Ship Form
Nomenclature & Principal Views
Lines & Offsets
Coefficients of Form
Ship Dimensions
Length Overall (LOA)
Forward
Perpendicular
After
Perpendicular
Designed Waterline Length (DWL)
Length Between Perpendiculars (LBP)
Beam
Designed Waterline Plane
Parallel Midbody
Afterbody
(STERN)
Forebody
(BOW)
Depth
Midship
Section
Lines Drawings: waterlines
DWL
WL2
WL1
Baseline
Length Between Perpendiculars (LBP)
Half-Breadth Plan
Lines Drawings: sections
AP
Sta 10
FP
9
8
7
6
4
After Sections
Sta 10 (AP)
Sta 8
3
2
1
Forward Sections
MIDSHIP
SECTION
Sta 6
Sta 0 (FP)
Sta 2
Sta 4
Body Plan
0
Section Nomenclature
Tumblehome
Flair
Camber
Freeboard
Depth
Beam
DWL
Half-breadth
Draft
Deadrise
Baseline
Lines Drawings: buttocks
DWL
DWL PLANE
Centerline Plane
BP1
BP2
Butt 1
Butt 2
Sheer Plan
Butt 3
BP1
BP3
Sheer & Camber
Sheer
DWL
DWL PLANE
Centerline Plane
BP1
Sheer Plan
Camber
Lines Drawings
 Three sets of drawings define the hull shape
Half-Breadth Plan
Body Plan
Sheer Plan
BP1
Offsets
 Ships lines may be represented numerically in a table
 For example
Sta No. Half-breadth Half-breadth
@ 30’ (DWL) @ 25 ‘
Half-breadth … etc. Half-breadth
@ 20’
@ Baseline
0 (FP)
16
12
10
4
2
35
33
30
6
4
50
48
45
40
5 (F)
50
50
48
45
6
50
48
45
40
8
45
42
35
10
10(AP)
40
32
15
0
Offsets
Sta No.
… etc.
Half-breadth @
30’ (DWL)
Half-breadth @
25 ‘
Half-breadth @
20’
0 (FP)
16
12
10
4
2
35
33
30
6
4
50
48
45
40
 Half-breadths
for different
WL’s at a
given station
may be used
to determine
the AF of that
station
(DWL)30’
Half-breadth @
Baseline
B1 = 35
25’ h= 5 B2 = 33 A1= ½ (35+33) x 5 = 170
A2
20’
A3
15’
A4
10’
A5
5’
(BL) 0’
A6
Hull Volume
 Section Areas define hull shape
 Volumes between sections summed to determine displacement
volume, 
Midship Section
(Station 5)
Area below
DWL
Section Volume V5 =
½ (A5+A4) x d
Offsets
 Likewise, waterplane areas may be calculated from
Offset tables
½ -brth
@ 30’
½ -brth
@ 25’
0 (FP)
16
12
2
35
33
4
50
48
5 (F)
50
50
6
50
48
8
45
42
10(AP)
40
32
Sta
No.
Sta. 10
9
8
7
6
5
4
3
2
1
0
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.)
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
B
LCB
KB
 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).
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
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.
Waterplane
Area
M
B
K
Hydrostatic Curves
MEAN
DRAFT
(FT).
KM
(FT)
LCF
(AFT FP)
(FT)
279
27
31.1
LCB
(AFT FP)
(FT)
MT1
TPI
(FT-TON)
268 1800
68
DISPL
in S.W.
(L.TONS)
19000
MEAN
DRAFT
(FT)
27
278
26
31.05
25
67
277
276
24
31.1
275
23
31.2
274
267 1700
18000
26
17000
25
16000
24
66
266
1600
65
15000
23
Coefficients of Form
 Block Coefficient: CB =  / (L x B x T)
AP
Beam, B
L (along DWL}
FP
Hull Volume, 
(under DWL)
Block Volume,
LxBxT
Draft, T
Coefficients of Form
 Prismatic Coefficient: CP =  / (AF x L)
Hull Volume, 
(under DWL)
Midship Section
Area, AF
Prism Volume,
(AF x L)
Coefficients of Form
 Midship Section Coefficient: CM = AF / (B x T)
Beam, B
 Note that CM = CB / CP
 COF’s are used in the
early stages of design
to compare
characteristics of new
design with existing
types for estimating
performance
Draft
T
AF
Rectangle, B x T
Same B & T
smaller CM