Alpa 21
Sailboat
21′ 4″
Since 1976
Overview
- Builder
- Alpa
- Model
- 21
- Type
- Sailboat
- Built
- 1976 on
- Designer
- Sparkman & Stephens
- Hull
- Fin w/transom hung rudder
- Hull material
- Fiberglass
- Rig
- Masthead Sloop
Dimensions
- Length overall
- 21′ 4″ (6.49 m)
- Waterline length
- 18′ 7″ (5.67 m)
- Beam
- 8′ 2″ (2.50 m)
- Displacement
- 2,868 lb (1,301 kg)
- Ballast
- 800 lb (363 kg)
Sails and rig
- Sail area
- 255 sq ft (23.7 m²)
- I (foretriangle height)
- 30′ (9.14 m)
- J (foretriangle base)
- 8′ 7″ (2.61 m)
- P (mainsail luff)
- 26′ (7.92 m)
- E (mainsail foot)
- 9′ (2.74 m)
Design ratios
- Sail area / displacement
- 20.2
- Displacement / length
- 199
- Ballast ratio
- 28%
- Capsize screening
- 2.31
Power from the sails for the boat's weight. Under 16 is modest, 16–20 a typical cruiser, over 20 lively.
How heavy the boat is for its waterline. Under 200 is light, 200–300 moderate, over 300 heavy.
Share of the weight that is ballast. Higher generally means stiffer in a breeze.
Under 2 is generally considered better for offshore use.
More details
- Construction
- FG
Data from Mauri Pro Sailboat Data. Check details with the builder before relying on them.