Page 23 - Introduction to Naval Architecture

DEFINITION AND REGULATION 11

where L pp is length between perpendiculars
B is the extreme breadth underwater
T is the mean draught.

Corresponding to their moulded displacement Lloyd's Register use a
block coefficient based on the moulded displacement and the Rule
length. This will not be used in this book.

where A w is waterplane area
L WL is the waterline length
B is the extreme breadth of the waterline.

Midship section coefficient, C M

where A M is the midship section area
B is the extreme underwater breadth amidships.

Longitudinal prismatic coefficient, Cp

It will be noted that these are ratios of the volume of displacement to
various circumscribing rectangular or prismatic blocks, or of an area to
the circumscribing rectangle. In the above, use has been made of
displacement and not the moulded dimensions. This is because the
coefficients are used in the early design stages and the displacement
dimensions are more likely to be known. Practice varies, however, and
moulded dimensions may be needed in applying some classification
societies' rules.
The values of these coefficients can provide useful information about
the ship form. The block coefficient indicates whether the form is full
or fine and whether the waterlines will have large angles of inclination
to the middle line plane at the ends. The angle at the bow is termed the
angle of entry and influences resistance. A large value of vertical
prismatic coefficient will indicate body sections of U-form, a low value