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Colvic Craft 31
Designer: John Bennet & Assoc.  ·  Builder: Covic Craft / Ardleigh Lam. Plastics  ·  First built: 1972
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About the Colvic Craft 31

Launched in 1972, this masthead ketch from John Bennet & Associates represents classic British yacht design philosophy of the early 1970s. Built by Colvic Craft and later Ardleigh Laminated Plastics, the design emphasizes seaworthiness and comfort over racing performance, making it well-suited for coastal cruising and offshore passages. The long keel configuration provides excellent directional stability and comfortable motion in seaways, though at the expense of maneuverability in tight quarters. With a displacement of 15,695 pounds and moderate sail area, this yacht prioritizes steady progress over speed, achieving a hull speed of 7.09 knots. The ketch rig offers versatility in sail handling and balance, particularly valuable for shorthanded sailing or heavy weather conditions. The comfort ratio of 39.04 indicates a motion that favors relaxed cruising over athletic sailing, while the capsize screening formula of 1.6 suggests good stability characteristics for offshore work. The SA/Displacement ratio of 7.53 confirms this is a cruising design rather than a performance-oriented yacht. This combination of characteristics makes the Colvic Craft 31 appealing to sailors seeking a traditional, seaworthy platform for extended coastal cruising or ocean voyaging.

Core Dimensions
LOA (Length Overall) 31.00 ft / 9.45 m
LWL (Waterline Length) 27.99 ft / 8.53 m
Beam 10.01 ft / 3.05 m
Max Draft 4.00 ft / 1.22 m
Displacement 15,695.00 lb / 7,119 kg
Sail Area (Reported) 294.00 ft² / 27.31 m²
Design & Construction
Hull Type Long Keel
Rigging Type Masthead Ketch
Construction FG
Designer John Bennet & Assoc.
Builder Covic Craft / Ardleigh Lam. Plastics
First Built 1972
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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
 7.53
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
 319.52
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
 39.04
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
 1.6
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. 7.09 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. 1,001.11 pounds/inch
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