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Flatfish
Designer: Herreshoff/Joel White  ·  Builder: Fairey Marine Ltd. / O'day  ·  First built: 1960
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About the Flatfish

Originally designed by the legendary Nathanael Herreshoff and later refined by renowned naval architect Joel White, the Flatfish represents a thoughtful blend of classic yacht design principles with practical cruising capabilities. This 20-foot fractional sloop emerged in 1960 through builders Fairey Marine Ltd. and O'Day, combining traditional wood construction with fiberglass elements. With her generous beam of 7.5 feet and substantial displacement of 3,094 pounds, the Flatfish offers impressive stability and interior volume for her size. The keel/centerboard configuration provides versatility, allowing access to shallow waters while maintaining good windward performance when the board is deployed. Her moderate draft of 4.25 feet strikes an excellent balance between shoal water capability and sailing efficiency. The boat's sail-area-to-displacement ratio of 20.1 indicates spirited performance in light to moderate conditions, while the comfortable 18.83 comfort ratio suggests she's well-suited for extended coastal cruising rather than aggressive racing. Her low capsize screening value of 2.06 reflects the inherent stability that made these designs popular among families and cruising sailors. The Flatfish excels as a weekender for protected waters and near-coastal exploration, offering the charm of classic design with practical sailing characteristics.

Core Dimensions
LOA (Length Overall) 20.25 ft / 6.17 m
LWL (Waterline Length) 16.08 ft / 4.90 m
Beam 7.50 ft / 2.29 m
Max Draft 4.25 ft / 1.30 m
Min Draft 2.16 ft / 0.66 m
Displacement 3,094.00 lb / 1,403 kg
Sail Area (Reported) 266.00 ft² / 24.71 m²
Design & Construction
Hull Type Keel/Cbrd.
Rigging Type Fractional Sloop
Construction Wood/FG
Designer Herreshoff/Joel White
Builder Fairey Marine Ltd. / O'Day
First Built 1960
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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
20.1
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
332.21
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
18.83
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
2.06
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. 5.37 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. 430.92 pounds/inch
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