The Inferno 31 is well-powered with enough sail area to move in light air, 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 25.6′, the Inferno 31 tops out around 6.8 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √25.6′ LWL = 6.8 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
18.4
Powerful cruiser/racer — quick in light air, reef early when it pipes up.
Comfort Ratio
25.6
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Capsize Screening
1.86
Below the 2.0 offshore threshold — acceptable for ocean passages.
Pounds/Inch Immersion
900lbs
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
25.6
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
1.86
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 Inferno 31 sits on the PHRF handicap spectrum — lower numbers mean faster boats.
Cruiser/Racer 90–150
Cruiser 150–210
Heavy Cruiser 210–300
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° |
2.8 |
3.5 |
4.0 |
4.1 |
| Close Reach60° |
3.4 |
4.3 |
4.8 |
5.0 |
| Beam Reach90° |
4.2 |
5.3 |
5.9 |
6.1 |
| Broad Reach120–135° |
3.8 |
4.9 |
5.4 |
5.7 |
| Run150–180° |
3.1 |
3.9 |
4.3 |
4.5 |
These are simplified estimates based on hull speed (6.8 kts),
SA/D (18.4), 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 Inferno 31 — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–6 kts
6–18 kts
18–26 kts
26+ kts
Ghosting
0–6 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
6–18 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
18–26 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
26+ 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 Inferno 31.
|
Inferno 31 |
Bristol 311 |
Cr 310 |
Hughes 31 |
Mp 31 |
Parker 31 |
| Dimensions |
| LOA |
31.0 |
31.0 |
31.0 |
31.0 |
31.0 |
31.0 |
| LWL |
25.6 |
24.8 |
25.6 |
24.0 |
24.6 |
28.3 |
| Beam |
9.8 |
10.2 |
9.8 |
9.7 |
10.5 |
10.0 |
| Displacement |
9 |
11 |
9 |
9 |
6 |
7 |
| Ballast |
2 |
4 |
3 |
3 |
— |
2 |
| Sail Area |
512 |
455 |
520 |
— |
473 |
448 |
| Performance |
| PHRF |
— |
— |
— |
191 |
— |
— |
| SA/Disp |
18.4 |
14.6 |
19.0 |
— |
21.6 |
19.7 |
| Bal/Disp |
— |
40.2 |
41.7 |
36.8 |
— |
— |
| Comfort |
25.6 |
29.6 |
25.0 |
— |
16.8 |
17.3 |
| Capsize |
1.86 |
1.82 |
1.88 |
— |
2.24 |
2.09 |
| Hull Speed |
6.8 |
6.7 |
6.8 |
— |
6.7 |
7.1 |