Originally launched in 1959, this classic design from Eldredge-McInnis represents traditional American yacht construction at its finest. Built by respected yards including Portsmouth Yacht Co. and C. E. Ryder, the SR 31 embodies the solid craftsmanship values of its era, with construction methods spanning wood, steel, and fiberglass depending on the individual hull.
The boat's substantial 11,000-pound displacement and generous 4,500-pound ballast create exceptional stability and seakeeping ability, making this an ideal platform for serious coastal cruising and offshore passages. Her long keel configuration provides excellent directional stability and comfortable motion in seaway conditions, though at some expense to maneuverability in tight quarters. The masthead sloop rig delivers reliable performance with 478 square feet of working sail area.
With a comfort ratio of 31.25, this design prioritizes seaworthiness and crew comfort over pure speed, reflecting the cruising priorities of her generation. The conservative capsize screening value of 1.77 further reinforces her offshore capability. Modern sailors will appreciate the 22-horsepower auxiliary engine for harbor maneuvering and calm-weather progress. This is quintessentially a cruiser's boat, built for those who value traditional sailing qualities and proven seaworthiness over contemporary performance metrics.
Core Dimensions
LOA (Length Overall)
30.50 ft / 9.30 m
LWL (Waterline Length)
24.00 ft / 7.32 m
Beam
9.82 ft / 2.99 m
Max Draft
4.16 ft / 1.27 m
Displacement
11,000.00 lb / 4,990 kg
Ballast
4,500.00 lb / 2,041 kg
Sail Area (Reported)
478.00 ft² / 44.41 m²
Design & Construction
Hull Type
Long Keel
Rigging Type
Masthead Sloop
Construction
Wood/Steel/FG
Designer
Eldredge-McInnis
Builder
Portsmouth Yacht Co./C. E. Ryder (USA)
First Built
1959
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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
15.52
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.
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
355.23
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
31.25
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
1.77
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.
6.56 kn
S# (Speed Number)
The Speed Number (S#) is a quick performance index. Higher values indicate a faster, more powerful design relative to its size.
Under 3.0 — Slow cruiser3.0–5.0 — Average cruiser5.0–7.0 — Performance cruiserOver 7.0 — Racer
1.24
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.
842.11 pounds/inch
SA/Displacement (Calc)
Calculated Sail Area to Displacement ratio using actual measured sail dimensions rather than reported values. More precise than the reported SA/Disp figure.
14.87
