Measurements Flashcards
Decimetre
10cm, 10/1m
Centimetre
1cm, 100/1m
Millimetre
0.1cm, 1000/1m
What is Area measured in?
m^2
Volume
LxBxD m^3
Weight is the same as…
Mass
Weight
Tonnes (t)
Density is Equal to
Mass/Volume
Length
measured in Metres (m)
Breadth
measured in Metres (m)
Draft
Waterline to keel
Depth
Measured in Metres (m)
Freeboard
Distance between waterline and first open deck
What is mass measured in
Kg or tonnes
1000kg = 1tonne
What is the Density of Fresh Water and Salt Water
Fresh water = 1
Salt water = 1.025
What is Ullage
Measures from top of the tank to the top of liquid/ cargo
What is Sounding
Measures from bottom of the tank to the top of the liquid, usually just used for ballast water
What is do you use to Measure Density
Hydrometer
Explain what a Load Line Mark is
Load line mark or Plimsole line is a symbol (a circle with a horizontal line midway through) marked on the hull amidship. The top of the horizontal line indicates the deepest load condition (summer zone).
What is Load Draught
Load draught is the draught of the vessel when loaded to the load line mark
There are Five Load Lines on the Side of a Hull, What are they and What do they mean
TF=Tropical Fresh Water
F=Fresh Water
T=Tropical Water
S=Summer
W=Winter
Define Loaded Draught
The draught when the vessel has been loaded to the load line mark
What is Waterline Length
The length of the vessel in metres, measured at the draught and trim, from where the waterline cuts the after most part of the vessel to where the waterline cuts the foremost part of the vessel
Define Breadth
The breadth of the vessel at its widest part
State the Laws of Floatation
The volume of liquid displaced by the floating body is equal to the underwater volume
The weight of the liquid displaced by a floating body is equal to the weight of the body
Describe Displacement in the context of equations
Displacement is measured in tonnes and is equal to the weight of the vessel and also the weight of the water displaced
What Is Light Displacement
The weight of the hull, engines, spare parts, water in the boilers and condensers to working level
What Is Load Displacement
The weight of the hull and everything on board when at a particular draught
What Is Summer Load Displacement
The Wight of the hull and everything on board when at the summer load mark
What Is Dead Weight
Weight of the cargo, fuel, fresh water, ballast, stores, crew, passengers, and effects. The difference between the load and the light displacement
What Is Summer Dead Weight
It is the difference between the summer load displacement and the light displacement
What Is Gross Tonnage
The measure of internal volume of the vessel (m^3)
What Is Displacement Measured In
Tonnes
Explain What “Coefficient of Waterplane Area” Is
The ratio between the actual waterplane area (Aw) and that of a rectangle having the same extreme dimensions
Explain What “Block Coefficient” Is
The ratio between the underwater volume and the volume of a block having the same extreme dimensions
What Does “TPC” Stand For
Tonnes per centimeter
What Is TPC Is In The Context Of A Draught
The TPC for any draught is the weight a vessel must load or discharge to change the mean draught by 1cm
State The Three Point Of Archimedes Principle
- An immersed or partially immersed body experiences an upthrust (force of buoyancy) which is equal to the weight of the water displaced
- The upthrust is known as buoyancy
*The force of buoyancy acts vertically upwards through the centre of buoyancy
Explain Centre Of Buoyancy
*This is situated at the geometric centre of the underwater volume
*It is denoted by ‘B’ and its height above the keel is denoted by ‘KB’
Explain Centre Of Gravity
*Point through which the weight of the body is said to act vertically downwards
*The ships CoG is denoted by ‘G’ and its height above the keel ‘KG’
*For a single weight we use ‘g’ and ‘kg’
*The centre of gravity depends entirely upon the weight distribution within the ship
Explain What Needs To Happen For A Vessel To Float At Rest
*Force of Buoyancy = weight of vessel
*Centre of Buoyancy and Centre of Gravity must lie in the same vertical line
Explain Reserve Buoyancy
*The volume of the enclosed watertight space above the waterline
*The volume of water which remains to be displaced before the vessel is totally immersed
*Expressed in m^3 or a % of total volume
Why Is Freeboard Important When Working With Reserve Buoyancy
The freeboard determines the reserve buoyancy
How Thick are the Load Line Marks
25mm thick
Where on the Plimsole Line Should You Load to
The top of the horizontal line
How are Ships Carrying Timber Different and Why
They have different load lines because timber floats and acts as more reserve buoyancy
What are The Reasons for Load Lines
To ensure that the vessel has sufficient reserve buoyancy to ensure a certain level of survivability in the event that compartment(s) are breached. They act as a visual check that the vessel hasn’t been overloaded
Explain Fresh Water Allowance (FWA)
The number of mm by which the mean draught changes when a vessel passes from SW to fresh water and vise-versa at the summer load draught
Explain Dock Water Allowance (DWA)
The number of mm by which the mean draught changes when a vessel passes from SW to dock water and vise-versa
Initial Transverse Metacentre (M)
The point of intersection of the vertical through B when the vessel is upright and in the slightly inclined positions. M may be considered fixed for small angles of heel
Height of the Metercentre (KM)
The height of the M above the keel
Initial Metercentric Height (GM)
The distance between G and M in the upright position measured along the centre line
List
When the vessel is inclined by an internal force. G moves off the centre line
Heel
When the vessel inclines by an external force. G remains on the centreline
Righting lever
*This is the perpendicular distance between the force of buoyancy and gravity
*Referred to as GZ
*The righting moment (force x distance) is Known as Moment of Statical Stability
What is the Equation for Moment of Statical Stability
MSS=∆xGZ
Name the Three States of Equilibrium
*Stable
*Neutral
*Unstable
Stable Equilibrium
When inclined to a small angle of heel she tends to return to the initial position
*G is below M and the vessel is said to have a positive GM
*The vessel has a positive Moment of Static Stability (righting moment)
Angle of Heel
When a Weight is Shifted, What Happens to G
G moves parallel to and in the same direction as the shift of weight
What Happens to G When a Weight is Loaded
G moves directly towards the loaded weight
What Happens to G When a Weight is Discharged
G moves directly away from a discharged weight
If G Increases, What Will Happen to GM and KG
GM will decrease
KG will increase
If G decrease, What Will Happen to GM and KG
GM will increase
KG will decrease
What is G
G is the Centre of Gravity
What is KG
The distance between the centre of gravity and the keel
What is KM
The distance between the keel and the metacentric height
What is K
The keel
What is M
Metacentric height
What Three Things Will Make G Move
*Loading a weight
*Discharging a weight
*Shifting a weight
If KM Is Not Given In The Question, What Should You Use
Hydrostatic Particulars
What is GGh
The Port/Starboard moments (divided by) total weight
