The Swampscott One Design Dory is aggressively canvassed for its weight, with a quick, snappy motion best suited to day sailing.
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 15.0′, the Swampscott One Design Dory tops out around 5.2 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √15.0′ LWL = 5.2 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
32.5
Performance-oriented — carries a lot of canvas for its weight.
Ballast / Displacement
27.3%
Light ballast — tends to be tender; reef earlier than the numbers suggest.
Displacement / Length
146
Ultralight — responsive and fast, but carries less stores.
Comfort Ratio
9.3
Quick, snappy motion — better for day sails and racing than long passages.
Capsize Screening
2.33
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Pounds/Inch Immersion
322lbs
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
9.3
Quick, snappy motion — better for day sails and racing than long passages.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
2.33
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
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° |
2.4 |
3.1 |
3.5 |
3.6 |
| Close Reach60° |
3.0 |
3.7 |
4.2 |
4.4 |
| Beam Reach90° |
3.6 |
4.6 |
5.1 |
5.6 |
| Broad Reach120–135° |
3.4 |
4.2 |
4.7 |
5.1 |
| Run150–180° |
2.7 |
3.4 |
3.8 |
3.9 |
These are simplified estimates based on hull speed (5.2 kts),
SA/D (32.5), 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 Swampscott One Design Dory — based on sail area, ballast, and displacement characteristics.
Ghost
Sweet Spot
Reef
Heavy
0–5 kts
5–14 kts
14–22 kts
22+ kts
Ghosting
0–5 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
5–14 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
14–22 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
22+ 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 Swampscott One Design Dory.
|
Swampscott One Design Dory |
Boothbay Harbor One Design |
Great Lakes 21 |
Great South Bay Shore Bird |
Vineyard 21 |
Yngling |
| Dimensions |
| LOA |
21.0 |
21.0 |
21.0 |
21.1 |
21.0 |
20.8 |
| LWL |
15.0 |
19.8 |
18.3 |
14.0 |
16.3 |
15.4 |
| Beam |
6.0 |
5.5 |
5.8 |
6.3 |
5.5 |
5.7 |
| Displacement |
1 |
2 |
1 |
1 |
2 |
1 |
| Ballast |
300 |
900 |
— |
350 |
— |
683 |
| Sail Area |
216 |
227 |
200 |
250 |
200 |
156 |
| Performance |
| SA/Disp |
32.5 |
22.2 |
21.7 |
27.1 |
18.2 |
20.8 |
| Bal/Disp |
27.3 |
42.9 |
— |
19.4 |
— |
— |
| Comfort |
9.3 |
16.6 |
14.1 |
14.8 |
21.2 |
11.9 |
| Capsize |
2.33 |
1.72 |
1.89 |
2.08 |
1.66 |
2.07 |
| Hull Speed |
5.2 |
6.0 |
5.7 |
5.0 |
5.4 |
5.3 |