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Naiad 18

Designer: Mark Ellis  ·  Builder: Luna Yachts  ·  First built: 1984
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About the Naiad 18

Designed by Mark Ellis and built by Luna Yachts beginning in 1984, this compact 18-footer represents an intriguing approach to small boat sailing with its unstayed catboat rig and centerboard configuration. The Naiad 18's relatively deep draft of 3.67 feet with board down suggests serious sailing performance despite its modest size, while the substantial ballast-to-displacement ratio of exactly 50% provides impressive stability for coastal adventures. The boat's cat rig eliminates the complexity of stays and multiple sails, making it an excellent choice for single-handed sailing or teaching newcomers the fundamentals. This simple yet effective sail plan, combined with 144 square feet of working sail area, delivers respectable performance while remaining manageable in varying conditions. The fiberglass construction ensures durability and lower maintenance compared to traditional wooden small craft. With a comfort ratio of 8.81, the Naiad 18 falls into the racing boat category, indicating a relatively stiff, responsive hull that prioritizes performance over pure comfort. The capsize screening formula of 2.33 suggests good stability characteristics for coastal sailing, though like most boats this size, it's best suited for protected waters, day sailing, and near-shore cruising rather than extended offshore passages.

Core Dimensions
LOA (Length Overall) 18.25 ft / 5.56 m
LWL (Waterline Length) 17.50 ft / 5.33 m
Beam 6.00 ft / 1.83 m
Max Draft 3.67 ft / 1.12 m
Min Draft 0.67 ft / 0.20 m
Displacement 1,100.00 lb / 499 kg
Ballast 550.00 lb / 249 kg
Sail Area (Reported) 144.00 ft² / 13.38 m²
Design & Construction
Hull Type Centerboard (Trunk)
Rigging Type Cat (unstayed)
Construction FG
Designer Mark Ellis
Builder Luna Yachts
First Built 1984
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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
21.66
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
50
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
91.63
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
8.81
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
2.33
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. 5.61 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. 375.18 pounds/inch
How It Compares

vs. Catalina 18 Mkii, Hunter 185, Precision 185, Sovereign 18, Windrose 18

This boat Similar boats
Dimensions
LOA
Naiad 18 ★
18.3 ft
Catalina 18 Mkii
18.1 ft
Hunter 185
18.4 ft
Precision 185
18.4 ft
Sovereign 18
18.0 ft
Windrose 18
18.5 ft
LWL
Naiad 18 ★
17.5 ft
Catalina 18 Mkii
15.9 ft
Hunter 185
15.5 ft
Precision 185
16.7 ft
Sovereign 18
14.5 ft
Windrose 18
15.8 ft
Beam
Naiad 18 ★
6.0 ft
Catalina 18 Mkii
7.8 ft
Hunter 185
7.1 ft
Precision 185
7.3 ft
Sovereign 18
7.0 ft
Windrose 18
7.0 ft
Displacement
Naiad 18 ★
1 lbs
Catalina 18 Mkii
1 lbs
Hunter 185
1 lbs
Precision 185
880 lbs
Sovereign 18
1 lbs
Windrose 18
1 lbs
Ballast
Naiad 18 ★
550 lbs
Catalina 18 Mkii
525 lbs
Hunter 185
520 lbs
Precision 185
375 lbs
Sovereign 18
540 lbs
Windrose 18
400 lbs
Sail Area
Naiad 18 ★
144 sq ft
Catalina 18 Mkii
155 sq ft
Hunter 185
176 sq ft
Precision 185
181 sq ft
Sovereign 18
123 sq ft
Windrose 18
Performance
SA / Displacement (higher = more powerful)
Naiad 18 ★
21.7
Catalina 18 Mkii
19.8
Hunter 185
20.6
Precision 185
31.6
Sovereign 18
16.1
Windrose 18
Ballast / Disp (higher = stiffer)
Naiad 18 ★
50.0 %
Catalina 18 Mkii
37.5 %
Hunter 185
32.5 %
Precision 185
42.6 %
Sovereign 18
40.0 %
Windrose 18
26.7 %
Comfort Ratio (higher = more comfortable offshore)
Naiad 18 ★
8.8
Catalina 18 Mkii
8.5
Hunter 185
11.1
Precision 185
5.6
Sovereign 18
10.0
Windrose 18
Capsize Screening (lower = safer)
Naiad 18 ★
2.33
Catalina 18 Mkii
2.77
Hunter 185
2.42
Precision 185
3.06
Sovereign 18
2.54
Windrose 18
Displacement / Length (lower = lighter)
Naiad 18 ★
91
Catalina 18 Mkii
154
Hunter 185
191
Precision 185
84
Sovereign 18
197
Windrose 18
168
Hull Speed
Naiad 18 ★
5.6 kts
Catalina 18 Mkii
5.4 kts
Hunter 185
5.3 kts
Precision 185
5.5 kts
Sovereign 18
5.1 kts
Windrose 18
Speed Number (higher = faster)
Naiad 18 ★
Catalina 18 Mkii
Hunter 185
2.9
Precision 185
6.2
Sovereign 18
2.6
Windrose 18
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