Includes Basic ship Terminologies and Investigation Check list
Sail Smooth, Sail Safe
Marine Kit – 4 Marine Kit – 4
MarineTech Project, Lean Institute ODU, May 2011
1. Ship Terminology………………………………………………………03
2. Motions of a Floating Body…………………………………………...09
3. Ship Stability…………………………………………………………….10
4. Free Surface Effect……………………………………………………..13
5. Effect of Water Density on the Draft…………………………………15
6. Displacement of Ship…………………………………………………..16
7. Loading of Ship………………………………………………………....17
8. Tanker Ships.…………………………………………………………....19
9. Speed of Ship..…………………………………………………………..20
10.Ship Power Plant………………………………………………………..21
11.SONAR……………………………………………………………………23
12.Unit Conversions……………………………………………………….26
Index
2MarineTech Project, Lean Institute ODU, May 2011
1. Ship Terminology
Starboard
Port
Stern
Bow
Bow : Front part of the ship
Stern : Rear part of the ship
Starboard : Right side of the ship
Port : Left side of the ship3
MarineTech Project, Lean Institute ODU, May 2011
Hull
•Most of the modern vessels have
double hull to prevent flooding in
case of accidents.
•Tankers have double hull to
prevent oil spilling in case of hull
damage.
•Double hull also serves as
ballast tanks in the partial loaded
or unloaded condition to keep
the center of gravity as low as
possible for stability.
Ship Hull
Hull is a body of a ship
Double Hull4
MarineTech Project, Lean Institute ODU, May 2011
Keel
http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module2/introductio
n.htm#
Keel of the ship is the
principal structural
member of a ship running
lengthwise along the
center line from bow to
stern, to which the frames
are attached.
Various terms used to define hull cross section
“fore” is the front part
“aft” is the rear part
5MarineTech Project, Lean Institute ODU, May 2011
Cross section of ship
Draft of a ship is the vertical distance between the waterline and the bottom
of the hull
Draft
FreeboardWaterline
Freeboard of a ship is the vertical distance above the waterline
Beam of a ship is the width of a ship at any cross section
Beam
6MarineTech Project, Lean Institute ODU, May 2011
Deadrise: Deadrise is an angle measured upward from a horizontal plane at
the keel level.
Flat bottomed vessels
have 0 (zero) deadrise.
Deadrise for “V” shaped
hull varies from bow to
stern.
Deadrise is very important feature in the stability of the vessel. A flat
bottomed boat rises on a plane quickly and provides a stable comfortable
ride in calm water – but will pound heavily in rough water. A vessel with
deadrise provides greater stability and comfort in rough conditions.
• Ocean going big ships are never flat bottomed in the fore and aft
hull sections, may be almost flat bottomed in the mid ship section.
• Ocean going vessel with full flat bottomed hull may capsize easily in
the heavy seas
Deadrise
7MarineTech Project, Lean Institute ODU, May 2011
Bulkhead: Bulkhead is a upright wall like structure within the hull of a ship.
• Bulkheads increase structural rigidity of the vessel
• Bulkheads create watertight compartments to prevent flooding in case of
hull breach or leak.
Longitudinal Bulkheads are used to create watertight compartments in
case of ship capsize. It also divides cargo into different sections and thus
helps improve stability of ship by creating different center of gravities for
different sections. (More on this in free surface effect)
Bulkheads
Bulkheads
8MarineTech Project, Lean Institute ODU, May 2011
2. Motions of a floating body
Any floating body has three motions namely Roll, Pitch and Yaw
Roll: Rolling is the motion of a floating body about the longitudinal axis ( axis
along the length of the body)
Pitch: Pitching is the motion about the transverse axis of the body (i.e axis
along the width of the ship.
Yaw: Yawing is the motion of a floating body about the vertical axis.
Control of all the three motions is very important for ship stability and
ride comfort. 9MarineTech Project, Lean Institute ODU, May 2011
3. Ship Stability
Center of Gravity (G), Center of Buoyancy (B), and Metacenter (M)
play very important role in stability of the ship.
The center of buoyancy, is the center of gravity of the volume of water
which the hull displaces. This point is referred to as B in naval
architecture. The center of gravity of the ship itself is known as G in naval
architecture. When a ship is upright, the center of buoyancy is directly
below the center of gravity of the ship.
10MarineTech Project, Lean Institute ODU, May 2011
Center of Gravity is the point where all the weight of the object can be
considered to be concentrated
Center of Buoyancy is the center of mass of the immersed part of ship or
floating object
Metacenter is the point where lines of action of upward buoyancy force intersect
When the ship is vertical, it lies above the center of gravity and so moves in the
opposite direction of the heel as ship rolls
Relationship between G and M
G under M: ship is stable
G = M: ship neutral
G over M: ship unstable
G
M
B
M
G
B
Stable Unstable11MarineTech Project, Lean Institute ODU, May 2011
When the cargo in the ship are evenly distributed, the ship will be
upright. The sum of the gravity forces of cargo and the ship will be
acting at one point - the Center of Gravity, G, acting downwards.
Similarly, the Center of Buoyancy of the ship will be acting at one point
B, acting upwards.
A ship is said to be in Stable Equilibrium if on being slightly inclined,
tends to return back to the original position.
However, a ship will be in Unstable Equilibrium when she tends to move
further from that original position on being tilted slightly. A ship in
Neutral Equilibrium will tend to neither return nor move further from that
position.
What is stable equilibrium?
12MarineTech Project, Lean Institute ODU, May 2011
Wave
• Force of wave heels the
ship to the starboard.
• Center of gravity of oil
shifts.
• Oil acts as a single
mass, hence the
change in the center of
gravity is drastic
• Force of wave and
change in the center of
gravity heels the ship
more and more without
giving it a chance to
come to its upright
position.
• As the ultimate effect of
wave force and big
change in center of
gravity ship capsizes.
4. What is the free surface effect?
This effect proves fatal in partially filled ocean going vessels in the
heavy seas.
13MarineTech Project, Lean Institute ODU, May 2011
Ship is fitted with
compartments, i.e.
(longitudinal bulkheads)
Now the liquid in the
tank acts as different
masses and center of
gravity of individual
mass changes.
But effect of changing
all the center of gravities
does not shift the center
of gravity of the ship as
significantly as before.
How to minimize the free surface effect?
The other way to minimize the free surface effect is to fill the tanks nearly full.
This does not give the liquid room and hence minimizes the free surface effect.
Tanker ships never sail partially filled 14MarineTech Project, Lean Institute ODU, May 2011
5. Effect of change in density of water on
the draft of a ship
Density of Fresh Water = 1000 kg / m3
Average Density of Sea Water = 1030 kg / m3
Draft of ship changes with the change in density of water
NewDensity
OldDensity
OldDraft
Draft New
Keeping the load same, change in the draft can be calculated
by following equation
Fresh water draft is more than salt water draft
Ships transiting between sea water and fresh water have to consider this
change in draft to avoid a danger of running aground15
MarineTech Project, Lean Institute ODU, May 2011
The word "displacement" arises from the basic physical law, discovered by
Archimedes, that the weight of a floating object equates exactly to that of the
water displaced
6. Displacement of ship
Displacement = actual total weight of the vessel
Unit of Displacement = long ton or metric ton
How to calculate Displacement of ship?
1. Volume of submerged part (cu. Feet) = length * Beam * Draft
2. Multiply this by block coefficient of hull
3. Multiply this figure by 64 to get weight of ship in pounds or divide by
35 to calculate weight in long tons
4. Using SI or metric system: displacement (in tons) is volume (in cubic
meters) multiplied by the specific gravity of sea water (nominally
1.025)
16MarineTech Project, Lean Institute ODU, May 2011
Lightship weight is the
displacement of the ship
only with no fuel,
passengers, cargo, water,
etc. on board.
Deadweight Tonnage
(DWT) is full load
displacement minus the
lightship weight. It includes
the crew, passengers,
cargo, fuel, water and
stores etc.
A ship can carry cargo weighing roughly 90% of its deadweight
tonnage
Full Load Displacement:
Displacement when ship is
loaded with cargo or
people to the point that it is
submerged to its load line
Plimsoll line or International Load Line
the mark on the hull of a ship that shows where the waterline is when the ship
is loaded to full capacity according to the condition of the water at the point
of loading.
17MarineTech Project, Lean Institute ODU, May 2011
7. Loading of Ship
• Cargo should be always evenly distributed
• Uneven distribution makes ship unstable
• Uneven distribution also creates stresses on the ship structure
• Cargo should be properly secured (e.g.in case of cargo like cars)
cargoofMass
cargoofVolumeStowage Factor =
Proper care should be taken to distribute the load evenly
when carrying high density cargo with stowage factor above
0.56
18MarineTech Project, Lean Institute ODU, May 2011
8. Tanker Ships
Slop tanks are provided for storage of dirty ballast residue and tank
washings from the cargo tanks
General Arrangement of Cargo and Ballast Tanks for Tankers
•Tankers are used to carry liquid and gaseous cargo
•All the tanker ships have double hull in order to prevent oil
leakage
•Partially filled tankers are highly unstable in heavy seas
because of the free surface effect
19MarineTech Project, Lean Institute ODU, May 2011
9. Speed of ship
Speed of a ship is measured in knots
• Modern ships are powered by diesel engines
• Some ships are powered by steam turbines also
• Nuclear power is used in defense naval ships
Propellers
Propeller
shaft
Power
Source
(Diesel
Engine /
Steam
Turbine/
Nuclear
power)
Loss of propulsion system can prove fatal, especially in heavy
seas as ship loses control over direction20
MarineTech Project, Lean Institute ODU, May 2011
10. Ship Power Plant
Most new ships today are powered by diesel engines,
though a few older ships are still powered by steam
turbines and reciprocating steam engines
Propeller
Propeller shaft
Power Plant
(Engine/ turbine)
21MarineTech Project, Lean Institute ODU, May 2011
• Power plant and propulsion system are the most critical
systems in any ship
• It gives the ship the force required to move
• Failure of power plant or propulsion system could be fatal as
ship loses control on the direction
• Loss of power or propulsion in heavy seas or near the shore is
very dangerous since ship may stray with the direction of
winds and waves and may run aground
22MarineTech Project, Lean Institute ODU, May 2011
11. SONAR
SONAR (Sound Navigation and Ranging)
SONAR is a technique that uses sound propagation under water
(primarily) to navigate, communicate or detect other vessels
Principle of SONAR: Reflection of sound waves
23MarineTech Project, Lean Institute ODU, May 2011
24
• A transmitter is used to transmit the signal
• A receiver is used to catch the reflection (echo)
• The time from transmission of a pulse to reception is measured
• Speed of sound in water is known
• Using the formula Speed = we can calculate the distance of
the object from the source of the pulse (transmitter)Time
ceDistan
SEA BED
Distance “d”
Time “t”
MarineTech Project, Lean Institute ODU, May 2011
Speed of sound in water is calculated using following equation
4388 + (11.25 × temperature (in °F))
+ (0.0182 × depth (in feet)
+ salinity (in parts-per-thousand)).
Speed of Sound
(feet /s)=
1 foot = 0.3048 meters
Distance from the object is calculated using formula
Distance =Speed of sound x time between transmission and reception
2
25MarineTech Project, Lean Institute ODU, May 2011
12. Unit Conversions
1 Metric ton = 2204.62 pounds = 1000 kilogram
1 long ton = 2240 pounds = 1016.05 kilogram
1 meter = 3.281 feet
1 knot = 1.151 miles / hour = 1.852 kilometer / hour
1 nautical mile = 1.151 miles = 1.852 kilometer
746 horsepower = 1 Watt = 1 Joule / second
26MarineTech Project, Lean Institute ODU, May 2011