BRIDGE - COMPASS

Question 1

What checks will you make on the compass?

Answer 1

Needs to be carried by all ships irrespective of size and must have a pelorus or compass bearing device.

Inspecting the binnacle for damage
Ensuring the gimbal is moving freely
No bubbles in the compass bowl
Light is working.

Ensure no tools or equipment left nearby on the monkey island.

It is required to take a compass error once every watch by transit, amplitude or azimuth.

Question 2

What information will be provided on the deviation card?

Answer 2

Who where and when compass swing was taken.
Time of next compass swing.
Location of iron correctors.

Question 3

When would a compass swing be required?

Answer 3

After any major structural work
Lay up
Or if in any doubt

Question 4

1. Why is the compass in the fluid?

2. What is the fluid?

Answer 4

1. The compass is in fluid to dampen to dampen its oscillation to ensure it settles.
2. The fluid is Bayol or 2 parts distilled water to 1 part ethyl alcohol
   - The water prevents mix from evaporating in warmer climates.
   - The alcohol prevents freezing in colder climates.

Question 5

What correctors are on the compass?

Answer 5

Quadrantal spheres for soft iron temporary quadrantal
Flinders bar for soft iron temporary vertical
For and aft and athwartships hard iron for permanent
Heeling error bucket for permanent for vertical heel and list

Question 6

What causes compass error?

Answer 6

Variation

• Due to earths magnetic field and is the difference between true north and magnetic.
• Changes depending on your position on the earth and changes each year.

Deviation

• Due to the magnetic properties of the ship and its movement through the earths magnetic field.
• Changes with heading found on the deviation card.

Question 7

When would sun set exactly true east or west?

Answer 7

Equinox march and september when day and night are equal length.

Question 8

What causes bubble in the compass?

Answer 8

Reduction in temperature or reduction in atmospheric pressure