Design and Construction
The Cape Dory 31 has a solid-fiberglass hull, a long keel, and about 258 square feet of wetted surface. Her hull sits on a 23.25-foot waterline, with a 9.75-foot beam and a 4.75-foot draft.
Her length-to-beam ratio is 3.22, making her slimmer than 54 percent of comparable designs. A displacement-length ratio of 408 places her among ultra-heavy cruisers; only 4 percent of similar sailboats are rated heavier. Her 11,500-pound displacement includes 4,350 pounds of lead ballast, for a ballast ratio of 38 percent—higher than 34 percent of similar designs. Together, these figures describe a conservative hull intended to track well and absorb sea state.
The Cape Dory 31’s motion comfort ratio is 33.1, making her more comfortable than 92 percent of similar sailboat designs. Her immersion rate of 790 pounds per inch indicates how stubbornly she holds her lines when loaded.
Rig and Handling
The cutter rig carries noticeably more sail plan than 73 percent of similar sailboats, leaving the Cape Dory 31 slightly overrigged. With the ISO reference sail, her sail-area-to-displacement ratio is 15.8. That figure rises to 18.9 with a 135 percent genoa, making her faster in light wind than 42 percent of similar designs.
Her capsize screening value is 1.73, and her theoretical hull speed is 6.5 knots. Halyard and sheet estimates call for 28-meter halyards at 10 mm and mainsheet runs near 24 meters at 12 mm—useful dimensions when rerigging.
Accommodations and Intended Use
The available description presents the Cape Dory 31 as a heavy, narrow, comfortable passage cruiser rather than documenting a specified interior plan. She’s a sailor’s cruiser in the Alberg mold: conservative, ballast-steady, and built by a yard with a long partnership with Alberg.
Verdict
The Cape Dory 31 is a small-production Alberg cutter that earns her keep as a steady, heavy-displacement cruiser. She combines exceptional motion comfort with a conservative long-keel hull. The numbers describe a boat built to be lived aboard in weather, not to win starts.
Pros
- More comfortable motion than 92 percent of similar designs
- Ultra-heavy-cruiser displacement for sea-kindly behavior
- Traditional long-keel cutter rig designed by Carl Alberg
Cons
- Slightly overrigged relative to 73 percent of similar sailboats
- Slimmer and slower in light wind than many comparable designs
