Chapter II. Definition & Regulation

2.1 Definition (Terminology):

•Principal Dimensions (length, breadth, depth etc) -Length.

Lbp ( or Lpp) Length between two perpendiculars •FP – 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 Length Lwl – Waterline Length (calculation length)

p31 figures 3.1, 3.2 & 3.3

W.L.

A.P

Loa

Lwl

Amid Ship

Lbp

F.P.

Forward Sheer

After Sheer

Sheer is the height measured between deck at side and base line.

Sheer forward = 0.2* ( ) 20

Sheer aft = 0.1* ( ) 10

L ft

L ft

Definition (Terminology):

•Principal Dimensions -Breadth, depth & draft.

• Breadth (moulded) (inside of plate on one side to another side)• Breadth maximum• Depth (measured at midship)• Camber – the rise of the deck at the centerline. 2% of breadth• Bilge radius• Rise of Floor• Flat of keel (thicker plate)• Tumber home• Rake of stem• Draught and trim

Flat of KeelRise of Floor

DepthMoulded

Breadth moulded

Bilge radius

Centerline

Deck

Base Line (Top of Flate keel)

CamberBreadth Extreme

Fonder

w.l.

Draft (d)

Mid Cross Section of a ship

• If W.L. is parallel to the baseline (keel line), the ship is floating evenly.

• Not parallel, the ship has a trim.

Trim = da – df

Trim (in radius) = (da – df )/ L

Average draft = (da + df )/ 2

• Free board (f.b) is the distance measured downwards from the deck to the W.L.

Usually f.b. is minimum at midship

• Minimum f.b is required by International Law.

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 views

•Sheer plane (Buttock plane, Buttock lines) : parallel to the longitudinal central plane (2m, 4m, etc are the distances from the center plane)

•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), 10-0 (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 lines•Table of Offsets

Line Drawing

Offset Table

•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 forms

•With the help of computers, use spline ‘interpolation functions’ to draw the “lines” using computers to “mold loft.”

2.3. Hull characteristics (main coefficients)

• Displacement and Weight Relationship

B (buoyancy) = W (weight). (conventional ship)

B = W - F (other support force) (non-conventional ships)

Δ – mold volume B = ρg Δ = γ Δ

Appendage volume ≈ 1% Δ

2.3. Hull characteristics (main coefficients (non-dimensional)

- Coefficient of Form ( Fatness of a hull)

Block Coefficient CB

where L= Lpp or Lbp and T = Draft

CB 0.38~0.80 even bigger

- Miship Section Coefficient

CM = immersed area of mishap section (A) / (BT) 0.67~0.98

BCLBT

-Prismatic or Longitudinal Coefficient: 0.55~0.80

-Waterplane Coefficient

-Displacement /Length Ratio

BP

M M

CC

L A L B T C C

area of water plane 0.67 - 0.87

where --Length of Load water plane

= Beam of W.P.

WPCLB

L

B

3 3B

B

C LBT B TC

L L L L

-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.

B

L

T

L

T

B

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.

Dead wight = Fully loaded weight - light weigt

Fully loaded weight = Cargo + fuel + Water + Crew + etc.

2.4 Displacement & Tonnage

• Tonnage: A volume measure not a weight measure

• 1994 International Convention on Tonnage Measurement of ships (see p39)

- Gross tonnage GT = K1 V

- Net tonnage

2

2 3 1 2

4/10

3c

TNT K V K N N

D

2.5 Rules and Regulations

• The 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)

Classification SocietiesAbbreviation Full Name Headquarters

ABS American Bureau of Shipping

N.Y.

BV Bureau Veritas Paris

GL Germanisher Lloyd Hamburg

HR Hellenic Register of Shipping

Greece

LR Lloyd’s Register of Shipping

London

NK(K) Nippon Kaiji Kyokai Tokyo

NV Norske Veritas Oslo

PC Registry of Shipping of USSR

Moscow

RI (NA) Registro Italiano (Navale)

Genoa

• Load line (freeboard, draft, Tonnage)

See Figure 3.5 at p41

• International Authorities, IMO (International Maritime Organization)

• International Load Line Convention (Load line)

• International Convention on Tonnage Measurement of ships

Government Regulatory Bodies

• Coast Guard

• Maritime Administration

• Public health service

• Safety convention – International Load line

• Convention. Safety of life at sea convention

• EPA