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Gk 34 Westerly
Designer: Ed Dubois  ·  Builder: Westerly Marine Ltd. (Uk)  ·  First built: 1980
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About the Gk 34 Westerly

Designed by renowned naval architect Ed Dubois during his early career, this distinctive 34-footer represents a brief but notable chapter in Westerly Marine's history. With only 17 hulls produced between 1980 and 1981, the GK 34 has become something of a rare find among British sailing yachts of the era. The design showcases Dubois' emerging talent for creating performance-oriented cruising boats. Her fin keel and spade rudder configuration, combined with a fractional sloop rig, delivers responsive handling that appeals to sailors who appreciate a spirited sail. The substantial ballast-to-displacement ratio of nearly 55% provides reassuring stability, while the moderate comfort ratio of 17.48 suggests she's built more for sailing performance than purely luxurious accommodation. With a sail area to displacement ratio approaching 20, the GK 34 offers lively performance in light to moderate conditions, making her well-suited for coastal cruising and club racing. Her hull speed of just over 7 knots and seaworthy construction make longer passages feasible, though her relatively small production run means finding parts or experienced mechanics familiar with her systems may require extra effort. For sailors seeking a distinctive British yacht with proven pedigree, the GK 34 offers both performance and exclusivity.

Core Dimensions
LOA (Length Overall) 34.00 ft / 10.36 m
LWL (Waterline Length) 27.67 ft / 8.43 m
Beam 11.25 ft / 3.43 m
Max Draft 6.25 ft / 1.91 m
Displacement 8,400.00 lb / 3,810 kg
Ballast 4,600.00 lb / 2,087 kg
Ballast Type cast iron
Sail Area (Reported) 512.50 ft² / 47.61 m²
Design & Construction
Hull Type Fin w/spade rudder
Rigging Type Fractional Sloop
Construction FG
Designer Ed Dubois
Builder Westerly Marine Ltd. (UK)
First Built 1980
Last Built 1981
Number Built 17
Associations Westerly Owners Association
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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
 19.91
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
 54.76
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
 177.01
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
 17.48
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
 2.22
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. 7.05 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
 3.54
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. 1,112.26 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. 21.48
Rig Dimensions
I (Foretriangle Height) 38.60 ft / 11.77 m
J (Foretriangle Base) 12.20 ft / 3.72 m
P (Mainsail Luff) 44.10 ft / 13.44 m
E (Mainsail Foot) 14.40 ft / 4.39 m
SA Fore 235.46 ft² / 21.87 m²
SA Main 317.52 ft² / 29.50 m²
SA Total (100%) 552.98 ft² / 51.37 m²
Est. Forestay Length 40.48 ft / 12.34 m
Engine & Accommodations
Engine Make Bukh
Engine Model DV20ME
Engine Type Diesel
Horsepower 20
Fuel Capacity 15 gals / 57 L
Water Capacity 30 gals / 114 L
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