The Alcona 31 is moderately powered for comfortable coastal cruising, with a steady, comfortable ride offshore.
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 22.7′, the Alcona 31 tops out around 6.4 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √22.7′ LWL = 6.4 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
15.4
Moderate sail power — a capable coastal cruiser, not overpowered.
Ballast / Displacement
42.0%
Stiff enough to carry a big genoa comfortably into moderate breeze.
Displacement / Length
397
Heavy displacement — a slow, steady, seakindly hull.
Comfort Ratio
32.7
Good offshore comfort — steady enough for multi-day passages.
Capsize Screening
1.70
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
4lbs
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
32.7
Good offshore comfort — steady enough for multi-day passages.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
1.70
Below the 2.0 offshore threshold — acceptable for ocean passages.
Under 2.0 — Acceptable for offshore
Over 2.0 — Coastal / protected waters
PHRF Fleet Position
Where the Alcona 31 sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser/Racer 90–150
Cruiser 150–210
Heavy Cruiser 210–300
Tartan 31
159s/nm
Niagara 31
162s/nm
Irwin 31 Citation
165s/nm
Hunter 31
183s/nm
Cape Dory 31
198s/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° |
2.4 |
3.1 |
3.4 |
3.6 |
| Close Reach60° |
2.9 |
3.7 |
4.1 |
4.3 |
| Beam Reach90° |
3.6 |
4.5 |
5.1 |
5.3 |
| Broad Reach120–135° |
3.3 |
4.2 |
4.7 |
4.9 |
| Run150–180° |
2.7 |
3.4 |
3.8 |
3.9 |
These are simplified estimates based on hull speed (6.4 kts),
SA/D (15.4), 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 Alcona 31 — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–7 kts
7–22 kts
22–32 kts
32+ kts
Ghosting
0–7 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
7–22 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
22–32 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
32+ 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 Alcona 31.
|
Alcona 31 |
Cape Dory 31 |
Hunter 31 |
Irwin 31 Citation |
Niagara 31 |
Tartan 31 |
| Dimensions |
| LOA |
31.3 |
31.3 |
31.3 |
31.3 |
31.3 |
31.3 |
| LWL |
22.7 |
23.3 |
26.3 |
26.5 |
24.3 |
26.0 |
| Beam |
9.3 |
9.8 |
10.9 |
11.0 |
10.3 |
10.9 |
| Displacement |
10 |
11 |
9 |
9 |
8 |
9 |
| Ballast |
4 |
4 |
4 |
3 |
3 |
3 |
| Sail Area |
455 |
504 |
458 |
474 |
492 |
506 |
| Performance |
| PHRF |
— |
198 |
183 |
165 |
162 |
159 |
| SA/Disp |
15.4 |
15.9 |
16.2 |
17.2 |
19.7 |
18.7 |
| Bal/Disp |
42.0 |
37.8 |
41.2 |
36.6 |
44.4 |
43.2 |
| Comfort |
32.7 |
33.3 |
22.4 |
21.1 |
21.1 |
20.9 |
| Capsize |
1.70 |
1.73 |
2.05 |
2.10 |
2.05 |
2.10 |
| Hull Speed |
6.4 |
6.5 |
6.9 |
6.9 |
6.6 |
6.8 |