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Cal 21
Designer: C. William Lapworth  ·  Builder: Jensen Marine (Usa)  ·  First built: 1969
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About the Cal 21

Designed by the renowned C. William Lapworth and built by Jensen Marine from 1969 to 1976, this compact fractional sloop represents an interesting chapter in California's sailboat manufacturing history. With 500 hulls produced during its seven-year run, the Cal 21 carved out a niche as an affordable entry-level sailboat that didn't compromise on sailing performance. The boat's most distinctive feature is its swing keel design, which allows the 4.30-foot draft to be reduced for shallow water exploration and trailering convenience. At just 1,100 pounds displacement with 360 pounds of ballast, this lightweight fiberglass construction delivers spirited performance while remaining manageable for new sailors. The 196 square feet of sail area provides adequate power for coastal cruising and daysailing adventures. Lapworth's design philosophy emphasized clean lines and efficient sailing characteristics, evident in the boat's respectable hull speed of 5.47 knots and favorable sail area to displacement ratio of 29.49. The low comfort ratio of 7.61 and moderate capsize screening value of 2.59 indicate this vessel is best suited for protected waters, coastal daysailing, and short cruises rather than extended offshore passages. For sailors seeking an affordable, trailerable boat with classic 1970s styling and proven sailing ability, the Cal 21 offers genuine appeal.

Core Dimensions
LOA (Length Overall) 20.50 ft / 6.25 m
LWL (Waterline Length) 16.67 ft / 5.08 m
Beam 6.67 ft / 2.03 m
Max Draft 4.30 ft / 1.31 m
Min Draft 0.80 ft / 0.24 m
Displacement 1,100.00 lb / 499 kg
Ballast 360.00 lb / 163 kg
Ballast Type Iron
Sail Area (Reported) 196.00 ft² / 18.21 m²
Design & Construction
Hull Type Swing Keel
Rigging Type Fractional Sloop
Construction FG
Designer C. William Lapworth
Builder Jensen Marine (USA)
First Built 1969
Last Built 1976
Number Built 500
Related Sailboats ["San Juan 21" · "Precision 21" · "Holder 20" · "San Juan 21 2" · "Newport 20"]
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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
 261
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
 29.49
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
 32.73
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
 106.01
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
 7.61
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
 2.59
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. 5.47 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
 5.95
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. 397.29 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. 29.41
Rig Dimensions
I (Foretriangle Height) 23.00 ft / 7.01 m
J (Foretriangle Base) 8.50 ft / 2.59 m
P (Mainsail Luff) 23.00 ft / 7.01 m
E (Mainsail Foot) 8.50 ft / 2.59 m
SA Fore 97.75 ft² / 9.08 m²
SA Main 97.75 ft² / 9.08 m²
SA Total (100%) 195.50 ft² / 18.16 m²
Est. Forestay Length 24.52 ft / 7.47 m
How It Compares

vs. Holder 20, Precision 21, San Juan 21 2

This boat Similar boats
Dimensions
LOA
Cal 21 ★
20.5 ft
Holder 20
20.3 ft
Precision 21
20.8 ft
San Juan 21 2
20.5 ft
LWL
Cal 21 ★
16.7 ft
Holder 20
18.4 ft
Precision 21
17.5 ft
San Juan 21 2
17.0 ft
Beam
Cal 21 ★
6.7 ft
Holder 20
7.8 ft
Precision 21
8.3 ft
San Juan 21 2
7.0 ft
Displacement
Cal 21 ★
1 lbs
Holder 20
1 lbs
Precision 21
1 lbs
San Juan 21 2
1 lbs
Ballast
Cal 21 ★
360 lbs
Holder 20
260 lbs
Precision 21
600 lbs
San Juan 21 2
400 lbs
Sail Area
Cal 21 ★
196 sq ft
Holder 20
194 sq ft
Precision 21
203 sq ft
San Juan 21 2
—
Performance
PHRF Rating (lower = faster)
Cal 21 ★
261 s/nm
Holder 20
186 s/nm
Precision 21
243 s/nm
San Juan 21 2
252 s/nm
SA / Displacement (higher = more powerful)
Cal 21 ★
29.5
Holder 20
28.2
Precision 21
21.4
San Juan 21 2
—
Ballast / Disp (higher = stiffer)
Cal 21 ★
32.7 %
Holder 20
22.4 %
Precision 21
32.0 %
San Juan 21 2
32.0 %
Comfort Ratio (higher = more comfortable offshore)
Cal 21 ★
7.6
Holder 20
6.1
Precision 21
9.4
San Juan 21 2
—
Capsize Screening (lower = safer)
Cal 21 ★
2.59
Holder 20
2.98
Precision 21
2.68
San Juan 21 2
—
Displacement / Length (lower = lighter)
Cal 21 ★
106
Holder 20
82
Precision 21
156
San Juan 21 2
113
Hull Speed
Cal 21 ★
5.5 kts
Holder 20
5.8 kts
Precision 21
5.6 kts
San Juan 21 2
—
Speed Number (higher = faster)
Cal 21 ★
6.0
Holder 20
6.4
Precision 21
3.7
San Juan 21 2
—
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