2 2.1 Definition (Terminology): Principal Dimensions (length, breadth, depth etc)-Length.Lbp ( or Lpp) Length between two perpendicularsFP – Forward perpendicular (vertical line through intersection of stem and waterline (w.l).)AP – Backward perpendicular (vertical line through the center of rudder pintle)Loa – Overall LengthLwl – Waterline Length (calculation length)p31 figures 3.1, 3.2 & 3.3
3 Sheer is the height measured between deck at side and base line. W.L.A.PLoaLwlAmid ShipLbpSheer is the height measured between deck at side and base line.Forward SheerF.P.After Sheer
4 Definition (Terminology): Principal Dimensions-Breadth, depth & draft.Breadth (moulded) (inside of plate on one side to another side)Breadth maximumDepth (measured at midship)Camber – the rise of the deck at the centerline. 2% of breadthBilge radiusRise of FloorFlat of keel (thicker plate)Tumber homeRake of stemDraught and trim
5 Mid Cross Section of a ship Flat of KeelRise of FloorDepthMouldedBreadth mouldedBilge radiusCenterlineDeckBase Line (Top of Flate keel)CamberBreadth ExtremeFonderw.l.Draft (d)Mid Cross Section of a ship
6 If W.L. is parallel to the baseline (keel line), the ship is floating evenly. Not parallel, the ship has a trim.Trim = da – dfTrim (in radius) = (da – df )/ LAverage draft = (da + df )/ 2Free board (f.b) is the distance measured downwards from the deck to the W.L.Usually f.b. is minimum at midshipMinimum f.b is required by International Law.
7 2.2 Line Drawing:Using the methods of descriptive geometry, the form of a hull is drawn on a scale (1:50 or 1:200) drawing, which is called “Lines Drawing,” or simply the “lines” or “lines plan”. (See p34 Figure 3.4 Lines plan).Lines drawing mainly consists of three plan viewsSheer plane (Buttock plane, Buttock lines) : parallel to the longitudinal central plane (2m, 4m, etc are the distances from the center plane)
8 Body Plan (Ordinate station, Transverse section, Half-Breadth plane (Water plane, Waterline planes): parallel to the base plane (2m, 4m, ….are the distance form the base plane)Body Plan (Ordinate station, Transverse section,0-10 bow stern (US), (UK)): parallel to the mid-section (# of stations indicated the distance from the mid-section or bow).Diagonals (Bilge Diagonal)Fair form and fairness of line, checking the consistency of point, smoothness of linesTable of Offsets
11 Preliminary offsets: line drawings (design) (computation of ship hydrostatics)“Returned” or finished offsets: (in shipyard) they may be (slightly) different from the preliminary offsets.Mathematical Formulas for ship hull formsWith the help of computers, use spline ‘interpolation functions’ to draw the “lines” using computers to “mold loft.”
12 2.3. Hull characteristics (main coefficients) Displacement and Weight RelationshipB (buoyancy) = W (weight). (conventional ship)B = W - F (other support force) (non-conventional ships)Δ – mold volume B = ρg Δ = γ ΔAppendage volume ≈ 1% Δ
13 2.3. Hull characteristics (main coefficients (non-dimensional) - Coefficient of Form ( Fatness of a hull)Block Coefficient CBwhere L= Lpp or Lbp and T = DraftCB ~0.80 even bigger- Miship Section CoefficientCM = immersed area of mishap section (A) / (BT)0.67~0.98
14 -Prismatic or Longitudinal Coefficient: 0.55~0.80 -Waterplane Coefficient-Displacement /Length Ratio
15 -Breadth /Length Ratio : -Draft/Length Ratio-Draft/Breadth Ratio-These coefficients are related to the resistance and stability of the ship and can be used to estimate them empirically.
16 2.4 Displacement & Tonnage Displacement: Load line (freeboard, draft)Dead weight: the difference between the load displacement up to the minimum permitted freeboard and the lightweight or light displacement.Lightwight: is the weight of the hull and machinery.
17 2.4 Displacement & Tonnage Tonnage: A volume measure not a weight measure1994 International Convention on Tonnage Measurement of ships (see p39)- Gross tonnage GT = K1 V- Net tonnage
18 2.5 Rules and RegulationsThe rules and regulations are issued by organizations which may be divided into three categories:-Classification societies: have established standards of construction by the production of rules which have done much to ensure the safety of ships.-Governmental Authorities: concern for the safety of ships and the well being of all who sail the ships. (behavior of the people)
19 American Bureau of Shipping Classification SocietiesAbbreviationFull NameHeadquartersABSAmerican Bureau of ShippingN.Y.BVBureau VeritasParisGLGermanisher LloydHamburgHRHellenic Register of ShippingGreeceLRLloyd’s Register of ShippingLondonNK(K)Nippon Kaiji KyokaiTokyoNVNorske VeritasOsloPCRegistry of Shipping of USSRMoscowRI (NA)Registro Italiano (Navale)Genoa
20 Load line (freeboard, draft, Tonnage) See Figure 3.5 at p41International Authorities, IMO (International Maritime Organization)International Load Line Convention (Load line)International Convention on Tonnage Measurement of ships
21 Government Regulatory Bodies Coast GuardMaritime AdministrationPublic health serviceSafety convention – International Load lineConvention. Safety of life at sea conventionEPA