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Islander 21
Designer: J. H. Mcglasson  ·  Builder: Mcglasson Marine/Wayfarer Yachts Corp. (Usa)  ·  First built: 1965
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About the Islander 21

Designed by J.H. McGlasson and first launched in 1965, this compact 21-footer represents classic small boat design from sailing's golden era. Built by McGlasson Marine and later Wayfarer Yachts Corp., the Islander 21 combines traditional proportions with modern fin keel efficiency in a package ideally suited for coastal cruising and day sailing. The masthead sloop rig delivers 215 square feet of working sail area, providing spirited performance while remaining manageable for small crews. With a displacement of 1,950 pounds and 1,000 pounds of ballast, the boat offers reassuring stability for its size. The fin keel and spade rudder configuration ensures responsive handling and good upwind performance, while the 18-foot waterline length helps the boat achieve its theoretical hull speed of 5.69 knots. At just under 21 feet overall with a modest 7.83-foot beam, this Islander fits easily into most marina slips and can be trailered behind a suitable vehicle. The fiberglass construction ensures durability and low maintenance. While compact accommodations limit extended cruising potential, the Islander 21 excels as a weekend coastal cruiser, sailing trainer, or spirited day sailor for those seeking authentic sailing character in a manageable package.

Core Dimensions
LOA (Length Overall) 20.82 ft / 6.35 m
LWL (Waterline Length) 18.00 ft / 5.49 m
Beam 7.83 ft / 2.39 m
Max Draft 3.33 ft / 1.01 m
Displacement 1,950.00 lb / 885 kg
Ballast 1,000.00 lb / 454 kg
Ballast Type Iron
Sail Area (Reported) 215.00 ft² / 19.97 m²
Design & Construction
Hull Type Fin w/spade rudder
Rigging Type Masthead Sloop
Construction FG
Designer J. H. McGlasson
Builder McGlasson Marine/Wayfarer Yachts Corp. (USA)
First Built 1965
Related Sailboats ["Precision 21" · "Venture 21" · "Hunter 212" · "Clipper Marine 21" · "Aquarius 21"]
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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
 279
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
 22.09
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
 51.28
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
 149.27
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
 10.31
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
 2.51
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. 5.69 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
 4.06
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. 503.59 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. 22.04
Rig Dimensions
I (Foretriangle Height) 26.50 ft / 8.08 m
J (Foretriangle Base) 7.70 ft / 2.35 m
P (Mainsail Luff) 22.50 ft / 6.86 m
E (Mainsail Foot) 10.00 ft / 3.05 m
SA Fore 102.03 ft² / 9.48 m²
SA Main 112.50 ft² / 10.45 m²
SA Total (100%) 214.53 ft² / 19.93 m²
Est. Forestay Length 27.60 ft / 8.41 m
How It Compares

vs. Clipper Marine 21, Hunter 212, Venture 21

This boat Similar boats
Dimensions
LOA
Islander 21 ★
20.8 ft
Clipper Marine 21
20.9 ft
Hunter 212
21.0 ft
Venture 21
21.0 ft
LWL
Islander 21 ★
18.0 ft
Clipper Marine 21
16.7 ft
Hunter 212
18.0 ft
Venture 21
18.5 ft
Beam
Islander 21 ★
7.8 ft
Clipper Marine 21
7.3 ft
Hunter 212
9.2 ft
Venture 21
6.8 ft
Displacement
Islander 21 ★
1 lbs
Clipper Marine 21
1 lbs
Hunter 212
1 lbs
Venture 21
1 lbs
Ballast
Islander 21 ★
1 lbs
Clipper Marine 21
410 lbs
Hunter 212
140 lbs
Venture 21
400 lbs
Sail Area
Islander 21 ★
215 sq ft
Clipper Marine 21
192 sq ft
Hunter 212
202 sq ft
Venture 21
—
Performance
PHRF Rating (lower = faster)
Islander 21 ★
279 s/nm
Clipper Marine 21
270 s/nm
Hunter 212
216 s/nm
Venture 21
252 s/nm
SA / Displacement (higher = more powerful)
Islander 21 ★
22.1
Clipper Marine 21
20.8
Hunter 212
21.9
Venture 21
—
Ballast / Disp (higher = stiffer)
Islander 21 ★
51.3 %
Clipper Marine 21
—
Hunter 212
7.8 %
Venture 21
26.7 %
Comfort Ratio (higher = more comfortable offshore)
Islander 21 ★
10.3
Clipper Marine 21
11.1
Hunter 212
7.7
Venture 21
—
Capsize Screening (lower = safer)
Islander 21 ★
2.51
Clipper Marine 21
2.39
Hunter 212
3.02
Venture 21
—
Displacement / Length (lower = lighter)
Islander 21 ★
149
Clipper Marine 21
—
Hunter 212
137
Venture 21
105
Hull Speed
Islander 21 ★
5.7 kts
Clipper Marine 21
5.5 kts
Hunter 212
5.7 kts
Venture 21
—
Speed Number (higher = faster)
Islander 21 ★
4.1
Clipper Marine 21
3.5
Hunter 212
4.3
Venture 21
—
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