SHIP
CONSTRUCTION

BULBOUS BOW

Objective
1) To understand the constructional
features of bulbous bow.
2) Operational requirement for
incorporating bulbous bow on ships.

Background
• Mr. Froude’s experiment
• Russian sciencetist Mr. VLADIMIR
• SS Normandie
• Mr. TAKAO INUI

1) A bulbous bow is an extension of the
hull just below the load waterline
2) The basic purpose is to create a low-
pressure zone to reduce or eliminate
the bow wave and reduce the
resulting drag

Working Principle
• The wave system generated by the bulb interferes
with the kelvin wave system of the ship.
• The length of the bulb defines the phase of
interference and its volume determines the width of
its wave system.
• Destructive interference of waves.

1) Generally at low speeds the effect
of the bulb is negative. When the
Froude Number (FN) increases, its
effect becomes positive and
increases up to a maximum value.
2) Until now, a bulbous bow has been
often designed using Kracht charts,
which were established based on
model test data, but these charts
apply only to ships with a block
coefficient CB = 0.56-0.82, Froude
number Fn = 0.20-0.40, and the

Advantages of bulbous bow
• Reduces bow generated waves.
• Act as a robust bumper in event of collision
• It reduces pitching to a small extent
• Allows installation of bow thrusters to maximum fwd of ship’s
length
• Act as reserve buoyancy at forward of ship or reserve for
floatation
• It increases the ship’s water line length, slightly increasing ships
speed
• Decreases fuel consumption by 10 to 15 percent.
• Typical use in ice breaking ships.

Constructional Features

Conclusion
• History
• Theory
• Advantages
• Construction