Manoeuvring is an operation during which a vessel enters or exits coastal waters of a country, crosses several ships on the way, and proceeds towards or departs from a berth or jetty of a port.

A ship may need to manoeuvre not only while arriving or departing a port but also while crossing canals and traffic zones. In this process, maximum number of man power is made available and all unmanned systems are change over to manual control so that full control of the ship is achieved.

Most of the collisions and grounding of ships are reported during manoeuvring of the vessels, and hence the manoeuvring operation is considered most crucial time a ship faces in her voyage, both from ship’s and seafarer’s perspective .

When entering or departing a port, a marine pilot, ship pilot, or maritime pilot is called on the ship, who manoeuvre the ship from a point of entry, known as the pilot point, up to the berth or vice versa.

Manoeuvering procedure

It is essential before starting any manoeuvre, to understand the effects of the wind, tide, state of the ship’s trim, draft and freeboard, the ship’s equipment and manoeuvring aides etc. along with the assistance received from tugs.

The master makes an assessment of the ship’s elements and situation and then devises a plan of action.

The plan of action needs to be flexible and the master should also have alternate plans in mind in anticipation of any change in the circumstances as the manoeuvre proceeds.

The pilot of the ship makes an effective contribution towards safe navigation in confined waters and the approaching port, of which, they have an up to date local knowledge.

It is very important to note that the responsibility for any vessel’s navigation cannot be transferred to the pilot. The master and the officer of the watch shall always remain responsible with regard to navigation duties and obligation.

The information exchanged between the master and the pilot shall include but not be limited to:

• Minimum water depth

• Tide

• Current

• General condition of the berth

• Use of tug boats during mooring

• Mooring arrangement (including length of lines, certified bollard strength,

• Use of anchors, thrusters and/or tug boats in case of surge or swell)

• Any special circumstances, which may be experienced.

• The pilot should indicate his intended passage plan, enabling the Master to fully utilise the pilot’s expertise.

Turning the ship

The master when planning his manoeuvre takes into consideration the above facts and also the effect the wind’s force and direction has on our ship, relative to its trim, draft, and speed, along with the factors governing the centre of turn and the positions for securing the tug and how they can be used in the most effective way.

The centre of turn of a ship is the pivotal point, around which, the ship will rotate as a result of a turning force.

Tugs

The situations as the berth approaches are various and depends on a lot of factors such as the under keel clearance, weather, wind, current, tide, available berth length and the distances to the vessel’s forward and aft from the berth, size of the harbour basin etc.

Based on these factors the manoeuvres and combination of tugs’ usage can be made. Even after a lot of planning and years of experience at sea, one can experience new and dangerous situations.

The situation described below is just a basic approach while berthing.

The most common position for securing the tugs, if we have two tugs is, the centre lead forward and aft. This way the tugs can control both the lateral and forward, and the aft movement by either pulling and/or pushing as required.

If there is only one tug that we are going to use then it is usually secured aft. Also most of the times we use the forward tug for pushing only, hence it is not secured to ship at all.

Berthing the ship

As the master closes the berth, he does not try to bring the ship directly alongside the berth, but plans to bring the ship parallel to the berth and stop just short of the berthing position, clear of the forward and aft ships (if there are any). It is normally one ship’s breadth distance between the ship and the berth.

Once the vessel is all stopped off the berth, the master uses the assistance of the tugs and thrusters to get the vessel in position. He asks the officers in charge of the mooring stations forward and aft to send the spring lines first (most commonly used).

The spring lines keep the vessel from moving forward and aft. The headlines/sternlines are then send. Once all the lines are made fast, all the winches are usually put to 40% auto tension (most common) and the springs are kept on brake.

If the configuration of the berth is such that long ropes cannot be used, it should be considered to change the configuration onboard the vessel i.e. use the `spring lines´ as `headlines´ and vice-versa.

When closing a berth, the master monitors the ship’s movement and the distance to the pier, and to other moored ships.

Ships are fitted with various instruments such as the conning display, Voyage management system etc. to indicate whether the ship is moving ahead or astern. The ship’s speed and the amount of set and drift is indicated as the ship makes sideways.

These are all excellent aids, but a visual assessment of the relative movements of objects ashore when berthing the ship will give the master a far quicker and more accurate indication of the direction and speed the ship is making over the ground.

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Tugs are commonly used at sea for berthing and unberthing ships. A number of methods are used for manoeuvre a ship. 

Let’s examine the most common manoeuvres involving tugs and discuss their usage.

1. Swinging the ship

In the above picture, we can see that vessel is being swung bow to the port using two tugs, the starboard tug is pushing at the starboard bow and after tug is pushing on the port quarter. Both the tugs are pushing at their respective locations assisting in swinging the ship.

Here is a close-up view of same manoeuvre resulting in anti-clock or counter clock swing.

Now in the above picture, we can see three tugs being used for assistance. Forward tug is pushing on the port bow, aft tug on the port quarter is pulling and aft tug on starboard quarter is pushing. This will enable the ship to complete a swing with a bow to starboard or a clockwise swing.

Related Reading:

Infographic: 6 Golden rules of safe berthing

2. Berthing manoeuvre

In the above picture, we can see the vessel is just off the berth and the tugs are pushing the ship onto the berth. Tugs are made fast so that when needed they can break the momentum to avoid making hard contact with the jetty. Once smoothly alongside tugs will keep on pushing till the vessel is made fast.

Both forward and after tugs need to be constantly controlled to keep the vessel absolutely parallel to the jetty.

Related Reading:

6 Common Mooring Methods Used For Ships

3. Unberthing the ship

Two tugs are used to pull the ship off the berth in the above photo. For an unberthing, challenge will again be to pull the vessel nearly parallel to the berth to avoid either end from making contact with the jetty.

Once the ship is safely clear from the berth, preparation for swinging can be made.

Related Reading:

Parallel Indexing Techniques For Ship Navigation

4. Single Tug Manoeuvres

For ships fitted with a Becker rudder and controllable pitch propeller (CPP) it will be impractical to use two tugs. In such cases, the vessel can either manoeuvre without tugs altogether or will use one tug if needed.

In the above photo, spring line will be taken ashore on the mooring boat. Once ashore, this line will prevent the bow from swinging out and also the vessel will not creep ahead. At the same time, the engine movement combined with rudder will be used to get the stern alongside. The tug can be used to break the momentum if needed, as it is made fast. The tug can also be used to keep the vessel in position once alongside by pushing.

Similarly with a bow thruster of sufficient power, depending on the ship size and manoeuvrability, one tug aft can be sufficient for berthing and unberthing.

Related Reading:

How Is Bow Thrusters Used For Maneuvering A Ship?

5. Other Uses

In river ports, tugs are made fast at centre leads fore and aft to enable controlling of ship’s bow and stern while turning at tight bends where helm and engine alone will leave the ship vulnerable.

When coming alongside, tug may have to be cast off from centre lead and made fast on shoulder (forward) and quarter. This is done to help keep the ship parallel to berth and to avoid trouble with passing of mooring lines.

At busy anchorages, generally inside the harbour area, tugs can also be used for assisting commonly when both anchors are dropped to ensure that the ship’s heading remains unchanged.

Related Using:

How A Ship Is Berthed Using An Anchor?

6. How to decide on number of tugs

Foremost consideration will be port regulations, In most of the ports, these are based on gross tonnage (GT) of a vessel being handled, while in other ports more weightage is given to length overall (LOA) of the ship for determining the number of tugs to be employed.

Most important factor, however, is the prevailing weather conditions. Both the wind and current factor need to be taken into account. For accurately knowing the effect of these forces, ship’s wind force area and underwater areas are calculated both forward/aft as well as laterally.

It is also necessary to know the direction and angle, from which, these forces will be acting on the ship’s hull.

It will be beyond the scope of this article to discuss the actual complex formulae applied and calculations involved which go to the extent of obtaining the density of air for accurate results of resultant acting forces.

Other important factors to take into account will include available under keel clearance and GM.

Bollard pull and type of tugs also factor during decision-making.

Related Reading:

What makes a ship unstable?

Understanding intact stability of ships

7. Other considerations and contingencies

In most container terminals, ships are berthed within one bollard length of each other and metal-to-metal clearance of 15-20 metres. In some tight cases, it may be down to even 10 meters. In these situations short engine kicks or adjustment of propeller pitch will help in maintaining required clearance.

But a lot of at times in busy ports, vessel ahead and astern may be berthing and/or unberthing at the same time and will have lines in the water close to ship’s propeller and thruster; then these cannot be used due to risk of fouling.

There have been cases where ships own lines have fouled the propeller and thruster.

To avoid such situation tugs are a must for safe operations.

If using only one tug, either forward or aft, the tug can check ship’s momentum in only one direction by pulling in opposite direction. This must be taken into account when planning manoeuvres with single-tug.

In some ports, it’s very common that the terminal will not be able to complete cargo operations of the previous vessel at the stipulated time and a ship, having reached, will have to hold position off the berth for several hours while waiting for the berth to be available.

At times, the ship will reach the berth and tugs will not reach on time, as they would not be free from their previous manoeuvre!

Related Reading:

Mediterranean mooring of ships

8. Final word

The most important requirement for safe mooring operations is a good Master Pilot exchange (MPX).

Tug’s bollard pull and strength of ship’s mooring bitts must be discussed to decide how much tug power can be safely used without endangering ship/tug and crew.

For berthing and unberthing, docking pilot will have the best knowledge of local conditions. She will know the limitations of tugs being used, the competence of tug crew, swinging room available, required angle and distance of towing line to best complete the manoeuvre.

Similarly, the master knows the ship and her handling characteristics and must share these details including any limitations or strange handling characteristics.

One thing to watch out for is that in almost every country pilot and tug will be communicating in the local language. Though a master should be aware of planned manoeuvres and anticipate tug actions.

But if needed, clarification must be requested and pilots world over are happy to oblige by repeating instructions if they speak English. If encountering language difficulties manoeuvre can be drawn and discussed during MPX.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

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“Crash” word is generally used to describe some kind of accident or damage when one object slams into another. However, in the shipping world, when the word is combined with the term “manoeuvring”; it becomes a procedure which is performed to avoid any kind of collision or accident.

Why Crash Manoeuvring?

In a sea going vessel, unlike land transport, there are no brakes that are provided to stop the ship when needed. The stopping of the vessel is done by reversing the rotational direction of the Main engine and thereby the propeller. This stops or reduces the speed of the vessel heading towards the collision course.

The crash manoeuvring is usually done to avoid any type of collision or crashing of ship to any other ship or structure (Jetty, land, Iceberg etc). In this type of manoeuvring the main engine is subjected to severe stress and loading, but the safety of ship and life is assured.

How to Perform Crash Manoeuvring?

Crash manoeuvring is turning the engine in opposite direction to reduce the heading speed of the ship. After certain time, the ship stops and starts streaming in astern direction. This is done by supplying starting air at about 30 bars from the air receiver to the engine. The stopping air is known as the brake air.

The brake air when sudden injected inside the engine cylinder, will try to resist the motion of the piston and the rotation of the crankshaft and propeller.

Procedure

Following Procedure is to be followed when a navigational officer calls engine room and says that we have to stop immediately to avoid collision

• When there is an emergency like collision, grounding etc. the controls are transferred immediately in to the Engine room controls

• The bridge will give astern direction in the telegraph, acknowledge the same

• When the telegraph is acknowledged only the starting air cam will reverse its direction but the fuel cam will remain in its running position due to running direction interlock since engine is still running in the ahead direction

• The fuel lever in the engine control room is brought to ‘0’

• As soon as the RPM of the engine drops below 40 % of the Maximum Continuous Rating or MCR rpm of the engine, give break air few times in short time frame

• The break air will inject with astern timing setting inside the ahead moving piston which will resist the piston motion

• Since fuel will not inject until running direction interlock opens, as soon as the rpm drops near to Zero, give fuel and air kick by bringing fuel lever to minimum start setting

• When carrying out Crash Manoeuvring, some safeties need to be bypassed to avoid tripping of engine in mid of emergency

• When the ship stops and situation is under control, a detailed Main engine inspection is to be carried out when there is a chance. 

You may also like to read-What are the Essential Requirements for Unattended Machinery Space ?

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Main marine engine is responsible for propulsion of the ship and its direction and rotation are controlled from either bridge or Engine Control Room (ECR) through telegraph and fuel lever control. This control system is a remote control type used for both sea voyage and manoeuvring of vessel.

If the remote control manoeuvring system fails to operate from both the remote stations, i.e. bridge and ECR, or the governor of the main marine engine goes faulty, additional safety is given to main marine engine by providing a local manoeuvring control system.

When the ship is in a narrow channel under manoeuvring, then it is very important for all engine room crew to know the change over and operating procedure for local or emergency control. Failure in knowing the remote control manoeuvring system, can lead to accident like collision and grounding.

Procedure for Local or Emergency Manoeuvring

The changeover and operating procedure differs from engine to engine as different control systems are adopted for different engine types; however the basic remains the same. When there is automation or remote control failure alarm then changeover of control is to be done from remote (either wheelhouse or ECR) to Local control stand.

The local control stand is normally located in the engine room near the fuel pump platform of the main marine engine.

Changeover Procedure

• The change over procedure can be done with marine engine in stopped as well as running condition, but if the situation permits it is better to be done when the engine is stopped.

• First change control from wheel house to ECR and both the telegraph on wheel house and ECR are to be in stopped position.

• Bring the fuel lever of wheel house and ECR in stop position.

• A changeover switch is provided in the ECR. Operate the switch from –“ECR to Local”.

• Go to the local control station and changeover the fuel pump control shaft from local to manual.

• A cone clutch arrangement or a mechanical lever arrangement may be provided, depending upon the engine type, which acts as manual control when attached to hand wheel for operating fuel rack.

• A locking pin or clip may be provided for the above arrangement as an additional safety so that it should not come out in normal operation.

Operating procedure

• After the fuel rack is attached to the manual hand wheel control, wait for the wheel house order.

• Respond to the telegraph and give fuel and air to the engine via local control levers.

• If the engine fails to start, give extra amount of fuel and air as now it is controlled manually and the linkage requires more push for the fuel supply.

• Once the marine engine starts, follow the telegraph and maintain the speed from local fuel lever.

Checks and Maintenance

• The remote control failure alarm is to be checked regularly.

• Local telephone and communication system are also to be checked and maintained.

• Local Telegraph bell and indication light are to be checked and maintained.

• All the linkages to be oiled and greased at regular interval of time.

• The safety clips or pins in the cone clutch or any other type of arrangement is to be checked.

• Emergency manoeuvring drills should to be conducted every month.

You may also like to read-Types of Lifeboat Release Mechanisms & SOLAS Requirements

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In the previous article, we had an overview of the different types of manoeuvres undertaken by a ship, along with their necessary trials done post-launch. We also learnt about Turning Circle; however, is knowing the turning ability of the ship in response to control sufficient to guarantee the entire manoeuvring ability of the ship?

To answer this question, we will discuss the remaining types of manoeuvres, their necessary check-trials and purpose. 

Types of Ship Manoeuvres:

Zigzag Manoeuvre

This type of manoeuvre is also known as the Z-Manoeuvre or the Kempf Manoeuvre. In some situations, a ship is required to change its course or heading. Sometimes in rough seas or in cases of directional errors, the ship may be required to change its direction more rapidly within a limited span of time. So, the ability to zigzag manoeuvre should be an inherent property in the manoeuvring characteristics of a vessel. The trial for this is conducted as follows:

• The ship is steadied on a straight line course in the sea conditions described in the previous article
• Then the rudder angle is applied to a pre-defined angle of 10 degrees or 20 degrees to either port or starboard. This is termed as the ‘First Execute’
• In response to the rudder, the ship changes its yaw motion towards the applied rudder angle and gradually changes its heading
• After a certain defined angle of heading is reached (not to be confused with the rudder angle as the heading angle is purely the angle between the ship’s own centreline and the reference space coordinates of the earth; a measure of the ship’s course), the rudder angle is immediately reversed to the exactly opposite value. If the first execute rudder angle had been to port, it is reverted to starboard and vice-versa
• Consequently, the ship’s yaw rate begins to change towards the applied direction. The ship begins to change its heading once again
• Again when it approaches the steady approach in that direction, the rudder is swung in the opposite direction
• The cycle is iterated for a definite number of times

What are the results inferred from the above test? The main objective of conducting this trial is to check that the ship response in changing its course in effect to a given rudder angle along with the variation in Yaw rate. It is also a measure of the path stability of a ship, the more it takes time and effort to change its heading, it is said to be ‘stable by path’. Vice-versa is path changing-ability. The requirements differ from one vessel to another. In naval vessels, there may be a need of greater path-changing ability whereas, for a cargo carrier, it may be the opposite.

Some Important Terms Determined during the test:

• Initial Turning Time: the time taken to change course or heading in response to rudder execute. Time taken to change yaw in a particular direction
• Overshoot angle: This is a very crucial parameter determined using this test. Overshoot angle is defined as the excess angle of heading reached by ship in its previous direction (after rudder is applied). Most designs seek least overshoot angle as it is desirable for better controllability
• Yaw rate/turning speed in the changed direction.
• Reach: The time between the first execute to when the heading angle is zero.

Based on the permissible values of rudder angle, zigzag test can be of two types:

• 10 degree zigzag manoeuvre
• 20 degree zigzag manoeuvre

Let us now analytically delve a bit further into the analysis of zigzag manoeuvre. (Figure 2)

First, the rudder angle is applied to starboard (at 10 degrees). This alters the ship’s heading angle to starboard gradually. After a certain span of time, the rudder angle is reversed. In effect to this change, the ship’s heading angle again starts reverting to port.

This is a point where the overshoot is measured from the curve. In all practical cases, the ship does not have the ability to immediately revert to port after rudder is applied. It yields to some heading angle in its ‘set direction’ after gradually yawing to port. This excess the angle of heading it attains before reverting again is a measure of the Overshoot angle.

The peak of the curve that is where the heading changes its “tendency” in response to the rudder angle. On similar lines, going through the time axis, the time taken to change its heading at each course in response to rudder action is also a measure of the manoeuvring efficiency of the ship. This is given as the ‘Time taken to check Yaw’. After crossing the zero line, it approaches towards the negative heading angle (to port, in this case).

Again after some time, the rudder is reversed to starboard. The ship reverts to starboard again after undergoing a certain overshoot.

Spiral Manoeuvre

This is a measure of the directional stability of the vessel. Imagine a situation where your vessel drifts off the course without any indication and when it is detected, the change in direction is already very large. This condition is not appropriate for navigational wellness.

Consider another situation where the vessel is required to swerve past some obstruction. The rudder angle is applied in the necessary direction to avoid a collision but for some time the vessel continues to go in that direction before changing the rate of heading. But it is already too late and the unwanted occurs. No one would prefer to face that situation, would they? So, the efficiency of the ship in terms of its directional stability is measured by its ability to change its direction in immediate response to its rudder action.

The spiral manoeuvre also known as Dieudonne spiral is conducted for this purpose. This test is somewhat similarly done as zigzag but the rudder deflection angles are constantly varied from port to starboard (+15, +10, +5,0,-5,-10,-15, for example).

The spiral manoeuvre trial is conducted as follows:

• The ship is steadied on a straight line course
• After that, the rudder is put hard over to one side until the rate of change of heading is constant (Constant Yaw rate)
• The ship is steadied for this new rate of heading. Then it is again given a rudder deflection to a higher value, say 10 degrees.
• The process is repeated for successive values of rudder angle till the rudder has covered the whole range to maximum rudder angle on the given side
• The entire process is conducted in the reverse direction, that is if the rudder turns are given for successive values on the starboard side (+5, +10, +15….) , it now given to the opposite direction to the port side ( -5, -10, -15….) to give a counter clock path
• The path observed, in either case, is a spiral as shown in the figure
• The rate of turn or yaw is noted for each rudder angle
• The yaw rate is plotted against rudder deflection angle for analysis

The above figure shows the rudder angle versus the rate of change of heading. In figure 5(a), the values are plotted for a perfectly directional-stable ship. Applying a rudder deflection to starboard yields a heading in that direction. So the yaw rate (rate of change of angular heading), “r” varies proportionally to the rudder deflection in the same direction. When the rudder angle is brought back to its mean position (zero deflection), the angle of heading also gets back to zero along with the yaw rate. Hence, the ship does not have any ‘residual heading’ in that direction and is considered perfectly stable. Similarly, again turning the rudder to port gives a proportionate increase of yaw rate to port. The curve passes through the origin.

But rarely do we find such ideal results. Environmental factors such as sea states, currents, waves along with the interplay of rudder response, engine performance and other hydrodynamic factors lead to instability as shown in figure 5(b). Here, even when the rudder angle is brought back to zero in either case of port or starboard the rate of heading angle remains non-zero. That is, in response to rudder angle change there is a ‘directional set’. This is indicated by the dotted lines. When the rudder is brought back to zero after the starboard turn, the rate of change of heading remains to some starboard value and then gradually starts reverting to port. Similarly, it is true in the opposite case. Thus the curve plotted (yaw rate vs rudder angle) in both clockwise and counterclockwise turn gives a kind of hysteresis loop. None of the yaw rates from any sense is zero for an immediate response to the rudder. This hysteresis loop is a measure of the ‘directional instability’ of the vessel.

This test should be essentially performed for yaw unstable ships going from port to starboard and from starboard to port. However, some of the big limitations of performing this tests are congenial sea states and a large expanse of water. Also, it is very time-consuming.

Reverse Spiral

As an alternative to spiral manoeuvres, reverse spiral tests were introduced by Bech. This is very much similar to direct spiral manoeuvre with one basic change. The ship is now strictly made to turn at a constant rate of turn (yaw rate). This is achieved by manipulating the rudder accordingly. Thus this is exactly the opposite of what was done in direct spiral manoeuvre (where the yaw rate was variant for a particular rudder deflection)!

This is conducted for a range of yaw rates from +0.5 degrees per second rate to starboard to -0.5 degrees per second to port. This is plotted against the rudder deflection as shown in the following figure.

The slope of the curve at the origin gives a measure of the degree of directional stability. In figure 6(a), the slope at the origin (r-δ at δ=0) is negative, hence the ship is said to be directionally stable.

On the contrary in figure 6(b), a kind of hysteresis is formed in the form of an S-shape similar to direct spiral (except it is an open loop in this case). The slope of the tangent at the origin is positive and the ship is said to be directionally unstable.

The aspect of rudder deflection versus yaw rate, in this case, is somewhat analogous to the righting lever (GZ) versus heel angle (φ) in the case of static transverse stability problem.

Pull-Out Test

This test is a relatively simpler to determine the stability of the ship on a straight course.

The steps taken to conduct this trial are:

• The ship is made to turn in both port and starboard directions for sometime.
• After a steady rate of yaw in the particular direction is achieved, the rudder is brought back to its mean position.
• The rate of turn exhibited over the entire span of time is recorded for both port and starboard turn.
• The nature of the rate of turn is characterised by plotting against time.

Theoretically, for ideal conditions the rate of heading must revert back to zero after the rudder is brought back to zero. But practically, this is rarely the case as there is always some nonzero value of heading in either direction (port or starboard). However, as long as this is similar in both directions, it is still considered stable. But if it is different in both port and starboard, it is unstable. In most of the ships, there is always this ‘residual rate’ of heading due to the asymmetry of flow across the hull and sometimes due to propeller influence (in the case of single screw ships).

Stopping Ability

Accelerations, stopping and backing are not part of manoeuvring exercises but they are still carried out in tandem with the above manoeuvres to check the safe stopping distance and motion efficiency of the vessel. Imagine a critical situation where there is an obstruction ahead at a limited distance and the ship is required to stop or reduce its speed.

Thus stopping trials such as “Crash Stop” are crucial for estimating the performance of the vessel under this kind of circumstances.

Stopping ability is measured by the “track reach” and “head reach” realised in a stop engine-full astern manoeuvre performed after a steady approach at the test speed until ahead speed in ship coordinates changes sign (i.e., vessel starts going backwards).

• Track Reach is defined as the distance traversed by the ship in its own path after the “astern command” is given (engine reversed) until the vessel starts heading backwards.
• Head Reach is the perpendicular distance (displacement) that is measured from the point of execute (reverse order given) to the point where the ship starts coming backwards (after stopping).

Both Head Reach and Track Reach along with the time taken to achieve so are of paramount concerns to the ship designer, the engine maker, as well as to the seafarer. Most safe designs tend to achieve the least distance and time required to decelerate and stop. However, propeller performance, sea conditions, displacement of the vessel and efficient control hierarchy on board are some of the other indispensable factors.

Motion and Control of a vessel along with their trials play a pivotal role in the design and also in the post-launch stage as we had already said earlier. IMO has its own criterion while performing each of the above trials which we leave it you to find out of interest. Modern techniques of model tests, Computational Fluid Dynamics (CFD) or Boundary Element Methods (BEM) aided by software have eased manoeuvring and seakeeping analysis to a great extent. Nevertheless, these full-scale trials still are considered the most holistic approaches and are continued to be carried out for each and every vessel.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

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