Lightning vs San Juan 21
How do the Lightning and San Juan 21 compare? Below, their dimensions, displacement, sail area and the standard design ratios side by side, followed by a data-driven summary.
Lightning 
San Juan 21 | Lightning | San Juan 21 | |
|---|---|---|
| Length overall | 19.0 ft5.79 m | 20.5 ft6.25 m |
| Waterline length | 15.3 ft4.65 m | 17.5 ft5.33 m |
| Beam | 5.0 ft1.51 m | 7.0 ft2.13 m |
| Draft | 5.0 ft1.51 m | 4.0 ft1.22 m |
| Displacement | 700 lb318 kg | 1,250 lb567 kg |
| Ballast | —— | 400 lb181 kg |
| Sail area | 189 ft²17.6 m² | 193 ft²17.9 m² |
| SA / Displacement | 38.36 | 26.61 |
| Displacement / Length | 88 | 104 |
| Comfort ratio | 7.8 | 7.9 |
| Capsize screening | 2.23 | 2.60 |
| Hull speed (kn) | 5.2 | 5.6 |
Lightning vs San Juan 21: the short version
- The San Juan 21 is the larger boat at 20.5 ft6.25 m LOA versus 19.0 ft5.79 m for the Lightning.
- The San Juan 21 is heavier, displacing about 79% more, which usually means a steadier but slower-to-accelerate hull.
- On sail area/displacement the Lightning carries the more powerful rig (38.4 vs 26.6), favouring lighter-air performance.
- The San Juan 21 scores higher on the Brewer comfort ratio, suggesting an easier motion in a seaway.
- By the capsize screening formula the Lightning rates better for offshore work (2.23 vs 2.60).
Ratios are guidelines computed from published specs; condition, layout and gear matter as much as the numbers.