Page 210 - Practical Ship Design

176 Chapter 6

From F,, = 0.21 to 0.29, x is constant at 0.83,
thereafter it increases steadily to a value at
F,, = 0.60 of 1.77.
From F, = 0.21 to 0.25, y is constant at 0.50,
thereafter it increases steadily to a value at
F,, = 0.60 of 1.47
A simple formula as given for single-screw ships is not possible, but an abbreviated
presentation is given in Table 6.1.

Table 6.1
Mumford indices for twin-screw ships (abbreviated list with rounded figures)

B2/B 1 Beam factor
_____~
F, 0.24 0.28 0.32 0.36 0.40 0.44
~ ~ ~ ~ ~ ~ ~ ~ ~ _ _ _ _ _ _ _ _ _ _ _ _
0.75 0.95 0.95 0.9 1 0.86 0.82 0.79
0.80 0.96 0.96 0.92 0.88 0.86 0.83
0.85 0.97 0.97 0.95 0.92 0.90 0.88
0.90 0.98 0.98 0.97 0.95 0.93 0.92
0.95 0.99 0.99 0.98 0.97 0.96 0.96

T2/T1 Draft factor

0.45 1.14 I .02 0.94 0.9 I 0.8 I 0.66
0.50 1.12 1.02 0.94 0.92 0.83 0.70
0.55 1.10 1.02 0.95 0.93 0.85 0.73
0.60 1.09 1.01 0.96 0.94 0.87 0.77
0.65 1.08 1.01 0.97 0.95 0.89 0.80
0.70 I .06 1.01 0.87 0.96 0.9 1 0.83
0.75 1 .os 1.01 0.98 0.97 0.93 0.86
0.80 1.04 1.01 0.98 0.97 0.94 039
0.85 1.03 1 .00 0.99 0.98 0.96 0.92
0.90 I .02 I .OO 0.99 0.99 0.97 0.94
0.95 1.01 I .00 I .00 0.99 0.99 0.97
_
_
~__ ~ ~ - ~~ ~_____ ~
__--
~
For values of B2/B 1 or T2/TI greater than unity use the reciprocal of the parameter and the reciprocal of the factor