Sail Skills - Stability Free guide to ship and small vessel stability. Aimed at small vessel users but suitable for professional mariners. Diagrams, text and animations explaining stability: from righting lever to movement of liquid in tanks – the free surface effect. Demonstrates adding weights to a vessel, heel and list. Especially recommended for RYA examination candidates. Righting moment and lever A small sailing vessel heeled by the wind Diagram: relating topweight in a sailing vessel to levers and moments Levers & moments Diagram: a vessel heeled showing righting lever (GZ) A vessel recovering from inversion Inverted Stability Heel & angle of heel Diagram: a vessel kept afloat by her buoyancy Buoyancy Diagram: centre ofbuoyancy (CB) of a vessel heeling Centre of buoyancy (CB) Diagram: a vessel at the angle of vanishing stability (AVS) Angle of vanishing stability (AVS) GZ Curve for a stiff and tender vessel - showing initial steepness of curves GZ Curves Centre of gravity (CG) Diagram: centre of gravity (CG) of a vessel heeling
Every penny helps … Stability Home>Stability Explained>Angle of Vanishing Stability The angle of vanishing stability (AVS) is the angle of heel at which the righting lever (GZ) is zero Beyond the AVS buoyancy and weight act together to capsize the vessel Once capsized, many vessels become stable in the inverted position. Both these vessels are stable in the inverted position, but one much more than the other: back to top Inverted vessels at varying angles of heel Inverted vessels at varying angles of heel A RNLI rescue vessel with large water-tight superstructure A RNLI rescue vessel with large water-tight superstructure “Inverted stability” - the tendency of a vessel to remain inverted - is discussed more fully in the relevant section
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