Shiphandling Under Power

8/9/2019 Shiphandling Under Power

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Ship Handling Under Power

Grade III


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Intro

• This lecture mainly deals with the use ofengines when docking and undocking, andany other tight- uarters manoeu!ring"

• Use of engine in open water isstraightforward, though any principlesdiscussed here can #e applied to thosesituations"


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$on%t think that this is #oring andeasy though"

• Ha!e you e!erwatched someone tryto #ring their &'-footmotor yacht into a

#erth(

• )!en #ringing in a *&-foot tin #oat with anout#oard can #edifficult if you don%tunderstand theprinciples in!ol!ed"


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+asics• or the rudder to turn the ship, there needs to #e water

flow"• There is no such thing as #rakes%, the #oat will always

#e mo!ing somewhat, e!en if all forward way has #eentaken off"

• actors affecting how a !essel will mo!e are. / 0ind 1$on%t forget 2) !s" 2345 / 2urrent / 6omentum / Trans!erse Thrust / 3ines7Springs78nchors

• $uring approach to a situation where tight manoue!ringwill #e re uired it is important to assess what factors will#e affecting the !essel, and in what way"


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+asics

• or the rudder to turn the ship, thereneeds to #e water flow / 0hen the ship is not mo!ing through the

water the rudder has no effect / The faster the ship is mo!ing the uicker she

will respond to the rudder

/ The rudder is most effecti!e when thepropeller is actually engaged, and forcingwater o!er the rudder9s surface


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luid $ynamics

• 0ater and air are #oth fluids" They #eha!ein !ery similar ways" / 8ir is not !ery dense relati!e to water, #ut it

still has an effect" This is particularly e!identwith strong wind"

• 0ater is uite dense, and will e:ert a lot of

force e!en if it is a slow-flowing current


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6omentum and Inertia

• It is important to realise that a ship doesnot stop when the engine is put in neutral" / 0ith any larger #oat, stopping the prop

spinning will ha!e little effect on the speed ofthe !essel for uite some time 1;' sec5

• 3ikewise, a ship will not mo!e immediately

when the engine is put in forward orre!erse"


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4elati!e 6otion

• Unlike #eing in a car, your motion relati!e to!isi#le points on shore is not particularly rele!antto the way the ship is acting" It is much more

important to understand your !essel9s motion inrelation to the fluid medium of water"

• 8 #oat mo!ing through a hea!y current and a#oat mo!ing through still water are doing entirelydifferent things, e!en if their motion apparent toa fi:ed point on shore seems similar"


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6omentum

• +ecause you are mo!ing through a fluid,you must always keep this in mind when


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0indage

• 0indage is the area of a !essel e:posedto the wind, upon which the wind will push"

• )!en with all sails struck and furled, thereis still considera#le windage due to thespars, lines, other rigging and the sides ofthe ship"


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2urrent

• 2urrent is the flow of water" This can #ethe result of !arious reasons. / 4i!er flow

/ Tidal currents / 8 large !olume of water flowing through a

small area 1such as at the town of 3ittle2urrent5

/ 0ind #lowing a long time in one direction canalso create currents, e!en in relati!ely large#odies of water


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Trans!erse Thrust

• This is the sideways force generated #ythe propeller spinning in the water"

• The water at the #ottom of the prop isdenser than that at the top, meaning thatthe sideways motion at the top is not asstrong as that at the #ottom / This creates trans!erse thrust


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Trans!erse Thrust

• This force is much more e!ident when inre!erse, particularly at high re!olutions

• It is still acting upon the !essel when inforward, #ut is much less e!ident due tothe rudder acting more efficiently


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Trans!erse Thrust


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Trans!erse Thrust

• +oth Pathfinder and Playfair ha!e left-handed propellers" This means that theyspin counter-clockwise when in forward

• In reverse they spin clockwise , pushingthe stern to Star#oard" 1The #ottom #ladesare pushing to Star#oard, the top to Port,#ottom wins5


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4e!ersing

• Single-screw !essels do not re!erse !erywell / The rudder has little effect / The stern will attempt to face windward / =ou need to stay in low re!olutions to pre!ent

trans!erse thrust from o!erpowering your

intended course


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Power Turns• To turn in a !ery short length you can use a power turn

/ Put the rudder hard o!er, put the transmission in fwd, thenthrottle up to close to cruise

/ Hold this for a few seconds, then go #ack to neutral #efore youpick up speed

/ 4epeat as necessary / To turn in e!en less length make sure you are turning to Port, so

you can use re!erse and use the trans!erse thrust to #ring thestern to St#d" 0ith this you can turn inside the length of the!essel

• This works #ecause the prop sends a lot of water pastthe rudder, allowing a turning action to #egin without anyforward motion"


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$ocking with 0ind• The wind will #e either #lowing you off the dock,

on the dock, or it will #e #lowing along the dock / If you are #eing #lown off the dock, it will re uire a

sharper approach, turning out later than normal

/ If you are #eing #lown onto the dock you will want todo a shallow approach, coming parallel to the dockfurther out and coming against the dock e!enly

/ If the wind is #lowing along the dock, try to dock headto wind so you can maintain good control with little

speed"• If you ha!e to dock stern to the wind ha!e a midship springor sternline ready to stop you with out tripping the #ow intothe dock" =ou will want to minimi>e your speed"


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$ocking with 2urrents

• This is !ery similar to docking with wind, e:ceptcurrent is much stronger for a gi!en !elocity dueto the density of the fluid" / $ocking head to current is uite easy" =ou can

maintain a high Speed through the 0ater while stillha!ing a low S?G" =ou maintain a lot of control thisway"

/ $ocking with stern to current can #e !ery difficult" =ou

need to keep your S?G low, so your ST0 is also low,resulting in slow reaction times with the rudder, andtherefore low le!els of control com#ined with higherapproach speeds"


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$ocking with 2urrents

• This is all related to the water flow past therudder"

• Say you ha!e a @ knot current" / If you head in the current a * knot o!er ground you

will #e a#le to manue!re as if you were going ; knots,while still #eing a#le to approach the wall slowly"

/ If you go down current, you will #e ha!e to #e making

at least @ knots o!er ground, plus whate!er you needto maintain some steerage" =ou will approach the wall

uickly and ha!e much less control"


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Use of 3ines

• 6ooring lines are !ery important duringdocking"

• 0here the line leads from and which wayit leads will dictate what effects it will ha!eon the ship"

• 3ength of line can also ha!e an effect"


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6ooring 3ines

• 0e ha!e A lines we use normally. / Head rope 1*5 / Head spring 1@5 / Stern spring 1;5 / Stern line 1A5

• 0e also ha!e the midship spring"


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Head 4ope

• 0hile the head rope is a key element tomaintaining an effecti!e mooring system, itis generally not used to control the motionof the #oat while docking or lea!ing" 8ssuch, it will often #e the last line put on,and the first line remo!ed in mooring

procedures"• 8 head rope can #e useful for #ringing the

#ow of the #oat in"


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Head Spring

• The head spring is a pretty important lineon#oard" / or coming alongside, the head spring can #e

used effecti!ely as #oth a #rake, and tocon!ert forward momentum into sidewaysmomentum, to #ring the #ow into the wall"

/ 0hen lea!ing the wall, you can 9spring9 off thehead spring, #y remo!ing the other lines,putting the #oat in forward momentum, andallowing the #oat to push its stern away from

the wall"


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Stern 3ine

• The stern line, like the head spring, can #eused as somewhat of a #rake, and to pullthe stern into the wall, although it9s morecommonly used to #rake when comingalongside under sail"


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6idship Spring

• 6ainly a line that is put on after the restare secure, the midship spring can also #eused to 9warp9 the #oat alongside, incon


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Surging 3ines

• This is when strain is taken, #ut the line isstill allowed to run out" If you need toreduce speed rapidly this is a !ery goodtactic" / Bust snu##ing a line while still mo!ing can

often cause an o!erly drastic change in

momentum, and undue strain on the line" 8!oid doing this"

• It can also #e effecti!e when warping theship to maintain control"


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• The #est docking is one where the lines goon when you are already in placeC Usinglines to affect motion is always asecondary optionD try not to rely on themtoo much"


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Use of 8nchors

• 8nchors are a!aila#le for use whenmanoeu!ring" / They can #e dropped to use as a pi!ot point" / ?r they can #e used to slow the ship and help

keep her heading while approaching the dock"

• The anchor should #e cocka#ill 1or on atrigger lashing5 and otherwise ready todrop for use at a moments notice"


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Use of Sails

• 0hen manoeu!ring in close uarters sailscan #e in!alua#le / To fall off the wind the Bi# is !ery useful" / If you want to head up uickly then use the

6ainsail" It is a good idea to ha!e it preppedand ready to go if you intend to use it"

• Haul the throat up a#out * foot, and then haul thepeak up to the point at which the end of the gaff is


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Use of Sails

• 0hen manoeu!ring in close uarters sailscan #e in!alua#le / To fall off the wind the Bi# is !ery useful" / If you want to head up uickly then use the

6ainsail" It is a good idea to ha!e it preppedand ready to go if you intend to use it"

• Haul the throat up a#out * foot, and then haul thepeak up to the point at which the end of the gaff is


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6otorsailing

• 6otorsailing is a !ery useful skill to know"• Unless you need to head directly into the

wind, then it is the o#!ious choice o!ernormal motoring / =ou reduce strain on the crew and !essel #y

ha!ing a steadier trip / =ou go faster and use less fuel 1up to ;'E

sa!ings #y some calculations5 / =ou still ha!e sails up, which is a good thing

as we are sailing !essels


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6otorsailing

• 6otorsailing really should #e thought of asmotor-assist sailing, as opposed to sail-assistmotoring"

/ =ou need to tack to get upwind / $on%t forget to #race as well, yards create a lot of

windage / Sail trim is still !ery important

• 0hile motorsailing, for the purposes of 2ollision4egulations, you are a MOTOR VESSEL "


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+ank Suction

• 0hile operation in narrow channels, suchas the 0elland canal, one must #e awareof the fact that #eing o!erly close to the#ank will cause the #oat to #e suckede!en closer" / If you are getting to a point where contact is

imminent, don9t try to ri!e out of itD you9ll mostlikely


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+ank suction is !ery e!ident especially whenlea!in the lock walls" 6ake sure the #ow iswell fended of #efore departing"


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S uat

• +ecause all of the moti!e force is locatedat the propeller, the trim of the ship willchange as you use the prop in differentdirections and at different speeds" / The stern sinks in forward, and the #ow will

sink in re!erse to increasing degrees as you

increase 4P6s" In shallow water, e!erythingis #etter done slowly"

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Shiphandling Under Power