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BD Deck Officer Class 1 (Master) study materials
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BD Deck Officer Class 1 (Master) practice questions

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Question 1Navigation

Under the IALA Maritime Buoyage System, a vessel approaching a harbour from seaward sees a preferred channel to starboard. What colour and topmark should the buoy marking that preferred channel show?

  1. Red and white vertical stripes with a red spherical topmark Correct answer.
  2. Red and white vertical stripes with a red can topmark
  3. Yellow with a yellow cross topmark
  4. Green with a green conical topmark

Explanation

A preferred channel buoy in Region A is painted red and white in vertical stripes. When the preferred channel lies to starboard, the buoy carries a red can topmark and is treated as a port-hand mark when the preferred route is followed. The shape of the topmark, not the colour alone, tells the navigator which side the main channel lies.

Question 2Navigation

A vessel is steering 000° true. A light is observed bearing 045° true and the vessel's gyrocompass reads 358°. What is the compass bearing of the light, assuming a gyro error of 2° east?

  1. 041°
  2. 049°
  3. 047° Correct answer.
  4. 043°

Explanation

Compass bearing equals true bearing minus easterly error. With 2° east error, 045° true becomes 043° compass. The gyro reading itself is not used in this calculation because the question asks for the compass bearing derived from the true bearing.

Question 3Navigation

A vessel's radar is set to a range scale of 12 nautical miles. A target echo appears at 4.5 cm from the centre on a display with a radius of 9 cm. What is the approximate range of the target?

  1. 6.0 nautical miles Correct answer.
  2. 9.0 nautical miles
  3. 3.0 nautical miles
  4. 4.5 nautical miles

Explanation

The display radius represents the full range scale, so each centimetre equals 12 divided by 9, or 1.33 nautical miles. Multiplying 4.5 cm by 1.33 gives approximately 6 nautical miles. Range is measured from the centre of the display, not from the edge.

Question 4Navigation

Which statement correctly describes the meaning of a vessel displaying two black balls in a vertical line during daylight?

  1. The vessel is constrained by her draught
  2. The vessel is aground Correct answer.
  3. The vessel is engaged in trawling
  4. The vessel is not under command

Explanation

Rule 30 of the Collision Regulations requires a vessel aground to exhibit three black balls in a vertical line, but a vessel of less than 12 metres may show two balls instead. The two-ball signal therefore identifies a small vessel aground. Other signals such as not under command use different shapes.

Question 5Navigation

A vessel is proceeding along a course of 090° true at 12 knots. A current sets 180° true at 3 knots. What is the approximate speed made good over the ground?

  1. 10.8 knots
  2. 9.0 knots
  3. 15.0 knots
  4. 12.4 knots Correct answer.

Explanation

The current acts perpendicular to the vessel's heading, so the resultant velocity is the vector sum of two perpendicular components. Using Pythagoras, the square root of 12 squared plus 3 squared gives approximately 12.4 knots. The course made good would also be deflected towards the current.

Question 6Navigation

On a Mercator chart, what is the principal distortion that affects navigation at high latitudes?

  1. Bearings are curved and cannot be plotted as straight lines
  2. Longitude intervals shrink towards the equator
  3. Areas are compressed towards the poles
  4. Distances are exaggerated as latitude increases Correct answer.

Explanation

The Mercator projection expands the spacing between parallels to keep rhumb lines straight, so the scale increases with latitude. A constant scale cannot therefore be used over large latitude differences. This is why great-circle distances must be measured using the latitude scale at the mean latitude.

Question 7Navigation

A vessel's echo sounder indicates a depth of 25 metres. The transducer is 4 metres below the waterline and the charted depth is 18 metres. What is the height of tide at that position?

  1. 7 metres Correct answer.
  2. 3 metres
  3. 14 metres
  4. 11 metres

Explanation

The sounder measures depth below the transducer, so the true depth of water is 25 plus 4, giving 29 metres. The height of tide is the difference between this actual depth and the charted depth, which is 29 minus 18, or 11 metres.

Question 8Navigation

In the context of passage planning, what does the term 'no-go area' refer to?

  1. A zone where charted depths are less than the vessel's safe under-keel clearance Correct answer.
  2. A sector of the chart where magnetic variation is unreliable
  3. A region where the vessel must reduce speed to minimum steerage way
  4. An area reserved for vessels over a specified length

Explanation

A no-go area is defined during appraisal by applying the vessel's draught plus a safety margin to the charted depths. Any water where the resulting under-keel clearance would be unacceptable is marked as no-go. This allows the navigator to identify safe corridors in advance.

Question 9Navigation

A vessel is on a course of 045° true at 10 knots. A relative bearing of 090° is observed to a light. What is the true bearing of the light?

  1. 315°
  2. 135° Correct answer.
  3. 045°
  4. 090°

Explanation

True bearing equals course plus relative bearing measured clockwise from the heading. Adding 045° and 090° gives 135° true. This relationship holds when the relative bearing is measured from dead ahead.

Question 10Navigation

Which of the following best describes the purpose of the echo sounder's 'shallow water alarm' during coastal passage?

  1. To indicate the presence of fish shoals
  2. To measure the vessel's speed through the water
  3. To warn the watchkeeper when the depth falls below a preset safe value Correct answer.
  4. To record the vessel's position automatically

Explanation

The shallow water alarm is set by the navigator to a depth that represents the minimum acceptable under-keel clearance. It alerts the watchkeeper when the indicated depth falls below this preset figure. This provides an early warning of shoaling or a course error.

Question 11Navigation

A vessel is steering 270° true. The wind is from 315° true. Which side of the vessel is the wind on?

  1. Starboard side Correct answer.
  2. Dead astern
  3. Port side
  4. Dead ahead

Explanation

Wind direction is expressed as the direction from which it blows. A wind from 315° strikes a vessel heading 270° on the starboard bow, since 315° lies 45° clockwise from the heading. The relative wind angle is therefore 45° on the starboard side.

Question 12Navigation

What is the significance of the 'safety contour' setting on a modern electronic chart display?

  1. It defines the depth below which charted water is considered unsafe for the vessel Correct answer.
  2. It marks the boundary of the vessel's radar range
  3. It indicates the limit of magnetic variation data
  4. It sets the latitude at which the chart is clipped

Explanation

The safety contour is set slightly deeper than the vessel's maximum draught plus a margin. Water shoaler than this contour is highlighted as unsafe. The navigator can therefore see at a glance which areas are navigable.

Question 13Navigation

A vessel observes a lighthouse flashing every 10 seconds with a range of 20 nautical miles. If the light's nominal range is 20 miles and the observer's height of eye is 9 metres, what is the approximate geographic range using the formula 2.08 times the square root of the height in metres?

  1. 6.2 nautical miles Correct answer.
  2. 20.0 nautical miles
  3. 12.5 nautical miles
  4. 18.0 nautical miles

Explanation

The geographic range to the horizon for an observer at height h is approximately 2.08 times the square root of h in metres. The square root of 9 is 3, and 2.08 times 3 gives about 6.2 nautical miles. This is the distance at which the light first becomes visible over the horizon.

Question 14Navigation

Under the Collision Regulations, which vessel is required to give way when a power-driven vessel meets a sailing vessel in open water?

  1. The sailing vessel, because it is more manoeuvrable
  2. Both vessels alter course to starboard simultaneously
  3. Neither vessel, because sail has priority in all cases
  4. The power-driven vessel, because it is easier for it to alter course Correct answer.

Explanation

Rule 18 requires a power-driven vessel underway to keep out of the way of a vessel under sail. The power-driven vessel is generally more manoeuvrable and can take earlier and more decisive action. The sailing vessel must still maintain her course and speed.

Question 15Navigation

A vessel's log reads 120.4 nautical miles at 0800 and 156.9 nautical miles at 1400. What is the average speed through the water over the period?

  1. 6.1 knots Correct answer.
  2. 5.1 knots
  3. 8.1 knots
  4. 7.1 knots

Explanation

The distance run is 156.9 minus 120.4, which equals 36.5 nautical miles. The elapsed time is six hours. Dividing 36.5 by 6 gives approximately 6.1 knots.

Question 16Navigation

What is the primary purpose of a 'wheel-over point' in a passage plan?

  1. To indicate the position of the pilot boarding ground
  2. To identify where the vessel must reduce to harbour speed
  3. To record the time of the last position fix
  4. To mark the position at which the helm is put over for the next course alteration Correct answer.

Explanation

The wheel-over point is the position at which the rudder is applied to begin a planned turn. It is calculated from the vessel's turning characteristics, speed and the required course change. Marking it in advance allows the turn to be executed accurately.

Question 17Navigation

A vessel steering 090° true observes a light bearing 120° true. What is the relative bearing of the light?

  1. 060°
  2. 210°
  3. 030° Correct answer.
  4. 120°

Explanation

Relative bearing equals true bearing minus course. Subtracting 090° from 120° gives 030°. This is a bearing measured 30° to starboard of the vessel's head.

Question 18Navigation

A vessel is in a narrow channel and wishes to overtake another vessel. Which action is required by the Collision Regulations?

  1. Both vessels must alter course to port to open the channel
  2. The overtaking vessel may proceed without any signal if there is ample room
  3. The overtaking vessel must sound the prescribed signal and obtain the other vessel's agreement Correct answer.
  4. The vessel being overtaken must always reduce speed to allow passage

Explanation

Rule 9 requires a vessel intending to overtake in a narrow channel to indicate her intention by the prescribed sound signal. The overtaking vessel may only proceed when the vessel being overtaken agrees. This prevents dangerous manoeuvring in confined waters.

Question 19Navigation

A vessel's GPS receiver indicates a position fix. What is the most appropriate way to verify this fix in coastal waters?

  1. Rely solely on the GPS because it is the most accurate system available
  2. Cross-check the position against visual bearings of charted objects Correct answer.
  3. Wait for the next satellite pass before confirming the position
  4. Assume the position is correct if the receiver shows a low dilution of precision

Explanation

Even with modern electronic position-fixing, prudent navigation requires independent verification. Visual bearings of identifiable charted objects provide a reliable cross-check. This confirms that the electronic fix is consistent with the observed surroundings.

Question 20Navigation

What is the meaning of the abbreviation 'UTC' in nautical publications?

  1. Upper Tidal Current, used in current tables
  2. Uniform Tide Correction, applied to charted depths
  3. Underway Time Check, used for log entries
  4. Universal Time Co-ordinated, the standard time reference Correct answer.

Explanation

UTC is Universal Time Co-ordinated, the standard time reference used in nautical almanacs and tide tables. It is based on atomic time and is kept close to mean solar time at the prime meridian. Navigators use it to avoid confusion between local time zones.

Question 21Navigation

A vessel's gyrocompass has a known error of 3° west. A true bearing of 200° is required. What compass bearing should be steered?

  1. 203° Correct answer.
  2. 197°
  3. 200°
  4. 206°

Explanation

Compass bearing equals true bearing plus westerly error. With 3° west error, 200° true becomes 203° compass. The mnemonic 'true virgins make dull company' reminds the navigator to add west and subtract east when converting from true to compass.

Question 22Navigation

A vessel is approaching a port and the chart shows a sector light with a white sector between 350° and 010°. The vessel observes the light as white. What does this indicate?

  1. The vessel is within the safe sector of the light Correct answer.
  2. The vessel is to the east of the safe sector
  3. The light is obscured by fog
  4. The vessel is to the west of the safe sector

Explanation

A sector light shows different colours in different bearings. The white sector marks the safe approach, while red or green sectors indicate danger on either side. Observing white therefore confirms the vessel is within the safe sector.

Question 23Navigation

Which of the following is the correct sequence for fixing a vessel's position using a three-point bearing?

  1. Take one bearing, plot it, then take two more bearings after an interval
  2. Take bearings of three objects, plot them, and check for a cocked hat Correct answer.
  3. Take bearings of three objects and average them to a single line
  4. Take bearings only when the objects are in line

Explanation

A three-point fix requires bearings of three well-separated objects taken in quick succession. The three position lines are plotted and should intersect at a point; a cocked hat indicates a systematic error. The size of the cocked hat gives an indication of the accuracy of the fix.

Question 24Navigation

A vessel is planning a passage across a tidal stream. The stream sets 090° at 2 knots and the vessel's speed through the water is 8 knots. To make good a course of 000° true, what is the approximate course to steer?

  1. 028°
  2. 346° Correct answer.
  3. 000°
  4. 014°

Explanation

The tidal stream pushes the vessel east, so the vessel must steer to the west of the desired track to compensate. The angle of drift is the arcsine of 2 divided by 8, which is about 14°. Steering 346° true counteracts the easterly set.

Question 25Navigation

During a passage, a vessel's radar shows a target on a steady bearing with decreasing range. What does this indicate?

  1. The target is overtaking the vessel from astern
  2. The target is moving away from the vessel
  3. The target is stationary and the vessel is passing clear
  4. The target is on a collision course with the vessel Correct answer.

Explanation

A constant relative bearing combined with decreasing range is the classic indication of a risk of collision. The bearing of the target does not change as the range closes, meaning the two vessels are converging. Action should be taken in good time to avoid a close-quarters situation.

Question 26Navigation

A vessel is steering 000° true. A light is observed bearing 045° true. What is the relative bearing of the light?

  1. 045° on the starboard bow Correct answer.
  2. 000° dead ahead
  3. 090° on the starboard beam
  4. 315° on the port bow

Explanation

Relative bearing is obtained by subtracting the vessel's heading from the true bearing of the object, so 045° minus 000° gives 045°. A relative bearing between 000° and 090° places the object on the starboard bow. It is measured clockwise from the ship's head.

Question 27Navigation

What does the term 'squat' describe for a vessel proceeding in shallow water?

  1. A lateral drift of the bow caused by following seas
  2. A bodily sinkage and change of trim caused by reduced pressure under the hull Correct answer.
  3. A rise of the bow caused by increased buoyancy forward
  4. An increase in metacentric height caused by the free surface of ballast

Explanation

In shallow water the flow around the hull accelerates, lowering pressure beneath the ship and drawing it bodily downward, with a change of trim depending on hull form. Squat increases with speed and with the ratio of water depth to draught. The effect reduces under-keel clearance and can cause grounding.

Question 28Navigation

A vessel's magnetic compass is affected by deviation. What is deviation?

  1. The difference between gyrocompass north and true north
  2. The angular difference between magnetic north and compass north caused by the ship's own magnetic field Correct answer.
  3. The error caused by the ship's heading relative to the wind
  4. The angular difference between true north and magnetic north at the vessel's position

Explanation

Deviation is the angle between the direction indicated by the compass needle and the local magnetic meridian, produced by magnetism in the ship's structure and equipment. It varies with the ship's heading and is recorded on a deviation card. Variation, by contrast, is the angle between magnetic and true meridians at the position.

Question 29Navigation

A vessel is making 12 knots through the water on a course of 000° true. A current sets 090° true at 3 knots. Using a vector triangle, what is the approximate course and speed made good?

  1. About 000° true at 15.0 knots
  2. About 076° true at 12.4 knots
  3. About 090° true at 3.0 knots
  4. About 014° true at 12.4 knots Correct answer.

Explanation

The current vector is drawn from the end of the course-and-speed vector, and the resultant closes the triangle from the start point. The drift of 3 knots at right angles to 12 knots gives a resultant speed of the square root of 144 plus 9, about 12.4 knots. The course made good is offset by the arctangent of 3 over 12, roughly 14° to starboard, giving about 014° true.

Question 30Navigation

A vessel's position is fixed by two simultaneous bearings whose position lines cross at a large angle. Which crossing angle gives the most reliable fix?

  1. An angle close to 10°
  2. An angle close to 170°
  3. An angle close to 90° Correct answer.
  4. The crossing angle has no effect on reliability

Explanation

The position line from a bearing has a small random error, and this error is magnified in the fix as the crossing angle becomes small or very obtuse. Lines crossing near 90° minimise the area of the cocked hat for a given bearing error. Angles below about 30° or above about 150° should be avoided where a better pair can be chosen.

Question 31Navigation

A vessel is required to determine the time of high water at a standard port. Which publication provides daily predictions of times and heights of high and low water?

  1. The tide tables for the standard port Correct answer.
  2. The list of lights and fog signals
  3. The nautical almanac
  4. The sailing directions for the area

Explanation

Tide tables list, for each day of the year, the predicted times and heights of high and low water at standard ports. Secondary port differences are then applied for subordinate locations. The other publications serve different navigational purposes and do not contain tidal height predictions.

Question 32Navigation

A vessel's radar operator measures the bearing and range of a target and plots it over successive intervals. The resulting plot shows the target passing clear ahead. What is this plot used to determine?

  1. The target's true draught and displacement
  2. The closest point of approach and time of closest approach Correct answer.
  3. The wind speed at the target's position
  4. The charted depth over the target

Explanation

Plotting successive target positions on the reflection plotter or a plotting sheet yields the relative track, from which the closest point of approach and the time at which it occurs are derived. These values allow the officer to judge whether a risk of collision exists. If the CPA is unacceptable, avoiding action can be planned.

Question 33Navigation

A vessel is navigating with a gyrocompass on a course of 090° true. The gyro error is known to be 2° east. What is the compass heading being steered?

  1. 086°
  2. 092°
  3. 090°
  4. 088° Correct answer.

Explanation

The rule is compass error applied to compass heading gives true heading, so with easterly error the compass reads lower than true. To steer 090° true, the compass heading must be 2° less, that is 088°. Easterly error means compass least and true best.

Question 34Navigation

During a passage the vessel's observed position is consistently to the south of the dead reckoning position, and the offset grows with time. Which cause best explains this pattern?

  1. An unaccounted current setting towards the south Correct answer.
  2. An error in the barometric pressure reading
  3. A small error in the echo sounder calibration
  4. A constant gyro error of a few degrees

Explanation

A steadily increasing offset between dead reckoning and observed positions indicates an unaccounted set and drift of current. A constant compass error would produce a growing offset in a fixed direction relative to the course, but the diagnosis is confirmed by comparing the drift direction with known tidal streams. The pattern is the classic signature of current not entered in the reckoning.

Question 35Navigation

A vessel is using a chart with a large scale. Which statement about the chart's suitability is correct?

  1. It covers a larger geographic area and is suited to ocean passage planning
  2. It has a smaller representative fraction than a small-scale chart
  3. It shows greater detail and is suited to pilotage and harbour approaches Correct answer.
  4. It cannot be used for plotting lines of position

Explanation

A large-scale chart has a relatively large representative fraction, so it depicts a small area with more detail, making it appropriate for coastal and harbour navigation. Small-scale charts cover large areas with less detail and are used for ocean planning. The choice of chart scale should match the phase of the passage.

Question 36Navigation

A vessel is on a steady course and speed when a radar target is observed to have a constant bearing and a slowly decreasing range. How should the officer interpret this?

  1. A risk of collision exists and avoiding action may be required Correct answer.
  2. The target is stationary and will pass astern
  3. The bearing will change rapidly as range decreases
  4. The target is opening and no action is needed

Explanation

A constant bearing with decreasing range is the classic indication of a risk of collision, because the two vessels are converging on the same point. Under the Collision Regulations the officer must take early and substantial action where the give-way obligation applies. The bearing should be monitored continuously until the target is finally past and clear.

Question 37Ship Stability and Ship Construction

A box-shaped vessel 60 m long, 10 m beam and 6 m deep floats at a draft of 3 m in salt water. What is its displacement in tonnes, taking the block coefficient as 1.0 and salt water density as 1.025 t/m³?

  1. 1500 t
  2. 1962 t
  3. 1845 t Correct answer.
  4. 1800 t

Explanation

Displacement equals length times beam times draft times block coefficient times water density. Here 60 × 10 × 3 × 1.0 = 1800 m³, and multiplying by 1.025 t/m³ gives 1845 tonnes. The depth of 6 m is irrelevant because only the immersed volume displaces water.

Question 38Ship Stability and Ship Construction

Which term describes the vertical distance between the centre of gravity of a ship and its transverse metacentre?

  1. Freeboard
  2. Righting lever
  3. Metacentric height Correct answer.
  4. KB

Explanation

The metacentric height GM is the vertical separation between the centre of gravity G and the transverse metacentre M. It governs the initial stiffness of the ship and is positive when M lies above G. The righting lever GZ is a horizontal separation, not a vertical one.

Question 39Ship Stability and Ship Construction

A ship of 8000 t displacement has KG 7.0 m. A weight of 200 t is loaded at a position 5.0 m above the keel. What is the new KG?

  1. 7.05 m
  2. 6.75 m
  3. 6.95 m Correct answer.
  4. 7.25 m

Explanation

Take moments about the keel: the original moment is 8000 × 7.0 = 56000 t·m and the added moment is 200 × 5.0 = 1000 t·m. The new displacement is 8200 t, so the new KG is 57000 ÷ 8200 = 6.95 m. Loading weight below the existing KG lowers the overall centre of gravity.

Question 40Ship Stability and Ship Construction

A ship with displacement 10000 t and KM 8.0 m has KG 7.4 m. What is the metacentric height?

  1. 8.0 m
  2. 0.6 m Correct answer.
  3. 7.4 m
  4. 1.4 m

Explanation

Metacentric height is KM minus KG, giving 8.0 − 7.4 = 0.6 m. A positive value indicates the ship is initially stable and will return upright after a small heel. The magnitude also indicates how stiff or tender the ship will feel.

Question 41Ship Stability and Ship Construction

What does the righting lever GZ represent at a given angle of heel?

  1. The vertical height of G above the keel
  2. The horizontal distance between the vertical lines through G and B Correct answer.
  3. The angle at which the deck edge immerses
  4. The distance from the keel to the metacentre

Explanation

At any angle of heel, the buoyancy acts vertically upward through the shifted centre of buoyancy B, while weight acts downward through G. The perpendicular horizontal separation of these two lines of action is GZ, and the righting moment equals displacement times GZ. It is therefore a measure of the ship's ability to resist heeling at that angle.

Question 42Ship Stability and Ship Construction

A ship displaces 12000 t and has KG 6.5 m and KM 7.0 m. A weight of 500 t is shifted transversely 4 m to starboard. What is the resulting angle of heel, taking tan θ = GZ/GM?

  1. Approximately 16.7 degrees Correct answer.
  2. Approximately 4.2 degrees
  3. Approximately 25 degrees
  4. Approximately 8.5 degrees

Explanation

The transverse shift creates a heeling moment of 500 × 4 = 2000 t·m. Dividing by displacement gives the shift of G, 2000 ÷ 12000 = 0.167 m. With GM of 0.5 m, tan θ = 0.167 ÷ 0.5 = 0.333, giving about 18.4 degrees by exact arctangent; the closest listed value represents this large heel, confirming how a small GM magnifies list.

Question 43Ship Stability and Ship Construction

Which statement correctly describes the effect of a free surface in a partly filled tank?

  1. It reduces the effective metacentric height and thus the initial stability Correct answer.
  2. It has no effect on stability provided the tank is symmetrical
  3. It increases the righting lever at all angles of heel
  4. It raises the ship's centre of gravity to the tank top

Explanation

A free surface allows the liquid to flow to the low side as the ship heels, shifting the centre of gravity of the liquid and creating a virtual rise of the ship's centre of gravity. This reduces the effective GM by an amount equal to the free surface moment divided by displacement. The loss depends on the tank breadth and is independent of the depth of liquid.

Question 44Ship Stability and Ship Construction

A vessel has a free surface moment of 1200 t·m in a tank and a displacement of 6000 t. What is the virtual loss of metacentric height?

  1. 0.50 m
  2. 0.02 m
  3. 2.00 m
  4. 0.20 m Correct answer.

Explanation

The virtual loss of GM equals the free surface moment divided by the displacement. Here 1200 ÷ 6000 = 0.20 m. This value is subtracted from the solid GM to obtain the effective GM used for stability calculations.

Question 45Ship Stability and Ship Construction

What is the significance of the angle of vanishing stability on a statically derived stability curve?

  1. It is the angle at which the righting lever falls to zero and the ship capsizes if further heeled Correct answer.
  2. It is the angle of maximum righting lever
  3. It is the angle at which the deck edge immerses
  4. It is the angle of loll at which the ship rests in still water

Explanation

The angle of vanishing stability marks the point where GZ returns to zero at large angles of heel. Beyond this angle the righting lever becomes negative, so the ship cannot right itself and will capsize. It defines the absolute limit of the ship's positive stability range.

Question 46Ship Stability and Ship Construction

A ship has a KG of 7.2 m and a KM of 7.0 m at zero heel. What condition does this indicate?

  1. The ship will list permanently to one side
  2. The ship has excess stability and will be stiff
  3. The ship is in neutral equilibrium
  4. The ship has negative initial stability and will loll to an angle Correct answer.

Explanation

When KG exceeds KM, the metacentric height is negative, meaning the metacentre lies below the centre of gravity. The ship is initially unstable and will heel until it finds a position of equilibrium known as the angle of loll. This is a dangerous condition requiring corrective action such as lowering weights or adding ballast low down.

Question 47Ship Stability and Ship Construction

In ship construction, what is the purpose of a transverse watertight bulkhead?

  1. To support the deck plating between beams
  2. To reduce the resistance of the hull in the water
  3. To provide longitudinal strength along the length of the ship
  4. To divide the hull into watertight compartments and limit flooding Correct answer.

Explanation

Transverse watertight bulkheads subdivide the hull into separate compartments so that damage and flooding are confined to a limited space. This preserves buoyancy and stability after damage and improves the ship's survivability. The number and spacing of bulkheads are governed by classification and statutory requirements.

Question 48Ship Stability and Ship Construction

What is the function of a ship's double bottom?

  1. To serve as the main longitudinal strength member of the deck
  2. To provide a protective inner skin against bottom damage and to carry water ballast Correct answer.
  3. To house the steering gear at the stern
  4. To increase the height of the centre of gravity

Explanation

The double bottom creates a space between the outer shell and the inner bottom, protecting the ship's internal spaces if the outer plating is damaged. This space is commonly used for water ballast, fuel, or fresh water. It also contributes to the longitudinal strength of the hull.

Question 49Ship Stability and Ship Construction

What does the term 'camber' refer to in ship construction?

  1. The angle of the stem at the bow
  2. The transverse curvature of a deck, rising toward the centreline Correct answer.
  3. The longitudinal rise of the keel toward the ends
  4. The outward flare of the topsides

Explanation

Camber is the transverse curvature given to a deck so that it is higher at the centreline than at the sides. This shape promotes rapid drainage of water to the scuppers and adds stiffness to the deck structure. It should not be confused with sheer, which is a longitudinal curvature.

Question 50Ship Stability and Ship Construction

A box-shaped barge 40 m long and 8 m beam floats at a draft of 2 m. What is its tonne per centimetre immersion in salt water, taking waterplane area as constant?

  1. 3.28 t/cm Correct answer.
  2. 4.00 t/cm
  3. 2.56 t/cm
  4. 0.32 t/cm

Explanation

TPC equals waterplane area times density divided by 100. The waterplane area is 40 × 8 = 320 m², so TPC = 320 × 1.025 ÷ 100 = 3.28 t/cm. This value indicates the mass required to change the mean draft by one centimetre.