From the following excellent article by Peter Johnstone on Sail Magazine:
By their nature, larger catamarans are exceptionally safe offshore. It is not unusual to sail through mildly uncomfortable conditions, such as a gale, only to arrive in port and hear sailors on keelboats talk of “surviving” horrendous weather. A large modern catamaran has plenty of buoyancy and exceptional roll inertia. Together these make a capsize, or inversion, highly unlikely. A 30-foot breaking wave hitting a cat abeam will simply make the boat surf sideways.
On most offshore passages, advanced communications and weather information should preclude you from ever experiencing true gale or survival conditions. The highest risks are run on passages sailed on a north-south axis between seasons. Early spring or late autumn passages between New England and the Caribbean, in eastern Atlantic waters off Europe, or on routes between the South Pacific and New Zealand are where you typically have a chance of experiencing a good wallop offshore. Follow the wisdom outlined in Jimmy Cornell’s World Cruising Routes, and these risks should be minimized. Regardless, anyone venturing offshore in a multihull should be prepared to handle the worst.
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