Page 149 - Introduction to Naval Architecture
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STRENGTH 135
Figure 7,8
from the ANA. The second moments of area give the moment of inertia
about the ANA and this can be corrected for the position of the true
NA. This is illustrated for the diagrammatic cross section shown in
Figure 7.8, noting that the second moments of thin horizontal
members about their own centroids will be negligible.
It will be noted that material in the centre of the top two decks is not
included. This is to compensate for the large hatch openings in these
decks. Because of the ship's symmetry about its middle line, it is
adequate to carry out the calculation for one side of the ship and then
double the resulting answer. In this example the ANA has been taken
at the keel.
From Table 7.1, the height of the NA
above the keel
Second moment of area of half
section about keel = 40.008 + 2.565
For the whole section the Z values are:
