The Dufour 31 is moderately powered for comfortable coastal cruising, with acceptable motion comfort for coastal passages, designed for cruising comfort rather than racing.
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 23.0′, the Dufour 31 tops out around 6.4 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √23.0′ 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.
PHRF Rating
168s/nm
Typical cruiser — designed for comfort and ease, not podium finishes.
SA / Displacement
14.0
Moderate sail power — a capable coastal cruiser, not overpowered.
Ballast / Displacement
38.5%
Stiff enough to carry a big genoa comfortably into moderate breeze.
Displacement / Length
352
Heavy displacement — a slow, steady, seakindly hull.
Comfort Ratio
25.5
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Capsize Screening
1.98
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
863lbs
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
25.5
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
1.98
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 Dufour 31 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
Typical cruiser — designed for comfort and ease, not podium finishes.
Pearson 31 2
180s/nm
Monsun 31
204s/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 |
3.0 |
3.3 |
3.5 |
| 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 |
4.1 |
4.5 |
4.7 |
| Run150–180° |
2.6 |
3.2 |
3.6 |
3.8 |
These are simplified estimates based on hull speed (6.4 kts),
SA/D (14.0), 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 Dufour 31 — 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 Dufour 31.
|
Dufour 31 |
Dehler 31 |
Ericson 31 Independence |
Hallberg Rassy 312 |
Monsun 31 |
Pearson 31 2 |
| Dimensions |
| LOA |
30.8 |
30.8 |
30.9 |
30.9 |
30.8 |
30.7 |
| LWL |
23.0 |
24.3 |
23.9 |
25.3 |
24.7 |
25.4 |
| Beam |
10.5 |
10.2 |
10.4 |
10.1 |
9.4 |
10.7 |
| Displacement |
9 |
7 |
11 |
10 |
9 |
10 |
| Ballast |
3 |
2 |
4 |
4 |
4 |
3 |
| Sail Area |
395 |
443 |
457 |
484 |
414 |
493 |
| Performance |
| PHRF |
168 |
162 |
— |
— |
204 |
180 |
| SA/Disp |
14.0 |
19.3 |
14.5 |
15.9 |
15.1 |
17.1 |
| Bal/Disp |
38.5 |
40.6 |
39.5 |
44.9 |
45.4 |
38.0 |
| Comfort |
25.5 |
18.9 |
29.9 |
28.5 |
27.2 |
24.5 |
| Capsize |
1.98 |
2.12 |
1.86 |
1.83 |
1.80 |
1.98 |
| Hull Speed |
6.4 |
6.6 |
6.6 |
6.7 |
6.7 |
6.8 |