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Aquarius 40 Ss
Designer: Sparkman & Stephens  ·  Builder: Turun Teräskaluste (Fin)  ·  First built: 1974
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About the Aquarius 40 Ss

Designed by the legendary Sparkman & Stephens firm, this rare Finnish-built sailboat represents classic 1970s yacht design philosophy with only five hulls ever constructed between 1974 and 1976. Built by Turun Teräskaluste in Finland using wood and fiberglass construction, the Aquarius 40 Ss embodies the quality craftsmanship that Finnish yards were renowned for during this era. At nearly 40 feet with a moderate beam and deep fin keel drawing 6.51 feet, this masthead sloop strikes an appealing balance between performance and comfort. The substantial displacement of 17,200 pounds, with 7,000 pounds of ballast, creates a stable platform well-suited for coastal cruising and offshore passages. Her comfort ratio of 38.59 suggests excellent seaworthiness for extended voyages, while the capsize screening value of 1.55 indicates good stability characteristics. The Sparkman & Stephens pedigree ensures refined sailing qualities and seakindly motion in challenging conditions. With 660 square feet of sail area, she offers respectable performance without being overpowered. Her rarity makes finding one a special opportunity for sailors seeking a distinctive yacht with impeccable design heritage and the robust construction typical of Scandinavian boatbuilding traditions.

Core Dimensions
LOA (Length Overall) 39.83 ft / 12.14 m
LWL (Waterline Length) 28.75 ft / 8.76 m
Beam 10.00 ft / 3.05 m
Max Draft 6.51 ft / 1.98 m
Displacement 17,200.00 lb / 7,802 kg
Ballast 7,000.00 lb / 3,175 kg
Sail Area (Reported) 660.00 ft² / 61.32 m²
Design & Construction
Hull Type Fin Keel
Rigging Type Masthead Sloop
Construction Wood/FG
Designer Sparkman & Stephens
Builder Turun Teräskaluste (FIN)
First Built 1974
Last Built 1976
Number Built 5
Related Sailboats S&S 40 (1964)
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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
 15.91
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
 40.7
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
 323.12
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
 38.59
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
 1.55
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. 7.18 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. 1,027.27 pounds/inch
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