Class 1 & 2 Oral Answers ( Part 5 )

Anchoring 

Preparation for anchoring: 

Appropriate personnel with helmet, goggles, torches to be sent forward. 

Both the anchors to be cleared away. 

Check the windlass is working properly. 

Anchor being used to be lowered to cockbill. 

Anchors to be used alternately. 

The brake is screwed and windlass is taken out of gear. 

Choice of anchorage Choosing the anchorage depends on various factors. 

Draft of the vessel. 

Depth of water. 

Nature of seabed. 

Any obstruction on the seabed. 

Tide, tidal stream, direction and rate. 

Shelter from heavy weather, sea, swell. 

Security of the vessel. 

Length of stay. 

Purpose of anchoring, eg, cargo operation, repair, transferring of persons. 

Traffic density. 

Distance from shore. 

Size of vessel. 

Loaded/ballast condition. 

Type of cargo.

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Class 1 & 2 Oral Answers ( Part 5 )

 Requirement of port.

Amount of cable to use The scope used depends on several factors: 

Nature of the holding ground. Stiff clay, rock, shells and stones are poor holding ground.Mud can be a good holding ground.Amount of swinging room available for the ship as the wind or stream changes direction.

 Degree of exposure to bad weather in the anchorage.

 Strength of wind or stream. As it increases, the ship moves stern. The cable is lifted from the bottom and it becomes long stay.

 Duration of stay at the anchorage.

 Type of anchor and cable.

 Length of mild steel cable may be taken approximately 25D (D is depth of water).

  

Anchoring in calm weather 

Approach at slow speed. 

Stop vessel by going astern. 

Let go anchor when the vessel looses headway. It can be determined by seeing the propeller was abeam.

 The engine is kept going dead slow astern as the anchor is let go.

 Engine is stopped immediately.

 Vessel drifts astern laying her cable.

 Engine is touched ahead when required scope is paid out, so vessel gets her cable gently.

 Anchoring may be done in slight headway, cable grows continuously astern. It may cause deterioration of the paintwork of the hull.

 Depth less than 20m

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Class 1 & 2 Oral Answers ( Part 5 )

 Cable is let go on the run.

 Allowed about double of the depth before checking it by brake.

 If anchor is snubbed as soon as it touches the bottom, it will be unable to grip.

  Depth over 20m 

The anchor is walked back to within 4-5m from sea bed. 

Let go from brake. 

It ensures anchor will not damage itself. 

Cable will not run rapidly as it becomes difficult to hold by brakes. Deep water over 60m 

Entire operation is done on winch. 

Gypsy should not be taken out of gear at all. 

Anchoring in wind 

Approach anchorage heading upwind. 

Ship is more easily controlled and will make little leeway. 

If wind cannot be brought ahead, the anchoring can be done usual way. 

In the case, engines to be used to reduce stress on the cable. 

Weather anchor to be used. 

 Anchoring in tide 

Stem the tide, even if wind is present. 

Lee anchor to be used if wind is present. 

Anchor on sternway (or headway). 

Helm to be used to control the heading. 

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Class 1 & 2 Oral Answers ( Part 5 )

If stream cannot be stemmed, cable to be laid out slackly across the axis of the stream.

 Floating objects overside may be used to determine whether the ship has headway.

 

Definitions Walk back: Lower the anchor under power. Long stay:Cable is taut and leading down to the water close to the horizontal. Scope:  Scope of the cable is the ratio of the amount of the cable outside the hawse pipe to the depth of the wter. Nipped cable:The cable is nipped when an obstruction, such as the stem or hawse pipe lip, causes it to change direction sharply. Render cable:The cable is rendered when the brake is applied slackly. The weight comes on the cable and it is able to run out slowly. 

Cockbill:Anchor is lowered clear of the hawse pipe and hanging vertically

Procedures for anchoring  

Order anchor party for anchor station. Prepare the anchors. 

Choose an appropriate anchorage. 

Check the nature of the bottom. 

Check the depth. 

Determine scope. 

Determine the wind direction and force. 

Determine tidal stream, rate and direction.

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Class 1 & 2 Oral Answers ( Part 5 )

 Head to wind if no tide.

 Stem tide.

 Follow the anchoring procedure.

   

Mooring on a single buoyKeep wind on one bow.Buoy on the other beam, almost one ship length.The vessel is drifted downwind.Occasional and weather helm is used to keep the vessel in correct attitude.A headline is run away to leeward well before the vessel reached the buoy (2).Vessel swung head to wind on this line.

 

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Class 1 & 2 Oral Answers ( Part 5 )

 

VARIOUS MOORINGSOpen moor 

Vessel anchored with both anchors leading ahead.Both the anchors remain 1point on the bow.

 

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Class 1 & 2 Oral Answers ( Part 5 )

Procedures 

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.Both the anchors are veered.Finally the anchors are one point at each bow.

 

Standing moor, ordinary moor, dropping moor, straight moor

Vessel required to moor with bridge along the dotted line.Stream ahead.Port anchor-5 shackles, stbd anchor-4 shackles.

 Procedure:

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Class 1 & 2 Oral Answers ( Part 5 )

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 plus 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 by 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.

 

 

Running moor, flying moor

Vessel required to moor with bridge along the dotted line.Stream ahead.Port anchor-5 shackles, starboard anchor-4 shackles.

Procedure:

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 (1).The cable is rendered as the vessel moves upstream.

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Class 1 & 2 Oral Answers ( Part 5 )

The cable is not allowed to be tighten, as bow will cant to starboard.The cable is rendered or veered 9 shackles and vessel moves to position-2.In position-2, port anchor is let go.The vessel moves stern.Five shackles weighed on lee (starboard) cable and five shackles veered on riding cable.The vessel is then brought up on her riding cable at position-3.

 

Advantages of mooring

Vessel occupies little swinging room.Vessel turns almost to her length about stem.Scopes can be pre-adjusted for the prevailing strength of wind or stream.Scope of each cable is estimated in the same way as single anchor.

Disadvantages

Lee anchor has no value to ship if headwind increases or vessel drags.Risk of getting a foul hawse.

Special precautions

Maintain a constant watch to prevent foul hawse.Determine foul arc and clear arc.Vessel should always swing to clear arc on each tidal change.

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Class 1 & 2 Oral Answers ( Part 5 )

Use engine to give vessel correct sheer.Keep eye on the weather.Know the times of tide change.

Preference:

I will prefer standing moor. Because:

SaferMore control on the ship.The anchor is let go after vessel stopped.There is no possibility of damage due to anchoring at headway.

 Baltic moor

Employed alongside a quay.Used when construction of the berth is no sufficiently strong enough to withstand ranging in bad weather.Can be employed for berthing a vessel in an onshore gale wind.

Procedures:

For a average size merchant ship, a 25-30mm wire is passed from the after ends on the poop, along the offshore side, outside and clear of everything.Offshore anchor is cockbilled.A man is send overside on a chair to secure the wire with the anchor, preferably at the shackle.The aft end of the wire is sent to a wrapping barrel, ready for heaving slack wire.

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Class 1 & 2 Oral Answers ( Part 5 )

When the stem is abreast the position of the quay where the bridge will be positioned, the anchor is let go.The vessel is still on headway.About half a ship's length of the cable, the cable is surged and then snubbed.The wire is hove-in aft.The onshore wind will drift the vessel to the berth.The scope of the cable and the wire is adjusted and veered slowly until the ship is alongside.Distance of ship, length of cable and wire must be considered.

 

Mediterranean moor

Method of securing a vessel stern to the berth.Both the anchors leading ahead to hold the bow in position.The approach should preferably be made with the berth on port side.The starboard anchor is let go about two ships length from the berth(1).The vessel continues to move ahead.Starboard helm is applied and the cable is veered.The engines are then put astern and the port anchor is let go (2).As the vessel comes astern, transverse thrust swings the stern to port towards the berth.Stern lines are sent away.

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Class 1 & 2 Oral Answers ( Part 5 )

Berthing port side with strong off-shore wind

Approach at a broad angle.Weather helm to hold the bow upwind.Head for the stern of the berth.Engine reversed when vessel's bow near stern of the berth (2).The swing created and lee drift increased.Head lines with messenger passed when bow is close in.A stern line is also passed when stern is close to berth.Lines are hove-in when the vessel is parallel to berth.An offshore anchor may be used. It is let go when the ship has bodily drifted from the berth (3).

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Class 1 & 2 Oral Answers ( Part 5 )

Berthing on port side - calm weatherVessel is headed  at an small angle (about 1½ points) with the quay.Approach at slow speed with steady head.The engines are stopped and worked stern when near the berth (1).Head way is checked by stern movement.Headline is passed when near to berth.As the engine is reversed, a swing to starboard is developed.The swing is checked by headline.

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Class 1 & 2 Oral Answers ( Part 5 )

SHALLOW WATER EFFECT

Shallow water:

When the depth of water is less comparing to the draft of the ship. The hydrodynamic forces affect the ship handlings in different ways. The effects become evident when the depth of water is less than 1.5 times of the draft of the ship.

In shallow waters, following effects may be evident:

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Class 1 & 2 Oral Answers ( Part 5 )

Sluggish movementVibrationErratic steering, slow response.Smelling the groundSquatBow cushion and bank suction effectCanal effect

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.

 Vibration:

In shallow water vibrations set up.It becomes very difficult to correct a yaw or sheer with any degree of rapidity.

 Steering:

Steering becomes erratic.Rate of turning is reduced.Turning circle becomes larger.Loss of speed due to turning is less in shallow water.

 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.

 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.

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Class 1 & 2 Oral Answers ( Part 5 )

This effect is called squat.

Factors governing squat:

Squat varies on the following factors:

Ship's speed: Squat is directly proportional to the square of speed.

Squat   V2    (V=speed in knots)

Block co-efficient: Squat directly varies with CB.

            Squat    CB

Blockage factor (S): It is the ratio between cross section of the vessel and cross section of the canal or river. Squat varies with blockage factor as.

Squat   S0.81

So, in confined water, squat is more than in open water.

Squat may be calculated by the following simplified formulae:

Squat =  (CB X V2 ) / 100              (In open waters)

Squat =  2 X (CB X V2 ) / 100        (In confined waters) 

Precaution

Squat may cause grounding in spite of enough UKC.Squat to be calculated beforehand.Speed to be reduced to reduce squat.While determining UKC, squat for the speed to be taken into consideration.

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.

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Class 1 & 2 Oral Answers ( Part 5 )

Canal effect:

Water level drops towards a bank.Vessel heels towards bank to displace constant volume.Varies as the square of speed.Corrective helm to be applied.

Clearing a foul hawse  

Preparation: 

Gears necessary should be made ready at slack water.Gears will include 20-25mm slack wires, a smaller wire about 10mm or fiber rope, a boatswain's chair, equipments for breaking joining shackles.Operation to be started as soon as ship swung to new stream.

 

Procedure: 

Turns are hove above the water line.

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Class 1 & 2 Oral Answers ( Part 5 )

Cable below turn lashed together.Sleeping cable is unshackled on the deck.A preventer may be used to prevent sudden loss of the parted cable and stress.A wire messenger then passed down through the hawse pipe, dipped around the riding cable, and returned to the forecastle deck.One inboard end of the wire is secured to the joining shackles, other end to the wrapping drum.Easing wire may surge on the bitts. It can be led to a wrapping barrel or may be veered under power.The messenger is hove and the easing wire is eased.When one turn is cleared, the weight taken off the stoppers.The wire is then cast off. The procedures are repeated until the cable is cleared.Later, the joining shackle is joined, preventer cast off and fiber lashing burned through.

 

  

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