Impulse 21
Impulse Marine · designed by William E. Cook · 1986
fin keelBermuda rigUnited States
The Impulse 21 is a 21-foot bermuda rig sailboat designed by William E. Cook and built by Impulse Marine, first launched in 1986.
General
| Builder | Impulse Marine |
|---|---|
| Designer | William E. Cook |
| Years built | 1986 |
| Hull type | fin keel |
| Rig type | Bermuda rig |
| Construction | fiberglass |
| Origin | United States |
Dimensions
| LOA | 21.00 ft6.40 m |
|---|---|
| LWL | 18.50 ft5.64 m |
| Beam | 8.00 ft2.44 m |
| Draft (max) | 3.25 ft0.99 m |
| Displacement | 1,300 lb590 kg |
| Ballast | 600 lb272 kg |
| Sail Area | 207 ft²19.2 m² |
Design ratios
Computed from the specs above using the standard formulas. Try the sailboat calculators with your own numbers.
SA / Displacement 27.81 Performance / racer — powered up
Ballast / Displacement 46.2 % Higher = stiffer / more sail-carrying power
Displacement / Length 92 Ultralight
Comfort Ratio 6.5 Racing / light coastal
Capsize Screening 2.93 Better suited to coastal use (> 2.0)
Hull Speed 5.8 kn Theoretical max displacement speed
How these numbers are calculated
- SA / Displacement
SA ÷ (Disp ÷ 64)^(2/3)— Power-to-weight. < 16 under-canvassed, 16–20 cruiser, > 20 racer.- Ballast / Displacement
Ballast ÷ Disp × 100— Stability/stiffness. Higher carries sail better.- Displacement / Length
Disp(lt) ÷ (0.01 · LWL)³— < 100 ultralight, 100–200 light, 200–300 moderate, > 300 heavy.- Comfort Ratio (Brewer)
Disp ÷ (0.65 · (0.7·LWL + 0.3·LOA) · Beam^1.33)— Motion in a seaway. Higher = more comfortable offshore.- Capsize Screening
Beam ÷ (Disp ÷ 64)^(1/3)— ≤ 2.0 favored for offshore; > 2.0 better for coastal use.- Hull Speed
1.34 · √LWL— Theoretical max displacement speed in knots.
Estimated price
$13,000 typical range $10,500 – $15,500
⚠ Rough estimate only — not market data. Derived from a simple model based on length and hull age; actual asking prices vary widely with condition, equipment, engine hours and location.
