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Swan 431
Designer: Sparkman & Stephens  ·  Builder: Nautor  ·  First built: 1976
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About the Swan 431

Designed by the legendary Sparkman & Stephens and built by Finland's prestigious Nautor shipyard, this classic Swan represents the pinnacle of 1970s cruising yacht design. With only 32 hulls produced between 1976 and 1978, the Swan 431 embodies the exclusivity and craftsmanship that made the Swan brand synonymous with quality bluewater cruising. The yacht's impressive 26,500-pound displacement and substantial 11,900-pound ballast create exceptional stability and seaworthiness, while the moderate comfort ratio of 35.55 indicates good motion characteristics in rough seas. Her fin keel with rudder on skeg configuration provides excellent directional stability and balanced helm feel, making her particularly well-suited for offshore passages and serious coastal cruising. The masthead sloop rig with 896 square feet of sail area delivers respectable performance while remaining manageable for shorthanded sailing. Her fiberglass construction ensures durability, and the favorable capsize screening formula of 1.8 confirms her blue water credentials. With a theoretical hull speed of 7.74 knots and well-balanced sail area to displacement ratio, the Swan 431 offers that perfect blend of comfort, safety, and performance that serious cruising sailors seek in a classic yacht.

Core Dimensions
LOA (Length Overall) 43.25 ft / 13.18 m
LWL (Waterline Length) 33.33 ft / 10.16 m
Beam 13.41 ft / 4.09 m
Max Draft 7.40 ft / 2.26 m
Displacement 26,500.00 lb / 12,020 kg
Ballast 11,900.00 lb / 5,398 kg
Ballast Type Lead
Sail Area (Reported) 896.00 ft² / 83.24 m²
Design & Construction
Hull Type Fin with rudder on skeg
Rigging Type Masthead Sloop
Construction FG
Designer Sparkman & Stephens
Builder Nautor
First Built 1976
Last Built 1978
Number Built 32
Related Sailboats ["Oyster 435" · "Hallberg Rassy 42 Frers" · "Baltic 43" · "Tartan 44" · "Cc 43 1"]
Owner Reviews

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Performance Ratios
PHRF Rating PHRF (Performance Handicap Racing Fleet) is a national racing handicap measured in seconds per nautical mile. Lower values indicate faster boats. Ratings are sourced from US Sailing's national database (median across 60+ regional fleets).
Under 0 — Ultralight racer0–90 — Performance racer90–150 — Cruiser/racer150–210 — Typical cruiserOver 210 — Heavy/slow cruiser
 87
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
 16.19
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
 44.91
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
 35.55
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
 1.8
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. 7.74 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
 1.55
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. 1,597.02 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. 16.19
Rig Dimensions
I (Foretriangle Height) 59.00 ft / 17.98 m
J (Foretriangle Base) 17.95 ft / 5.47 m
P (Mainsail Luff) 53.25 ft / 16.23 m
E (Mainsail Foot) 13.75 ft / 4.19 m
SA Fore 529.53 ft² / 49.19 m²
SA Main 366.09 ft² / 34.01 m²
SA Total (100%) 895.62 ft² / 83.21 m²
Est. Forestay Length 61.67 ft / 18.80 m
Engine & Accommodations
Engine Make Perkins
Engine Model 4.108 M
Engine Type Diesel
Horsepower 37
Fuel Capacity 40 gals / 151 L
Water Capacity 100 gals / 379 L
How It Compares

vs. Baltic 43, Hallberg Rassy 42 Frers, Tartan 44

This boat Similar boats
Dimensions
LOA
Swan 431 ★
43.3 ft
Baltic 43
43.3 ft
Hallberg Rassy 42 Frers
43.4 ft
Tartan 44
43.1 ft
LWL
Swan 431 ★
33.3 ft
Baltic 43
35.8 ft
Hallberg Rassy 42 Frers
34.0 ft
Tartan 44
32.7 ft
Beam
Swan 431 ★
13.4 ft
Baltic 43
13.8 ft
Hallberg Rassy 42 Frers
13.0 ft
Tartan 44
12.3 ft
Displacement
Swan 431 ★
26 lbs
Baltic 43
19 lbs
Hallberg Rassy 42 Frers
27 lbs
Tartan 44
18 lbs
Ballast
Swan 431 ★
11 lbs
Baltic 43
8 lbs
Hallberg Rassy 42 Frers
10 lbs
Tartan 44
—
Sail Area
Swan 431 ★
896 sq ft
Baltic 43
—
Hallberg Rassy 42 Frers
958 sq ft
Tartan 44
—
Performance
PHRF Rating (lower = faster)
Swan 431 ★
87 s/nm
Baltic 43
59 s/nm
Hallberg Rassy 42 Frers
—
Tartan 44
98 s/nm
SA / Displacement (higher = more powerful)
Swan 431 ★
16.2
Baltic 43
—
Hallberg Rassy 42 Frers
16.9
Tartan 44
—
Ballast / Disp (higher = stiffer)
Swan 431 ★
44.9 %
Baltic 43
43.0 %
Hallberg Rassy 42 Frers
37.6 %
Tartan 44
—
Comfort Ratio (higher = more comfortable offshore)
Swan 431 ★
35.6
Baltic 43
—
Hallberg Rassy 42 Frers
38.2
Tartan 44
—
Capsize Screening (lower = safer)
Swan 431 ★
1.80
Baltic 43
—
Hallberg Rassy 42 Frers
1.72
Tartan 44
—
Displacement / Length (lower = lighter)
Swan 431 ★
319
Baltic 43
192
Hallberg Rassy 42 Frers
314
Tartan 44
240
Hull Speed
Swan 431 ★
7.7 kts
Baltic 43
—
Hallberg Rassy 42 Frers
7.8 kts
Tartan 44
—
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