TOPIC 3 - SHIP HANDLING, TOWAGE AND NAVIGATION NEAR ICE

Question 1

Describe the effect your ship will have on a ship moored alongside when you pass her at anything but a slow speed.

Answer 1

Such a vessel will surge considerably, to and fro in the wash of a passing ship. The speed of the latter must therefore be reduced whenever a vessel is to be passed close by at, say, a river berth. The surging is due to the cushioning and suction effects existing at a travelling ship’s bow and stern. There is also the fore-and-aft flow of water down her side to be considered. The figures above shows the movements to which a moored ship will be subject. Due to the speed of the travelling ship, the moored vessel cannot be considered a fixed object in that it will repel or attract the former’s bow and stern. On the contrary, the moored vessel is regarded as a floating object which is subjected to these sheering forces. Strictly speaking, ship ‘A’ should have her lines tended during the passage of ‘B’, and the latter should proceed as slowly as possible in order to keep her wave-making to a minimum. Ship ‘B’ must also be kept well clear of the other bank so that she does not take a colliding sheer into ‘A’.

Question 2

Describe how a ship’s pivot point moves from ahead to astern.

Answer 2

The pressure of the water that acts on the bow or at the stern brings about a shift in the position of the pivot point.
Ship stopped: In this figure no forces are involved and the ship has a pivot point coinciding with its centre of gravity approximately amidships.
With Headway: Two forces now come into play. Firstly, the forward momentum of the ship and secondly longitudinal resistance to the forward momentum created by the water ahead of the ship. These two forces must ultimately strike a balance and the pivot point moves forward. As a rough guide It can be assumed that at a steady speed the pivot point will be approximately 25% or a 1/4 of the ship’s length from forward.
With Sternway: The situation is now totally reversed. The momentum of sternway must balance longitudinal resistance this time created by the water astern of the ship. The pivot point now moves aft and establishes itself approximately 25% or a 1/4 of the ship’s length from the stern.
Although not intended some publications may give the impression that the pivot point moves right aft with sternway. This Is clearly not correct and can sometimes be misleading. It should also be stressed that other factors such as acceleration shape of hull and speed may all affect the position of the pivot point. The arbitrary figures quoted here however, are perfectly adequate for a simple and practical working knowledge of the subject

Question 3

Describe the general effects of the wind on ship

when moving ahead and astern.

Answer 3

When moving ahead, the pivoting point in most ships is well forward, so that the pressure on the greater exposed area abaft this point tends to turn the ship into the wind.
When going astern, the pivoting point moves aft and the stern tends to fly into the wind.
The degree to which these effects are felt depends largely on the shape and disposition of the ship’s superstructure. For example, a ship with a very high forecastle is not affected a great deal when going ahead, but her stern seeks the eye of the wind rapidly as soon as she gathers sternway.
Wind effects are felt more strongly when speed is slow, and when she is lightly laden.

Question 4

Describe the meanings of the following three terms in ship handling with the wind:
1 To lie across it when stopped;
2 To run across it under headway; and
3 To sternbore into it under sternway.

Answer 4

In the figure the ship is shown running with the wind on the port quarter. As she loses headway she runs across the wind to (2). She is now lying across the wind. As she gathers her sternway, her bow develops a reverse swing to starboard and she bores her stern into the wind’s eye as in (3). She does not, of course, reach her original position (1) due to the leeway which she is continually experiencing.
A twin-screw ship which is attempting to swing into the wind must do so under headway and not rely merely on the offset and push-pull effect of her screws. If she attempts to lie stationary and turn upwind using her engines ahead and astern her bows will pay off the wind. She must therefore turn into the wind under headway, full helm, and a reversed inside engine.
A twin-screw ship desirous of turning downwind will, as in the case of a single-screw ship, swing much more rapidly if sternway is gathered, so that the stern seeks the wind’s eye.

Question 5

Discuss using a current in ship handling.

Answer 5

• Effects of current are important especially when the ship is under the effect of on shore winds, near off shore platforms, while maneuvering in narrow channels and open seas, or in inland waters or harbors.
• When the ship is in harbors or inland waters and the current is at constant strength and direction, the ship’s handling becomes considerably easier.
• Currents are usually complex, with varying rates and directions that can change hourly. Current from ship’s ahead will reduce the ship’s speed over ground, improve ships response to the rudder, and also give more time to assess and correct developing situations.
• A berth should be approached bow into the current in order to give the advantage of relatively high speed through the water with a reduced speed over the ground. Consequently, steerage at low ground speed is improved by the good water flow over the rudder. The ship will be easier to stop.
• The current can be used to push a ship alongside. Position the ship off the intended berth but at a slight angle towards it. Then allow the current to produce a sideways movement of the ship towards the berth.
• A ship making headway into a current, but stopped over the ground, will have a forward pivot point.

Question 6

Describe how you would use a current when berthing your ship.

Answer 6

Stem the current. (Bow into the current). Approach at a shallow angle.
Too large an angle between the berth and the direction of the current will cause the ship to move rapidly sideways. Unless corrected, contact with the berth may be unavoidable.

If during berthing the bow’s angle to the berth is over-corrected then the ship could move away from the berth as the wedge of water between ship and berth becomes established. This may cause the ship’s stern to strike the berth.
Once alongside, care must be taken to prevent the ship dropping astern before back springs and head lines are set.
Points to remember:
• In many places a counter current flows in opposition to the main current close to the bank. Only local knowledge will provide this information.
• Current can vary with depth of water and large deep draught ships can experience different current effects at differing parts of the hull. Caution is needed.
• When close to the berth in a head current, there is a danger that flow inshore of the ship becomes restricted and the ship is subject to interactive forces. These forces can cause the ship to either be sucked towards or pushed away from the berth. Local knowledge will help anticipate this phenomenon.

• As speed is reduced, take care that the increased proportion of the ship’s vector which is attributable to current does not set the ship close to obstructions.
• Always make a generous allowance for current. Its effect on the ship increases

Question 7

Describe how you moor to two buoys in calm weather?

Answer 7

The approach should be made with the minimum of headway in order to avoid a swing developing when the engine is worked astern. In calms, with no wind braking-effect present, the risk of overshoot¬ing exists. For this reason, the ves¬sel is headed for the head buoy fine on the starboard bow. When the engine is working astern to reduce headway the swing is favourable.

Question 8

Describe how you moor to two buoys with a wind from ahead?

Answer 8

The method shown is to drift bodily downwind, using occasional ahead movement on the engine with weather helm in order to keep the vessel in the correct attitude. A headline is run away to leeward well before the vessel has reached the buoy (2), and the vessel swung head to wind on this line.
When the engine is worked ahead under these conditions it will have to be used boldly, because with little headway on her the ship will tend continually to run beam-on to the wind.

Question 9

Describe how you moor to two buoys with no room to approach from windward?

Answer 9

Securing to Two Buoys with no Room to Approach from Windward
A sternboard is executed into the wind from (1) to (2) crossing the line of buoys. In this case it does not matter if the wind comes on the port quarter, because the stern is secured in (2) and the bow will rapidly fall downwind until (3) is reached.

Question 10

Describe how you moor to two buoys with current ahead?

Answer 10

The vessel approaches under slow headway over the ground with the headbuoy fine on the port bow (1). While the line is secured to the head-buoy, the engine must be worked slow ahead. With the buoy situated on the port bow, the effect of trans¬verse thrust is favourable. The ves¬sel is then allowed to drop down¬stream so that the sternbuoy can be picked up.

Question 11

Describe how you moor to two buoys with turning the vessel before mooring in calms?

Answer 11

The head buoy is approached on the port bow and a line secured. The engine is then worked slow ahead on the taut line, with the helm hard over towards the buoy. The vessel is thus swung to (2), when a line to the sternbuoy is used to complete the swing.
By keeping the head buoy to port, the transverse thrust effect is favour¬able.

Question 12

Describe how you moor to two buoys with current astern?

Answer 12

This is very similar to “Turning the Vessel before Securing to Two Buoys in Calms” , since the vessel will secure to the first buoy on her port bow (1). She will then, having been given a slight cant to port, allow the current to carry her round to (2) and (3). Once she is beam-on to the stream, her engine should be worked slow ahead with port helm to relieve the stress on the headline.
In this instance the buoy could very well have been picked up on the starboard bow,

Question 13

Turn a vessel with s single right handed propeller short round.

Answer 13

The vessel is turned round in her own length. No headway or stern-way is gathered. When the engine is reversed a powerful swing to star¬board is generated, and so these ships are always swung to starboard, unless they have small high-speed propellers, when transverse thrust is small. In (1) the engine is worked full ahead on full starboard helm. At the first sign of headway the helm is put amidships and the engine reversed fully. The swing to starboard continues, (2). The se¬quence is repeated in (3) and (4), and so on, until the vessel is turned. If the astern power is small the watch for headway must be ex¬tremely diligent

Question 14

Turn a vessel with a right handed propeller short round in an
ahead river-stream.

Answer 14

The vessel is run close to the port-hand bank into slacker water, and the bow given a cant into the fast water, (1). The swing develops, the stern being kept as close to the bank as is prudent. In (3) the engine is reversed fully to prevent bodily drift downstream, and port helm used to complete the swing. In mak¬ing the turn at the port bank, trans-verse thrust is favourable through¬out.

Question 15

Turn a vessel with a right handed propeller short round using the anchor in a following stream.

Answer 15

In (1) the bow is swung into the slacker water at the starboard bank and the engine is reversed. The helm is over to starboard for the cant inshore and is about to be placed amidships. The reversed engine produces a favourable transverse thrust and also prevents excessive lee drift. In (2) the upstream anchor is let go and held at short stay. This rapidly snubs the bow round to (3), by which time the engine should be working ahead under starboard helm to complete the swing to (4). The anchor is held at short stay so that an excessive stress on the cable causes it to dredge rather than be strained. In (4) the cable appears to have been further veered, but this is only for the sake of clarity— actually the vessel swings very nearly in her own length at (3).

Question 16

Berth a right handed propeller vessel starboard side too in calm weather.

Answer 16

The vessel is headed in at a fine angle to the quay, and since there will be a swing to starboard when the engine is reversed, the helm is put hard over to port with a burst ahead on the engine in (1). This starts a port swing, and when the engine is reversed, as in (2), the swing is checked and the vessel loses her headway lying close to, and parallel with her berth in (3). The sternline may be used to check a marked swing to starboard.

Question 17

Berth a right handed propeller vessel port side too in calm weather.

Answer 17

The vessel is headed in at an angle of about 1½ points with the quay, under slow headway and with steady head. As the engine is re¬versed, a swing to starboard de-velops and the vessel will arrive abreast of her berth with no way upon her and parallel to it. She will, however, be slowly swinging to star¬board, and this must be checked with the headline.

Question 18

Leave a berth starboard side too with a right handed propeller. No wind no current.

Answer 18

cases of clearing a berth the stern must be canted clear. This is done by steaming slowly ahead on a fore headspring, while the helm is put hard over towards the quay. The spring must be absolutely tight when the engines are worked ahead, otherwise any momentum of the ship will part a slack spring. The spring may be made tight by putting a headline on the windlass barrel and heaving on it. These two lines are shown in the figure.
The ship is therefore canted in to the quay forward, (2), and the engine is then reversed. The helm is initially amidships and the lines are let go. After the first few revolutions astern the rudder is put hard over to starboard to correct the swing to starboard generated by the trans¬verse thrust. As the slipstream flows in between the fore body and quay, the undesirable starboard swing is further damped, but as soon as she clears the quay the swing may tend to develop again, the transverse thrust overcoming the full rudder angle. In this case the engine must be stopped in order to have a straight run astern.

Question 19

Leave a berth port side too with a right handed propeller. No wind no current.

Answer 19

Here, both the transverse thrust when reversing the engine in (2) and the cushioning slipstream be¬tween the forebody and quay cause the stern to swing rapidly back into the quay. The helm will be of no avail, because this will occur before sternway is gathered. However, the undesirable swing of the bow on to the quay in the figure does not exist here, and providing the manoeuvre is correctly done, the clearing is, in many ways, more simple. The stern must be canted out to a very large angle as in (2) before the engine is reversed. By the time the stern has swung back parallel to the quay, the ship will be under sternway and will be at (3). Starboard helm will correct the swing of the stern inshore, but even so, a burst ahead on the engine with port helm will soon achieve this.

Question 20

How would you go about anchoring your ship keeping her clear of a danger nearby.

Answer 20

In the figure the vessel is moored close to a shoal. This is hardly advisable, but the occasion may arise. In position (1) the vessel is initially moored riding to her off-shore anchor. When she swings with the change of stream to position (2) she must do so to starboard, so avoiding running her stern close to the shoal. Because she is riding to the off-shore anchor, her hawse remains clear. In (2) she again rides to the off-shore anchor— the starboard one.

Question 21

How would you go about making a standing moor in a river with the wing blowing across the river with a ship having installed right handed propeller?

Answer 21

The ship is to anchor on the line AB. The stream is as shown.
Head to stream or wind
When both are present, head to one has stronger effect.
With sufficient headway, take vessel to position 1.
Position-1 is roughly 5 shackles minus half ship’s length beyond line AB.
Let go port anchor.
The vessel drifts downstream, render port cable to nine shackles, the sum of two lengths.
She is brought up on her cable.
Then the starboard anchor is let go at position-2.
Vessel then moves to the position 3 by going ahead and rendering or veering the starboard cable and heaving in four shackles on the riding cable.
Engines may be used to reduce stress on the windlass.

Question 22

How would you go about making a standing moor in a river with the wing blowing across the river with a ship having installed right handed propeller?

Answer 22

Head to stream or wind
When both are present, head to one has stronger effect.
Let go starboard anchor on run, when vessel is 4 shackles and half of ship’s length, position -1.
The cable is rendered as the vessel moves upstream.
The cable is not allowed to be tighten, as bow will cant to starboard.
The cable is rendered or veered to 9 shackles as the vessel moves to position-2.
In position-2, port anchor is let go.
The vessel moves astern.
The vessel is then brought up on her riding cable at position-3. Five shackles on the lee (starboard) cable and five shackles veered on the riding cable.

Question 23

Bring your ship up to an “open moor”.

Answer 23

Approach the anchorage with wind or current on one bow.
Weather anchor or upstream anchor is let go on the run (1).
The headway continued and cable is laid up 1/3 rd of the final length of the cable.
The second anchor is let go (2).
First anchor snubbed at the gypsy.
The vessel brings-to on her weather cable. It gradually grows taut to windward.
Bow develops a rapid swing into the stream or wind.
In (3) the vessel is turned if necessary using a small ahead movement with the rudder hard a port.
Both the anchors are veered. Engine reversed.
Finally the vessel is brought up with the anchors are one point at each bow(4).

Question 24

How would you moor your ship to a waek jetty?

Answer 24

Baltic moor is employed to hold the vessel off the quay.
Carried out to protect the hull from an unfended concrete quay or to
hold a large heavy vessel off a light, weak jetty

Question 25

Describe how you would make a Mediterranean moor with its advantages and disadvantages.

Answer 25

a. Advantages: Allows for best use of limited space in crowded harbors. Allows for each ship to have a brow to the pier; strong moor.
b. Disadvantages: Possibility of fouling anchors exists with adjacent ships.
c. Place two anchors about 100 - 150 meters apart on line parallel to the pier, and equidistant on either side of the position of the ship when moored.
d. Place anchors at an angle of 20 - 30 degrees off the bow for each chain, allow for 120 meters off the pier in addition to ship’s length.
e. Planned positions of the anchors should be marked on the harbor charts.
Shiphandling and execution.
a. Approach should be made parallel to the pier and towards first anchor point.
b. Position A - Reduce speed to bare steerageway. Drop anchor about fifty meters before bow comes abreast of assigned point on the pier
c. Position B - Ship should apply full rudder to steer towards second drop point, and keep the chain clear of the ship. Chain is veered to the first anchor as the ship heads to the second point.
d. Position C - Passing through the second point, the second chain is dropped with slight sternway.
e. As stern moves towards pier, chain is veered or taken in to locate the bow 90 degrees from the pier where stern is to be located.
f. As the ship comes into line, it is backed against catenary of the chain to locate at desired distance from the pier.
g. Once stern lines secure, chains are adjusted to keep stern safely off the pier.
h. Getting back underway, the last anchor dropped should be the first recovered. Stern line should be retained as long as possible to keep the stern under control

Question 26

What danger is associated with ship interaction and a tug working close alongside?

Answer 26

• When the tug approaches the aft part of the ship (position 1), an increase of her speed may occur due the incoming flow velocity. In the close proximity of ship’s hull, a low pressure starts to move the tug towards the hull.
• For ships in ballast condition or for ships having particular overhanging stern, the tug can easily come to position 2, which creates danger of damages to the tug’s hull and superstructure.
• Proceeding further along the hull (position 3), the tug is under important suction force oriented towards the ship’s hull and outward turning moment due to tug bow-cushion. Once sucked alongside it is very difficult to get off again and to continue the way.
• Tug in position 4 enters the high-pressure area. Arising outward turning moment must be eliminated by appropriate use of rudder and engine.
• When arriving to position 5 close to the bow, very strong “out force” acting on the stern tries to bring the tug to position 6 broad side under the bow with risk of capsizing. Immediate action of rudder and use of available power (full astern) can correct the position. Tractors type tugs are less vulnerable in such a situation.

Question 27

What is squat and what causes it?

Answer 27

When a ship proceeds through water, she pushes water ahead of her. In order not to leave a hole in the water, this volume of water must return down the sides and under the bottom of the ship. The streamlines of return flow are speeded up under the ship. This causes a drop in pressure, resulting in the ship dropping vertically in the water.
As well as dropping vertically, the ship generally trims for’d or aft. The overall decrease in the static underkeel clearance for’d or aft, is called ship squat. It is not the difference between the draughts when stationary and the draughts when the ship is moving ahead.
If the ship moves forward at too great a speed when she is in shallow water, say where this static even-keel under keel clearance is 1.0 1.5 m, then grounding due to excessive squat could occur at the bow or at the stern.
For full-form ships such as Supertankers or OBO vessels, grounding will occur generally at the bow. For fine-form vessels such as Passenger Liners or Container ships the grounding will occur at the stern. Squat is not pronounced on small vessels because the flow under the keel is not impeded as severely by the ship’s length.

Question 28

What effects become evident on the ship’s manoevring when entering shallow water?

Answer 28

A. Vessel develops sluggish movement:
As the hull moves along the water, the water which is displaced is not instantly replaced by surrounding water
A partial vacuum is created.
The vessel takes longer to answer helm.
Response to engine movement becomes sluggish.
Speed reduces.
B. Vessel starts to vibrate:
In shallow water vibrations set up.
It becomes very difficult to correct a yaw or sheer with any degree of rapidity.
C. Steering is affected:
Steering becomes erratic.
Rate of turning is reduced.
Turning circle becomes larger.
Loss of speed due to turning is less in shallow water.
D. Vessel starts smelling the ground:
Occurs when a ship is nearing an extremely shallow depth of water, such as a shoal.
The ship likely to take a sudden sheer
The sheer is first towards the shallow, then violently away from it.
The movements of a sluggish ship may suddenly become astonishingly lively.
These effects are called smelling the ground.
E. Vessel will squat:
Water displaced by the hull is not easily replaced.
Bow wave and stern wave increase in height.
Trough becomes deeper and after part is drawn downwards.
Under keel clearance decreases.
Vessel can touch bottom.

Question 29

What is bow cushion and bow suction effecr?

Answer 29

Bow cushion and bank suction effect: Occurs in narrow channels near proximities of banks.
There is a tendency for the bow of a ship to be pushed away from the bank, called bow cushion.
The ship moves bodily towards the bank, which appears at the stern, called bank suction.
Caused by the restricted flow of water on the bank’s side. Velocity of water to the bank increases and pressure reduces.
Results in drop of water level towards the bank.
As a result, a thrust is set up towards bank.
A vessel approaching to the bank will have to apply helm to the bank and reduce speed to prevent the sheer from developing.

Question 30

How is a bow tug girted?

Answer 30

In the figure at left, a
tug working on a line is assisting a ship making a turn to starboard (position 1). Ship is suddenly accelerating to improve turning ability. The speed after few moments becomes too high and the consecutive tug positions are more and more aft with high tension in the towline (positions 2 and 3). The danger of capsizing is then real.
ALTERNATIVELY:
Due to misunderstandings between a pilot and a tug master, a tug continues the straight forward motion (position 1), even when the ship starts to swing starboard. As the result of it, the dangerous situation to the tug may develop (positions 2 and 3). To avoid this, the tug master always should be informed about ship’s intention.

Question 31

How is a stern tug girted?

Answer 31

An unexpected increase in the ship’s speed, often result of sudden increasing of propeller revolutions, makes working positions 1 and 2 difficult to keep, and the tug moves more and more towards position 3, where it will be exposed to a risk of girting.

Question 32

What are the results of ship interaction?

Answer 32

Squat
Drawn towards the quay when passing at speed.
Listing towards the shallow bank and smelling the ground.
Ships passing close or overtaking close to one another are drawn towads each other.
Pilot boats are sucked alongside a bigger ship and cannot get away.
Surging a moored ship off the quay when pasing at speed.
Drawing an anchored vessel in towards own vessel when passing at speed.

Question 33

Describe the interaction between a harbor tug and a ship?

Answer 33

When the tug approaches the aft part of the ship (position 1), an increase of her speed may occur due the incoming flow velocity. In the close proximity of ship’s hull, a low pressure starts to move the tug towards the hull. For ships in ballast condition or for ships having particular overhanging stern, the tug can easily come to position 2, which creates danger of damages to the tug’s hull and superstructure.
Proceeding further along the hull (position 3), the tug is under suction force oriented towards the ship’s hull and outward turning moment due to tug bow-cushion. Once sucked alongside it is very difficult to get off again and to continue the way.
Tug in position 4 enters the high-pressure area. Arising outward turning moment must be eliminated by appropriate use of rudder and engine. When arriving to position 5 close to the bow, very strong “out force” acting on the stern tries to bring the tug to position 6, broadside under the bow with risk of capsizing. Immediate action of rudder and use of available power (full astern) can correct the position. Tractors type tugs are less vulnerable in such a situation.

Question 34

Discuss how you would go about anchoring your vessel?

Answer 34

In calm weather the anchorage is approached at slow speed.
The anchor is let go while the ship has either headway or sternway.
The cable is laid out, and engines are used to relieve stresses in the cable just before the vessel brings-to.
The officer who is anchoring his own ship usually prefers to stop his vessel at the anchorage by going astern. When the propeller wash reaches the ship abeam of the bridge he uses that as a guide that the ship has lost way.
The engines are then kept going dead slow astern as the anchor is let go.
Engines are stopped almost immedi¬ately and the vessel drifts astern laying out her cable, which grows con¬tinually ahead.
Just before the required scope is out, the engines are touched ahead so that the vessel gets her cable as gently as possible.
This method ensures the chain being clear of the hull plating at all times.
In a wind it is better to approach the anchorage heading upwind.
In a tideway the vessel should stem the tide and again anchor with headway as in calm or in a wind.
When anchoring stemming a stream and also having wind abeam, the lee anchor should be let go first. As the vessel gets her cable, the bow will then swing into the wind, causing the cable to grow clear.
In waters up to 10 fathoms deep the anchor and cable should be let go on the run, allowing about double the depth (of cable) to run before checking it on the brake. If the cable is snubbed as soon as the anchor touches the bottom the anchor will be dragged along the sea-bed and will be unable to grip. Further, with the weight of the anchor off the cable, it sometimes happens that when the brake is released the cable will not render itself. This happens when there is a heavy weight of cable abaft the gypsy, leading down into the locker, and when the gypsy

Question 35

What you take into consideration when deciding on how much cable to lay out when anchoring?

Answer 35

The scope of cable (the length of cable laid out), is measured from the hawse pipe to the anchor, divided by the distance measured vertically from the hawse pipe to the sea-bed. The scope used, depends upon several factors:
The nature of the holding ground. Stiff clay, rock, shells, and
stones are considered poor holding ground. Very soft mud can be a poor material in this respect.
The amount of swinging-room available for the ship as the wind or stream changes in direction.
The degree of exposure to bad weather at the anchorage.
The strength of the wind or stream. As this strength increases so
the ship moves astern, lifting her cable off the bottom so that it
assumes long stay.
The depth of water—probably the most important factor.
If the cable leads from the anchor shackle in a direction 5 degrees above the shank axis the holding power of the anchor is reduced by one-quarter. If the angle becomes 15 degrees the loss of holding power is one-half. For this reason, it is most important that a length of cable shall lead from the anchor shackle along the sea-bed before rising gently to the hawse pipe. Only a good scope will ensure this. Very often, when a ship drags her anchor, more cable is veered and the anchor holds. The action is correct, but the oft-resulting belief is a fallacy— that it is the resistance of the extra cable which has held the ship. The anchor was no doubt dragging because the angle between the cable and shank axis, at the shackle, was more than zero. The veering of cable removes this angle and the anchor holds once more.

Question 36

What is breaking sheer in anchor work?

Answer 36

The vessel will normally lie with the anchor and cable fine on its own bow, say a point to a point and a half. This angle is known as the vessel’s natural sheer, because she lies sheered slightly across the stream or wind. In a strong wind the vessel will tend to yaw about as shown in the figure. At the extremity of her yaw she surges ahead and then drops back on her anchor, jerking the cable. If during the yaw the wind catches her on the opposite side to that normally exposed by her natural sheer (i.e. catches her on the port side when using her starboard anchor), she may, at the extremity of her yaw, surge rapidly across her anchor to the other extremity of yaw, i.e. from position 6 to 8 in the figure, nip¬ping her cable round the stem and breaking the anchor out of its holding position. This is called breaking sheer. If the anchor fails to re-trip the other anchor must be let go at once.

Question 37

If your vessel starts to drag anchor what can you do?

Answer 37

Once a vessel begins to drag, more cable should be veered. It should not be surged out slackly, otherwise the cable may part as the vessel brings-to. By veering it, the vessel may be brought up gently.
The second anchor should be let go in good time, otherwise it may be found that so much cable has been veered on the first anchor (say 8 out of 11 shackles), that very little can be veered on the second (in this case only 2 to 3 shackles).
Engines should be used to relieve stresses. If there is room it may be better to heave up and seek better holding ground.
If the vessel is yawing about the anchor position then:
Let go the second anchor underfoot at the centre of yaw. This is
an excellent plan if the brake is held just slackly.
If the first anchor starts to drag the second will bite and its cable will render itself.The noise of this gives warning of dragging, and the second cable is veered without delay. This is sometimes done by seamen as a regular practice, whether or not the weather is bad. OR
Let go the second anchor at the extremity of yaw and veer both
cables so that the ship rides comparatively quietly to her two
anchors. OR
Steam up to the first anchor, sheer away, and let go the second
anchor. The first cable is hove in while approaching its anchor.
Both cables are then veered so that vessel rides quietly with an
anchor fine on each bow.

Question 38

Are there any instances when the anchor may be permitted to drag?

Answer 38

Generally speaking, once an anchor starts to drag, the vessel gathers sternway, and this may become excessive. Prompt action is necessary. However, there are exceptions, and a vessel riding out a gale has been known to drag slowly and steadily for some days at roughly a mile per day.

Question 39

How would you break-out a fouled anchor.

Answer 39

If the anchor is wedged in an underwater obstruction:
The vessel should be moved very slowly ahead, veering cable until it grows well astern.
When the vessel is brought up and the cable is taut the engines are worked ahead very gently to see if the anchor will break out.
The vessel can then slowly be steamed round in a circle with the cable taut (turning towards the anchor of course), to try to rotate the anchor and break it out by constant movement.
If this fails, together with an attempt under sternway with the cable growing for¬ward, then the cable must be slipped from the deck, buoying the end, and the anchor later recovered by a salvage crew.
If the anchor has fouled a cable, wire, or other similar underwater obstruction
the anchor and fouling is hove well up to the hawse pipe.
A strong rope, such as a mooring line in the case of a heavy submarine cable, is passed round the obstruction and both ends are hove taut and made well fast on deck.
In the case of an unimportant obstruction a wire rope can be used, but a fibre rope must be used in cases where the obstruction may be a telegraph cable or one carrying high-tension current.
When the line is hove taut the anchor is walked back clear of the obstruction and then hove home into the pipe.
Pro¬vided the hanger is secured at the forecastle deck in a region of maximum flare, the fouling will swing clear when the anchor is walked back.
The hanger is then slipped from the deck to release the fouling.

Question 40

In anchoring a vessel what is meant by “Dropping down”?

Answer 40

A vessel is said to drop down when she drifts with the tidal stream.
A vessel at anchor wishing to do this will heave her anchor just clear of the sea-bed.
Her speed through the water will be nil, but her speed over the ground will be equal to that of the stream.
Her rudder will have no effect, because there is no water flowing past it.
She cannot be controlled except by means of the engines or the anchors.

Question 41

In anchoring a vessel what is meant by “Dredging down”?

Answer 41

A vessel is said to dredge when she moves under the influence of the tidal stream but with her anchor held at short stay so that it drags along the bottom.
Her speed over the ground is therefore retarded and is not so great as the rate of the stream.
She therefore has headway through the water.
Her rudder may be used to steer her. A strong tidal stream is necessary for her helm to be sensitive.

Question 42

How would you go about hanging off an anchor?

Answer 42

Usually, the first shackle of cable includes a joining shackle 1-2 fathoms from the anchor shackle, so that when the anchor is stowed the joining shackle is between the gypsy and the hawse pipe.
If the cable can be passed through a forward Panama Canal fairlead, then the anchor can simply be secured in the pipe using wire lashings and the bow stopper.
The cable can then be eased off the gypsy and broken. It is then passed to the fairlead using chain hooks.
If the cable is to be passed through the hawse pipe the anchor must be removed from its housing and secured at the ship’s side.
First, the anchor is lowered clear of the pipe and a’cockbilled.
Calculate the SWL required for a wire strong enough to support the wire and the joining section of chain.
The wire rope is passed from bitts situated just abaft the hawse pipe, and preferably at maximum flare, through the anchor shackle and back on deck.
Both parts are hove taut and belayed.
Another suitable wire of similar strength, “No. 2 wire”, is passed from bitts, through the cable forward of the shackle and then led to the nearest winch warping barrel.
The cable is eased to No. 2 wire and then broken.
No. 2 wire is then veered slowly so that the anchor swings abaft the pipe.
Both wires can be left taut (No. 2 wire will be stoppered off and belayed) so that the anchor is suspended equally by both, or else the whole of the weight can be transferred to the first wire.
A man can then be sent overside to cast off No. 2 wire, which is hove inboard. This is advisable, because if this wire is left in the pipe it will be severely chafed by the cable.
Vessels which frequently engage in this operation use a specially made strop instead of the overside wire, and with this the anchor can be hung off in about 10 minutes.

Question 43

What is the difference between a ‘fouled anchor’ and a ‘fouled hawse’?

Answer 43

The fouled anchor is the description given to when the anchor itself is fouled by some object like a cast off fishing wire, or even by its own cable turned around the fluke.
A fouled hawse occurs when the vessel has moored with two anchors and ship’s anchor cables have become entwined, usually caused by a change in the wind direction, causing the vessel to swing in opposition to the lay of cables.

Question 44

How would you go about clearing a fouled hawse?

Answer 44

The ship can be turned using her engines or a tug until the hawse is clear. Alternatively, a joining shackle can be broken and the sleeping cable heaved around the riding cable until the hawse is cleared. This is done as follows:
Assemble the following gear.
Minimum of at least three 25mmØ steel wire ropes(Check SWL is adequate).
A smaller wire, say 18mm Ø
some lengths of 18mm Ø fibre rope;
a boatswain’s chair; and
equipment necessary for breaking open a cable joining-shackle.
Commence the operation soon after the ship has has swung to a new stream, thus giving about 6 hours freedom. Use experienced crew.
the turns are hove above water and the cable lashed to¬gether the light wire rove through the links, the ends secured on deck out of the way.
There should be no difficulty in bringing the cables together, since the sleeping cable will be reasonably slack.
One of the bigger wires is then passed around the sleeping cable below the turns, hove tight, and belayed.
This wire acts as a preventer in case the unshackled end of the cable is lost, and also relieves the turns of some of the cable weight.
A round turn may be used when passing this preventer around the cable. This enables the wire to be slipped later from the deck. The vessel is shown riding to her starboard cable.

In the figure above, a wire messenger has been passed down through the hawse pipe, dipped around the riding cable, following the run of the port cable, and returned to the forecastle deck. It is dipped only once, and only half a turn will be removed at any one time.

In the plan view of the foc’sle above, the port cable has been veered until a joining shackle is forward of the gypsy.
The third wire is secured to the cable just forward of the shackle, both parts are led to the bitts, belayed, and then the cable is eased to this wire.
The shackle is broken open. When the cable is parted the shackle may be replaced and assembled.
The easing wire should be passed through the open end link to allow for slipping from the deck.
One inboard end of the messenger is now secured to the joining shackle, the other is taken, with as good a lead as possible, to a warping barrel, and set tight.
The easing wire is shortly going to be surged on the bitts—if desired, one end of it can also be led to a warping barrel; it can then be surged without risk of fouling the other end of the wire, or it can be veered under power. All is now ready for removing the first half-turn.
The messenger is hove-in and the easing wire eased.

When the end of cable is about to be dipped the easing wire is slipped (see the figure above), the messenger hove, and the end of cable dips around the starboard chain. It then continues on up to the hawse pipe and on to the forecastle deck.
On deck the easing wire is again set up, the weight is taken on it; the messenger cast off and re-dipped as before to remove the remaining half-turn. When this has been achieved the situation is as shown in the figure below.

The cable is re-joined and the preventer cast off.
The light wire is eased from the deck to part the cables, one end id slipped and the wire is hove-in.

Question 45

Turning circle explain with a diagram
advance
transfer
drift angle

Answer 45

• The advance of a ship for a given alteration of course is the distance that her compass platform moves in the direction of her original line of advance, measured from the point where the rudder is put over.
The transfer of a ship for a given alteration of course is the distance that her compass platform moves at right-angles to her original line of advance, measured from the point where the rudder is put over.

Question 46

What is Synchronized rolling?

Answer 46

Vessel starts to roll heavily with no period of lull.

The angle of roll is almost same or increasing in with every roll.

Question 47

What causes synchronized rolling?

Answer 47

Occurs when the vessel’s period of roll is equal or nearly equal to the apparent period of the encountered waves. This is caused primarily by the synchronization of the relative period of the vessel’s natural period for rolling. Can also result is synchronized pitching.

Question 48

What are the dangers associated with synchronized rolling?

Answer 48

Synchronized rolling is to be determined immediately. A very dangerous and undesirable condition.
More dangerous in small vessels or vessels with low stability.
Most dangerous when a beam sea is experienced and the ship reaches a greater maximum inclination at each trough and crest of wave.
Successive waves tend to increase the angle of roll of the vessel, thereby producing a risk of capsizing.
Danger of cargo shift, damage to vessel and injury to the crew.

Question 49

What is a Smit Bracket?

Answer 49

The bracket works using a large sliding pin which receives the towing chain and locks it quickly and securely into place. On request, smit brackets can be supplied with type approval from Lloyds, ABS, BV or DNV.
It is welded to the deck and shall of adequate strength taking into account the size and deadweight of the ship and expected forces during bad weather. Deign and type shall be approved by the flag administration. In other words, approved by Class.
Emergency towing arrangements shall be fitted on all tankers of not less than 20 000 tonnes deadweight.

Question 50

How would you go about making preparations to tow a disabled ship to a safe port?

Answer 50

a) Communications with the ship to be towed is imperative.
b) Consult owner and/or charter party regarding permission to undertake the tow.
c) Ensure own ship is strong enough to undertake the tow.
d) Consider environmental factors
• Proximity to shore
• Depth of water and land features (lee shore?)
• Wind and the profile of the vessel
• Forecasted weather for duration of tow
• Wave size and character
• Visibility
• Darkness
e) Confirm you have enough fuel for the additional time on voyage.
f) Ensure you have enough stores and water for the additional time on voyage.
g) Plan the tow connection. What type of hawser? How will it be connected? How is to be passed? How will it be protected from chaffing?
h) Extra crew on watch to maintain a watch over the hawser.
i) Brief crew with a toolbox workshop on how the connection is to be made.
j) Personnel involved in rigging and un-rigging towing gear and handling lines shall wear life jackets and PPE.
k) Be careful when handling towing hawsers and observe the precautions for using synthetic fiber ropes.
l) Ensure that the tow line and the appendages are in good condition. Never use a hawser that is kinked
m) The towing hawser must have a scope of at least 200 fathoms (1200 feet) especially for long tows and in heavy weather. However, the urgency of the situation or navigational hazards may dictate the use of a single hawser rig, [100 fathoms (600 feet)], even in heavy weather, in order to get the tow under way. A second hawser can be added when conditions permit.
n) Make provisions for emergency release of the tow line. (An axe, large bolt cutters, cutting torch, release stopper.
o) Ensure that all rigging is adequate. If questionable, always over-rig.

Question 51

How would commence the tow once having made connected.

Answer 51

a) When getting underway, build up speed slowly; never go from dead-in-the-water to full ahead.
a) Never let the hawser be sprung so much that it straightens out clear of the water or be allowed to drag on the bottom.
b) During favorable weather and seas, ensure that a sufficient catenary exists to absorb shock loading. Never tow at short stay in rough weather.
c) Inspect the towing hawsers regularly; especially where is passes through the Panama lead. Check for chaffing. Adjust tow length to move point of chaffing.
d) If the tow is sinking, disconnect the tow line immediately.
e) Keep a lookout for small weather fronts. A sudden unexpected weather front can cause great damage.
f) Keep all unnecessary personnel away from the vicinity of the tow line.
g) Set a towing watch on both ships.
h) If the towing ship losses power, the course of the towing ship should be altered immediately to prevent being overrun by the towed ship.
i) Display appropriate lights and shapes. If not available, then issue navigation warning and light up tow wire at night with a search light.

Question 52

Describe a typical tow wire connection?

Answer 52

Insert figure 4.1

Question 53

A. Describe the approach to make a tow connection with Converging Approach on the Windward Side of the Vessel to be Towed

Answer 53

This approach is advisable when the two ships have similar drifting rates and attitudes when stopped. The disadvantage of this method of approach is that it is difficult to regain a suitable position if contact is not made. Going astern to regain a position on the casualty’s bow is inadvisable because the stern will fly into wind so it is usually best to go all the way round and make another approach.

Question 54

B. Describe the basic downwind approach to make a tow connection.

Answer 54

The basic downwind approach. The towing ship should aim to cross 30 metres clear across the bow of the ship to be towed. Watch carefully for any sign of the disabled ship drifting ahead and, if the gap appears to be narrowing, make a substantial early alteration away. Then, when a position of advantage on the bow has been attained, alter back to run in from further ahead. Always make the final part of a downwind approach at slow speed, but retain sufficient speed to be able to steer accurately on passing the bow of the disabled ship. The best position from which to fire the gun line is from forward. The messenger should already be led outboard and aft to speed up passing the tow but care has to be taken to keep the propellers clear of the messenger and towing hawser while they are being paid out. While the tow is being secured the M aster should keep his ship a short way down wind of the disabled ship’s bow by holding her stern into the wind. Once the hawser is secured the towing ship should gather way slowly and gradually take the strain. Getting the tow under way can be difficult because the towed vessel will be at right angles to the towing ship while the tow is being passed and will tend to turn upwind as she gathers speed. The towing ship should start by moving on to the lee bow of the tow and trying to turn beam-on to the wind to avoid putting undue strain on the towing hawser. The Master should not pull a disabled ship that is stopped in the water at right angles to her heading as this may part the tow.

Question 55

C. Describe the approach to make a tow connection with Downwind Approach to a Disabled Ship with the Wind Abaft her Beam.

Answer 55

A disabled ship that is lying with the wind abaft her beam will be making headway and it will be dangerous to attempt to pass close across her bow. If a downwind approach is to be made, the towing ship must keep well ahead of the disabled ship in order not to
risk collision. At the same time she must pass close enough for the line throwing appliance to reach as they pass. The Figure above shows the position that should be reached to pass the tow conveniently. Once past the bow, there should be no difficulty in keeping the stern to wind conveniently close to the other ship. However, with one ship drifting ahead and the other directly downwind and therefore with no lateral drift, the relative positions of
the two ships will change as shown by position C in the Figure. This may complicate passing the tow and make getting the tow under way difficult. This can be remedied by turning to a heading parallel to that of the disabled ship while the tow is being paid out thereby preventing the gear being nipped when a strain is put on it. A large ship will drift downwind faster than a small ship, so the Master will have to take care to move clear ahead if this is likely to happen.

Question 56

D. Describe the approach to make a tow connection. Downwind Approach to a Vessel lying with the Wind on her Bow.

Answer 56

If the disabled ship is lying with the wind before her beam, she will be making slight sternway so it should be possible to approach close across her bow without danger. The aim should be to stop just beyond her bow as shown in Figure above and turn under low power
before starting the tow. The strain must be taken very cautiously because ships will be on nearly opposite headings and it will be necessary for the towing ship to turn at rest side-on to the wind before getting the tow under way.

Question 57

E. Describe the approach to make a tow connection. Ship lying Head to Wind

Answer 57

A ship with high superstructure aft or with a hole in the bow will lie head into wind when stopped. Making a downwind approach will give good control of the towing ship while the tow is being passed but has the disadvantage of putting her in an awkward position from which to get the tow under way because the two ships are likely to be on opposite headings. A tug, which is a handy vessel with the towing deck close to the bridge, will probably make a downwind approach to a ship lying head to wind. However, a cargo ship will usually find that crossing at right angles to the disabled ship’s heading is more suitable. An approach at a right angle makes it easier to get the tow under way and avoids the unfortunate predicament of the warship being held ‘in irons’ by the wind and the tow. When making this approach, the Master must be careful not to drift on to the bow of the disabled ship; once past, he must keep the stern close to her while keeping his ship at right angles to the wind. Under these circumstances, the towing party must handle the towing gear quickly as there will be little time to spare if the line throwing appliance misses.

Question 58

Turn short around in heavy seas?

Answer 58

a. Heave-to.
b. Achieve more comfort with less rolling.
c. Slow down for more positive ship control.
d. Inform all crew of what you are about to do.
e. Close all watertight doors.
f. Two steering motors on.
g. Man on the wheel.
h. Engineers on standby for quick engine response.
When heaving to, consideration must be given to the cargo securing arrangements, as violent rolling motions can overstress the lashing arrangements, resulting in the loss of cargo or containers overboard.
1. Look aft and study the wave pattern. Look for the larger sea. This will often be followed by a series of smaller waves. Attempt to establish a rough estimate of the time interval in seconds from one larger sea to the next larger sea in the series.
2. Square your ship’s stern to the seas. Wait for the larger sea to pass beneath your keel and past your bow. That way, you will be in a position just behind the larger sea to complete the manoeuvre. Start counting the time interval in seconds calculated earlier the moment the sea passes you. Keep a sharp lookout astern to make sure that the next larger sea has not formed earlier than expected. If it has, wait for it pass beneath you before you go to the next step.
3. Put the wheel hard a port for a right handed single screw propeller. Again, emphasis here will be to do this immediately after that larger sea in the series clears your keel and bow.
4. Increase to full ahead to get around fast. Get the ship’s bow pointed toward the seas before the next larger sea in the series arrives at your position. Count off the time interval estimated earlier. If done correctly the ship you swinging through the 90⁰ off course line in the trough between the two crests.
5. Point the bow a few degrees to one side of the oncoming seas. This will offer a better ride and less stress on the crew, hull and deck gear. Reduce speed to the absolute minimum to hold position. Speed causes damage, severe pitching, possible pounding and elevates the likelihood of crew injury and seasickness. Slow down to maintain maximum control.

Question 59

What to do when your ship encounters heavy weather?

Answer 59

As master it is your responsibility to avoid heavy weather. Make use of synoptic charts, weather forecasts and weather routing to determine the best course to avoid heavy weather.
Time is a critical factor for reacting in a situation like rough weather. If a pre-warning is available, then the crew can prepare for the worst; but if the warning period is short or if there is a sudden onset of heavy weather, then handling of the ship depends on you the master.
Steering control
a. change over to hand or manual control to avoid excessive hunting of the rudder.
b. check all the oil levels, linkages and other important parameters of the steering gear.
c. run both steering motors to get maximum available torque to turn the rudder.
d. Sufficient man power including senior officers to be present in the bridge.
Machinery control
a. If engine room is on UMS mode, man the engine room and make sure sufficient man power is available.
b. Monitor the main propulsion plant and auxiliary power plants.
c. all the spares in the engine room are to be stowed and lashed properly.
d. Reduce RPM to reduce propeller running away when it pitches clear of the sea.
e. Ensure correct sump level in all the engine room power plants to avoid false level alarms which could trip running machines.
f. Maintain high levels in all important tanks to avoid pump inlets loosing suction.
g. Stand by generator is to be kept on load until the bad weather situation stops.
h. Water tight doors in the machinery spaces to be closed.
i. Sky light and other opening to be closed.
j. All drip trays to be emptied to avoid spills in heavy weather.
Other common precautions
a. Crew not permitted to venture out on open deck in rough weather.
b. All the deck items such as mooring ropes, lashing equipments, drums etc. to be stored and lashed properly after their use.
c. All openings in the deck for cargo and other spaces to be kept shut.
d. All opening to the accommodation to be kept shut.
e. Shaft tunnel and other internal access space are to be used to go to steering room or other compartment.
f. All crew must be aware of his/her duties posted on the muster list.
g. Elevator to be switched off to avoid tripping and trapping person(s) inside.
h. Always wear all the PPE’s and use railings and other support while walking through any part of the ship to avoid trips and fall.
AND FINALLY
Go through the ISM procedure of the company regarding ship preparation for heavy weather.

Question 60

Is stopping a ship at sea the best option when minimizing the effects of heavy weather?

Answer 60

Stopping the main engine in heavy weather could result in violent rolling, pitching and heaving motions, causing unusual high stresses cargo securing equipment on deck.
This may result in the failure of the cargo securing equipment and the consequent loss of deck cargo overboard.
In heavy weather where it is unsafe for the ship’s crew to venture out on deck for purposes of checking deck cargo lashings, the master should consider heaving to, to permit the checking of deck cargo lashings.