Pratical Ship HandlingEffects on vessels Manoeuvring capabilitiesTurning CirclesStopping Distances

The Ship DeadweightThe Larger the ship:Greater inertia A 50,000t ship does not require twice the power to attain the same speed of a 25,000t vesselBut larger ship will be more difficult to stop

Draught & TrimShallow water effects turning abilityEffective depth of water less than twice the draftie UKC less than draftHigh speeds can influence this rule of thumb

Draught and TrimLoaded 12 m draftUKC 3mStarboard TurnList 3 degreesRudder force less effective

Speed and Rudder angleSlow speed requires larger rudder angles to initiate turn and too increase rate of turnAlso larger rudder angles required to arrest turns More speed, more water acting on rudder therefore more sensitive to rudder angles

Directional StabilityVessels ability to hold course against external influencesFine lined vessel better than a blunt ended tankerGood directional stability rudder amidship vessel should assume a straight coursePoor directional stability will continue to turn even though rudder is amidshipIn any case steering is less effective when speed is reduced

Windage AreaGreater the windage area the following effects are manifested.

The Effect of WindWhen vessel is light a gentle breeze has the same effect as a laden vessel in a galeWhat is the tendancy for a vessel stopped?When vessel is stopped she adopts a position such that the wind is roughly on the beam

Wind AheadEasily steered and stopped. Pays off easilyDifficult to bring backTries to cross wind

Wind AsternEasily steered. Pays off easilyDifficult to bring backTries to cross windDifficult to stop due to leeway direction.

Wind on BowNeeds constant weather helmResulting skid adds to leewayGreater speed needed to swing upwindTries to cross wind

Wind on beamMaximum LeewayLittle effect on steering

Wind on QuarterQuarter blows down windBow luffs upVessel tries to crosswindLee helm required

Summarise Wind EffectTo Lie across it when stoppedTo run across it when under headwayTo Sternbore into it under Sternway

Run Across WindVessel Under headway tends to run across wind

Lie across windWhen stopped a vessel tends to lie across wind

SternboreA vessel tends to sternbore into the wind under sternway

Effect of CurrentCurrents Effect all ships equally with regard to handling qualitiesregardless of trim or loadingdownstream drift to be accounted forAnchored or berthed rudder effective if there is a flow of water past itWhen berthing a vessel should stem the current

Stemming CurrentStemming current good control due to braking effect of currentTight SwingWide Swing

Stopping DistancesThe minimum distance over the ground that a vessel requires to come to rest.Speed trials on new tonnages determine:Stopping distances in the followingFrom full ahead after ordering stopFrom full ahead after ordering Crash stop Full astern (aqpprox 10 x length of v/l)

Crash Stopping Crash STOP = Full Ahead- Stop- Full asternMore Effective if =Slow AheadStop EnginesSlow AsternFull Astern

Crash StoppingHigh Frequency cyclingUsing the Drag of the rudderHard over each way and reduce engine revs in stages

Crash Stopping Low Frequency CyclingHard a starboard until 40 degrees off course Hard a port until back on courseHard a starboard Full astern

Crash StoppingA Full turn with gradual engine reduction If sufficient sea room

Best to e proceeding at correct speed then vessel not required to Crash stop

Turning CirclesDependent on following factors:Structural design and length of vesselDraught and Trim of VesselSize and motive power of Main EngineDistribution and stowage of CargoEven Keel or listedPosition of turning in relation to available depth of waterAmount of rudder angle appliedExternal forces affecting drift angle

Shell International Trading and Shipping Company Limited

Bridge Information Book - Turning Circles

STASCO-OTS/2, Reporting & Recording ManualAuthorised by : OTS/216 February 1996

FORM-422 Filename:-FORM-422Page 1 of 1

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Slow. Speed

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Time 20.5 mins

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Time 12.5 mins

Speed App 2.4 kts

Course # 180 deg

TACTICAL DIAMETER

Wheel over point

Turning Circle at

Time 8 mins

Speed App 4.3 kts

Course # 90 deg

TRANSFER

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Wheel over point

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PropellersTransverse thrust (wheeling effect) Caused by bias of suction behind propellers and Paddle effect.

PropellersRight handed PropellerThrust AheadTransverse ThrustThrust AheadTransverse ThrustBow to Port

Ahead ThrustRight handed PropellerThrust AheadBow to PortStern to Starboard

Astern ThrustRight handed PropellerThrust Astern

Bow to StarboardStern to Port

Left Handed PropellersSame Principles as Right except Vice Versa

Twin ScrewGood and Bad handling abilities dependent on:-Rudder configurationEffect of TorqueEffect of transverse thrustPivot PointTurning ability

Rudder ConfigurationRudder response poorAt slow speeds no propulsion from either propeller acting on rudder

Effect of Torque1 prop turning ahead and 1 turning asternVessel should turn to the opposite ahead engine ie Port engine ahead vessel turns to StarboardIf props are close together the effect of the torque is disappointing.

Ideal Configuration2 Props are set wide apart

Twin Fixed Pitch PropsOutward Turning

Twin Fixed Pitch PropsInward Turning

Pivot Point & Turning AbilityPivot point acts the same as a single screw shipTurning ability is enhancedCorrect use of engines kicks ahead and astern can be taken advantage by using the opposing torque of the props.

CPPGood speed control No pitch no thrust no transverse motionCant of vessel is unknown/ or at best erratic when run astern.

Diesel and Steam EnginesDiesel quick responseNumber of startsSteamSlow responseNumerous movements

Canals Rivers Narrow Channels SquatBank EffectShallow waterInteraction

Effect of Narrow ChannelsSurge EffectBuild up of water ahead of vesselA drop in water level astern of vessel

Closing in on one sideVenturi EffectCauses increase in velocity of water on the bank sidedrop in water at the bank sideCushion effect at bow suction effect at stern

SquatThe bodily sinkage of a vessel making waymost noticeable in shallow waters

Girding TugsGirding a tug occurs:-When a towline under stress is allowed to lead directly abeam from a tug

Passing Moored VesselsVessels are surged by passing vesselsReduced speed whenever a moored vessel is being passed

Heavy WeatherDangersSynchronismPoopingPounding & PitchingBroaching

SynchronismIf vessel disabled or stopped will lie beam on to sea synchronised rollingAttempt to bring head to wind. use anchor chain as a dragIf Making way a small adjustment of courseIf Synchronised pitching adjust speed

PoopingFollowing wavesCrashing down on poopstructural damage

Pounding & PitchingFord end slamming into seato prevent Slow downor change course

BroachingSurfing with following seasLoosing steerage and stern being pushed beam on to sea

Heavy Weather ManouveringPoints to consider:StabilityLength of swellForce of windSychronism - Rolling & PitchingHead to sea - PoundingStern to sea pooping and broaching

Turning in heavy weatherCheck the state of the seaHave man on wheel and engines readyInform all departmentsWatch for lull or an area of relative calm seaAt this juncture wheel over and engine full to kick her round keeping a close watch on oncoming waves.

Heave toHeavy seas endangering ship Option to heave toVessel head is brought to wind and speed is adjusted to maintain vessels head to windBeware pitching & poundinga point off the wind to ride the waves is more advantageous

ManouvresTurning Short RoundManoverboardManoeuvre to minimise collision damage

Turning Vessel Short round

Manoverboard Manouvre Determined by Type of VesselProximity of trafficTime of discovery and circumstances of Case immediate or delayed turn?Williamson, Scharnow, single turn, double turn.

Williamson TurnHelm initially placed hard over to the side from which the man fellImmediate and Delayed Action

Scharnow TurnRudder Hard OverAfter deviation from original course by 240 degrees rudder hard over to the opposite sideWhen heading 20 degrees short of opposite course rudder to midships position so that ship will turn to opposite courseDelayed action Manoeuvre

Single Turn (270 degree)Rudder hard overAfter deviation from original course by 250 degrees rudder to midships position and stopping manoeuvre to be initiatedImmediate Action Situation

Double Turn30Rudder hard over to side of casualtySteadied on reciprocal courseHard over again when original position 30 degrees abaft

Manoeuvre to Reduce Collision DamageIf imminent collision is foresawVessel should be manoeuvred to minimise damage eitherA Glancing blow Or if no optionPresent the bow as engineroom and sensitive areas are aft.

TestList factors /components with regard to turning circlesDescribe Bank effect, following current.Describe transverse thrust right handed propDescribe how to heave to for a vessel proceeding with the weather