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Introduction Multi-purpose shipttCapricorntt

Open container ship "Nedlloyd Europa" Car & Passenger Ferry "Pride of Hull" Chemical tanker and a product tanker Anchor Handling Tirg Supplier (AHTS) Fishing vessel@urocutter) "2575"

l lntroductionThis chapter shows some 3-dimensional views of ships. All visible parts and spaces are numbered and named. This is meant as an introduction to different types of ships and can be used as a reference for the following chapters. It can also be used as an indication of the size of a compartment comparedto the whole ship.

2 Multi-purpose 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

ship "Capricorn" 20. 21. 22. 23. 24. 25. 26. 21. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. Generalcargo,rolls of paper Shear strake Hold fan Fixed bulkhead Containerpedestal Tanktop, max. load 15 t/m2 Containers,5rows, 3 bays Vertical bulkhead or pontoon Hatch coaming Wing tank (ballasr) Bulk cargo Gangway Stackedhatches Top light, range light Breakwater Anchor winch Collision bulkhead Deeptank Bow thrusterin nozzle Forepeaktank in bulbous stem Port side Starboardside

Rudder Propeller Main engine with gearboxand shaft generator CO2 bottles in CO2 room Man overboardboat (MOB) Free fall lifeboat Crane for MOB, lifeboat, liferaft and provisions. Funnel with all exhaustpipes Rear mast with navigation lights Cross trees with radarscanners Topdeck with magnetic compassand searchlight Accommodation Hatch cradle Heavy fuel oil tank Bulk cargo Vertical bulkhead or pontoon Heavy cargo, steel coils Project cargo Horizontal decks or hatchcovers

Ship Knowledge, a modern encyclopedia

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Principal Dimensions Length o.a. 1 1 8 . 5m 5 Lengthb.p.p. 111.85 m Breadthmoulded 1 5 .2 0 m Depth to maindeck 8.45m DesignDraught 6 .3 0 m Correspondingdeadweight 6600 tons (excl. grain bulkheads/tweendeck) Capacities (14 ton homogeneous, Containers v.c.g.457o)in accordance with ISO standardat mean draught of appr. 6.30 mtr. in hold 174TEU on hatches 96 TEU Containers in hold on hatches

I'74TEU 242TEU4900 GT 328500 cbft

TonnageRegulation (London 1969) Grain capacity (excl. bulkheads) Speed

At a draught of 6.30 m service speedwill be 14 knots, at a shaft power of 3321 kW. (main engine = 3840 kW / 150 kW for PTO / 907oMCR)

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3 Opencontainer ship "NedlloydEuropa"Rudder Propeller J. Stem 4 . Containerwith a length of 40 feet (FEU) on a 40' stack 5 . Containerwith a length of 20 feet (TEU) on a 20' stack 6 . Accommodationladder '7 Pilot or bunker door 8 . Containerguide rail 9. Row no 11 1 0 . Row no 04 l l . Tier no 08 t 2 . Wing tank (water ballast) 1 3 . Servicegallery 1 4 . Fixed stack 1 5 . Movable stack 16. Bayno l5 1 7 , Bay no 06 1 8 . Tier no 86 t 9 . Cells, hold I and2, for containers with dangerous goods(explosives)l.

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Principal Dimensions IMO no 8915691 Name Nedlloyd Europa Gross Tonnage 48508 Net Tonnage 19254 Deadwt Tonnage 50620 Year when Built t99l Engine 41615 Sulzer hp Ship Builder Mitsubishi H.I.Nagasaki Japan Speed 23.5knots Yard Number 1184 Dimensions 266.30-32.24-23.25 Depth 12.50 VesselType Container Ship Call Sign PGDF Containers 3604teu Flag Neth. In Service t997

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4 Car & Passenger Ferry "Pride

of Hull"

1. Becker rudder 2. Controllable pitch propeller 3. Sternfibe 4. Ballast tank 5. Aft engine room with gearbox 6. Seawaterinlet chest 7. Forward engine room with I of the 4 main engines 8. Stern ramp 9. Mooring gear 10.CO2 - battery space 11.Harbour control room for loading officer 12.Maindeck for trailers and double stacked containers 13.Gangway 14.Outsidedecks 15.Lifeboat hanging in davits 16. Dec k11 17.Funnel lS.Exhaustpipes 19.Panorama lounge 20.Officer and crew mess 2l.Passenger cabins 22.Fast-rescueboat 23.Div er accommodation 24.Upper trailer deck 25.Ramp to lower hold 26. Stabili zer, retliactable 27. Shops and restaurants

28.Helicopter deck 29.Entertainment spacesand bars 30.Fan room 3l.Heeling tank 32.Void 33.Ro-ro cargo 34.Web frame 35.Car deck 36.Marine evacuation system 37.Cinema 38.Satellite dome for internet 39.Satellite dome for communication (Inmarsat) 40.Radar mast 41.Officer cabins 42.Wheelhouse 43.Car deck fan room 44.Forecastle 45.Anchor 46.Bulbousbow 47.Bow thrusters


I4

Principal Dimensions: Delivered: Nov.2001

Access: Sternramp(l x w) 1 2 .5 x 1m 8 Machinery: (4): Main engines Output,Kw each 9450 Output,BHP ttl 51394 Rpm 500 (2): Aux engines 4050 kWeach 720 Rpm

Contract Price: 128 million USD Classification: +100A1, Lloyd'sRegister Roll-on Roll-off Cargoand Passenger Ship +LMC, UMS, SLM. Dimensions: m o.a. 215.10 Length 203.70m Lengthb.p. m Beammld. 31.50 6.05m Draughtdesign Depth to maindeck 9.40m Tonnage: 59,925 GT 26,868 NT 8,800 tDW design tDW scantling 10,350 Passengers: Totalcapacity - cabins 1360 546

(2): Propellers Diameter Rpm

4.9 m 720

"Pride of Rotterdont" itl Venice Sister,shiJt

(2): Bowthrusters 2000 kWeach Speed/ Consumption: Trial speed 23.8knots Servicespeed 22.0knots Fuel consump.l30.8t.l24hr 380 cSt Fuel quality Thnk Capacities: HeavyRretoit 1000 50 Lub oil 400 Freshwater 3500 Ballastwater m3 m3 m3 m3

Car I Tbailer Deck: 1380 Cars Lane 3355m. t4l

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5 Chemicaltanker and a product tankerBalancedrudder with conventionalpropeller Auxiliary unit Lifeboat in gravity davits Hydraulic prime mover Cargo control room Tank heating / tankwashroom Cofferdam, empty space betweentwo tanks Vent pipes with pressurevacuum valves Hydraulic high pressureoil-and return lines for anchor and moonng gear. 10. Hose crane 11. Manifold 12. Wing tank in double hull

1 3 . Double bottom tank t4. Tanktop 1 5 . Longitudinal verticallycorrugatedbulkhead

16. Transversehorizontally17. 18. 19. 20. 21. 22. 23. 24. 25. corrugatedbulkhead Cargo pump Catwalk Railing Deck longitudinals Deck transverses Cargo heater Forecastledeck with anchorand mooring gear Bow thruster Bulbous bow

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6. Anchor Handling Tirg Supplier (AHTS)1. 2. 3. 4. 5. 6. 7. 8.Stern roll for anchor handling Stoppersfor anchor handling Steering engine Starboardducted propeller 15. MOB-boat with crane 16. Storagereel for steel wires for anchor handling 17. Anchor handling winch 18. Bridge with controls for deck gear and ship's steering 19. Fire fighting monitor 20. Radar antennas 2 r . Antenna for communication system / satellite antenna 22. Watertight bulkhead 23. Anchor windlass,below deck 24. Azimuth thruster 25. Bow thruster

Stern tube Transversethruster Cofferdam Tanks for dry bulk cargo e.g. cement 9 . Mud tanks 1 0 . Propeller shaft 1 1 . (Reduction) Gear box t 2 . Main engine 1 3 . Fire pump t4. Life rafts

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(Eurocutter) "2575" 7 FishingvesselPrincipal Dimension: 1. 2. 3. 4. 5. 6. 7. Rudder Jet nozzle Propeller Engine room Engine room bulkhead Main engine Fuel tanks, two wing tanks and a center tank 8 . Starboardbracket pole, used when fishing is done with nets and otter boards. The derrick will not be used in that case 9 . Mast aft 10. Revolving drum for nets 1 1 . Funnel 1 2 . Messroom,dayroom 1 3 . Bridge with navigational equipmentand control panels for main engine, drum for nets and fish winch 14. Cabin for four 1 5 . Railing 1 6 . Capping 1 7 . Scupperhole 1 8 . Wooden workdeck 19. Hatch on fish tank 20. Drop chute 2 t . Fish tank, with an insulation layer of about 20 cm all around 22. Bilge keel 23. Shearstrake 24. Double bottom 25. Bow thruster installation 26. Name of the ship and fishery (registration) number 27. Fish winch 28. Conveyor belt and fish cleaning table 29. Guide pulleys for fish line 30. Forecastledeck 3I. Fish wire blocks 32. Fish wire 33. Fish derrick 34. Mast 35. Radar antennaon mast Dimensions: Length: Breadth: Depth: Grosslbnnage: Delivered: Main Engine: 23.99m 6.20m 2.70m 102 GT 2000 300 hp

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1. Principal Dimensions1.L General MeasurementT[eaty All aspectsconcerningthe measurements seagoingvesselsare aranged in of the certificate of registry act of 1982. Part of the certificate of registry act is the International treaty on the measurement of ships, as set up by the IMOconferencein 1969. The treaty applies to seagoingvesselswith a minimum length of 24 metresand came into force in July1994. Perpendicular Line perpendicular to another line or plane (for instancethe water line). On a ship there are: Fore Perpendicular(FPB or FP) This line crossesthe intersection of the water line and the front of the stem. Aft Perpendicular(APR or AP) This line usually aligns with the centerline of the rudder stock (the imaginary line around which the rudder rotates). Load Line The water line of a ship lying in the water. There are different load lines for different situations.such as: Light water line The water line of a ship carrying only her regular inventory. Deepwater line The water line of maximum load draught in seawater. Water line The load line at the summer mark as calculatedin the design of the ship by the ship builder. Constructionwater line (CWL) The water line used to determine the dimensions of the various components from which the vessel is constructed. Deck line Extended line from the topside of the fixed deck covering at the ship's side. Moulded dimensions Distance between two points, measured on inside plating (or outside framing). BaseLine Top of the keel. Plimsoll Mark The Plimsoll mark or Freeboardmark consists of a circle with diameter of one foot, which through a horizontal line is drawn with as upper edge the centre of the circle. This level indicates the minimum freeboard insalt water summer conditions. Beside the circle is a number of horizontal lines indicating the minimum freeboard as above. Summer freeboard: S. Other conditions: Tropical: T, Winter: W, Fresh(water): F, Tropical Fresh: TF, and for small ships, less than 100 m: Winter North Atlantic: WNA. All connectedby a vertical line. For easychecking of the position of the Mark, above the mark a reference line is drawn: the Deck line. Normally at the level of the weather deck, but in casethe weather deck is not the freeboard deck (e.g. Ro-Ro), at the level of that deck. When the distance is impractically large, or the connection deck shellplate is rounded off (tankers, bulkcarriers), the reference line is positionedat a lower level. The Mark and the Deckline are to be marked permanently on port and starboardside, midlength.

The draughtmarks,Plimsoll Line and Plimsoll Mark are permanent marks. Usually this means that they are carvedinto the hull.

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Explanation of the picture at the right: = Summer (for water with a densityof 1.U25 tlm3) = Winter (ditto) W = Tropics (ditto) T WNA = Winter North Atlantic (ditto) = Tropical Fresh water TF = Fresh water F S

-

I'lintsoll ntark I'lint.sollline I)ruught marks I)eckline

When a ship carries a deck cargo of timber, and certain demands are met, this ship is allowed to have more draught (less freeboard). This is because of the reserve buoyancy causedby the deck cargo. To indicate this, the ship has a special Plimsoll's mark for when it is carrying a deck cargo of timber, the so-called timber mark. A i r D raught

1.2DimensionsLength betweenperpendiculars(Lpp) Distance between the Fore and the Aft Perpendicular. Length over all (Loa) The horizontal distance from stem to stern. Length on the water line (Lwl) Horizontal distance between the moulded sidesof stem and stern when the ship is on her summer mark. Breadth (B) The greatest moulded breadth, measured from side to side outside the frames, but inside the shell plating. Breadth over all The maximum breadth of the ship as measured from the outer hull on starboardto the outer hull on port side. Draught at the stem (Tfwd) Vertical distance between the water line and the underside of the keel, as measuredon the fore perpendicular. Draught at the stern (Ta) The vertical distance between the water line and the underside of the keel as measuredfrom the aft perpendicular. T, T[im The difference between the draught at the stem and the draught at the stern.

trreeboard

Draught

(r)

Depth (D)

Loa

Tr

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Down and trimmed by the head. If the draft is larger at the stem, than at the stern. Dqwn and trimmed by the stern. If the draft is larger at the stern, than at the stem. On an even keel, in proper trim. The draft of the stern equals the draft of the stem. Depth The vertical distance between the base line and the upper continuous deck. The depth is measured at half Lpp at the side of the ship. Freeboard The distance between the water line and the top of the deck at the side (at the deck line). The term surlmer freeboard means the distance from the top of the S-line of the Plimsoll's mark and the topside of the deck line. Air draught The vertical distance between the water line and the highest point of the ship. The air draught is measured from the summer mark. If the ship has less draught one can ballast until it reaches the summer draught and so obtain its minimum air draught.

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Proportions

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The ratios of someof the dimensions discussedabove can be used to obtain information on resistance, stability and manoeuvrabilityof the are: ship.Somewidely usedrelations UB The ratio of length and breadthcan differ quite dramatically depending on the type of vessel. Common values: Passenger ships 6-8 5-7 Freighters 3-5 Tirg boats A larger LIB value is favourablefor speed, but unfavourable for manoeuvrability. LID The length/depth-ratio.The customary valuesfor L/D varies between 10 and 15. This relationplays a role of in the determination the freeboard and tHelongitudinal strength. B/T (T = Draught) The breadth/draught-ratio,varies 2.3 A between and4.5. largerbreadth in relation to the draught (a larger B/T-value) gives a greater initial stability.

Sheer This is the upward rise of a ship's deck from amidships towards the bow and stern. The sheer gives the vessel extra reserve buoyancy at the stem and the stern. Camber Gives the athwart-ships curvature of the weather deck. The curyature helps ensure sufficient drainage. Rise of floor Unique to some types of vesselslike tugboats and fishing boats. This is the upward rise of the lower edges of the floors from the keel towards the bilges. Thrn of bilge Gives the turn of bilge of the ship.

(NT) NettTonnage

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BI) Thc breadth / depth-ratio; varies 'rc'tr\ n 1.3 and 2. If this value becomes larger, it will have an unt-avourable effect on the stability ,becausethe deck will be flooded ri hen the vesselhas an inclination) and on the strength. 1.4 Volumes and weights General The dimensions of a ship can be erpressed by using termsm which ,lescribe the characteristics of the :hip. Each term has a specific abbreviation. The type of ship determinesthe term to be used. For instance, the size of a container vesselis expressedin the number of containersit can transport; a roll-on roll-off carrier's size is given by the total deck-areain squaremetresand a passenger ship in the number of people it can carry. At the IMOconference in 1969 the new units "Gross Tonnage" and "Nett Tonnage" were introduced, to establish a world-wide standard in calculatingthe size of a ship. In many countries the Gross Tonnage is used to determine port dues and pilotage, or to determinethe number of people in the crew. Register ton To determine the volume of a space the register ton is used. One register ton equals100 cft, or 2.83 m3.

(mostly containers)can be placed on deck. It is typical for small container ships to use this strategy. As a consequence of this, dangerous situationscan occur becausethe loss of reserve buoyancy can result in a "water on loss of stability and more deck". Nett Tonnage The Nett Tonnage is also a dimensionlessnumber that describes the volume of the cargo space.The NT can be calculated from the GT by subtracting the volume of space occupiedby: - crew - navigation equipment - propulsion equipment - workshops

The NT may not be lessthan307oof the GT. Displacement(in m3) The displacementequals the volume of the part of the ship below the water line including the shell plating, propeller and rudder. Underwaterbody (in m3) The underwaterbody of a ship equals the displacement minus the contribution of the shell, propeller and rudder. Or: the calculatedvolume of the part of the hull which is submergedin the water,on the outsideof the frames without extensions.

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GrossTonnage The grosstonnageis calculatedusing a formula that takes into account the ship's volume in cubic metre below the main deck and the enclosed spaces above the main deck. This volume is then multiplied by a constant, which results in a dimensionless number (this means no values of T or m3 should be placed after the number). All distancesused in the calculation are moulded dimensions. In order to minimize the daily expensesof a ship, the ship owner will keep the GT as low as possible. One way of doing this is by keeping the depth small, so more cargoShip Knowledge, a modern encyclopedia

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A Displacement (in t) The displacementis the weight of the volume of water displacedby the ship. One could also say: the displacementequalsthe total mass of the ship.

Displacement (t) = waterdisplacement(m) * density of water (t/m)

(in Light displacement t) This is the weight of the hull including the regular inventory. The regular inventory includes: anchors,life-saving appliances,lubricating oil, paint, etc. Dead weight (in t) This is the weight a ship can load until the maximum allowable submersionis reached.This is a constant,which is unique for every ship. Dead weight (t) = maximum weight A(t) - light displacement (t) Dead weight (t) = maximum weight A(t) - actual weight A(t) Cargo, carrying or dead weight capacity (in t) This is the total weight of cargo a ship can carry. The cargo capacity (in t) is not a fixed number, it dependson the ship's maximum allowable submersion, which will include the capacity(in t) of fuel, provisions and drinking water.For a long voyage there has to be room for extra fuel, which reduces the cargo capacity. If, on the other hand, the ship refuels (bunkers) halfway, the cargo capacity is larger upon departure.The choices for the amount of fuel on board and the location for refuelling depend on many factors, but in the end the masterhas final responsibility for the choicesmade.

(t) Cargocapacity = deadweight(t) - ballast,fuel, provisions(t).

Tlte. corgo cupat:itt, Iargell, deterntines the arnount of morrc1,a ,ship generates.

2. Form coefficientsof Form coefficients give clues about the characteristics the vessel's shape from the water line down into the water. This makes it possibleto get an impressionof the shapeof the underwaterbody of a ship without extensive use of any data. However, the form coefficients do not contain any information on the dimensions of the ship, they are non-dimensionalnumbers.

2.1 Waterplane-coefficient Cw.The waterplane-coefficient gives the ratio of the area of the water line A and the rectangular plane spanned by Lpp and Bmld. A large waterplane-coefficient in combination with a small block-coefficient (or coefficient of fineness)is favourable for the stability in both athwart and fore and aft direction.

Waterplane-coefficient (Cw) =

Aw

Lpp * Bmld

Ship disc'hargingbulk cargl


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2.2 Midship sectioncoefficient,Cm.The midship-coefficientgives the ratio of the areaof the midship section(Am) and the area spannedby Bmld and T.

Midship-coefficient (Cm) =

Am Bmld x T

2.3 Block coefficient, coefficient of fineness, Cb. The block coefficient gives the ratio of the volume of the underwater body and by rhe rectangularbeam spanned Lpp, Bmld and T. A vesselwith a small block referred to as 'slim'. In general, fast ships have a small block coefficient is coefficient. Customaryvalues for the block coefficient of severaltypes of vessels: Tanker Freighter Containervessel Reefer Frigate

A ship v,ith a smoll bbc'k-coffic'ient ancl coe'fJicient o large midship ,recticnt

0.80-0.90 0.70-0.80 0.60-0.75 0.55-0.70 0.50-0.55 V LppxBmldxT

Block coefficient (Cb) =

aml A ship with a large block-coe.fficient of Graplilcal representotion the bktck cofficient. a large midship secticn cutd prismatic c'oqfficient.

= Prismatic coefficient(Cp)

V Lpp x Am

2.4 Prismatic coefficient,Cp.The prismatic coefficient gives the ratio of the volume of the underwater body and the block formed by the areaof the midship section (Am) and Lpp. The Cp is important for the resistance and hence for the power of propulsion (if the necessary decreases, the necessary Cp propulsion power also becomes smaller). The maximum value of all these coefficients is reached in case of a rectangularbeam, and equals 1. The minimal value is theoreticallv 0.

of Graplit:ul represetztcrtion the prismatic c'officient.

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3. Lines and offsets(Lines plan)When the principal dimensions, displacement and line-coefficients are known, one has an impressive amount of design information, but not yet a clear image of the exact geometrical shape of the ship. This can be obtained bv the use of a lines plan. The shape of a ship can vary in height, length and breadth of the ship's hull. In order to representthis complex shape on paper, crosssections of the hull are combined with three sets of parallel planes, each one perpendicular to the others.

Water lines. Horizontal cross-sectionsof the hull are called water lines. One of these is the water lines/design draught. This is the water line used in the design of the ship when it is hypothetically loaded. When the water lines are projected and drawn into one particular view, the result is called a water line model.

Thewaterlines Ordinates. Evenly spacedvertical cross-sectionsin athwart direction are called ordinates. Usually the ship is divided into 20 ordinates, from the cenfie of the rudder stock (ordinate 0) to the intersection of the water line and the mould-side of the stem (ordinate 20). The boundaries of these distances are numbered I to 20, called the ordinate numbers. A projection of all ordinates into one view is called a body plan.

Theorclinates Buttocks Vertical cross-sectionsin fore and aft direction are called buttock lines. These cross-sections are parallel to the plane of symmetry of the ship. When the buttocks are projected and drawn into one particular view, the result is called a sheerplan.

Buttock lines

Diagonals The diagonals are cross-sections of fore and aft planes that intersect with the water lines and verticals at a certain angle. On the longitudinal plan they show up as straight lines. The curvature of the watet (nes and buttocks are compared to each other they are until and modified consistent. When this procedure is executed, the results can be checked using the diagonals. The most common diagonal is called the bilge diagonal.Ship Knowledge, a rnodem encyclopedia

The diagonals

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\. - *jrr s the lines plans are being -:'r' rr ith the aid of computer:,' jr.lnlr that have the possibility to .':--.t,)rrn the shape of the vessel --: :retically when modificationsin .-6 .11p'sdesign require this. When -,: .inc'splan ready, the programs is - ;'. h used to calculate, among ,:-.crthin-qs. volume and stability the I ;1g .,hip. r.. .hon'n in the lines plan below, -. i:: rhe water lines and the buttocks is Jrau'n in one half of the ship. In '-..: b.td1'plan, the frames aft of the -:::J.hips are drawn on the left side -::..i the fore frames are drawn on the -::rt. The linesplanis drawn on the :..rJc of the skin plating. l:.' lines plans shown here are of .:'..els that have underwaterbodies

that differ quite dramatically. The reader can tell from these plans that a ship will be slimmer with smaller coefficients, when the water lines, ordinates and buttocks are more

closely spaced. For instance, a rectangular forecastle has only one water line. one ordinate and one buttock. the coefficients are 1.

Lenglhov.r rll :219,3:16 [ml Length over c/ul :212,@0 lml Mouldedbre rdth :32.221O [ml :122Q lml Drall Disgl.emeni :59279 [tl ; 0,691 [-l Cb Cp : 0 , 7 0 7[ l Cm : 0.878 [.1 :.0,3213 Lppl LCB [$ : 1O2.5Al[ml Xb KMtfensrEe :14.490lml

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plan o.f'acontoiner vesselw'ith a lengtlt over all of'203.5 meter,\ I'lte line.c a ShipKnowledge, modernencyclopedia

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Tugboat? 500 5 000

Lpp Cb

= 35.ooo m = 0.565

2 sto

Volume = 896 m3 Bmld Cm LCB Tmld = 10.080 m = 0.908 = 2.90Vo = 4.500m

Yacht Lpp Cb = 23.500 m = 0.1575 000

2.500

Volume = 92 m3 Bmld = 6.250m Cm LCB Tmld cp KM = 0.305 = -3.16Vo = 4.000m = 0.515 = 6.06m5.000 I"0.000 l-5.000

0 000

5.000

2 .500

0.000

1:{Lp, +. d X X20.000

1,lflfl8:588

Coast guard ship with a somewhat exceptional underwater-shape.

Lpp Cb

= 73.200 m = 0.637

Volume = 4196rrf m Bmld = 18.000 Cm LCB Tmld cp1 _: 1 *_ l i i**---*

= 0.933 = -0.75Vo = 5.000m = 0.683 - 8.67m

KM

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32

Ecor cargo ship, multi-purpose.

Lpp

= 134.ooo m

= 0.710 Cb Volume = 18644m3 m Bmld = 28.000 = 0.992 Cm = -2.24Vo LCB TmId = 7.000m = 0.715 cp = 14.46m KM

f ngole

= 96.ooom tfp = 0.452 Cb \folume = 1620m3 m Bmld = 11.500 = 0.752 Cm l-CB = -2.30Vo Tmld - 3.250m = 0.601 cp = 6.17 m KM

Frigate

5 .0 0 0 2.500 0 .0 0 0

rbbreviations used in the drawings: r..Pp rlmld f nld

r-b

= length between perpendiculars = breadth moulded = draught moulded = block coefficient or coefficient of fineness

= midship section coefficient - prismatic coefficient Cp Volume = volume of the underwater body, as measured on the water lines, to the outside of the frames (m3).

Cm

LCB

KM

- point of application of the resultant of all upward forces; longitudinal centre of buoyancy (m). = Height of meta-centre above the keel (m).

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4. DrawingsOf the many drawings, only the most important ones are mentioned here. In general, the following demands are made: The general arrangementplan, safety plan, docking plan and capacity plan have to be submitted to the Shipping Inspectoratefor approval. The general arrangement plan, midship section drawing, shell expansion and construction plan (or sheer plan or working drawing) have to be submitted to the classification bureau for approval. 4.1. General arrangement planPEOPI'ECK EOA TDE OTFICERSDECK

i Ir I The general plan roughly depicts the of division and arrangement the ship. The following views are displayed: - a (SB) side-view of the ship. - the plan views of the most important decks. - sometimes cross-sections, a or front and back view are included. The views and cross-sections mentioned above, display among other things: - the division into the different compartments (for example: tanks, engine room, holds) - location of bulkheads. - location and arrangementof the superstructures. - parts of the equipment (for example: winches, loading gear, bow thruster, lifeboat). Next to these, some basic data are included in the drawing like: principal dimensions,volumes of the holds, tonnage, dead weight, engine power, speedand class.H-Hrtr+|1-H l lr l C

Fig: General arrangement plan of a multi-purpose vessel that carries mainly paper, timber products and containers.

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4.2 Midship section shows or more one Thiscross-section of athwart cross-sections the ship.In case of a freighter it is always a of cross-section the hold closestto the midship.Someof the datashows includes:Veb Frorre Fnone Sooclno 700 nm Veb evenv Znd flaBe Prlncloqt dlnenslons tLenoht b,o.o.

- principal dimensions - engine power and speed - data on classification - equipment numbers - maximum longitudinal bending moment.

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20. Bilge-line arrangement

The bilge-line arrangement is an important safety system that is required by law. Rules made up by governmentsand classificationsocieties have to comply with international As soon as the holds are empty and SOLAS-rules. The law states that the bilge-line clean, the bilge-line arrangementhas arrangement, the ballast-line atran- to be tested.When it has been found gement and the fire-fighting arran- in order, this is noted in the ship's gement must be three independent journal. For some kinds of dangerousgoods, systemsthat can take over the work has to have the the bilge arrangement of the other systemsif necessary. The purpose of the bilge-line arran- capability to pump bilge water from gement is to pump water, which has any individual cargo hold. Certifienteredthe ship unwanted,out of the cation takes care of what kind of dangerousgoods may be transported ship. The ingress of water into the engine by a ship. The valve (in the engine room or the holds after grounding, room) in the bilge well must be fitted with a safety device to ensure that collision or as the result of firegoodscan not accidentally fighting can have serious conse- dangerous pass into the environmentor inside quences. the ship. Condensationcan occur when warm air hits a cold surface. In the most favourable circumstancesthe water flows down the sides into the bilge well and from there it can be pumped overboard. When the water remains on (relatively cold) cargo or seeps into the cargo, damage to the cargo may occur.Ship Knowledge, a modern encyclopedia

As soonas the alarm in the bilge well is activated,the bilge alarm on the alarm panel in the engine room is activatedas well. With an un-manned engine room a muster alarm sounds on the bridge. of The bilge-linearrangementconsists the following parts: 1. Bilge pumps 2. Mountings 3. Main bilge line 4. Suctionlines 5. Bilge well 6. Ejector 7. Bilge water cleaner/ separator 1. Bilgepumps These pumps must be available for immediateuse when the ship is being emptied, even though they may be used for other purposesaccording to the regulations. They must be self-priming. This means that they do not need help to take care of the water in the compartmentwhere they are situated after they have been started.

To determine the amount of fluid inside a bilge well or a ballast tank have to be present. two systems - Manual. Soundingwith soundingtape using a soundingpipe that endsin a tank or a bilge well to measurethe height of the fluid.

232

2. Mountings (fittings) In shipping mountings mean safety devices, valves, filters, distributors etc. Severalsuction lines are mounted on a manifold. The suction lines are fitted with valves to open or close the lines. To keep the capacity as high as possible, one valve at a time should be opened. When more valves are opened at the same time, the suction capacityin the well is reduced.Check valves are used as non-returnvalves. Example: The fluid removed from the bilge well must not be allowed to flow back to the bilge well. A non-return valve is placed in the suction line. valves. nvo ntpes nott-return of 1. Hinge point 2. Direction of flow 3. Closed valve (dotted lines: open valve) 3. Main bilge line. The main bilge line is situatedin the engine room and runs from the manifold to the suction side of the pumps.The suction lines run from the manifold to the compartmentsthat are connected. The main bilge line is made of galvanized steel. The bilge arrangement in the engine room consists of one (compulsory) direct system and one indirect system.The indirect system operates through a manifold. 4. Suction lines The suction lines run from the manifold through the double bottom to the bilge wells. Every well is connected to the manifold by a separate bilge line. This enablesus to operate the bilge lines from the manifold in the engine room. Bilge wells are usually situatedat the fore and aft ends of the holds, both on starboard side and on port side, becausethe water flows to the lowest point in the hold. The position of this point is determined by the trim of the vessel.The suction lines are made of galvanized steel. Synthetic lines are not allowed becauseof the poor fire resistance the material. of

5. Bilge well A bilge well has two compartments, separatedby a bulkhead that extends to half or three quarters of the height of the well. A lid with small holes covers the well. As soon as the water reaches a certain height, it will flow to the well next to it. The suction part of the bilge line is situatedin that part of the well.

Hold v,itht:overed bilpewell 1. Tank top 2. Lid of the bilge well On emergency system that has its suctionpoint at the lowest point in the engine room is compulsory. This system must be connected to the suction line of the seawatercoolingwater pump or the general service pump when no seawater coolingwater pump is available. 6. Ejector The ejector creates a vacuum by the speedof the water flowing past it. The pressureof the water flowing through the ejector is created by the firefighting pump, which can build a higher pressure than the bilge and ballastpumps.(Seesection13) 7. Bilge-watercleaner/separator. According to the MARPOL-treaty bilge water from the engine room must go to a separatorto separatethe oil from the water before it may be pumped overboard. This is to prevent pollution. The oil goes to a dirty-oil tank. This separatoris compulsory for ships of more than 1000 GT. The residue of oil in the water that is pumpedoverboardmay not exceed15 ppm (parts per million).

Distribuot thut can be .fittedvvithnon(bilgearrangement) stop returnvalve,s or (balIast arran gement valves ). 1. Suction of the pump 2. Suction from the bilge well 3. Hand wheel to operatethe valve 4. Stop valve The manifold is made of cast iron on the outside, with a bronze linins Bronze is seawaterresistant.

When a stop valve is opened there are t'wo possibilities: 1. The water can flow in two directions 2. The water can flow one way only. A non-return valve can achieve this. These valves exist in two main designs: 1. The valve can be opened or closed as is needed 2. The valve is automatically operated and is solely used for safety reasons.


233

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21.The ballastarrangement.The ballast arrangement is used to pump seawater(weight) in or out of the ballast tanks. There are fewer rules for the ballast system than for the bilge arrangement as it is less important for the safety of the ship. Reasons taking ballast on board or for shifting ballastare: - To improve the stability of the ship, especiallywhen the ship does not carry cargo. - To alter the trim - To reducebendins momentsor shearforces - To control the list during loading Many shipsuse a and discharging. anti-heelingsystemfor this purpose. An anti-heeling system is used to minimize the list (in port). Pumps with a large capacity (1000m3/hour) are placed in the vicinity of two tanks (one on port side and one on starboard side).Thesepumps can transferwater from one tank to the other at great speed.The system is fully automatic and much used on ships with cranes, container vesselsand Ro-Ro vessels to reducethe list that can occur durins cargo handling.

Forepeak tanks, deeptanks, doublebottom tanks, and wing tanks are usually used for ballast water. The advantage of using ballast instead of fuel in the double bottom is that welding is allowed on the tanktop as a meansof fasteningthe cargo.The owner of the vessel determines the ballast capacity. The duration of the voyage and the purpose of the ship will be taken into account when deciding on the available space for ballast and the capacity of the ballast pumps. Ballast pumps are usually also suitableto act as bilge pumps and thus they form an integrated part of the bilge affangement, to the extent that a ballast pump may even serveas main bilge pump. Contrary to the valves in the bilge arangement, the valves in the ballast arrangement have to be two-way valves as the tanks must be filled or emptied according to the demand. Double bottom tanks can also be filled directly from outside through the sea-inlet.The wing tanks also can use this system, but the draught determines the efficiency of this system as the water will not get higher into the tanks than the draught allows. Nowadaysthe ballast system is often designedas a ring line.

Remote controlled valves are used to empty or fill the ballast tanks. Ballastlines insidethe doublebottom may be made of synthetics.

Syntheticsfor piping systems. More and more pipes on board are made of synthetics, not only for accommodation and sanitary means but also in ballast systems.The main advantageis the corrosion resistance of synthetics. The small weight is another adventage. The pipes are easier to handle on board as well as on the yard and the reduced weight allows the ship to carry more cargo. Disadvantagesare the sensitivity to temperature changes and the lower strength compared to steel. Classification Societies often state that "synthetic pipes may be used when they have no adverse effect on the continuity of vital installations in caseof fire or breakdown". Means for repair of synthetic pipes iue compulsory when a vesselmakes use of syntheticpipes.

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235

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236

Ba llas t ar r an- qe m e no n a l a r-9 e t containervessel.Each tank has its o w n c o n n e c t i o n .B a l l a s t i n g a n d of Lrnballasting each tank simultan e o us ly pos s ibl e . is I 2 3 .t Overboard Ballastdistributor Anti-heeling system Lines to the tanks(in the duct k eel) -5 Valveswith remotecontrol o Filter' 7 Pump

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241

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242

22Firc-frghting amangementstill on deck,an isolatingvalve must be placed. When shut, this valve, ensuresthat the rest of the bilge systemremainsisolatedin the event pump of bilge lines in the emergency roomcomparfrnent becoming damaged. The emergencypump may not be The fire-fighting arrangement to drivenfrom the engine roombut must has transport seawater to the fire be driven independently a diesel by hydrants. The system consists of engine or electrically driven by an generator. lines, pumps,valveswith couplings, emergency hoses, nozzles sprayinstallations. and Both main pumpsmust deliver suffiA minimum of three fire-fighting cient pressure. This pressureshould pumps is compulsoryon all ships. be enough get at leasta pressure to of One of thesepumpsmustbe situated 4 bar at the highestpoint on the ship outsidethe engineroom. This is the (the bridge). There must be enough emergencyfire-fighting pump. As hydrants (connection point for fire closeto the pump as possible,while hose)to ensure that everylocationon Fire on board ships has probably more often caused loss of a ship the than grounding, collision or bad weather.A good fre-fighting arrangement,conforming to legal requirementsis therefore necessity. athe vessel can be reached by at least two hoses.In caseof fire in the engine room an isolating valve outside the engine room must be shut to keep pressure on the fre line from the emergency fire pump.

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Ship Knowledge,a modemencyclopedia

243

1.1.1 1.2 1.3 1.4 1.5 1.6 1.7

PropellersGeneral Fixed propellers Controllable pitch propellers Nozzles Rudder propellers Electrical rudder propellers Propeller shafting

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In order for a ship to obtain a certain constant speed,a force needsto be exerted on the ship. The magnitudeof this force dependson the ship's resistance that at particular speed.If the ship is travelling at constant speedthe force exerted on the ship equals the resistanceof the ship. The force that moves the ship can come from an outside sourcelike a towing line or the wind, but generally the force is generated a power sourceon the ship itself (engine).The propulsion by system usually consistsof the engine or turbine, reduction gearbox,propeller shaft and propeller. The efficiency of a propeller takes an important place in the design-process of the propeller becauseits efficiency and the ship's f\rel consumption are directly rclate{/ The efficiency depends on the flow field of the propeller, which depends on the ship's underwater body, the power of the propeller, the number of blades, rotations per minute, the maximum possible propeller diameter, the blade surface area and the ship's speed. If the diameter of the propeller increases, the rotations per minute can decrease; this generally increases the efficiency and reduces the fuel consumption. The propeller pitch is the distance in the direction parallel to the propeller shaft that a point on the propeller covers in one revolution in a solid substance. Similar to a point on a corkscrew turning in a cork. When rotating in a fluid a propeller will have a (small) slip. Rotations or per revolutions minute are abbreviated as rpm.

thepropul sionsvstent In short, the diameter of the propeller should be as large as possible so that a maximum amount of wake, caused by the ship's hull, is used.The choice for high efficiency with a largediameter propeller and a low number of revolutions per minute is easily justifiable, but requires a significant investment. RPM and the number of blades have influence on vibrations on board and the resonancefrequency of the ship. Most ships use a 4-bladed propeller while 5-blade propellers are more common when a large power (20000 kW) is necessary.

1 Engine 2. Engine shaft 3. Reduction gear-box;this reduces the number of revolutions of the engine(e.g.1000 rpm) to an rotation rate of the acceptable propeller (e.g. 200 rpm) The reduction 5:1. is 4. Shaft generator;this suppliesthe ship with electricity when the engine is running 5. Stern tube with bearing 6. Propeller shaft 7. Propeller


246

However, more and more ships use the 5-bladed version nowadays,even when less power is needed. The 3bladed propellers are used on ships with a high number of revolutions per minute and a low power (700 rpm,

Ship resistance the A ship encounters following types of resistance: a. Frictional resistance The friction between the water and the ship's skin is the causeof this type of resistance. The water in the by boundary layer will be accelerated the ship's speed.This boundary layer becomes larger when the shell is fouled.

600kw).The shapeof the blades Every propeller is designed individually, basedon the specific demands set for this propeller. As a result of this, there is a large variety in shapes of blades.

boundary layerLNG-tanker v,ith a vveLl-desi.cned buLb

wake Tlrcu,ake theship r4f b. Pressureresistance The ship's momentum pushes the water asideat the bow and as a result, the pressure of the water increases. This increase in pressure will also take place at the aft. The pressurewill fall where the boundarv laver is released. to Difterenttltpeso.fbktdesattctchecl rt lrub.Thisutmbhrution neverbe can used actu(tpropul.si l on .for The remarks for each shape of blade apply to both the fixed and the controllable pitch propellers. Blade 1: Is hardly used anymore. BIade 2: Is used when there are strict demandsregarding noise and vibrations on board. Blade 3: Is used when the rpm is high and, consequently, the diameteris small. A large blade surface area somewhatreducesthe efficiency, but it is very favourable for the ability to stop the ship and for the reversepropulsion force. Blade 4: Is used in nozzles Blade 5: Is also used in nozzlesif the noise and vibration levels have to be limited to a minimum.. c. Wave resistance This is a result of wave-systems along the hull that originate from the differences in pressure.The use of a bulb at the stem can significantly decrease wave-making resistance. the The bulb generates its own wave system, which is designed to be opposite to the ship's wave system. These two wave systems then neutralize each other. If the rate of flow of water (or air) is higher, then the pressure will be lower compared to the pressure in parts of the water where the rate of flow is lower. So in waves, water in a trough has a higher speedthan water in a wave top. See also chapter 4 'design' and Bernoulli's law. In oil tankers and container ships it can be seen very clearly that the bulb prevents an increasein pressurenear the stem. The improved streamlineof the ship's underwaterbody reducesa wave system around the ship. In suppliers and hopper suction dredgers, there is a large wave system presentaround the ship.

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g Trailerin hopltersuctiott redger d a v'ithout bulb d. Added resistance waves in This type of resistanceis caused by the pitching and rolling of the ship. e. Air resistance This depends on the vertical area above the waterline. which varies with the draught. Types 'd' and 'e' are variable, depending on wave direction and wind direction as experiencedby the ship.


247

aft, therefore the pressureside is also called 'the face' and the suction side 'the back'. Cavitation As described above, the propeller pressureof a rotating propeller is not just the result of the water-pressure on the pressure side, but also of the underpressureon the other side of the propeller. Propellers that rotate rapidly can create an under-pressure that is so low that watervapour bubbles are being formed on the suction side of the propeller. These gas-bubblesimplode continuously on the same spot and cause damage to the suction side of the blade. This is calledcavitation. Severe cavitationcauses: - a reduction in propulsion power - wear of the blades - vibrations that bend the blades - noise in the ship - high cost to rectify A proper working propeller often shows, light cavitation wich is not harmful.

Fixed right-handed propeller on a tanker (deadweight 30,000 tons). Propeller being polished to reduce roughness,for less rotation.friction and le.ss fuel consumption.

1.

A drawingof the upper fixed propeller propellerseen bladeof a right-handed from above 1. Cross-sectionof propeller blade 2. Propeller shaft 3. Suction side 4. Pressureside 5. Leading edge 6. Trailing edge

Pressure and suction sides of the propeller The approach velocity of the water is a result of the ship's movement through the water. If the ship is lying still, this Ve = 0. The approach velocity can be calculated by subtracting the wake velocity from the ship's speed. The speed of rotation of the propeller and the approach velocity result in the speed (V). This V hits the propeller blade at a certain angle: ct = 9o-10"at service speed The speed of the incoming water creates an under-pressure on the forward side of the blade (suction side) and an over-pressureon the aft side of the blade (pressure side). The propeller blade acts as a wing profile. Propellers are usually viewed from Ve = approach velocity = ship's speed - wake speed U = speedof rotation of the propeller = angular velocity x radius T*r V = resulting speed A = lift W = drag P = resulting force S = propulsion force (thrust) T = shaft moment

ls

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Cavitation damage on a rudder blade

Forces on the upper propeller blade when the propeller is rotating and the ship is movingShip Knowledge, a

Cavitation damage on a rudder blade plug. due to mi,ssing

248

Propeller

Turning directionright left right left

Sailing direction ahead astern astern ahead

right-handed right-handed left-handed left-handed

Direct effect Aft starboard

propeller Fore

Indirect effect Aft port starboard

propeller Fore starboard

ponstarboard

portstarboard

portstarboard

port

port

Wlteele.ffec'r propellers o.f The influence of the propeller on the ship's manoeuvringability Propellers can be divided into righthanded and left-handed propellers. Ships with a fixed propeller usually have a right-handedversion. A right-handed propeller can be recognised in the following way. Stand aft of the propeller, look at the face and hold on to the top blade with both hands. If the right-hand side of the blade is furthest away, it is a righr handedpropeller. If the ship is going ahead, a right-handed propeller is rotating clockwise. If a propeller is rotating, the ship has the tendency to turn to a particular side, even if the rudder is in the midships position and there are no additional forces acting on the ship. This effect is called the propeller effect or wheel effect (seethe module on manoeuvring). Propellers with adjustable blades (controllable pitch propellers, cpp) are often left-handed. When the ship goes astern,the effect of the propeller is the same as in a right-handed propeller going astern. Going ahead they have the same effect as a lefthanded propeller. This is done not to confuse pilots. When going astern, the efficiency of the propeller can drop below 50Vo, depending on the type of blade and the type of propeller. The diameter of fixed propellers varies between 36 cm and 12 metres. The choice of a fixed or controllable pitch propeller (CPP) in ships up to 7000 kW depends on, among other things, the need for a shaft generator and the need for easy manoeuvring qualities. Advantagesof a fixed propeller over a controllable pitch propeller are: a. They are less fragile b. The propeller does not revolve when berthing, so it posesless danger to mooring boats and there is less risk6f ropes getting entangled in the propeller. Disadvantage: adverseweather,the in propeller may turn too heavily, this can hamper propulsion.

Instcr llationo.fu .fhed riglrt-lmnded propeller v,ithshuft Fixed propellers also have a limited RPM for manoeuvring. Alternative propeller designs Propellers with tip plates have been invented around 1850, but have only Tip recently been rediscovered. plates attached to the blade tips. The are platesprevent the water from flowing

1.2 Fixed propellersThe propeller blades of a fixed propeller have a fixed position. As a consequence direction of rotation the of the propeller has to change if the ship is going astern.This is realised with a reversingclutch or a reversible engine. A reversing clutch, and therefore also the fixed propeller, is economicalin ships up to 1250 kW.Ship Knowledge, a modern encyclopedia

(CT 80942) with a rever,sible [;'i.redriglt-handed propeller ol a cotttcrinerv'essel v,eighs95 tons, has 6 bladesartd n tlicrmeter 8.95nt. of etryine.Tlrctrtntpeller

249

from pressure areas to the suction areas of the propeller too fast. This increases the efficiency by reducing the energy loss. The improved hydrodynamics of the water-flow also caused the tip-platepropellers by contribute to the reduction of vibrationsand noise of the propeller. Another developmentis the contrarotating propeller. This system consistsof two propellersplacedone behind the other, which are driven by

p t [ ) r u $ i r r e t t . fr t < ' o t t t t r t l l u b l c i t c h l t n t p t , l l e r n i t l t l u t t p a l l c r r l t r r . l t . ' l ' l t ct i t c l t u d . i t t s t n t c n o l l t h t ' b l r r d t , s i s d t t t t t t ' i t r r t i l l ) r a . \ . \ u r tl:l t o u g l t t h t ' l t o l l t t v ' : l t t t . l i . ( [ ' - r t rt t l t l u t t r t l i o t t o f / l t c r t t t t t t t l t c r s \ ' ( ' (n ( . \ t 1 t u , q c ' l ' h c I i , q u r c ru 1 r y t l :l o u l t r r t p t ' l l t r v v i r l t r d i t t n r t t t c rt 4 2 . 5 n t ( l t ' ( . \ . . ' )

energy.The combined propellers can reducethe fuel-consumption l5%a. by 1.3 Controllable Pitch hropellerc (adjustable pitch propellers)

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meansof concentricshafts(inner and outer shafts)with oppositedirections of rotation. Both the number of blades and the diameter differ. The principle behind this system is that, normally, water is brought into rotation by the propeller, which Adding a resultsinto a loss of energy. second propeller rotating in the opposite direction reducesthe loss of

The blades of this type of propeller can be turned, thereby changing the propeller pitch. These propellersare more complicated than fixed-pitch propellers. The mechanism that adjuststhe propeller pitch is located in the boss of the propeller. It is activated from the engine room, remotely controlled from the bridge by a hydraulic cylinder. The most striking feature of the controllable pitch propelleris that it only rotatesin one direction, making the reversing clutch or the reversible ensine

obsolete. Unlike the fixed-pitch propeller, the controllable pitch propeller is an integrated part of the propulsion system. This makes it possible that power and necessary propulsive forces can all be controlled by simply changing the positionsof the blades. The figure on the next page shows of cross-sections a propeller blade and the forces that act on that part of a rotatingpropellerblade. and On the left are the cross-sections forces when the ship is going ahead. All the vectors point backwards,the ship is going forward. Now the blades are rotated towards the zero-position. This meansthat the propulsive forces above and below are equal in magnitude,but opposite in direction.The nett propulsiveforce is zero, but the propellerstill absorbs a large amount of energy that is converted to turbulence of the wake. To go astern, the blades are rotated even further, resulting in a forward propulsiveforce. Safetyprecautions 1. The position of the bladescan be changedmanually without loss of propulsiveforce. 2. If the hydraulic systemfails, the blades can be locked in the ahead position.

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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Propellerblade (tip speed31,4 m/s) Boss Watertight / oil tight seal Stern frame Propeller shaft, 240 rpm Stern tube Intermediateshaft (to engine shaft) Reductiongearbox (1:2.5) Mechanically driven lubricating oil pump Collar shaft (thrust) Actuating motor, coupled to a mechanismof bars that servesthe blades The shaft generatorcan supply the electrical power on a ship as long as the main engine keeps running. With controllable pitch propellers the generator frequency can be kept constant because the rpm of the engine remains constant. The engine drives the shaft generator via the reduction searbox.

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;il#.,:"','J,",t1l ;fllttpropulsive force' The efficiency of the nozzle is at a maximum when the water can pass unobstructed.This is why the top of the nozzle should always be as free as possible in relation to the aft body. Not only does a nozzle increase the propulsive force, it also reducesnoise and vibration levels. Furthermore,the incoming water-flow is more homogeneousin anozzle, minimising local

tlte r:r,trollableTtitt:lt ltropelle.r; upperbludeis tlrcltladein rltetlrcrt:irtgs. Advantages a controllable pitch of propeller 1. It can propel the ship at all speeds, even at very low speedwithout loss of power. 2. It can changequickly from ahead to asternand vice versa. 3. Improved efficiency on ships with alternating loads like fishing crafts and tugs. 4. It can easily be combined with a shaft generator(seeon the right). 5. It can stop a ship with maximum power. Disadvantage: It is a vulnerable system due to the hydraulic components and many sealingrings. A damagedsealingring results in oil pollution.Ship Knowledge, a modern encyclopedia

If the auxiliary generatorsprovide the shaft generator with energy, it can also be usedas: - additional power supply during navigating - emergencypropulsion** ** If the shaft generatoris to be used as an emergencypropulsion,the main from the enginemust be disconnected reduction gear box in order to prevent the cog wheels from being damaged. Class does not prescribe this system and the maximum speedit can obtain. The system is sometimes used on small ships.

Controllable pitclt propeller irt a.fixed rttt?.i,Le.

251

The main characteristic of rudder propellers their ability to rotatelike is the The combinationof a propeller in a a rudder,unobstructed, full 360'. nozzle is often called a ducted Rudder propellers are also called propeller.In principle,the nozzle can 'azimuthingthrusters'or'Z-drives'. be used on every type of vessel To achievethis freedomof rotation,a except on very fast ships like high- right angle underwater-gear box is driven by a vertical power shaft.This speed ferries where they have no increasing effect on the propulsive vertical shaft is centeredin the rudder force. If the frictional resistance stock. (caused by the nozzle) becomes

pressure differences that are responsible for cavitation and vibrations.

1.5 Rudderpropellers

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order to get sufficientpropulsive force efficiencywithout the need for ballast. 2. Deck units.The diesel-drive units are placedon deck; the rudder propelleris attached the back of to the drive unit. Thesetypes can also have a depth-adjustment system. 3. A retractable unit. Is can be withdrawn entirely into the ship and is only loweredwhen the ship is at sea.When in top position,the propellerscan be part of a tunnel thrusterand are then called'retractable thrusters'. Not usedfor main propulsion. 4. Bow thrusters sternthrusters or are also calledtunnel thrusters. They are basedon a transverse propellerand a right angle gearbox.Theseare underwater usedexclusivelyto positionthe bow with a starboard port side or thrust. Types I and 2 function as main propulsion units while type 3 is an auxiliary propulsion unit. Type 4 is for low-speedmanoeuvring. The most important advantageof a rudder propeller is its ability to give optimal thrust in each rudder posltlon.

larger than the increase propulsive in force, there is a loss of efficiency. Nozzles are often used on inland vessels, hopper suction dredgers, tugs, fishing vesselsand suppliers. The advantages disadvantages and of fixed or controllablepitch propellers are the samefor propellersin a nozzle and propellers without one. For shallowdraughtshipsthe samethrust can be delivered with a smaller systemdiameter. Nozzlescome in two main types: 1. Fixed versions 2. Rotatingversions ( s eeS ec t ion1 .5 ) One particulartype of fixed nozzlesis the wing-nozzle. In spite of its modest dimensions, this still increasesthe propulsive force if the speedexceeds12-18knots.

A gear driven by a pinion is attached to the top of the rudder stock. This makes the unlimited rotation possible. Nowadays, rudder propellers can have a power up to 7500 kW. There are several versions of rudder propellers, namely: L A fixed unit assembled an in assemblybox. It can be equipped with a depth-adjustment system.When ship is empty, the the propeller can be lowered in

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252

Except for the tunnel thruster, all rudder propellers can steer the ship 360o,therebygiving the ship excellent manoeuvrability. Nowadays, modern electronic equipment for satellite navigationcan be employedto couple the rudder propellers to the dynamic positioningsystem(DP-system). This can keep a ship in a predetermined position irrespectiveof the influences of currents and wind. Retractable thrusters are often used for this purpose.When the ship is in position, the azimuth thrustersare lowered and the ship switches to DP. Other advantages the rudder propeller are of the very compactengineroom (because there is no need for a long propeller shaft); this results in lower installation costs as compared to a conventionalpropeller. Rudder propeller installations are often used on passengerliners, cable ships, floating cranes, suppliers, dredgers,bargesetc. 1. Horizontal connectins shaft from engine 2. Horizontal gearbox to vertical shaft 3. Vertical shaft 4. Yertical gearbox to horizontal propeller shaft 5. Nozzle 6. Fixed pitch propeller

Schemuticpresentutiotto.fthe comrnundpnth from bridge contrutlto the ruclde:r propeller

Aeriul plnto,qrctpltol'a ,suppliershov,stlrc ct2ttintul nunoeurring c'upabilitiesof a rudder prolte.ller in combinatiort. vvitha bow,thruster

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1.6 Electical rudder prcpelle$ (Brands: Azipod,Dolphin,Mermaid,

ssP)The difference between the rudder propeller of paragraph 1.5 and the electric rudder propeller or podded propulsor is that the latter has its propulsion engine located outside the ship. The electrical engine with adjustable rpm is placed in a pod that is attached to the bottom of the ship. Every pod has a propeller attached to it, driven by the electric motor. There are two main types: a fixed pod with a rudder or a 360 degree rotating pod without a rudder. Both thesetypes can either push or pull. The propeller is then located on the back or the front of the pod, respectively. The electric rudder propeller does not require gearboxes, clutches,propeller shafts and rudders. The diesel engines can be placed anywhere on the ship, as long as there is space available, unlike the ships with a mechanical drive where the engines are connectedto the propeller by a long shaft and other parts. So this propulsion system is a compact system that simplifies the design and constructionof the ship as comparedto conventional propulsion systems. Although the system was originally developed for icebreakers, it is now in use on suppliers, cruise ships, tankers, ferries and ships with a DP-system. Advantages are: 1. It is possibleto separate power the sourceand the propulsion system 2. It can combine the power supply of the auxiliaries and the propulsion system 3. Few vibrations and little noise 4. Excellent manoeuvring capabilities 5. Lower fuel-costs

Cros,s-section the azipod instaLlation of

1. Propeller 2. Bearing andshaftlabyrinth(seal) unit 3. Hydraulicsteering with toothedrim

4. Collector rings for the \-tr/nsmission of data and power 5. Ship's bottom 6. Electro-motor 7. Bearing (radial and thrust)

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1. Azipod with a 1200volts cycloconverter 2.Five diesel enginescoupled to 5 generators(2 times 11.2 MW and 3 times 8.4MW. These supply theShip Knowledge, a modern encyclopedia

energy for all the ship's systems like propulsion,AC, galley, watermakers etc. 3. Main grid, 11000volts l60Hz 4. Bow thrusters

255

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The lubricating agent between the propeller shaft and the shafting can be: a. oil b. water a. Lubricating oil Approximately 70Voof all ships use oil as a lubricant for the propeller shaft. When oil is the lubricant, the bearing is usually made of white metal, and sometimes of synthetic material.The disadvantage syntheof tics is that they poorly transmit the frictional heat between bearing and shaft. At the front side of the front bearing there is a sealing case,which prevents oil from leaking into the ship. The sealing system at the backside consistsof a sealing case and mostly three sealing rings. These sealing rings are made of synthetic rubber. The spacebetween the two bearings is completely filled with lubricant. The aft seal prevents oil from leaking to the outside.The lubricant pressure is only slightly higher than the water pressure. So if seawater should somehow enter the two water-seals, the higher lubricant pressureprevents it from reaching the propeller shaft. Seawatercould seriously damagethe unprotected propeller shaft. The higher lubricant pressure is maintained by a small pressuretank (A), which is placed a few metres above the load line. Tank A is part of the main lubricating system, tank B contains lubricating oil for the seawatersealingrings. The oil in the main lubricating system is self-circulating due to the fact that warmer oil rises upwards. Tank C is both the drainagetank and the storage tank. If oil leakage should somehow occur, it is usually limited to small amounts. If not, drydocking is neccesary.A chrome steel bush is fitted around both the propeller, shaft aft near the propeller and forward in way of the aft peak bulkhead. The spacebetween the bush and the tube contains lubricant. The aft chrome steel liner is attachedto the propeller bosswith bolts, the chrome-steel liner of the forward bush is attachedto the propeller shaft with a clamped ring. Around both bushes,attachedto the ship, are non-rotating housings, where the sealingrings are fitted.Ship Knowledge, a modern encyclopedia

14.

Stern l:eoring and seals

outer seal

4. 11.

inner seal

Outer and irmer seals

CIosed s\,stem lubricating w'ith oil 1. 2. 3. 4. 5. 6. 7. 8. Propeller boss Propeller shaft Chrome-steelliner Seawaterseal Oil seal Stern frame Aft bearing Propeller shafting 9. Clamped ring 10. Oil tank 11. Fasteningwith bolts on the stern post 12. Bolt attachmenton the aft peak bulkhead 13. Stern tube 14. Forward bearing

257

Advantagesof placing a chrome-steel bush are: - it preventsthe propeller shaft from getting into contact with seawater - very resistantto wear should During dry docking, measures determine how much the be taken to propeller shaft has sunk. This is indicative of the wear of the aft bearing.A specialdepth gauge,the so 'poker gauge', is present on called board that can measurethe saggingof the shaft. Normal saggingis zero. b.Wateras a lubricant When water is the lubricant for the propeller shaft, the bearingsare made of rubber or synthetics.Water lubrication can be achievedwith both open and closed systems. In the open system,the water is pushedout where the propeller shaft leaves the ship, thus preventing seawaterfrom entering the ship. In the closedsystem,the water is pumpedround the shaft,from fore to aft. This meansthat the water as always has a slight over-pressure compared to the seawater.The navy enemy useswater lubrication because vesselscan detect lubricating oil. In some countries water lubrication is compulsory for local shipping to protect the environment.

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2 Water-jet propulsionThe main principles of the water-jet are: - the impeller (propeller) draws in seawaterthrough an inlet - the sameimpeller adds head / pressureto the water flow - when the water is pushedthrough a nozzle - the nozzleconvertsthe water presjet sureinto a high-speed - the accelerationof the water flow generatesa thrust force that gives the ship its speed - for sailing astern,the waterflow exiting from the nozzle can be reversedin the forward direction with the reverseplate and reverse section.tI\'B' SrllCl {l} PruP {2) ttfi rrErrfi

The same principle as for a water jet is applied in an aircraft jet engine, but here air is the medium instead of water. The principle is basedon Newton's law F = fiI X 4, where F is the force in Newton, m the mass of the water and a is the accelerationof the water. The waterjet has an electronic steeringsystem.This meansthat the the bridge are orders from immediately processedby microThis makesit possiblefor processors. the water-jet, engine and gearbox to be controlled directly from the bridge. Along with yachts,a lot of passenger and car ferries, rescue and patrol boats are nowadays equipped with water jets. In 1998 the first cargoships were built with water-jet propulsion. The maximum speed of modern water-jetslies around 10-75 knots (appro-ximately 135 km/h). The fastest ferries can reach a speed 50 of appro-ximately knots.

1. Propellerboss 2. Shaft 3. Bearing (rubber,lignum vitae, tufuse) 4. Stern tube

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I nlet Driving shaft Impeller Hydraulic steeringcylinder Jetavator,steeringpart Hydraulic cylinder that altersthe directionof the propulsion 7. Reversingplate,can be moved by the cylinder 8. Reversesection 9. Sealingbox to preventwater from entering the ship l0.Combinedguide and thrust bearing I l . Noz z le

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