Page 142 - statbility for masters and mates

130 Ship Stability for Masters and Mates
This is the Wall-sided formula.
Note. This formula may be used to obtain the GZ at any angle of heel so long as the ship's side at WW1 is parallel to LL1, but for small angles of heel (y up to 5 ), the term 12 BM tan2 y may be omitted.
Example 1
A ship of 6000 tonnes displacement has KB 3 m, KM 6 m, and KG 5.5 m. Find the moment of statical stability at 25 degrees heel.
GZ GM 12 BMtan2y siny
0:5 12 3 tan2 25 sin 25 0:8262 sin 25
GZ 0:35 m Moment of statical stability W GZ
6000 0:35 Moment of statical stability 2100 tonnes m
Example 2
A box-shaped vessel 65m 12m 8m has KG 4m, and is ¯oating in salt water upright on an even keel at 4 m draft F and A. Calculate the moments of statical stability at (a), 5 degrees and (b), 25 degrees heel.
W L B draft 1:025
65 12 4 1:025 tonnes
KB 1 draft 2
KB 2 m
2m 3m 5m 4m 1m
GZ GMsiny 1 sin 5
BM B2
12d
12 12
12 4 BM 3 m
W 3198 tonnes
KB BM KM
KG GM
At 5 heel
GZ 0:0872 Moment of statical stability W GZ
3198 0:0872 278:9 tonnes m