Hull Speed
The theoretical displacement-mode speed limit — determined by waterline length, not engine or sail power.
4.6 kts
A displacement hull pushes a bow wave whose speed is limited by the waterline length.
With a waterline of 11.8′, the Firefly tops out around 4.6 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √11.8′ LWL = 4.6 kts
Performance Ratios
Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.
Displacement / Length
72
Ultralight — responsive and fast, but carries less stores.
Hull Speed
4.6kts
Pounds/Inch Immersion
1lbs
Weight needed to sink the hull one inch — loading sensitivity.
How It Compares
Side-by-side with the boats most often cross-shopped against the Firefly.
| Firefly | Butterfly | Byte | Cherub | Comet Duo | Tech Dinghy | |
|---|---|---|---|---|---|---|
| Dimensions | ||||||
| LOA | 12.0 | 12.0 | 12.0 | 12.2 | 12.2 | 12.0 |
| LWL | 11.8 | — | 10.5 | — | — | — |
| Beam | 4.7 | 4.5 | 4.3 | 5.9 | 5.0 | 4.7 |
| Displacement | 260 | 137 | 99 | 110 | 195 | 250 |
| Sail Area | — | 75 | 58 | — | — | 72 |
| Performance | ||||||
| SA/Disp | — | — | 43.4 | — | — | 29.1 |
| Comfort | — | 2.6 | 2.0 | 1.5 | 3.2 | — |
| Capsize | — | — | 3.68 | — | — | 2.97 |
| Hull Speed | — | 4.3 | 4.3 | 4.3 | 4.3 | — |