2. • Ships are subjected to various forces, such as waves, wind,
and weight distribution, which can cause them to roll from
side to side. The roll motion of a ship can have significant
implications for passenger comfort, crew safety, and cargo
stability.
SHIP ROLL MOTION
• Ship roll motion refers to the side-to-side movement of a
ship. It is primarily caused by external forces acting on the
vessel, such as waves, wind, and the distribution of weight
onboard. Waves exert forces on the ship's hull, causing it to
roll as the waves pass beneath. Wind can also induce roll
motion by exerting pressure on the ship's superstructure.
Additionally, the distribution of weight on the ship can affect
its stability, leading to roll motion.
• Ship roll motion can be classified into two types: natural roll
and forced roll. Natural roll refers to the rolling motion
caused by the sea state and the ship's natural dynamics.
Forced roll, on the other hand, is induced by external factors
like wind and waves. The goal of antirolling features is to
reduce the amplitude and frequency of ship roll motion,
ensuring stability and safety for the vessel and its occupants.
3. IMPORTANCE OF
ANTIROLLING FEATURES
Passenger comfort: Reduces
discomfort and seasickness.
Crew safety: Minimizes the
risk of injuries and accidents.
Cargo stability: Ensures safe
transport of goods.
Maneuverability: Improves
the ship's control and
navigation.
Structural integrity: Preserves
the ship's structure and
prevents damage.
4. GYROSCOPIC
STABILIZER
• Gyroscopic stabilizers are active
antirolling features widely used in
ships to reduce roll motion.
• These stabilizers incorporate
spinning gyroscopes to generate
gyroscopic torque, which opposes
the roll motion of the ship.
• Gyroscopic stabilizers are primarily
used for their precise control over
roll reduction and their effectiveness
in various sea conditions.
5.
6. ADVANTAGES
Precise Control: Gyroscopic
stabilizers provide precise
control over the ship's roll
reduction, allowing for fine
adjustments based on roll
angle and speed.
1
Real-Time Response: These
stabilizers offer real-time
response to changing sea
conditions, ensuring
continuous roll reduction
and enhanced stability.
2
Effectiveness: Gyroscopic
stabilizers are highly
effective in reducing roll
motion during normal
operating conditions and
moderate sea states
3
7. LIMITATIONS
COST: INSTALLATION AND
MAINTENANCE COSTS FOR
GYROSCOPIC STABILIZERS ARE
RELATIVELY HIGH COMPARED TO
PASSIVE SYSTEMS.
POWER CONSUMPTION:
GYROSCOPIC STABILIZERS REQUIRE
A POWER SOURCE TO MAINTAIN
THE GYROSCOPES' ROTATION,
ADDING TO THE OVERALL ENERGY
CONSUMPTION OF THE SHIP.
LIMITED IN EXTREME CONDITIONS:
WHILE EFFECTIVE IN NORMAL TO
MODERATE SEA CONDITIONS,
GYROSCOPIC STABILIZERS MAY HAVE
LIMITATIONS IN EXTREMELY SEVERE
SEA CONDITIONS OR AT VERY LARGE
ROLL ANGLES.
8. FIN STABILIZERS
- Fin stabilizers are active antirolling features commonly
used in ships to minimize roll motion. Let's explore their
function, advantages, and limitations.
- Fin stabilizers consist of retractable fins installed on
the ship's hull, typically near the bow and stern.
- The fins can be extended or retracted based on the
ship's roll angle and sea conditions.
- When extended, the fins create lift forces as water
flows past them, counteracting the rolling motion of the
ship.
- By adjusting the angle and position of the fins, the
ship's roll motion can be effectively dampened.
9.
10. ADVANTAGES
Fin stabilizers offer quick response time, providing
immediate roll reduction as the ship encounters
varying sea conditions.
They are highly effective in reducing roll motion,
particularly in moderate to rough sea states.
Fin stabilizers enhance ship stability, improving
passenger comfort and crew safety.
These stabilizers can be customized to meet the
specific requirements of different ship types and
sizes.
11. LIMITATION
- Fin stabilizers may have limitations in
extremely severe sea conditions or at very
large roll angles.
- They require a power source to extend
and retract the fins, adding to the overall
energy consumption of the ship.
- Installation and maintenance costs of fin
stabilizers are relatively higher compared
to passive antirolling systems.
12. BILGE KEEL
Bilge keels are passive
antirolling features commonly
incorporated in ships to
minimize roll motion.
Purpose: Bilge keels utilize
hydrodynamic forces to
counteract the rolling motion
of the ship.
13.
14. Advantages:
Cost-effective: Bilge keels have relatively low
installation and maintenance costs compared to active
systems.
Simple design: They do not rely on complex mechanical
systems or external power sources.
Minimal maintenance: Bilge keels require minimal
maintenance, making them easy to manage.
Suitable for calm to moderate sea conditions: They are
effective in reducing roll motion in normal operating
conditions.
15. Limitations:
Effectiveness in severe conditions: Bilge keels may have
limited effectiveness in extreme sea conditions or with large
roll angles.
Additional antirolling features: In challenging sea conditions,
bilge keels may need to be combined with other antirolling
features, such as active systems, to enhance stability.
Limited adjustability: Unlike active systems, bilge keels
cannot be adjusted in real-time based on changing sea
conditions.
Reduced effectiveness at high speeds: At high speeds, the
hydrodynamic forces acting on the bilge keels may be
diminished,
reducing their effectiveness in roll reduction
16. ANTIROLL TANKS
Antiroll tanks are passive antirolling features commonly
employed in ships to mitigate roll motion. Let's explore why
they are used, their advantages, and their limitations.
Antiroll tanks are integrated compartments within the ship's
structure that are partially filled with liquid, typically water.
These tanks utilize fluid motion to counteract the rolling
motion of the ship.
As the ship rolls, the liquid inside the antiroll tanks flows
from one side to the other, generating a counteracting force
against the roll motion.
17.
18. Advantages:
• Cost-effective: Antiroll tanks offer a relatively low-cost
solution for roll reduction compared to active systems.
• Simple Installation and Maintenance: They do not require
complex mechanical systems or external power sources,
resulting in simpler installation and minimal maintenance
requirements.
• Versatility: Antiroll tanks can be implemented in various
types of ships, providing a flexible solution for roll reduction.
• Effective in Calm to Moderate Sea Conditions: Antiroll tanks
are particularly effective in reducing roll motion in calm to
moderate sea conditions.
19. Limitations:
Limited Effectiveness in Severe Sea
Conditions: Antiroll tanks may have
reduced effectiveness in extreme sea
conditions or when the ship experiences
large roll angles.
Additional Measures May Be Needed: In
challenging sea conditions, antiroll tanks
may be combined with other antirolling
features, such as active systems or bilge
keels, to enhance stability and roll
reduction capabilities.
