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Estuary One Design Uk
Designer: Morgan-Giles  ·  First built: 1911
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About the Estuary One Design Uk

Dating back to 1911, this classic Morgan-Giles design represents over a century of refined sailing heritage. With just 115 hulls built, the Estuary One Design UK holds distinction as an exclusive centerboard dinghy that bridges traditional craftsmanship with practical sailing performance. At 18 feet overall with a modest 6-foot beam, this fractional sloop-rigged vessel offers an ideal platform for coastal day sailing and competitive racing. The centerboard configuration provides versatility for exploring shallow estuaries and protected waters, while the 850-pound displacement ensures reasonable stability for crew comfort. Wood and fiberglass construction reflects both its historical origins and practical durability needs. The boat's sail area of 210 square feet delivers spirited performance without overwhelming smaller crews, making it well-suited for club racing and recreational sailing. Its relatively light 200-pound ballast suggests this design relies more on crew weight and sailing technique than pure stability, characteristic of responsive dinghies that reward skilled handling. With a hull speed of 5.48 knots and moderate comfort ratio, the Estuary One Design appeals to sailors seeking a traditional sailing experience with competitive potential. This rare design offers collectors and enthusiasts access to a piece of British sailing history while maintaining practical modern sailing capabilities.

Core Dimensions
LOA (Length Overall) 18.00 ft / 5.49 m
LWL (Waterline Length) 16.75 ft / 5.11 m
Beam 6.00 ft / 1.83 m
Max Draft 3.00 ft / 0.91 m
Min Draft 0.90 ft / 0.27 m
Displacement 850.00 lb / 386 kg
Ballast 200.00 lb / 91 kg
Sail Area (Reported) 210.00 ft² / 19.51 m²
Design & Construction
Hull Type Centerboard Dinghy
Rigging Type Fractional Sloop
Construction Wood/FG
Designer Morgan-Giles
First Built 1911
Number Built 115
Associations Estuary One Design
Owner Reviews

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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
37.51
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
23.53
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
80.75
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
7.05
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
2.54
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. 5.48 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. 359.10 pounds/inch
How It Compares

vs. Cape Cod Knockabout, Duxbury Duck, Interlake, Mercury 18, Rhodes 18

This boat Similar boats
Dimensions
LOA
Estuary One Design Uk ★
18.0 ft
Cape Cod Knockabout
18.0 ft
Duxbury Duck
18.0 ft
Interlake
18.0 ft
Mercury 18
18.0 ft
Rhodes 18
18.0 ft
LWL
Estuary One Design Uk ★
16.8 ft
Cape Cod Knockabout
15.5 ft
Duxbury Duck
15.1 ft
Interlake
Mercury 18
13.0 ft
Rhodes 18
17.0 ft
Beam
Estuary One Design Uk ★
6.0 ft
Cape Cod Knockabout
6.0 ft
Duxbury Duck
6.3 ft
Interlake
6.3 ft
Mercury 18
5.3 ft
Rhodes 18
6.3 ft
Displacement
Estuary One Design Uk ★
850 lbs
Cape Cod Knockabout
650 lbs
Duxbury Duck
700 lbs
Interlake
650 lbs
Mercury 18
1 lbs
Rhodes 18
1 lbs
Ballast
Estuary One Design Uk ★
200 lbs
Cape Cod Knockabout
Duxbury Duck
Interlake
Mercury 18
635 lbs
Rhodes 18
Sail Area
Estuary One Design Uk ★
210 sq ft
Cape Cod Knockabout
165 sq ft
Duxbury Duck
342 sq ft
Interlake
175 sq ft
Mercury 18
Rhodes 18
162 sq ft
Performance
SA / Displacement (higher = more powerful)
Estuary One Design Uk ★
37.5
Cape Cod Knockabout
35.2
Duxbury Duck
69.5
Interlake
Mercury 18
Rhodes 18
25.1
Ballast / Disp (higher = stiffer)
Estuary One Design Uk ★
23.5 %
Cape Cod Knockabout
Duxbury Duck
Interlake
Mercury 18
57.7 %
Rhodes 18
Comfort Ratio (higher = more comfortable offshore)
Estuary One Design Uk ★
7.1
Cape Cod Knockabout
5.7
Duxbury Duck
5.8
Interlake
5.4
Mercury 18
Rhodes 18
8.2
Capsize Screening (lower = safer)
Estuary One Design Uk ★
2.54
Cape Cod Knockabout
2.77
Duxbury Duck
2.85
Interlake
Mercury 18
Rhodes 18
2.46
Displacement / Length (lower = lighter)
Estuary One Design Uk ★
80
Cape Cod Knockabout
Duxbury Duck
91
Interlake
81
Mercury 18
223
Rhodes 18
Hull Speed
Estuary One Design Uk ★
5.5 kts
Cape Cod Knockabout
5.3 kts
Duxbury Duck
5.2 kts
Interlake
5.2 kts
Mercury 18
Rhodes 18
5.5 kts
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