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SELF-RIGHTING BOAT DESIGN 45
W1L1 GM
B
GZ
₠ Slope= GM=0 φ
Neutral stability
c) A ship with negative GM: In this condition, the center of gravity is above its
metacenter point. The slope of the righting arm curve is negative at zero degree heel.
W1L1 ZG
M
GZ
B
₠ φ
Negative stability
Slope= GM
Figure 2. Ship’s Stability Conditions
2.2 Self – Righting Stability
Self-righting stability is an old term in naval architecture history but, it is relatively new
practical concept. On any self-righting vessel, GZ curve does no turns negative throughout 360°
of roll cycle.
All traditional boats have a heel angle which righting levers have degraded to zero. This term is
defined as Point of Vanishing Stability. Frequently, this point does not occur until ship is
completely inverted, but for those have enough buoyancy to stay afloat, any heel angle beyond
Sayı 6, 2016 GiDB|DERGi
