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
Sheer is the height measured between deck at side and base line.
A.P
Forward Sheer
After Sheer
F.P.
W.L.
Amid Ship
Lbp
Lwl
Loa
Sheer forward = 0.2* L ( ft )  20
Sheer aft = 0.1* L ( ft )  10
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
Breadth Extreme
w.l.
Camber
Deck
Breadth
moulded
Depth
Moulded
Draft (d)
Fonder
Centerline
Bilge radius
Rise of Floor
Flat of Keel
Mid Cross Section of a ship
Base Line (Top of
Flate keel)
•
•
•
•
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 midsection (# 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 =
Appendage volume ≈ 1% Δ
γΔ
2.3. Hull characteristics (main
coefficients (non-dimensional)
- Coefficient of Form ( Fatness of a hull)
Block Coefficient CB

CB 
LBT
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
-Prismatic or Longitudinal Coefficient: 0.55~0.80
CB


CP 


L  A L  B  T  CM CM
-Waterplane Coefficient
area of water plane
CWP 
0.67 - 0.87
LB
where L--Length of Load water plane
B = Beam of W.P.
BT
-Displacement /Length Ratio  CB LBT

 CB
3
3
L
L
LL
-Breadth /Length Ratio :
B
L
-Draft/Length Ratio T
L
T
-Draft/Breadth Ratio
B
-These coefficients are related to the resistance and
stability of the ship and can be used to estimate
them empirically.
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
 4T 
NT  K 2Vc 
  K 3  N1  N 2 /10 
 3D 
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 Societies
Abbreviation
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