I think the discussion should take into consideration that many of the CCA and IOR era boats were not designed to be "bluewater" cruisers. Most were designed to out-perform their competition on a race course with plenty of crew. Now that they are no longer competitive many have been converted over to dedicated cruisers; some being more well suited to it than others. It really depends on the particular boat you are talking about. I think motion comfort index is a good indicator of how well suited a boat is to extended cruising. If the boat is stiff and pounds it's way through the chop you are going to get fatigued long before you make your destination. Many of the "bluewater" designed boats are heavy displacement and full keeled to resist pounding and awkward rolling motions.
Capsize ratio seems to be less relevant in terms of overall "seaworthiness" than you might think. A big breaking wave is bad news regardless of the hull form; as described below. Does that mean I want a boat that has a low capsize ratio? No; but a high number does not mean you boat won't capsize in certain conditions.
There is some good information on the US Sailing website here are a few quotes:
US Sailing Website
Quote:
According to Andrew Claughton in Heavy Weather Sailing 30th ed. p 21 "This (the test data presented in the chapter) suggests that alterations in form (of a sailboat) that improves capsize resistance may be rendered ineffective by a relatively small increase in breaking wave height."
If a boat is positioned into a breaking wave, most boats (wide and narrow beamed) can survive a 55% LOA (overall boat length) breaking wave. However, a 35% LOA breaking wave hitting a wide-beamed boat beam-on can easily capsize the boat. All yachts tested rolled to 130 degrees. No yacht, no matter how stable, could consistently resist capsizing when hit, beam-on, with a 55% LOA breaking wave. (K. Adlard Coles' and Peter Bruce's (editors) Adlard Coles' Heavy Weather Sailing (30th edition) Stability of Yachts in large breaking waves. Chapter 2 pp11-23 International marine, Camden, Maine)
Putting this in perspective in a 40 foot (LOA) sailboat: In a highly stable boat wave survivability would increase by 8 feet, if hit beam-on by a breaking wave. A 40 foot sailboat no matter how stable will not consistently survive a 22 foot breaking wave. Thus, in a strong gale with 22 foot seas and breaking waves, a 40 foot sailboat is at risk of capsizing no matter how stable.
Most important factor is an experienced crew: Of all the factors, it is far more beneficial to have an experienced crew that can either avoid or position the boat into large breaking waves.
The 1998 Sydney - Hobart race was one of the worst sailing disasters in recent maritime history. And from it many lessons were learned regarding the functioning of boats and crews in heavy weather. 115 boats left Sydney and were hit by an unexpected typhoon. Seven boats were abandon and five were lost. The 1998 Sydney to Hobart Race Review Committee report, summarized by Peter Bush, committee chair, reported the following as one of the significant findings: "There is no evidence that any particular style or design of boat fared better or worse in the conditions. The age of yacht, age of design, construction method, construction material, high or low stability, heavy or light displacement, or rig type were not determining factors. Whether or not a yacht was hit by an extreme wave was a matter of chance." (Ref: Rob Mundle in Fatal Storm, Publisher's Afterward p 249. International Marine/McGraw-Hill Camden, Maine.)
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