The Irwin 31 Citation 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 26.5′, the Irwin 31 Citation tops out around 6.9 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √26.5′ LWL = 6.9 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
165s/nm
Typical cruiser — designed for comfort and ease, not podium finishes.
SA / Displacement
17.2
Moderate sail power — a capable coastal cruiser, not overpowered.
Ballast / Displacement
36.6%
Typical cruising ballast — balanced stability and motion underway.
Displacement / Length
223
Moderate — a good balance of speed and load-carrying ability.
Comfort Ratio
21.1
Acceptable coastal comfort — fine for weekends, notice the chop offshore.
Capsize Screening
2.10
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Pounds/Inch Immersion
1lbs
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
21.1
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
2.10
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Under 2.0 — Acceptable for offshore
Over 2.0 — Coastal / protected waters
PHRF Fleet Position
Where the Irwin 31 Citation 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
Typical cruiser — designed for comfort and ease, not podium finishes.
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° |
2.8 |
3.5 |
3.9 |
4.1 |
| Close Reach60° |
3.3 |
4.2 |
4.7 |
4.9 |
| Beam Reach90° |
4.1 |
5.2 |
5.8 |
6.0 |
| Broad Reach120–135° |
3.8 |
4.8 |
5.4 |
5.6 |
| Run150–180° |
3.0 |
3.8 |
4.3 |
4.5 |
These are simplified estimates based on hull speed (6.9 kts),
SA/D (17.2), 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 Irwin 31 Citation — 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 Irwin 31 Citation.
|
Irwin 31 Citation |
Cape Dory 31 |
Hunter 31 |
Niagara 31 |
Tartan 31 |
Tartan 31 Piper |
| Dimensions |
| LOA |
31.3 |
31.3 |
31.3 |
31.3 |
31.3 |
31.3 |
| LWL |
26.5 |
23.3 |
26.3 |
24.3 |
26.0 |
26.0 |
| Beam |
11.0 |
9.8 |
10.9 |
10.3 |
10.9 |
10.9 |
| Displacement |
9 |
11 |
9 |
8 |
9 |
9 |
| Ballast |
3 |
4 |
4 |
3 |
3 |
3 |
| Sail Area |
474 |
504 |
458 |
492 |
506 |
— |
| Performance |
| PHRF |
165 |
198 |
183 |
162 |
159 |
— |
| SA/Disp |
17.2 |
15.9 |
16.2 |
19.7 |
18.7 |
— |
| Bal/Disp |
36.6 |
37.8 |
41.2 |
44.4 |
43.2 |
39.9 |
| Comfort |
21.1 |
33.3 |
22.4 |
21.1 |
20.9 |
— |
| Capsize |
2.10 |
1.73 |
2.05 |
2.05 |
2.10 |
— |
| Hull Speed |
6.9 |
6.5 |
6.9 |
6.6 |
6.8 |
— |