Boat Stability Calculator
The boat stability calculator utilizes the Capsize Screening Formula (CSF) to evaluate a vessel's theoretical resistance to capsizing. Developed after the tragic 1979 Fastnet race, this calculation helps determine if a boat's beam and displacement make it better suited for protected coastal waters or rigorous offshore ocean passages.
Understanding the Capsize Screening Formula
The Capsize Screening Formula (CSF) compares a boat's maximum width (beam) against its overall weight (displacement). It is based on the principle that exceptionally wide, light boats are harder to capsize initially, but if they do flip, they tend to stay inverted. Conversely, heavier, narrower boats are more likely to right themselves after a severe knockdown.
How to Interpret Your Score
- CSF Under 2.0: Considered appropriate for Offshore and Ocean Passagemaking. A lower number indicates a heavily ballasted vessel that is much more capable of surviving severe ocean storms and recovering from a capsize.
- CSF Over 2.0: Better suited for Coastal or Protected Waters. These boats are generally lighter and wider (often providing more interior space and faster speeds), but are more prone to remaining inverted if flipped by a massive breaking wave.
Limitations of the Formula
While the CSF is an excellent quick-reference tool, it is not a complete measure of stability. It does not account for where the weight is located in the boat (ballast placement deep in a keel vs. weight high up in the rigging), the hull shape, or the boat's ultimate limit of positive stability (AVS). It should be used as a general guideline rather than a definitive safety guarantee.