The capsize screening formula (CSF) is a controversial method of establishing the ability of boats to resist capsizing. It is defined for

sailboats A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...

as:

Beam Beam may refer to: Streams of particles or energy * Light beam, or beam of light, a directional projection of light energy ** Laser beam * Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized g ...

/ ((

Displacement Displacement may refer to: Physical sciences Mathematics and Physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

/64.2)^1/3), with Displacement measured in pounds, and Beam in feet. A lower figure supposedly indicates greater stability, however the calculation does not consider factors such as hull shape or ballast.

Background

The formula came into being after the 1979 Fastnet race in England where a storm shredded the race fleet. The

Cruising Club of America The Cruising Club of America (CCA) is an international organization of cruisers whose objects are to promote cruising and racing by amateurs, to encourage the development of suitable types of cruising craft, to stimulate interest in seamanship, navi ...

(CCA) put together a technical committee that analyzed race boat data. They came up with the formula to compare boats based on readily available data. The CCA characterizes the formula as "rough". A lower value is supposed to indicate a

sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...

is less likely to

capsize Capsizing or keeling over occurs when a boat or ship is rolled on its side or further by wave action, instability or wind force beyond the angle of positive static stability or it is upside down in the water. The act of recovering a vessel fr ...

. A value of 2 is taken as a cutoff for acceptable to certain race committees. However this is an arbitrary cutoff based on the performance of boats in the 1979 Fastnet race. The CSF does not consider the hull shape or

ballast Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, ...

location. Any two

will have the same CSF value if their displacement and beam are the same. As an example, one could have a light hull with 50%

in a bulb at the bottom of an eight foot fin

keel The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in B ...

, the other could have a heavy hull with 20% ballast in a full-length

. The stability characteristics of the two

will be drastically different despite the identical CSF value.

References

* Davis, Stephen L. ''Desirable and Undesirable Characteristics of the Offshore Yachts'', W.W. Norton, 1987. * Howard, J. ''Handbook of Offshore Cruising: The Dream and Reality of Modern Ocean Cruising'', Sheridan House, 2000. * Rousmaniere, John. ''Fastnet Force 10'', Nautical Publishing, 1980. * Vigor, John. ''The Practical Mariner's Book of Knowledge'', McGraw-Hill Professional, 1994.

External links

Capsize formula for displacement sailboats.

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