The Commander 31 Bianca is modestly canvassed and unhurried, with acceptable motion comfort for coastal passages.
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 22.0′, the Commander 31 Bianca tops out around 6.3 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √22.0′ LWL = 6.3 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
13.7
Modestly canvassed — a comfortable, unhurried cruiser.
Ballast / Displacement
45.7%
Race-oriented ballast ratio — very stiff and powerful.
Displacement / Length
323
Moderate-heavy — carries provisions well, deliberate in light air.
Comfort Ratio
26.6
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Capsize Screening
1.79
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
694lbs
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
26.6
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
1.79
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 Commander 31 Bianca sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser/Racer 90–150
Cruiser 150–210
Heavy Cruiser 210–300
Dehler 31
162s/nm
Dufour 31
168s/nm
Nicholson 31
194s/nm
Monsun 31
204s/nm
Mariner 31
231s/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 |
3.3 |
| Close Reach60° |
2.7 |
3.5 |
3.9 |
4.0 |
| Beam Reach90° |
3.4 |
4.3 |
4.8 |
5.0 |
| Broad Reach120–135° |
3.1 |
3.9 |
4.4 |
4.6 |
| Run150–180° |
2.5 |
3.1 |
3.5 |
3.7 |
These are simplified estimates based on hull speed (6.3 kts),
SA/D (13.7), 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 Commander 31 Bianca — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–8 kts
8–24 kts
24–34 kts
34+ kts
Ghosting
0–8 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
8–24 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
24–34 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
34+ 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 Commander 31 Bianca.
|
Commander 31 Bianca |
Dehler 31 |
Dufour 31 |
Mariner 31 |
Monsun 31 |
Nicholson 31 |
| Dimensions |
| LOA |
30.7 |
30.8 |
30.8 |
30.7 |
30.8 |
30.5 |
| LWL |
22.0 |
24.3 |
23.0 |
25.5 |
24.7 |
24.2 |
| Beam |
8.8 |
10.2 |
10.5 |
9.8 |
9.4 |
10.2 |
| Displacement |
7 |
7 |
9 |
11 |
9 |
13 |
| Ballast |
3 |
2 |
3 |
5 |
4 |
4 |
| Sail Area |
334 |
443 |
395 |
482 |
414 |
484 |
| Performance |
| PHRF |
— |
162 |
168 |
231 |
204 |
194 |
| SA/Disp |
13.7 |
19.3 |
14.0 |
15.2 |
15.1 |
14.1 |
| Bal/Disp |
45.7 |
40.6 |
38.5 |
— |
45.4 |
— |
| Comfort |
26.6 |
18.9 |
25.5 |
31.6 |
27.2 |
35.0 |
| Capsize |
1.79 |
2.12 |
1.98 |
1.73 |
1.80 |
1.74 |
| Hull Speed |
6.3 |
6.6 |
6.4 |
6.8 |
6.7 |
6.6 |