When do single-handed sailors radio in to Channel Zero?

Five typical doors:

• The first long passage alone. The first night without a watch change is a different kind of night.
• The solo race or the record attempt. Weeks of load, in which no one day can rescue another.
• The incident that stayed with you. Damage, a capsize, a night you would rather not think about, and since then something else is aboard with you.
• The change you did not choose. Your crewmate has pulled out; the plan has not.
• The calm that has tipped over. You have been sailing alone for years, and being alone has turned into loneliness.