Question 1. What is a ‘Mason’s hygrometer’ and what is it used for?

Answer: It is the name given to dry and wet bulb thermometers, usually

contained in the Stevenson’s screen often found on the ship’s

bridge wing. It is used for measuring the ‘humidity’.

Question 2. For what would you use a hydrometer when aboard ship?

Answer: A hydrometer is used to obtain the density of dock water.

The obtained value is then used in conjunction with the Fresh Water

Allowance (FWA) to obtain the Dock Water Allowance, i.e. the amount

that the vessel may submerge her load line mark, in any water other

than sea water.

Question 3. When reading the precision aneroid barometer, what

corrections would you make to the reading?

Answer: The barometer is supplied with a calibration correction

card which allows for a correction to be added to the reading to adjust

to mean sea level (table of height in metres _ air temperature in °C).

Question 4. How would you check that the azimuth bearing circle, of

the compass was correct?

Answer: By taking a bearing of a terrestrial object, e.g. a lighthouse,

with the arrow indication uppermost. Take a second bearing of the

same object, with the arrow in the downward position.

Both readings should be the same and the bearing circle can be used

with confidence.

Question 5. What is the liquid found inside a magnetic compass bowl?

Answer: The older design of liquid magnetic compass contained

a mixture of one part alcohol to two parts distilled water. The more

14 THE SEAMANSHIP EXAMINER

modern magnetic compass would be filled with a clear oily fluid,

derived from ‘Bayol’.

Question 6. The purpose of the alcohol in the liquid compass was to

prevent the fluid from freezing in cold, high latitudes. What was the

purpose of the distilled water in the mixture?

Answer: Distilled water was included in the fluid mixture to prevent

the alcohol evaporating in warm latitudes.

Question 7. How would you check the performance of the radar on

the navigation bridge?

Answer: I would operate the ‘performance monitor’ (if fitted) on

the instrumentation panel. Once activated the range of the ‘plume’

could be compared with the Radar Specification Manual details.

Note: New radars are usually fitted with a self-test control to meet instrument

specifications.

Question 8. When taking a visual three-point position fix, you find

the charted plot produces a ‘cocked hat’. What would you do?

Answer: I would consider the position as unreliable and take another

set of bearings. It would be prudent to also obtain a secondary fix by an

alternative method, e.g. radar or GPS.

Question 9. How would you test the steering gear prior to the vessel

departing from a port?

Answer: Having ascertained that the rudder and propeller area is

clear of obstructions, I would turn the ship’s wheel, hard over each way

to port and starboard. When in the hard over positions I would note

the ‘Helm Indicator’ and the ‘rudder indicator’ are both shown in the

hard over positions.

The auto-pilot would also be tested to port and starboard, together

with the tiller control. The rudder indicator should be noted to reach

the hard over position on each occasion.

Question 10. What information can you obtain from a barograph?

Answer: The barometric tendency measured over the last three (3)

hours.

QUESTIONS FOR THE RANK OF OFFICER OF THE WATCH 15