Compasses (Bridge management)

Question 1

Where is the magnetic compass placed? (2)

Answer 1

Monkey island on the top of the ship.
Away from large pieces of metal.(ferrous materials)

Question 2

List the five carriage requirements under SOLAS Ch V Magnetic compass.

Answer 2

• 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

Question 3

What is a gyro compass?

Answer 3

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

Question 4

When should magnetic compasses be adjusted? (5)

Answer 4

• 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

Question 5

Will magnetic properties of a vessel change over time?

Answer 5

Yes

Question 6

Can magnetic properties of a ship be affected by cargo?

Answer 6

Yes

Question 7

Who must a compass be adjusted by?

Answer 7

Certified compass adjuster

Question 8

What is the construction of the liquid compass?

Answer 8

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

Question 9

Why is the card smaller than the bowl (liquid compass)

Answer 9

To keep it clear of turbulence created around edge of bowl as the ships swings

Question 10

What is the liquid compass bowl mounted in?

Answer 10

Gimbals within a binnacle

Question 11

Gimbal

Answer 11

Pivoted support that permits rotation of an object about an axis

Question 12

What is the binnacle?

Answer 12

The house of the compass

Question 13

What is the binnacle made of?

Answer 13

Non-magnetic materials

Question 14

What does the binnacle need to be clear of?

Answer 14

Anything that may alter its magnetic fields.

Question 15

How are air bubbles removed from the binnacle?

Answer 15

Injecting distilled water

Question 16

Define hard magnetic material

Answer 16

Those which if comes under the influence of of magnetic field become permanent magnets

Question 17

Define soft magnetic material

Answer 17

Those which when comes under magnetic field become magnets and lose their magnetism as soon as the magnetic field is removed

Question 18

What is the azimuth mirror/ring?

Answer 18

A device for taking compass bearings

Question 19

What is a pelorus?

Answer 19

used for taking relative bearings of objects when compass bearings cannot be taken

Question 20

What is the first law of magnetism?

Answer 20

Like poles repel each other; unlike poles attract each other

Question 21

What is the second law of magnetism?

Answer 21

The force between two poles varies directly as the product of their pole strengths and inversely as the square of the distance between them.

Question 22

Define variation

Answer 22

The angle between the magnetic and true meridian

Question 23

Define deviation

Answer 23

The angle between the compass needle and the magnetic meridian

Question 24

Define compass error

Answer 24

The combined effect of variation and deviation