Different types of welds in Ship COnstruction

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6. Block Co-efficient:
This is a measure of the fullness of the form of a ship and is the ratio of volume of
displacement at a given water line, and the volume of the circumscribing solid of
constant rectangular cross section having the same length, breadth and draught as the
ship.
CB = ----------
L BP x B x T
Typical values
Very fast ships (War ships) ------0.5 to 0.65 (Fine form)
Ordinary cargo ships ------0.65 to 0.75 (Moderate form)
Slow cargo ships (Large tankers, bulkers) -------0.75 to 0.85 (Full form)
Prismatic Co-efficient:
This is the ratio of the volume of displacement of the ship to the volume of
the circumscribing solid having a constant section equal to the immersed
midship section area AM and a length equal to the L BP
cp= -------------
AM x L BP 6

7. Ranges from 0.55 to .0.85
Mid ship section area C-efficient:
This is the ratio of the immersed area of the mid ship to the area of the circumscribing
rectangle having a breadth equal to the breadth of the ship and a depth equal to the
draught.
AM
CM = -------------------------
B x T
Ranges from 0.85 to 0.99
Water plane Area Co-efficient:
This is the ratio of the water plane area to the area of the circumscribing rectangle having a
length equal to L BP and breadth equal to B.
A W
C wp = --------------
L BP X B
Ranges from 0.70 to 0.90
Tonnes per centimeter immersion (TPC)
This is the mass that must be added to or deducted from, a ship in order to change its
mean draught by 1 cm. 7

8. Centre of floatation (F)
This is the centre of gravity or centroid of the water plane area of the ship.
Centre of Buoyancy (B):
this is the centroid of the underwater form of a ship and is the point through which the
total force of buoyancy may be assumed to act. Its position is defined by:
a. KB the vertical distance above the base.
b. FB the longitudinal distance from the forward perpendicular.
c. LCB the longitudinal distance from amidships
Centre of Gravity (G):
This is the point through which the total weight of the ship may be assumed to act. Its
position is defined by
a. KG the vertical distance above the base.
b. FG the longitudinal distance from the forward perpendicular
c. LCG the longitudinal distance from amidships.
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