Design and Construction
The Commander 31's hull is fiberglass built as a balsa-cored sandwich, a layup that improves the indoor climate while demanding special care where fastenings or fittings must penetrate the core. Bianca also built the design at other yards besides the home Danish facility, and the boat was offered with different keel alternatives including a fin keel. With the deeper fin, draft runs about 5.45 to 5.75 feet depending on load, letting her into most marinas; a shoaler fin option draws only about 3.71 to 4.01 feet, opening even shallow harbors. Displacement is near 7,715 pounds with roughly 3,525 pounds of iron ballast, a 46 percent ballast ratio that, with a length-beam ratio of 3.50 and a displacement-length ratio of 317, marks her as a beamy, heavily loaded cruiser rather than a featherweight.
Rig and Handling
The Commander 31 was delivered with more than one rig, either a masthead or a fractional sloop, giving buyers a choice between classic overlap and modern fractional power. Under power, a Volvo Penta MD1B diesel with shaft drive gives a calculated maximum of about 4.0 knots, while her theoretical displacement-hull speed is 6.3 knots. The capsize screening value is 1.81 and the Motion Comfort Ratio falls between 25.4 and 26.6, figures that describe a stable, forgiving coastal cruiser. The immersion rate of about 673 pounds per inch and a wetted surface near 236 square feet round out a picture of a solid, slow-to-react hull in loading but steady on the water.
Accommodations
Below, the boat sleeps six and comes with a galley and a head, finished in mahogany like many of her contemporaries. The interior volume supported by her 8-foot-8-inch beam makes the six-berth layout practical rather than cramped for a boat of her length, and the enclosed head and dedicated galley mark her as a proper cruising accommodation rather than a weekend racer's minimal interior.
Known Issues
Because balsa is used as the sandwich core in the hull, any work requiring penetration of the sandwich construction calls for special care to avoid core damage or moisture ingress. A buyer or owner should treat through-hulls, chainplate bolts, and added fittings with particular attention to sealing the core from water.
The Verdict
The Commander 31 is a thoughtfully specified Danish cruiser from the late-sixties design of Hansen and Kjærulff, offering shoal and deep fin options, a choice of rigs, and a mahogany interior with six berths. Her balsa-cored hull demands respect at every penetration, but her heavy-cruiser numbers and modest power profile suit her to comfortable coastal and inland sailing.
Pros
- Shoal and deep fin keel options widen her cruising range
- Choice of masthead or fractional rig suits owner preference
- Six berths with galley and head in a beamy 31-foot hull
- Stable, comfort-oriented heavy-cruiser proportions
Cons
- Balsa-cored hull requires careful sealing at all penetrations
- Modest 4.0-knot engine maximum limits motoring pace
