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Ra 18
 ·  Builder: Plasto Gmbh  ·  First built: 1971
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About the Ra 18

Built by German manufacturer Plasto GmbH between 1971 and 1974, this compact 18-footer represents European small boat design from sailing's fiberglass boom era. With 200 hulls produced during its brief production run, the Ra 18 carved out a niche as an affordable entry into keelboat sailing. The boat's proportions reveal a design optimized for spirited daysailing and weekend adventures. Its fin keel with spade rudder configuration provides responsive handling, while the masthead sloop rig delivers straightforward sail management. The generous beam of just over seven feet creates surprising stability and interior space for such a compact hull. With a displacement of 1,323 pounds and 40% ballast ratio, this lightweight design favors performance over load-carrying ability. The sail area to displacement ratio of 21.42 suggests lively performance in light to moderate conditions, making it well-suited for lake sailing, protected coastal waters, and sailing instruction. However, the relatively high capsize screening value indicates this boat is best kept in sheltered waters rather than venturing offshore. The Ra 18's low comfort ratio reflects its focus on sailing performance rather than accommodations, positioning it as an ideal choice for sailors seeking an affordable, manageable keelboat that prioritizes fun on the water.

Core Dimensions
LOA (Length Overall) 17.88 ft / 5.45 m
LWL (Waterline Length) 16.40 ft / 5.00 m
Beam 7.05 ft / 2.15 m
Max Draft 3.28 ft / 1.00 m
Displacement 1,323.00 lb / 600 kg
Ballast 529.00 lb / 240 kg
Sail Area (Reported) 161.00 ft² / 14.96 m²
Design & Construction
Hull Type Fin w/spade rudder
Rigging Type Masthead Sloop
Construction FG
Builder Plasto GmbH
First Built 1971
Last Built 1974
Number Built 200
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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
 21.42
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
 39.98
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
 133.9
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
 9
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
 2.57
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. 5.43 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. 413.12 pounds/inch
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