Introduction
Historically it has always been the domain of the Master to conduct the handling and manoeuvring of the vessel and rarely will another officer become directly involved. This state of affairs has been the practice for many years and does nothing for the training of the budding Chief Officer seeking command who will be expected to become the most experienced man afloat overnight.
It is understandable for a Master to be reluctant to allow another to handle the vessel in close confined waters, but with more sea room junior officers should be encouraged to advance their knowledge and skills for the future. Various texts, including this one, can expand on the theory and virtues of ship handling practice, but there can be no substitute for the ‘hands on’ operation.
Figure 6.1 The Wellington Star berthed alongside. Forward moorings well spread and taut (four inshore headlines and a bight, one offshore headline plus two backsprings). Starboard anchor deployed and cable in the up and down position. Accommodation ladder landed from all aft superstructure
Factors affecting ship performance
The speed of a vessel can only be maintained if the hull form is retained in a condition to offer least resistance
to the motion. Such resistance can be increased by numerous factors including marine growth below the water line, modifications or damage to the hull, and corrosion being allowed to accelerate.
Periodic dry docking of the vessel allows overside maintenance to be carried out, permitting growth to be cleaned off and anti-fouling paint to be applied. At the same time similar activity can take place where corrosion is noticeable. Layers of rust tend to build up on the hull and touching up with paint can result in a mixture of proud areas and bare patches producing an uneven finish. Shot blasting or sand or high pressure water blasting techniques can clean large hull areas relatively quickly in the perimeter of a dry dock.
Damage to the hull, although not seemingly major, will also occur on a continuous basis while berthing. Small indents into the hull form will eventually produce an uneven surface and affect the water flow about the lines of the vessel. Additional resistance will result, causing reduced performance.
Not all water resisting factors are adverse and some are often deliberately incorporated in a trade-off for increased performance in other areas. An example of this could be where a propeller is retrofitted with ducting. Like the propeller this could increase the known ‘drag effect’ but the trade-off could be reduced cavitation and improved fuel/speed cost effectiveness.
Other modifications such as a bulbous bow are often incorporated to decrease the size of the bow wave and reduce the water resistance. However, it should be realized that the additional wet surface area of a bulbous bow will cause greater frictional forces to be present, the theory being that reduced wave resistance is more substantial than the increased frictional forces.
Some shipboard elements like bow thrust or stern thrust units, whether fitted at the building stage or added as a modification at a later date, are known to posi- tively increase water resistance. This becomes accept- able where greater manoeuvrability and cost-effective savings can be achieved by reducing the need for tugs in berthing operations.
Ship handling and manoeuvring aids 125
Ship trials and manoeuvring data
Prior to a shipowner accepting delivery of a new vessel the builders will be required to demonstrate the standard of the ship during performance trials. A Master taking over a new vessel could well be asked to join other observers from such organizations as underwriters, the Marine Coastguard Agency and/or representatives from the Classification Society to monitor and assess such trials.
Checks and tests
1. Tests on anchors and cables are usually carried out in shallow water and the length of time taken to bring the anchor ‘home’ is noted.
2. The windlass performance is monitored during (1) and the efficiency of the machine assessed. 3. Stopping distances under normal conditions are
assessed.
4. Stopping distances under emergency conditions are assessed.
5. Speed trials which could be timed runs over a given distance are carried out.
6. Turning circles at various speeds are conducted. 7. Routine helm movements are ordered and move-
ments checked against the helm indicator, the rudder and the rudder indicator.
8. Emergency steering gear arrangements are also tested to satisfaction.
9. Deceleration trials assess the time taken to stop the vessel from various speeds.
10. Emergency crash stop assessment from full ahead to full astern is checked. (Also checked at other speeds.)
11. All emergency shutdown systems are tested and checked for operation.
12. Navigational equipment is tested and assessed. 13. Fuel consumption for distance and speed compar-
isons is measured and usually monitored over a period of voyage time.
Results are recorded and charted and a copy normally remains on the bridge for direct access by the Master and ship’s officers.
Deck preparations for arrival/departure The most regular of shipboard activities occurs when arriving to berth alongside or to let go and take the vessel off the berth. This procedure has been carried out so many times one could be forgiven for assuming that it would never go wrong, even with experienced officers and men. Unfortunately, the operations do go awry very
often through complacency, forgetfulness or overlapping circumstances. The minor task of getting heaving lines out and ready could easily cause a delay and allow the wind to affect the vessel’s position. The proverb ‘for want of a nail the shoe was lost, for want of a shoe the horse was lost, for want of a horse the rider was lost’ comes to mind.
This is not to say that the Master of the vessel is expected to prepare heaving lines and dot all the i’s and cross all the t’s, but the Master should think ahead and brief his station officers in ample time to ensure that stations are called early enough to provide adequate preparation time at the mooring positions. Special mooring operations discussed beforehand can ensure a smooth and unambiguous operation, and may save the day.
Communications should be tested well in advance, and station officers should ensure that their areas of responsibility are fully operational. Any defects in equipment or problems in manning must be reported to the Master earlier rather than later, to allow remedial action to be taken or amendments made to the docking plan, e.g. engaging manual steering and testing astern motion on engines well in advance.
The control of external parties such as tugs, pilots, linesmen, mooring boats, etc. are often out of the con- trol of the Master and therefore due allowance and early booking through Port Authorities/company agents should be the order of the day. Confirmation of the same should be made at an appropriate time to ensure no unwanted, delays. If confirmation is made early enough and delays are expected, then the vessel’s speed could be adjusted and ETAs revised.
Docking and undocking operations will vary from berth to berth. Some quays will not be well fended while others may require slip wires, buoy moorings, or the use of anchors. Different ports have local practices and for the Master new to the area, it would be prudent to ascertain as many details as possible by consulting the sailing directions/charts, communicating with pilots or Port Authorities, or discussing with own ship’s officers with past experience.
All berthing activities are recorded in the Deck Log Book, and previous old log books could be a valuable source of information when a Master is docking in a port for the first time, or, of course, if the Master is newly appointed.
Checklist for arrival in port
1. Prepare an approach plan to include pilotage well in advance and consider use of the following: large- scale charts and port plans, sailing directions, tidal and current data, projected weather reports, and any available port information such as local by-laws.
126 The Command Companion of Seamanship Techniques
2. Conduct a thorough check on the planned tracks to ensure that the underkeel clearance is adequate throughout the passage. Draughts and trim should be accounted for, which may require adjustment of cargo or ballast, especially if operating speeds are likely to cause encumbrance through ‘squat’. 3. Sight and note any navigation warnings affecting
the area of operation and ensure all working charts are up to date.
4. Test steering gear and carry navigational equipment checks prior to entering enclosed waters. Engines should be tested in astern motion.
5. Open up communications in accordance with the local regulations and pass on ETA together with details of dangerous or hazardous cargoes/goods carried and/or passenger numbers, etc.
6. Order pilot, tugs, linesmen, mooring boat and any other relevant berthing requirements.
7. Confirm communication channels and report in to any VTS system in operation.
8. Establish pilot rendezvous and boarding arrange- ments, local weather detail, vessel’s heading and which side to create a ‘lee’ (assuming launch deliv- ery). Delivery of the pilot by helicopter would require separate preparations as per the ICS guide ‘Helicopter Operations at Sea’.
9. Engage manual steering and conduct operational checks on deck equipment, such as: windlass, anchors and cables, mooring winches and leads, mooring ropes and wires prepared, internal communications to fore and aft stations, signalling apparatus and deck lighting.
10. Warn crew departments in advance of standby, pilot boarding time, stations, berthing time and once Customs have cleared the vessel.
Clarify berthing details: use of anchors, gangway, shore connections, etc., as soon as practicable.
NB. Some vessels specifically equipped will need to ‘house fin stabilizers’ and retract recording logs in ample time, before entering narrow/shallow waters.
Mooring deck arrangement
Figure 6.2 shows the open fore deck of a passen- ger vehicle ferry. The figure clearly shows the centre line ‘bull ring’ with ‘international roller fairleads’ and ‘Panama leads’ set either side; split windlass with sep- arate power/control units for cable and gypsy arrange- ments, tension drums and warping drums attached; two additional tension winches positioned either side, aft of windlass positions; bitts (bollard sets) strategically sit- uated, to suit the lead positions; and the forward hatch leading to rope store.
Figure 6.2 Open fore deck of passenger/vehicle ferry
Ship handling: equipment and control
With the pace of new design and increased technology, ships are being fitted with more and more manoeuvring equipment. The bridge has tended to remain as the main control ‘conning’ position, but even this, on occasions, can be removed to a remote station. The modern bridge is now usually open plan and design has been generated by ergonomics and the specialist’s needs of the trade. Bridge wing controls to port and starboard are now in common use in addition to the main control consul (see Figure 6.3). They are usually inclusive of pitch angle controls for controllable pitch propellers, thruster controls, stabilizer control units, steering and auto helm unit (usually on the fore and aft line). Depending on the size of the ship and type of trade it is engaged in, certain vessels may be fitted with doppler radars, rate of turn indicators and other sensing/monitoring instrumentation. The modern vessel with the integrated bridge is designed to suit navigational needs as well as manoeu- vring requirements and communication units, navigation light sentinels, depth recorders, speed logs and the like, all of which are incorporated to meet operational needs. The move towards open plan has also moved the chart room into the bridge space providing the navigational Watch Officer with continuity for lookout duty as well as position monitoring and other similar watchkeeping duties.
Current ship building activity is meeting the needs of an increased cruise ship market and the fast, high speed ferry traffic. Bridges are being optimized with 360° all round viewing, a requirement which might be considered essential aboard a high speed craft moving in excess of 50–60 knots. Other building reflects the specialized operations market with increased numbers of offshore standby/supply vessels or diving support vessels employing dynamic positioning control systems.
Ship handling and manoeuvring aids 127
Figure 6.3 Enclosed bridge wing situated either side in an overside position and fitted with control consul to port and starboard. Main engine and thruster controls, fore and aft communications together with gyro repeater/bearing site vane are also visible
With all the changes taking place it is easy to forget the conventional ship, of which there are still a great number in operation. These vessels have been and con- tinue to be regular workhorses for deep sea trades and are usually without bridge control consuls, stabilizers or thruster units. The skill of the Master with only a right-hand fixed blade propeller, basic rudder assembly and a marine diesel engine is paramount in achieving berthing objectives, and ship handling in these circum- stances should in no way be seen as an easy option.
Modern rudders: manoeuvring
The need to improve efficiency when manoeuvring con- tinues to be an ongoing process and the application of the type of rudder assembly employed will define the eventual outcome of any ship movement. From around 1975 the Schilling rudder became a noticeable advance in improving the turning ability of a vessel. Earlier, the use of rudder flaps and power rotors had evolved and these subsequently combined to provide the tighter turn- ing circle.
Vectwin rudders (Schilling)
This system provides better course stability in com- parison to a conventional rudder construction. It was appealing because unlike other rudder assemblies, i.e. the ‘mariner rudder’, there were no moving parts under- water which lent itself to longer service and reliability (see Figure 6.4).
Vectwin rudders have been fitted with rotary vane steering units and can operate with a single fixed pitch
Figure 6.4 Arrangement of Vectwin rudders
propeller. The manufacturers claim the use of the sys- tem equals that of a controllable pitch propeller (CPP) when considering speed control. Savings could then be achieved by shipowners at the building stage by alterna- tively installing Vectwin rudders as opposed to the more expensive installation of a CPP.
From the point of view of a Watchkeeping Officer, a single joystick control would ensure easy manoeuvrabil- ity for the ship – the vessel responding to the direction in which the joystick is moved and the propulsive thrust being proportional to how far the joystick is moved from the hover position. Bridge instrumentation pro- vides visual feedback on rudder angles throughout any manoeuvre.
A powerful braking effect can also be achieved by this system and the amount of headreach a vessel would normally carry could be drastically reduced. It must also be anticipated that any lateral deviation of the vessel would be virtually eliminated when compared to, say, an engine put into an astern movement, as when taking all way off.
When the turning circle is considered, the rapid speed reduction caused by larger rudder angles of 65° or 70° results in lesser angles of heel than those incurred by a conventional rudder. Also, because speed is reduced,
128 The Command Companion of Seamanship Techniques
Figure 6.5 Typical rudder angles for basic manoeuvres ‘advance’ and ‘transfer’ are considerably less and the subsequent turning ability of the vessel is expected to be a lot tighter than a conventional ship (see Figure 6.5).
The Becker rudder
The Becker rudder is a two-part design, with a hinged flap connected to the main body of the rudder. When causing movement of the main rudder, the direction of the flap is altered by mechanical linkage to approxi- mately double the angle of deflection placed on the body of the main rudder (see Figure 6.6).
The Becker designs can be fully supported with a heel pintle bearing arrangement set into the ‘sole piece’ of the ship’s stern frame. Alternative designs include a semi- spade or a full-spade option, where the lower part of the rudder is left unsupported (see Figures 6.7 and 6.8).
Figure 6.9 shows the Becker, king support rudder. This type of rudder is secured to the hull by means of a rudder trunk with an inside bore to accept the rudder stock. The end part of the rudder trunk accommodates
Figure 6.6 The resultant combination of both rudder and flap produces a strongly curved ‘aerofoil’ section generating a lift increasing effect
an inside bearing for mounting the stock while an outer bearing supports the rudder blade.
An example of a Becker flap rudder can be seen in Figure 6.10. All the moving parts and those turn- ing against each other are manufactured in stainless chromium–nickel steel, or plastic (polyamide, nylon),
Ship handling and manoeuvring aids 129
Figure 6.7 Fully supported rudder
L
Figure 6.8 Semi-spade rudder
material. The use of such materials has distinct advan- tages in that no lubrication problems become appar- ent because all bearing points are in touch with water. The bearings are smooth in operation with a low fric- tional coefficient, while the ‘bushes’ have a high wearing resistance.
The bodywork of the rudders is welded steel sheet plate and they are manufactured to meet classification standards. In the event of damage occurring to the flap by way of the mechanical linkage failing or the flap is taken off, the rudder would still function as a conventional standard rudder but with diminished manoeuvrability.
Rudder response
In tests and in practice the Becker rudder reflected between 60 and 80 per cent higher transverse forces when compared with similar forces on a conventional
Figure 6.9 The Becker, king-support rudder
style rudder. A tighter flow was achieved at angles of up to 30°onto the low pressure side of the rudder which also provided a desirable underpressure effect. While at a larger 45°angle with the flap at 90°a generally superior turning effect was achieved in comparison with rudders of similar areas set at similar angles.
The drag effect of any rudder is notable, however, with the action of the flap at small angles of, say, 1° or 2° – the deflection is more immediate because of the double deflection which affects the ship’s ahead course more quickly, while at the same time not increasing the drag effect. Practically, because the Becker design only requires about half the rudder angle of a conventional design the drag effects are correspondingly reduced. This means that an improved speed can be realized by the vessel.
130 The Command Companion of Seamanship Techniques
Heel arm of the ship Heel pintle Future burnout for shaft removal Web
Main rudder blade Neck bearing Outer trunk Rudder trunk Rudder stock Turning axis of the rudder
Turning axis of the link system
Mechanical link system Flap Hinge Turning axis of the flap Rudder carrier bearing
Figure 6.10 Design of Becker flap rudder
A vessel fitted with the Becker rudder and a bow