Intro
Only training and « hands-on » experience take the mystery
out of shiphandling
Intro
Manoeuvring characteristics of ships:
– « Course keeping ability » and « Dynamic stability »
• Dynamically stable ship after small disturbance move along a
new straight course without using rudder
• Dynamically unstable ship performs turning circle with rudder
amidships
• Dynamically unstable ships are more difficult to handle
– « Turning ability »
• Measure of ability to turn the ship with hard-over rudder
• Obtained by performing a « turning circle » manœuvre
• « Initial turning ability » is defined by the amount of heading
deviation per unit of distance travelled
Intro / Dynamic stability
Intro/ Dynamic stability
• Dynamically stable
- Fine line ships (cargoships, containerships,
passengerships) tend to be directionally stable
- directionally stable ship will move on a straight course if
rudder is kept amidships
- When during a turn, rudder is put amidships: rate of turn
reduce to zero and vessel continues on straight course
• Directionally unstable
- ship deviates with the smallest disturbing cause
- If rudder put amidships during turn: reduction of rate of turn
but vessel keeps turning on a track with larger diameter
Turning
Ability
Intro / Inertia - Momentum
Intro / Inertia - Momentum
Intro / Inertia - Momentum
Intro / Inertia - Momentum
Intro / Qualities of a good shiphandler
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Patience
Anticipation: be « proactive »
instead of « reactive »
Quietness
Experience
Steadfastness
Concentration
Knowledge / Know-how
The « Art » of shiphandling
You will see:
Fast captains,
You will see:
Old captains,
Very seldom will
You see:
Old and fast Captains
Chapter One
Various factors
influencing the manoeuvring of the ship
Ch1. Effect of Fixed Factors on shiphandling
Fixed factors of the ship
– Design and
dimensions of the
ship
– Propulsion unit
– Propellers
– Rudders
Ch1. Effect of Variable Factors on shiphandling
Variable factors inherent
to the ship
- Draft
- Trim
- Displacement
- Fouling
Variable factors outside ship
- Wind, Sea, Swell
- Current
- Interaction: Depth of water / Shallow waters
- Interaction: Proximity of other ships
Ch1. Factors influencing the shiphandling
Size of the ship
• Ships are designed to make speed , not to stop
• Engine power does not increase in proportion to
ship’s size
• Large ships:
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Difficult to judge speed from the bridge
When swinging in port: large swinging room required
Estimation of distances to berth difficult
Bridge is isolated from forecastle or poop
Large ship causes more damage when colliding with berth
Ch1. Factors influencing the shiphandling
What is a large ship?
• In 1952 biggest tanker in the world was 45000DWT
• Lenght is a more relevant criterion than tonnage:
- Below 100m : small ship
- Longer than 200m: large ship
- Between: medium size
Size of ship versus available space gives degree of
difficulty:
- For small ports 5000DWT ship is big
- A 5000 DWT ship does not present same problems of
dimensions, mass, inertia and momentum as a 50.000DWT.
Ch1. Design of ship / Bridge amidships
Bridge amidships:
Advantages
Shiphandler near the pivoting point when swinging
Best position in a small ship
Close to forecastle and poop / visual communication
Good indication of rate of swing
Disadvantages
On large vessels: each end far from the bridge
Ch1. Design of the ship / Bridge forward
Bridge forward
Advantages
Shiphandler has excellent view of berth on arrival
Close to anchor when anchoring / easy communication with
anchor party
Close to entrance of locks + good visual communication with
the shore
Disadvantages
Difficult to assess the ship’s heading without looking aft
From the wings: objects on one bow may appear on the other
Ch1. Design of the ship / Bridge after
Bridge after
Advantages
Easy to judge rate of swing / start and end of swing
All ship is seen when looking ahead / ship’s heading
visualized
If bridge is near stern: astern clearance easy to assess
Disadvantages
Shiphandler far from forecastle : visual communication
impossible when mooring, anchoring, approaching lock
or berth
Difficult to select precise spot for anchoring
Vessel passing ahead from bridge may still collide with
foredeck
With restricted visibility
Ch1. Design of the ship
• Ratio Lenght/Breadth (L/B)
– Big L/B : bad turning / good course keeping (dynamically
stable ship) / good speed
• Ratio Lenght/Draft (L/D)
– Big L/D: bad dynamical stability (example: bulkcarrier or
tanker in ballast)
• Ratio Block coefficient (Cb = V/LBT)
– Big Cb: bad dynamical stability, easy turning
Ch1. Effect of ship parameters on manoeuvring perf.
Good
Bad
turning
course keeping ability
Bad
Good
Ch1. Effect of the bulb on performance
Reduce the water resistance:
Increase of speed: one knot / depending on
draft/trim
Consumption reduced
Better course keeping ability
Worse turning ability
Ch1. Vorm achtersteven / Forme de la poupe
Design of the stern influences the flow of
the water striking the propeller and the
rudder
Ch1. Design of the Hull
New hulls are designed to improve the quantity of water
passing through the propeller/rudder area.
Ch1. Design of the Hull
Ch1. Propulsion of the Ship / Diesel motor
• Manoeuvrability is function of type of propulsion
• Most common: diesel engine + fixed pitch propeller
Ship is called m/s (for motorship) or m/v (for motor vessel)
• advantages
- Can be instantly stopped
- Can be quickly reverted
- During a stop manœuvre: engines can be stopped at the
moment that the ship is stopped / propulsion ceases
immediately.
- Can be quickly accelerated for emergency or kick ahead
Disadvantages
- Compressed air : quantity limited / N°of cons.starts.
- Big engines cannot run slowly / deadslow = 9 or 10knots
- Difficult to start astern when speed ahead to high
Ch1. Propulsion of the Ship / Diesel motor
Ch1. Propulsion of the Ship / Steam turbine
• Second most common: Steam turbine. Ship is called s/s for
steamship.
• Disadvantages:
– Stern power only 40 to 50% of ahead power (smaller turbine used
for astern)
– Problems to stop the vessel ; mostly in emergency
– Turbines can keep turning slowly ahead when supposed stopped.
Ch1. Propulsion of the Ship / Steam turbine
Ch1. Propellers
• Fixed right handed propeller
• Variable pitch propellers
•Twin propellers
• Outturning
• Inturning
• Kort Nozzle
• Azimuth stern drive (ASD)
• Voith Schneider
Ch1. Variable Pitch propeller
Ch1. Kort Nozzle / Tuyère Kort
Ch1. Propulsion « Voith Schneider »
Ch1. Rudders
Ch1. Effect of Variable Factors on shiphandling
Variable factors inherent to the ship
- Draft
- Trim
- Displacement
- Fouling
Ch1. Effect of Draft / Fully loaded ULCC
Difficult to stop and to bring in a turn
Ch1. Effect of draft / Ship in ballast
Ship heavily affected by wind
Ch1. Effect of Trim
Trim by the head:
- will turn into the wind
- difficult to steer
- rudder and propeller come out of the
water when ship is pitching
Trim by the stern: vessel tends to fall off with
side wind
Ch1. Fouling / Salissure de coque
Ch1. Effect of Fixed Factors on shiphandling
• Variable factors outside ship
– Wind, Sea, Swell
– Current
– Interaction: Depth of water / Shallow waters
– Interaction: Proximity of other ships
Ch1. Effect of the wind
Lijgierig schip
Loefgierig schip
Ch1. Effect of waves on the ship
The stability of the ship is affected by stern waves
Ch1. Effect of current
Ch1. Effect of current
Ch1. Interaction between ship and shore
Closeness of obstacles like shore, berth, etc… will
modify the pressure fields around the ship and
provoke changes of heading, uncontrollable swings,
due to suction and repulsion forces.
Ch1. Interaction between ships
Close quarters
Ch1. Interaction between ships
Overtaking ships
Ch1. Interaction between ship and assisting tugboat
The tug is affected by the closeness of the ship
Dangerous position when close to the bow
Ch1. Comparison between ratios mass/power
• Airplane :
4 to 6 kg/Pk
• Car:
25
kg/Pk
• Coaster:
50
kg/Pk
• Sea ship: 2000 to 3000 kg/Pk