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Stuart Knockabout
Designer: L. Francis Herreshoff/Bill Harding  ·  Builder: E&D  ·  First built: 1932
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About the Stuart Knockabout

Dating back to 1932, this classic design represents the collaborative genius of L. Francis Herreshoff and Bill Harding, blending traditional craftsmanship with thoughtful sailing characteristics. Built by E&D in both wood and fiberglass construction, the Stuart Knockabout earned its reputation as a capable coastal cruiser and club racer during sailing's golden era. At 28 feet overall with a 22.83-foot waterline, this fractional sloop strikes an appealing balance between manageable size and seaworthy performance. The substantial 2,400-pound ballast ratio and deep 5.5-foot draft provide excellent stability and upwind performance, while the moderate beam keeps the boat responsive and lively. With 291 square feet of sail area driving 4,000 pounds of displacement, the Stuart Knockabout offers spirited performance in moderate conditions. The hull's keel/centerboard configuration enhances versatility, allowing access to shallow harbors while maintaining the tracking ability of a fixed keel offshore. With only 81 hulls produced, these boats represent a rare find for enthusiasts seeking classic lines and proven seaworthiness. The design excels in coastal cruising, club racing, and weekend adventures, offering the timeless appeal of a well-proportioned traditional yacht with modern sailing capabilities.

Core Dimensions
LOA (Length Overall) 28.00 ft / 8.53 m
LWL (Waterline Length) 22.83 ft / 6.96 m
Beam 6.92 ft / 2.11 m
Max Draft 5.50 ft / 1.68 m
Min Draft 2.75 ft / 0.84 m
Displacement 4,000.00 lb / 1,814 kg
Ballast 2,400.00 lb / 1,089 kg
Ballast Type Lead
Sail Area (Reported) 291.00 ft² / 27.03 m²
Design & Construction
Hull Type Keel/Cbrd.
Rigging Type Fractional Sloop
Construction Wood or FG
Designer L. Francis Herreshoff/Bill Harding
Builder E&D
First Built 1932
Number Built 81
Related Sailboats ["Rozinante Herreshoff" · "Cal 28" · "Pied Piper 28" · "Pearson 28 1975 80" · "Sabre 28 1"]
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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
 189
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
 18.53
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
 60
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
 150.07
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
 19.26
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
 1.75
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. 6.40 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
 3.58
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. 564.49 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. 18.52
Rig Dimensions
I (Foretriangle Height) 24.00 ft / 7.32 m
J (Foretriangle Base) 8.75 ft / 2.67 m
P (Mainsail Luff) 28.60 ft / 8.72 m
E (Mainsail Foot) 13.00 ft / 3.96 m
SA Fore 105.00 ft² / 9.75 m²
SA Main 185.90 ft² / 17.27 m²
SA Total (100%) 290.90 ft² / 27.03 m²
Est. Forestay Length 25.55 ft / 7.79 m
How It Compares

vs. Cal 28, Pearson 28 1975 80, Pied Piper 28

This boat Similar boats
Dimensions
LOA
Stuart Knockabout ★
28.0 ft
Cal 28
28.0 ft
Pearson 28 1975 80
28.0 ft
Pied Piper 28
28.0 ft
LWL
Stuart Knockabout ★
22.8 ft
Cal 28
22.5 ft
Pearson 28 1975 80
24.0 ft
Pied Piper 28
21.3 ft
Beam
Stuart Knockabout ★
6.9 ft
Cal 28
9.0 ft
Pearson 28 1975 80
9.3 ft
Pied Piper 28
8.8 ft
Displacement
Stuart Knockabout ★
4 lbs
Cal 28
6 lbs
Pearson 28 1975 80
7 lbs
Pied Piper 28
8 lbs
Ballast
Stuart Knockabout ★
2 lbs
Cal 28
2 lbs
Pearson 28 1975 80
3 lbs
Pied Piper 28
2 lbs
Sail Area
Stuart Knockabout ★
291 sq ft
Cal 28
352 sq ft
Pearson 28 1975 80
395 sq ft
Pied Piper 28
345 sq ft
Performance
PHRF Rating (lower = faster)
Stuart Knockabout ★
189 s/nm
Cal 28
204 s/nm
Pearson 28 1975 80
—
Pied Piper 28
246 s/nm
SA / Displacement (higher = more powerful)
Stuart Knockabout ★
18.5
Cal 28
17.1
Pearson 28 1975 80
16.1
Pied Piper 28
13.4
Ballast / Disp (higher = stiffer)
Stuart Knockabout ★
60.0 %
Cal 28
—
Pearson 28 1975 80
45.0 %
Pied Piper 28
—
Comfort Ratio (higher = more comfortable offshore)
Stuart Knockabout ★
19.3
Cal 28
20.6
Pearson 28 1975 80
24.9
Pied Piper 28
31.0
Capsize Screening (lower = safer)
Stuart Knockabout ★
1.75
Cal 28
1.98
Pearson 28 1975 80
1.86
Pied Piper 28
1.72
Displacement / Length (lower = lighter)
Stuart Knockabout ★
150
Cal 28
—
Pearson 28 1975 80
253
Pied Piper 28
—
Hull Speed
Stuart Knockabout ★
6.4 kts
Cal 28
6.4 kts
Pearson 28 1975 80
6.6 kts
Pied Piper 28
6.2 kts
Speed Number (higher = faster)
Stuart Knockabout ★
3.6
Cal 28
2.3
Pearson 28 1975 80
2.0
Pied Piper 28
—
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