A ship of 18 000 tonne displacement has KB 5.25 m, KG 9.24 m and second moment of area about the centreline of 82 × 103 m4. Using the wall-sided formula calculate the righting levers at intervals of 5° heel up to 20° and sketch the stability curve up to this angle.

A ship of 18 000 tonne displacement has KB 5.25 m, KG 9.24 m and second moment of area about the centreline of 82 × 103 m4. Using the wall-sided formula calculate the righting levers at intervals of 5° heel up to 20° and sketch the stability curve up to this angle.

Reference: REED'S NAVAL ARCHITECTURE FOR MARINE ENGINEERS (4^th edition), Exercise – 5.16

 

Solution:

GZ = sinθ (GM + 0.5BM*tan²θ)

BM = I/∇

       = 82*10³ * 1.025/18000

       = 4.67 m

GM = KB + BM – KG

        = 5.25 + 4.67 – 9.24

        = 0.68 m

θ	0.5BM*tan2θ	GM + 0.5BM*tan2θ	Sinθ	GZ
0	0	0.68	0	0
50	0.018	0.698	0.087	0.061
100	0.073	0.753	0.177	0.131
150	0.168	0.848	0.258	0.219
200	0.309	0.989	0.342	0.338