Stability – I : Chapter 9

5. A ship of 4000t displacement has KG 5.1 m, KB 2.1m, KM 5.5m . Find the moment of statical stability when she heels 24 degree , assuming that she is wall- side.

Solution :

Displacement (W) = 4000t,
KG = 5.1m ,KB = 2.1m &  KM = 5.5m,
Heel =24degree

Here we can calculate :
GM = (KM – KG)
= (5.5 – 5.1)
= 0.4m

Similarly, BM = ( KM – KB)
= (5.5 – 2.1)
= 3.4m

We know that RM can be calculated as :
RM (Righting moment or moment of statical stability)
= (W.GZ)
= W.sinθ ( GM + 1/2 BM tan²θ)  
= 4000  x sin24⁰(0.4 + 1/2 x 3.4 x tan²24^{0 )}  
= 1200tm.