The Southern Cross 31 is modestly canvassed and unhurried, 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 25.0′, the Southern Cross 31 tops out around 6.7 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √25.0′ LWL = 6.7 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
225s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
SA / Displacement
12.6
Modestly canvassed — a comfortable, unhurried cruiser.
Comfort Ratio
37.6
Good offshore comfort — steady enough for multi-day passages.
Capsize Screening
1.59
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
849lbs
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
37.6
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
1.59
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 Southern Cross 31 sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser/Racer 90–150
Cruiser 150–210
Heavy Cruiser 210–300
Bristol 35
189s/nm
Ohlson 35
212s/nm
Southern Cross 31
225s/nm
Heavy or slow cruiser — all about the journey, not the elapsed time.
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 |
3.3 |
3.4 |
| Close Reach60° |
2.8 |
3.6 |
4.0 |
4.2 |
| Beam Reach90° |
3.5 |
4.4 |
4.9 |
5.1 |
| Broad Reach120–135° |
3.2 |
4.0 |
4.5 |
4.7 |
| Run150–180° |
2.6 |
3.2 |
3.6 |
3.8 |
These are simplified estimates based on hull speed (6.7 kts),
SA/D (12.6), 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 Southern Cross 31 — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–8 kts
8–22 kts
22–30 kts
30+ kts
Ghosting
0–8 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
8–22 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
22–30 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
30+ 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 Southern Cross 31.
|
Southern Cross 31 |
Bristol 35 |
Fantasia 35 Bingham |
Fuji 35 |
Ohlson 35 |
True North 34 |
| Dimensions |
| LOA |
34.5 |
34.7 |
34.5 |
34.6 |
34.5 |
34.5 |
| LWL |
25.0 |
23.8 |
27.5 |
26.0 |
24.0 |
30.5 |
| Beam |
9.5 |
10.0 |
11.0 |
10.0 |
10.5 |
11.0 |
| Displacement |
13 |
12 |
22 |
16 |
10 |
26 |
| Ballast |
4 |
5 |
6 |
5 |
5 |
8 |
| Sail Area |
447 |
529 |
610 |
538 |
484 |
— |
| Performance |
| PHRF |
225 |
189 |
— |
— |
212 |
— |
| SA/Disp |
12.6 |
15.8 |
12.5 |
13.4 |
16.3 |
— |
| Bal/Disp |
— |
41.6 |
29.6 |
36.6 |
49.2 |
32.7 |
| Comfort |
37.6 |
33.3 |
47.1 |
41.1 |
25.8 |
— |
| Capsize |
1.59 |
1.73 |
1.57 |
1.58 |
1.93 |
— |
| Hull Speed |
6.7 |
6.5 |
7.0 |
6.8 |
6.6 |
— |