Coastal Skipper and Yachtmaster Quiz · Heavy weather and stability
This is a stability (GZ) curve for a yacht. What does the ringed point at 125° tell you?
A graph of a yacht's righting lever, GZ, against angle of heel from 0 to 180 degrees. The curve rises from zero to a peak at about 50 degrees, falls back to cross the zero line at 125 degrees, and stays below the line from there to 180 degrees. The crossing point at 125 degrees is ringed in gold.
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The angle of vanishing stability: heeled beyond it, she tends to carry on over, not come back upright. The curve shows the righting lever at each angle of heel. Where it crosses zero is the angle of vanishing stability: up to that angle the yacht tends to come back upright, and beyond it she tends to go on over and stay inverted until a wave rights her. The curve is for the yacht intact and loaded as tested: water getting below changes it. The higher that angle, and the smaller the area under the line beyond it, the better.
