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Sigma 36 Thomas
Designer: David Thomas  ·  Builder: Marine Projects Ltd. (Uk)  ·  First built: 1979
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About the Sigma 36 Thomas

Designed by David Thomas and built by Marine Projects Ltd. in the UK starting in 1979, this 36-footer represents solid British yacht design philosophy of the late 1970s. The Sigma 36 Thomas combines respectable performance with comfortable cruising capabilities, making it well-suited for coastal sailing and extended offshore passages. With a moderate displacement of 12,350 pounds and a fin keel with spade rudder configuration, the boat strikes a practical balance between stability and sailing performance. The fractional sloop rig carries 605 square feet of sail area, providing adequate power while remaining manageable for a small crew. Her 28.75-foot waterline length delivers a theoretical hull speed of 7.18 knots, making her competitive in club racing while comfortable for cruising. The comfort ratio of 23.86 indicates this yacht leans toward the performance end of the spectrum while still providing reasonable accommodation for extended voyaging. Her capsize screening value of 1.99 falls within acceptable parameters for offshore sailing, though coastal and near-shore cruising remain her primary strengths. The fiberglass construction and proven David Thomas design have helped many examples remain seaworthy decades after launch, earning respect among sailors seeking a capable, well-built cruiser-racer.

Core Dimensions
LOA (Length Overall) 36.00 ft / 10.97 m
LWL (Waterline Length) 28.75 ft / 8.76 m
Beam 11.50 ft / 3.51 m
Max Draft 6.42 ft / 1.96 m
Displacement 12,350.00 lb / 5,602 kg
Sail Area (Reported) 605.00 ft² / 56.21 m²
Design & Construction
Hull Type Fin w/spade rudder
Rigging Type Fractional Sloop
Construction FG
Designer David Thomas
Builder Marine Projects Ltd. (UK)
First Built 1979
Related Sailboats ["Sigma 362" · "S2 110 C" · "Cs 36 Merlin" · "Sabre 36" · "C&C 36"]
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
 18.18
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
 232.01
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
 23.86
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
 1.99
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. 7.18 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
 2.47
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. 1,181.36 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. 18.17
Rig Dimensions
I (Foretriangle Height) 41.00 ft / 12.50 m
J (Foretriangle Base) 12.70 ft / 3.87 m
P (Mainsail Luff) 45.00 ft / 13.72 m
E (Mainsail Foot) 15.30 ft / 4.66 m
SA Fore 260.35 ft² / 24.19 m²
SA Main 344.25 ft² / 31.98 m²
SA Total (100%) 604.60 ft² / 56.17 m²
Est. Forestay Length 42.92 ft / 13.08 m
Engine & Accommodations
Engine Make Volvo
Engine Model MD11
Engine Type Diesel
Horsepower 23
How It Compares

vs. Cs 36 Merlin, S2 110 C, Sabre 36

This boat Similar boats
Dimensions
LOA
Sigma 36 Thomas ★
36.0 ft
Cs 36 Merlin
36.0 ft
S2 110 C
36.0 ft
Sabre 36
36.0 ft
LWL
Sigma 36 Thomas ★
28.8 ft
Cs 36 Merlin
29.2 ft
S2 110 C
28.3 ft
Sabre 36
29.3 ft
Beam
Sigma 36 Thomas ★
11.5 ft
Cs 36 Merlin
11.5 ft
S2 110 C
11.9 ft
Sabre 36
11.3 ft
Displacement
Sigma 36 Thomas ★
12 lbs
Cs 36 Merlin
13 lbs
S2 110 C
16 lbs
Sabre 36
13 lbs
Ballast
Sigma 36 Thomas ★
—
Cs 36 Merlin
5 lbs
S2 110 C
6 lbs
Sabre 36
5 lbs
Sail Area
Sigma 36 Thomas ★
605 sq ft
Cs 36 Merlin
608 sq ft
S2 110 C
625 sq ft
Sabre 36
610 sq ft
Performance
PHRF Rating (lower = faster)
Sigma 36 Thomas ★
—
Cs 36 Merlin
126 s/nm
S2 110 C
—
Sabre 36
144 s/nm
SA / Displacement (higher = more powerful)
Sigma 36 Thomas ★
18.2
Cs 36 Merlin
17.7
S2 110 C
15.8
Sabre 36
17.5
Comfort Ratio (higher = more comfortable offshore)
Sigma 36 Thomas ★
23.9
Cs 36 Merlin
24.9
S2 110 C
29.8
Sabre 36
25.9
Capsize Screening (lower = safer)
Sigma 36 Thomas ★
1.99
Cs 36 Merlin
1.96
S2 110 C
1.90
Sabre 36
1.91
Displacement / Length (lower = lighter)
Sigma 36 Thomas ★
232
Cs 36 Merlin
233
S2 110 C
—
Sabre 36
—
Hull Speed
Sigma 36 Thomas ★
7.2 kts
Cs 36 Merlin
7.2 kts
S2 110 C
7.1 kts
Sabre 36
7.3 kts
Speed Number (higher = faster)
Sigma 36 Thomas ★
2.5
Cs 36 Merlin
2.4
S2 110 C
1.5
Sabre 36
2.4
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