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San Juan 21
Designer: Don Clark  ·  Builder: Clark Boat Co.  ·  First built: 1970
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About the San Juan 21

Designed as an accessible and capable daysailer, the San Juan 21 earned a loyal following among sailors looking for an affordable entry point into keelboat sailing without sacrificing genuine performance on the water. Built by Clark Boat Company in the Pacific Northwest, the design became popular across North American lakes and protected coastal waters throughout the 1970s and 1980s, offering a stable and responsive platform for beginner and intermediate sailors alike. The San Juan 21 is well suited to daysailing and casual racing on inland lakes and sheltered bays, where its lively sailing characteristics can be fully appreciated. The boat's manageable size makes it easy to trailer, launch, and maintain, which contributed significantly to its widespread appeal among weekend sailors. Its fin keel configuration provides solid stability and a reasonably predictable feel at the helm, making it forgiving enough for those still developing their skills while remaining engaging for more experienced crews. For buyers researching the used market, the San Juan 21 represents a practical and enjoyable choice for recreational sailing, with an established class community and a reputation for durability and fun.

Market Price Estimate Beta
Small sample size. This estimate is based on fewer than 5 listings and may not be representative of the true market. Use with caution.
$1,000 – $2,500
typical asking price
Median $1,750  ·  4 listings used
All listings
$1,000 – $2,500 4
Rate a listing price
$
About this estimate
  • Prices are based on recent asking prices from public listings — not actual sale prices, which are typically lower.
  • Condition is not factored in. A well-maintained boat with new sails and engine can be worth significantly more than a project boat of the same model.
  • Location affects price. Boats in landlocked states or areas with fewer buyers often sell for less than those on the coast.
  • Year of manufacture is not filtered. Older examples of this model will generally be priced lower than newer ones.
  • Included equipment varies widely. A boat with a full suite of electronics, dodger, and new standing rigging may command a large premium.
  • Outliers are automatically excluded using statistical filtering to improve accuracy, but some bad data may remain.
Core Dimensions
LOA (Length Overall) 20.50 ft / 6.25 m
LWL (Waterline Length) 17.00 ft / 5.18 m
Beam 7.00 ft / 2.13 m
Max Draft 4.00 ft / 1.22 m
Min Draft 1.00 ft / 0.30 m
Displacement 1,250.00 lb / 567 kg
Ballast 400.00 lb / 181 kg
Sail Area (Reported) 190.00 ft² / 17.65 m²
Design & Construction
Hull Type Swing Keel
Rigging Type Fractional Sloop
Construction FG
Designer Don Clark
Builder Clark Boat Co.
First Built 1970
Last Built 1977
Owner Reviews

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Performance Ratios
PHRF Rating PHRF (Performance Handicap Racing Fleet) is a national racing handicap measured in seconds per nautical mile. Lower values indicate faster boats. Ratings are sourced from US Sailing's national database (median across 60+ regional fleets).
Under 0 — Ultralight racer0–90 — Performance racer90–150 — Cruiser/racer150–210 — Typical cruiserOver 210 — Heavy/slow cruiser
 258
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
 26.25
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
 8.01
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
 2.6
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. 5.52
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
 5.35
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. 425.2
Rig Dimensions
I (Foretriangle Height) 22.5
J (Foretriangle Base) 8.0
P (Mainsail Luff) 23.0
E (Mainsail Foot) 8.75
SA Fore 90.0
SA Main 100.63
Find a San Juan 21 For Sale
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