The Vanishing Angle, or Angle of Vanishing Stability (AVS), is the heel angle beyond which a sailboat loses its ability to right itself, resulting in a capsize or becoming "turtled" (inverted). As the mast moves past this angle of instability, the boat's righting moment becomes zero or negative, making it unlikely to recover without external help.

Key Characteristics
Capsize Point: If a boat heels beyond this specific angle, it will no longer return to an upright position and will instead continue to roll until it is completely inverted or "turtled".

Stability Marker: It is a critical indicator of a vessel's seaworthiness, particularly for offshore sailing. A higher AVS generally indicates a more stable boat that can recover from more extreme knockdowns.

Influencing Factors: This angle is determined by the vessel's hull shape, weight distribution (ballast), and center of gravity.