Page 273 - statbility for masters and mates

Second moments of areas 261
Example 2
Fig. 29.6
A ship's waterplane is 18 metres long. The half-ordinates at equal distances from forward are as follows:
0, 1.2, 1.5, 1.8, 1.8, 1.5, 1.2 metres, respectively.
Find the second moment of the waterplane area about a transverse axis through the centre of ¯otation.
12 ord. SM Area func Lever Moment func Lever Inertia func.
0100000 1.2 4 4.8 1 4.8 1 4.8 1.5 2 3.0 2 6.0 2 12.0 1.8 4 7.2 3 21.6 3 64.8 1.8 2 3.6 4 14.4 4 57.6 1.5 4 6.0 5 30.0 5 150.0 1.2 1 1.2 6 7.2 6 43.2
25:8 S1 84:0 S2 332:4 S3
Area of waterplane 13 CI S1 2 Area of waterplane 1 18 25:8 2
Distance of the Centre of S2 CI Flotation from forward S1
36
51:6 sq. m