The Alden O Class Mk Ii is well-powered with enough sail area to move in light air, 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 15.4′, the Alden O Class Mk Ii tops out around 5.3 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √15.4′ LWL = 5.3 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
SA / Displacement
19.4
Powerful cruiser/racer — quick in light air, reef early when it pipes up.
Ballast / Displacement
27.5%
Light ballast — tends to be tender; reef earlier than the numbers suggest.
Displacement / Length
244
Moderate — a good balance of speed and load-carrying ability.
Comfort Ratio
15.2
Quick, snappy motion — better for day sails and racing than long passages.
Capsize Screening
2.12
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Pounds/Inch Immersion
368lbs
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
15.2
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
2.12
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
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° |
2.2 |
2.8 |
3.2 |
3.3 |
| Close Reach60° |
2.7 |
3.4 |
3.8 |
4.0 |
| Beam Reach90° |
3.3 |
4.2 |
4.7 |
4.9 |
| Broad Reach120–135° |
3.1 |
3.9 |
4.3 |
4.5 |
| Run150–180° |
2.5 |
3.1 |
3.5 |
3.6 |
These are simplified estimates based on hull speed (5.3 kts),
SA/D (19.4), 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 Alden O Class Mk Ii — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–6 kts
6–16 kts
16–24 kts
24+ kts
Ghosting
0–6 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
6–16 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
16–24 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
24+ 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 Alden O Class Mk Ii.
|
Alden O Class Mk Ii |
Duxbury Duck |
Geary 18 |
Marlin 18 Rhodes |
Rhodes 18 |
Y Flyer |
| Dimensions |
| LOA |
18.2 |
18.0 |
18.2 |
18.1 |
18.0 |
18.2 |
| LWL |
15.4 |
15.1 |
— |
12.3 |
17.0 |
14.5 |
| Beam |
6.7 |
6.3 |
5.5 |
5.3 |
6.3 |
5.7 |
| Displacement |
2 |
700 |
525 |
1 |
1 |
500 |
| Ballast |
550 |
— |
— |
430 |
— |
— |
| Sail Area |
192 |
342 |
200 |
— |
162 |
161 |
| Performance |
| SA/Disp |
19.4 |
69.5 |
49.2 |
— |
25.1 |
41.0 |
| Bal/Disp |
27.5 |
— |
— |
34.4 |
— |
— |
| Comfort |
15.2 |
5.8 |
5.2 |
— |
8.2 |
4.9 |
| Capsize |
2.12 |
2.85 |
2.71 |
— |
2.46 |
2.86 |
| Hull Speed |
5.3 |
5.2 |
5.3 |
— |
5.5 |
5.1 |