Limit of positive stability
The limit of positive stability (LPS) is the angle from the vertical at which a boat will no longer stay upright but will capsize, becoming inverted, or turtled. It is also known as the angle of vanishing stability (AVS).
For example, if a boat with an LPS of 120 degrees rolls past this point, i.e. its mast is already at an angle of 30 degrees below the water, it will continue to roll and be completely upside down in the water. Except for dinghy sailboats and multihulls, most larger sailboats (monohull keelboats) have lead or other heavy materials in their keel at the bottom of their hulls to keep them from capsizing or turtling.
The LPS was a part of the Offshore Racing Rules and is used to measure how stable or seaworthy a sailboat is. The modern offshore racing rules published by the International Sailing Federation may also use the measurement.
- Dashew, Steve (8 January 2012). "Evaluating Stability and Capsize Risks for Yachts". setsail.com. Retrieved 22 November 2013.
- Keilman, John (30 October 2011). "Report: Boat in deadly accident unfit for Mackinac race — Craft that capsized called too unstable for long competition in area prone to severe weather". Chicago Tribune. Retrieved 22 November 2013.
- Hawley, Chuck; Rousmaniere, John; Naranjo, Ralph; McCurdy, Shiela (18 October 2011). "Inquiry Into the Chicago yacht Club-Race to Mackinac Capsize and Fatalities" (PDF). US Sailing. Retrieved 23 November 2011.
- Rousmaniere, John (13 September 2012). "Sailing Accidents: Lessons Learned". Sail (magazine). Retrieved November 27, 2013.
- Rousmaniere, John (1980). Fastnet, Force 10: The Deadliest Storm in the History of Modern Sailing (Paperback). W. W. Norton & Company (17 April 2000). p. 304. ISBN 0393308650. ISBN 978-0393308655
- Rousmaniere, John (January 2000). "Revisiting Lessons from the Fastnet". SailNet.com. Retrieved 25 November 2013.
- Forbes, Sir Hugh; Laing, Sir Maurice; Myatt, Lt. Col. James (1979). "1979 Fastnet Race Inquiry" (PDF). Blur.se. Royal Yachting Association, Royal Ocean Racing Club. Retrieved 23 November 2013.