The Aquarius 21 is moderately powered for comfortable coastal cruising, with a quick, snappy motion best suited to day sailing.
Hull Speed
The theoretical displacement-mode speed limit — determined by waterline length, not engine or sail power.
A displacement hull pushes a bow wave whose speed is limited by the waterline length.
With a waterline of 18.3′, the Aquarius 21 tops out around 5.7 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √18.3′ LWL = 5.7 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
PHRF Rating
267s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
SA / Displacement
17.0
Moderate sail power — a capable coastal cruiser, not overpowered.
Ballast / Displacement
35.0%
Typical cruising ballast — balanced stability and motion underway.
Displacement / Length
140
Ultralight — responsive and fast, but carries less stores.
Comfort Ratio
9.9
Quick, snappy motion — better for day sails and racing than long passages.
Capsize Screening
2.53
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Pounds/Inch Immersion
510lbs
Weight needed to sink the hull one inch — loading sensitivity.
Motion & Offshore Suitability
Two ratios that matter most when you're planning passages — how the boat feels in a seaway, and whether the hull geometry is suitable for open ocean.
Comfort Ratio
9.9
Quick, snappy motion — better for day sails and racing than long passages.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
2.53
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Under 2.0 — Acceptable for offshore
Over 2.0 — Coastal / protected waters
PHRF Fleet Position
Where the Aquarius 21 sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser 150–210
Heavy Cruiser 210–300
Venture 21
252s/nm
Santana 21
264s/nm
Aquarius 21
267s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
Clipper Marine 21
270s/nm
Estimated Speed by Wind
Rough boat speed estimates at different true wind speeds and points of sail — derived from hull speed, SA/D, and displacement, not measured polars.
| Point of Sail |
6 kts TWS |
10 kts TWS |
15 kts TWS |
20 kts TWS |
| Close-hauled40–50° |
2.3 |
2.9 |
3.2 |
3.4 |
| Close Reach60° |
2.8 |
3.5 |
3.9 |
4.1 |
| Beam Reach90° |
3.4 |
4.3 |
4.8 |
5.2 |
| Broad Reach120–135° |
3.1 |
4.0 |
4.4 |
4.8 |
| Run150–180° |
2.5 |
3.2 |
3.5 |
3.7 |
These are simplified estimates based on hull speed (5.7 kts),
SA/D (17.0), and empirical efficiency curves — not instrument-measured
polars. Real-world speed varies with sea state, bottom condition, sail trim, and current.
Speeds in gold approach hull speed;
bold gold means near or at hull speed.
Wind Range & Comfort Envelope
Estimated wind ranges for comfortable sailing on the Aquarius 21 — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–7 kts
7–20 kts
20–28 kts
28+ kts
Ghosting
0–7 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
7–20 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
20–28 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
28+ kts
Storm conditions. Storm jib or bare poles. Seek shelter if coastal.
How It Compares
Side-by-side with the boats most often cross-shopped against the Aquarius 21.
|
Aquarius 21 |
Balboa 21 |
Clipper Marine 21 |
Santana 21 |
Venture 21 |
Windward 21 Luger |
| Dimensions |
| LOA |
21.0 |
21.0 |
20.9 |
21.3 |
21.0 |
21.0 |
| LWL |
18.3 |
18.3 |
16.7 |
19.3 |
18.5 |
19.5 |
| Beam |
7.8 |
7.9 |
7.3 |
7.5 |
6.8 |
8.0 |
| Displacement |
1 |
2 |
1 |
1 |
1 |
1 |
| Ballast |
665 |
665 |
410 |
550 |
400 |
— |
| Sail Area |
163 |
178 |
192 |
189 |
— |
— |
| Performance |
| PHRF |
267 |
— |
270 |
264 |
252 |
— |
| SA/Disp |
17.0 |
18.0 |
20.8 |
21.3 |
— |
— |
| Bal/Disp |
35.0 |
— |
— |
32.4 |
26.7 |
— |
| Comfort |
9.9 |
10.3 |
11.1 |
9.0 |
— |
— |
| Capsize |
2.53 |
2.52 |
2.39 |
2.52 |
— |
— |
| Hull Speed |
5.7 |
5.7 |
5.5 |
5.9 |
— |
— |