Firefly (Sea Swallow)
Description
The Firefly is a classic 12-foot (3.66 m) British sailing dinghy designed by Uffa Fox in 1946. Originally named the Sea Swallow, it was renamed Firefly and became one of the first mass-produced dinghies, built initially by Fairey Marine (UK). It was selected as the single-handed class for the 1948 Olympics (though later replaced), and has remained a popular one-design racer ever since—especially in the UK for team racing, university sailing (e.g., MIT, British universities), and club fleets. It's a fractional rigged sloop (Bermuda rig), two-person boat (crew of 2), with a lightweight plywood (originally hot-molded) or modern fiberglass/epoxy construction. Known for being fun, fast, responsive, and accessible—great for learning advanced skills like hiking, trapezing (optional), and tactics in team racing.
Construction Details
| Designer | Uffa Fox |
|---|---|
| Builder | Fairey Marine Ltd. (also known as Fairey Marine) |
| Length | 12.000 ft |
| LOA | 12.000 ft |
| LWL | 11.750 ft |
| Beam | 4.670 ft |
| Displacement | 260 lb |
| Max Draft | 3.750 ft |
| Min Draft | 0.830 ft |
| Year Built | 1946 |
The standard boat dimensions
| i | 16.60 ft |
|---|---|
| j | 3.33 ft |
| p | 17.50 ft |
| e | 8.04 ft |
| p2 | - |
| e2 | - |
| i2 | - |
| j2 | - |
| I | J | P | E | P2 | E2 | I2 | J2 |
|---|---|---|---|---|---|---|---|
| 16.60 ft | 3.33 ft | 17.50 ft | 8.04 ft | - | - | - | - |
Sails
Firefly (Sea Swallow) - MAINSAIL
| Luff | * 17.5 ft - (5334 mm) |
|---|---|
| Foot | * 8.04 ft - (2451 mm) |
| Leech | * 18.83 ft - (5739 mm) |
| Tack Angle | * 88 ° |
| Diagonal | * 19 ft - (5791 mm) |
| Head (inches) | * 3.5 in - (89 mm) |
| Area | * 72.55 ft² |
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Firefly (Sea Swallow) - JIBSAIL
| Luff | * 13.54 ft - (4127 mm) |
|---|---|
| Foot | * 4.17 ft - (1271 mm) |
| Leech | * 12.49 ft - (3807 mm) |
| Percentage LP | * 115.02 % |
| Length Perpendicular | * 3.83 ft - (1167 mm) |
| Deck Angle | * 11.99 ° |
| Area | * 25.92 ft² |
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Firefly (Sea Swallow) - GENOA
| Luff | * 16.08 ft - (4901 mm) |
|---|---|
| Foot | * 5.18 ft - (1579 mm) |
| Leech | * 15.51 ft - (4727 mm) |
| Percentage LP | * 149.85 % |
| Length Perpendicular | * 4.99 ft - (1521 mm) |
| Deck Angle | * 4.27 ° |
| Area | * 40.11 ft² |
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Firefly (Sea Swallow) - SPINNAKER
| Stays | * 16.08 ft - (4901 mm) |
|---|---|
| MidGirth | * 5.99 ft - (1826 mm) |
| Foot | * 5.99 ft - (1826 mm) |
| Perc LP | * 180 % |
| Area | * 82 ft² |
| Edit in Calculator |
Disclaimer. Boats are not all the same -- even when produced in the same factory of the same model. Sailrite does its best to publish accurate dimensions, but we often find it worthwhile to have our customers measure their boats carefully before we produce kits for them. You should take the same precautions, especially when the data is not from Sailrite. The information on this site is not guaranteed to be accurate. Sailrite offers this content as a service to our community, but takes no responsibility for the reliability of the data provided.
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