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
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
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)
QUESTIONS FOR THE RANK OF OFFICER OF THE WATCH 15