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Capsize Factor
special to anyboat.com
The capsize risk factor sounds rather like a formula for predicting disaster. Actually it
is a formula that was used after the Fastnet Race disaster - to help guide designers and
sailors. To help understand a particular value it is best to look at the values
generated by the designs of some very respected naval architects.
Thanks to Jim Manzari an analysis of 67 cruising designs is shown in
the below table. The boat parameter data was compiled by John Holtrop.
Designer | Median Capsize Risk | Number of Designs |
Brewer | 1.72 | 9 |
Crealock |
1.62 | 15 |
Holman | 1.61 | 4 |
Paine | 1.75 | 10 |
Perry | 1.70 | 25 |
Roberts | 1.66 | 4 |
All designs | 1.67 | 67 |
Jim Manzari has also allowed anyboat.com to reproduce the following commentary, which can be found in the World Crusing archives. "One way to look at this question is the average (or better yet, the median) capsize screen factor carried by boats created by some arguably eminent offshore boat designers. Some sailors might consider Brewer, Crealock, Perry, Holman, Paine, and Roberts sort of the fathers of blue-water offshore cruising -- there are certainly other fine offshore designers -- for the purposes of answering your question, these will probably do. Selected all the designs contained in John Holtrop's boat database and calculating the median (50% greater, 50% less than) point gives: - The range of cap-risk is from 1.48 (Holman's Oyster 70) to 1.85 (Perry's Royal Pasport 47). Hope this is helpful." I am sure it is Jim, thank-you.
According to the capsize formula published in the May 1997 issue of Practical
Boatowner, anything less than 2 is considered "good". If you would like to
find the capsize "value" of your vessel divide the displacement of the vessel by
64, then take the cube root of that number and divide into the beam of the vessel,
or just use the form below! Just a word of caution, anyboat does not recommend the
use of any one formula for determining vessel stability or if a vessel's design is
seaworthy.
CAPSIZE CALCULATOR
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