Ship floating upright :
• The centers of gravity ( CG ) and Buoyancy ( B ) are on the center line.
• The resultant force acting on the ship is zero .
• The resultant moment about the center
of gravity is zero .
• Upright Hydrostatic Analysis
Why to Use Upright Hydrostatic Analysis ?
Used to determine hydrostatic equilibrium and stability for Ship .
If the vessel is subject to classification, hydrostatic properties must be
submitted as part of that procedure .
Hydrostatic properties will be communicated to the owner/operator of the
vessel to be utilized during loading and operation .
In Case of Grounding & Collision , hydrostatic properties may be crucial in
the conduct and success of salvage operations .
Hydrostatic Calculations :
• The input to the hydrostatic calculation is in most cases a form of offsets on
transverse stations.
• Graphic views of the offsets are beneficial .
 Longitudinal View : Gives good indications of the
quantity and quality of data.
 Transverse view: Good supplement
to the longitudinal view.
Curves of Form
• For a vessel that operates at a significant range of loadings
(displacements), the hydrostatic properties must be presented for a
range of flotation conditions.
• It is customary to use vessel draft as the independent variable, and to
tabulate properties at a reasonable number of draft values .
• This information is presented graphically at curve called
curves of form :
 The Draft (T) is the vertical axis : Because draft is a vertical
 Dependent quantities are plotted horizontally.
If plotted it will
appear as follow:
The plot is
complicated by the
fact that the various
hydrostatic quantities
have different units
and widely varying
 Therefore, a generic “scale
of units” from 0 to 10 is
used, and quantities are
scaled by powers of 10
(and sometimes other
factors) to fit on the plot.
 The range of draft should go
from somewhat below the
minimum working
displacement to somewhat
above the deepest loading
expected .
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