jor the MaiadPage l+1.
3 Port Rcvcl Shiphandhng R{aznct rllarual Unic 3 Pagc
Using the bank effect wirh engines but without
n:dder, withour anchors, the ship has to be controlled 4 Pon Revel S,trprtandliag R{acncc Manual Unit 4 Pagc L
in the final approaches to whichever bank she has 5 Pon Rc"el S,lrptandlhg R{nncc ManualUnit 4 Page l.
prefercnce. Using the bow cushion and propeller or 6 Pon Re"el S,trp,land.ling ReJacna Maaual Unit 4 Page 3.
stern suction, going ahead on rtre starboard bank will 7 Ardley Page I 18.
5ring the stcrn in. Going astern on the engines will 8 G. Danton The Tfuory and Practicc oJ Scaaatship 198 r-

page 24.
Jringthe stern out- On the port bank, ir is the reverse. 9 -a-pt Ojo, !I)II, arrd Prof King, lvlSc, FNI'
Using the bank effect, with rudder but wirhout 'Anchonng Sysrcms-some insighrs for Nlariners'
engines, without anchors, control can only be Naurical Instirute rVa uical Surucyor P a.ge 176.
- achieved head to tide. Bow cushion effect and venturi l0 Ardley 118.
et-fect can give some assistance ro bring the vessel ro a l1 Danton 24.
coasting stop ifsreeragc can be maintained. 12 NlacElrevey t 32.
l3 MacElrevcy l3l.
Williamson turn l4 MacElrcvcy l3l.
l5 MacElrcvcy l3l-
No paper on emergency stopping would be 16 MacElrevcy 132.
complete without reference to this most effective I 7 Pon Rcvel Unit 6.
method ofbringinga ship back to the original position l7a E. F. Fulkcrson and R. J. Clcmenrs 'Revicw of
or track, on which a man has gooe overboard. The Anchorine Reouircmcnrs for larqe talkcrs.' Para I &
Williamson turn works for all ships but should bc 10. Sympisiuni on thc behi"io ui o f d isablcd tankcrs'
slightly modified for use by VLCCs co allow for an 18 MacElrevcy 136.
initial change ofcourse of{0" insread oIthe staldard l9 MacElrevev l{1.
600 beforc reversing tIe helm. 20 Big Slnps ia' Shatlow Wdtd'f ti s of Esrla Osaka Ex'xoa
Marinc Vol 24 No l.
Thcre are orher methdds, the'single delayed turn' 21 Pon Revcl Unit 7.
and thc 'double turn'26, but this measure, which 22 Pon Re"cl Unit 7.
takes about 16 minutes on an average size ship, is 23 Trials of Esso Oruka Page 7
imple to pe rform and to remcmber and is prove n. I 24 -MacElrcvey 142.
, ..ave in lact used it in dcnse fog in the lower reaches of 25 Daaton 66.
the River Thames to great effcct. 26 Da:rton 197.
PILOTAGE 327