Statical stability curve. (GZ curve)

Introduction

The Statical stability curve or the GZ curve is drawn by plotting the GZ values against the angle of heel. It is drawn for each voyage condition for a particular displacement and KG.

Illustration 1: GZ curve - Source - http://thenauticalsite.com/NauticalNotes/Stability/MyStability-Lesson06-CurvesofStatStab.htm

 Following data can be extracted from a GZ curve,

1. Initial metacentric height (GM). Its the point of intersection when a tangent drawn at the origin and the purpendicular at 57.3° or 1 radian meets. The scale on the GZ shows the value of initial GM.
2. Point of contra fexture. Point of Contra flexture means the point on the curve where the direction of bending. Angle of heel at this point represents the angle of deck edge immersion (DEI).
3. Maximum GZ and the angle of heel it occurs.
4. The range of piositive stability.
5. Angle of of vanishing stabitlity.
6. The moment of stability for a given angle of heel. (GZ x Displacement = FLM)
7. The dynamical stability for a given angle of heel. (Dynamical stability at Ɵ° = Ship's displacement in tonnes (W) x Area between the GZ curve and the baseline upto the angle of heel in im meter-radians. (A))