Join Date: Feb 2000
Location: Annapolis, Md
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Caliber 28 Stability
The capsize screening formula only has two factors, the gross weight of the boat and its beam. The formula does not include such extremly major items as sail area, or draft for example. It first becomes widely circulated shortly after the Fastnet Disaster as a short hand for comparing light vs heavy boats. That seemed logical at the time that the formula was developed because the only popular light weight boats of that era were early IOR boats which had notoriously high vertical centers of gravity, comparatively deep canoe bodies, lots of flare and heeled form stability, and very little dampening.
If you attempted to develop a formula during the period that the Capsize Screening Factor was developed and which was so simple that it took away all of the real factors that control the likelihood of a capsize, you would have only two types of craft to lok at in developing your numbers. At that point in time you only had traditional heavier weight sailing craft and early IOR boats, so you would of course conclude that weight was a major factor in predicting capsize.
BUT, in the twenty five years of studies that have followed the Fastenet Disaster, and the initial period of advocacy of the Capsize Screen Formula, weight in and of itself has been pretty much proven to have no real impact on predicting stability and the likelihood of capsize, which is why when the CE developed its STIX (Stability index), the formulas included so many other factors as well. Without sail area and vertical center of effort, weight distribution, buoyancy distribution at various heel angles, draft and keel area etc., any single formula that attempts to rate the likliness of a capsize is bound to be grossly misleading.