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Ship Form Nomenclature & Principal Views Lines & Offsets Coefficients of Form.

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Presentation on theme: "Ship Form Nomenclature & Principal Views Lines & Offsets Coefficients of Form."— Presentation transcript:

1 Ship Form Nomenclature & Principal Views Lines & Offsets Coefficients of Form

2 Ship Dimensions Length Overall (LOA) After Perpendicular Forward Perpendicular Designed Waterline Length (DWL) Length Between Perpendiculars (LBP) Afterbody (STERN) Forebody (BOW) Designed Waterline Plane Beam Parallel Midbody Depth Midship Section

3 Lines Drawings: waterlines Length Between Perpendiculars (LBP) DWL WL2 WL1 Baseline Half-Breadth Plan

4 Lines Drawings: sections Sta FPAP Sta 0 (FP) Sta 2 Sta 4 Sta 6 Sta 8 Sta 10 (AP) Body Plan Forward Sections After Sections MIDSHIP SECTION

5 Section Nomenclature Baseline DWL Freeboard Draft Depth Deadrise Beam Half-breadth Camber Flair Tumblehome

6 Lines Drawings: buttocks DWL Sheer Plan Centerline Plane BP1 BP3 BP2 BP1 DWL PLANE Butt 1 Butt 2 Butt 3

7 DWL Sheer & Camber Sheer Plan Centerline Plane BP1 DWL PLANE Camber Sheer

8 Lines Drawings Three sets of drawings define the hull shape Half-Breadth Plan Body Plan Sheer Plan BP1

9 Offsets Ships lines may be represented numerically in a table For example Sta 30’ (DWL) 25 ‘ 20’ … Baseline 0 (FP) (  ) (AP)

10 Offsets Half-breadths for different WL’s at a given station may be used to determine the A  of that station Sta 30’ (DWL) 25 ‘ 20’ … Baseline 0 (FP) (DWL)30’ 25’ 20’ 15’ 10’ 5’ (BL) 0’ h= 5 B1 = 35 B2 = 33 A1= ½ (35+33) x 5 = 170 A2 A3 A4 A5 A6

11 Hull Volume Section Areas define hull shape Volumes between sections summed to determine displacement volume,  Midship Section (Station 5) Area below DWL Section Volume V 5 = ½ (A 5 +A 4 ) x d

12 Offsets Likewise, waterplane areas may be calculated from Offset tables Sta No. ½ 30’ ½ 25’ 0 (FP) (  ) (AP) 4032 Sta NOTE: The above is distorted because the frame spacing (probably 60’ is not at the same scale as the half-breadths. (Plot to scale below.)

13 Other Hull Form Dimensions Besides areas & volumes, hull form determines the location of other critical dimensions. The centroid (geometric center) of the underwater portion of the hull is the Center of Buoyancy KB LCB B The vertical location of B is measured from the keel (KB). The Longitudinal Center of Buoyancy (LCB) is measured from the Forward Perpendicular The location of B changes with draft (displacement).

14 Other Hull Form Dimensions Besides areas & volumes, hull form determines the location of other critical dimensions. The centroid of the waterplane area is the Center of Floatation (F) Its location (distance from the fwd perpendicular – LCF) is also a function of displacement LCF F

15 Other Hull Form Dimensions Besides areas & volumes, hull form determines the location of other critical dimensions. The distribution of waterplane area determines the Metacentric Radius (BM) The Center of Buoyancy moves along this arc as the ship rolls With KB known, the Metacentric Height (KM) becomes an important parameter in stability calculations. M B K Waterplane Area

16 Hydrostatic Curves MEAN DRAFT (FT). KM (FT) LCF (AFT FP) (FT) LCB (AFT FP) (FT) MT1 (FT-TON) TPI DISPL in S.W. (L.TONS) MEAN DRAFT (FT)

17 Block Coefficient: C B =  / (L x B x T) Hull Volume,  (under DWL) Coefficients of Form AP FP L (along DWL} Beam, B Draft, T Block Volume, L x B x T

18 Coefficients of Form Prismatic Coefficient: C P =  / (A  x L) Hull Volume,  (under DWL) Midship Section Area, A  Prism Volume, (A  x L)

19 Coefficients of Form Midship Section Coefficient: C M = A  / (B x T) Beam, B Draft T AA Rectangle, B x T Same B & T smaller C M Note that C M = C B / C P COF’s are used in the early stages of design to compare characteristics of new design with existing types for estimating performance


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