Compasses (Bridge management) Flashcards
Where is the magnetic compass placed? (2)
Monkey island on the top of the ship.
Away from large pieces of metal.(ferrous materials)
List the five carriage requirements under SOLAS Ch V Magnetic compass.
- A properly adjusted standard magnetic compass independent of any power supply.
- A pelorus or compass bearing device independent of any power supply
- Means of correcting heading and bearing to true at all times
- A spare magnetic compass interchangeable with the magnetic compass
- A properly adjusted transmitting heading device to transmit heading information for input to specified equipment
What is a gyro compass?
A gyrocompass is a type of non-magnetic compass which is based on a fast-spinning disc and the rotation of the Earth to find geographical direction automatically
When should magnetic compasses be adjusted? (5)
- When ship is built
- Undergoes structural repairs/modification that could affect compass
- Electronic equipment is added/removed that could affect the compass
- The compass becomes unreliable
- Every 2 years except when regular compass errors taken
Will magnetic properties of a vessel change over time?
Yes
Can magnetic properties of a ship be affected by cargo?
Yes
Who must a compass be adjusted by?
Certified compass adjuster
What is the construction of the liquid compass?
Bowl is brass with clear glass top and frosted glass bottom (to allow card to be illuminated from below)
Expansion ring is fitted to bowl with a filling cap on the side
Why is the card smaller than the bowl (liquid compass)
To keep it clear of turbulence created around edge of bowl as the ships swings
What is the liquid compass bowl mounted in?
Gimbals within a binnacle
Gimbal
Pivoted support that permits rotation of an object about an axis
What is the binnacle?
The house of the compass
What is the binnacle made of?
Non-magnetic materials
What does the binnacle need to be clear of?
Anything that may alter its magnetic fields.
How are air bubbles removed from the binnacle?
Injecting distilled water
Define hard magnetic material
Those which if comes under the influence of of magnetic field become permanent magnets
Define soft magnetic material
Those which when comes under magnetic field become magnets and lose their magnetism as soon as the magnetic field is removed
What is the azimuth mirror/ring?
A device for taking compass bearings
What is a pelorus?
used for taking relative bearings of objects when compass bearings cannot be taken
What is the first law of magnetism?
Like poles repel each other; unlike poles attract each other
What is the second law of magnetism?
The force between two poles varies directly as the product of their pole strengths and inversely as the square of the distance between them.
Define variation
The angle between the magnetic and true meridian
Define deviation
The angle between the compass needle and the magnetic meridian
Define compass error
The combined effect of variation and deviation
