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Commander 31 Bianca
Designer: Knud E. Hansen & Jan Kjærulff  ·  Builder: Bianca Yachts  ·  First built: 1969
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About the Commander 31 Bianca

Designed by the renowned Danish duo Knud E. Hansen and Jan Kjærulff, this classic 1970s cruiser represents solid Scandinavian yacht design principles during sailing's golden era. Built by Bianca Yachts from 1969 to 1976, the Commander 31 combines moderate proportions with seaworthy characteristics that made it appealing to cruising sailors of the period. The boat's traditional fin keel with rudder on skeg configuration provides directional stability and easier steering, particularly valued for longer passages. With a displacement of 7,715 pounds and substantial ballast ratio, she offers the steady, predictable motion preferred by cruising sailors over racing-oriented designs. The fractional sloop rig keeps sail handling manageable while providing adequate power for coastal and light offshore work. Her 22-foot waterline length and moderate beam create comfortable interior volume without sacrificing sailing characteristics. The comfort ratio of 26.62 suggests pleasant motion in seaway conditions, while the capsize screening value of 1.79 indicates reasonable stability margins for coastal cruising ventures. With 150 hulls produced during her seven-year run, the Commander 31 found favor among sailors seeking reliable, unpretentious cruising boats. Today, these well-built fiberglass classics appeal to sailors appreciating traditional design values and proven seaworthiness for coastal and near-offshore adventures.

Core Dimensions
LOA (Length Overall) 30.70 ft / 9.36 m
LWL (Waterline Length) 22.00 ft / 6.71 m
Beam 8.83 ft / 2.69 m
Max Draft 3.70 ft / 1.13 m
Displacement 7,715.00 lb / 3,499 kg
Ballast 3,525.00 lb / 1,599 kg
Sail Area (Reported) 334.00 ft² / 31.03 m²
Design & Construction
Hull Type Fin with rudder on skeg
Rigging Type Fractional Sloop
Construction FG
Designer Knud E. Hansen & Jan Kjærulff
Builder Bianca Yachts
First Built 1969
Last Built 1976
Number Built 150
Owner Reviews

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Performance Ratios
SA/Displacement Sail Area to Displacement ratio measures how much sail power a boat has relative to its weight. Higher values mean more performance and speed.
Under 14 — Heavy cruiser, slow14–18 — Cruising sailboat18–22 — Cruiser/racerOver 22 — Performance racer
13.73
Ballast/Displacement Ballast to Displacement ratio shows what percentage of the boat's total weight is ballast. Higher values generally mean better initial stability and stiffer sail carrying.
30–35% — Typical cruiser35–45% — Stiff performance boatOver 45% — Racing oriented
45.69
Displacement/Length Displacement to Length ratio measures how heavy a boat is relative to its waterline length. Lower values mean a lighter, faster boat.
Under 100 — Ultralight racer100–200 — Light cruiser/racer200–300 — Moderate cruiser300–400 — Heavy cruiserOver 400 — Very heavy
323.46
Comfort Ratio Ted Brewer's Comfort Ratio predicts how comfortable a boat will feel in offshore conditions. Higher values mean a steadier, more comfortable motion in a seaway.
Under 20 — Uncomfortably rough20–30 — Acceptable coastal30–40 — Good offshore comfortOver 40 — Very comfortable offshore
26.62
Capsize Screening Formula The USHS Capsize Screening Formula estimates offshore capsize risk. Lower is safer — values under 2.0 are considered acceptable for offshore sailing.
Under 2.0 — Safe for offshore2.0–2.2 — Borderline offshoreOver 2.2 — Coastal use recommended
1.79
Hull Speed Hull Speed is the theoretical maximum speed of a displacement hull, calculated from waterline length. Most cruising sailboats reach this speed in moderate conditions. 6.29 kn
Pounds/Inch Immersion Pounds per Inch Immersion (PPI) tells you how much weight is needed to sink the boat one inch. Useful for calculating how additional gear and stores affect waterline. 694.11 pounds/inch
Engine & Accommodations
Engine Make Volvo Penta
Engine Type Diesel
Horsepower 10
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