Notes: Also known as the SIRIUS 21 (later to become SIRIUS 22).\nThe SIRIUS 21 is said to be the first North American production-built, ballasted cruising boat with positive flotation. In a more expensive procedure, closed-cell foam was injected into some compartments, then into the gap between the inner and outer hull the full length and up to the deck level. \nIn the early 1980s, the hull was modified to include a reverse sheer transom at which point the boat was renamed the SIRIUS 22. A fixed-keel model was also offered. (See related sailboat SIRIUS 22).\nHeadroom increases to 6.25 ft / 1.9 m with the pop-top up.\nSail Area:\n-Mail: 93 ft² / 8.64 m² \n-Jib: 110 ft² / 10.23 m²\n-Genoa: 156 ft² / 14.5 m²