San Juan 21
Clark Boat Company · designed by Don Clark · 1970
centerboardBermuda rigUnited States
The San Juan 21 is a 21-foot bermuda rig sailboat designed by Don Clark and built by Clark Boat Company, first launched in 1970.
General
| Builder | Clark Boat Company |
|---|---|
| Designer | Don Clark |
| Years built | 1970 |
| Hull type | centerboard |
| Rig type | Bermuda rig |
| Construction | fiberglass |
| Origin | United States |
Dimensions
| LOA | 20.50 ft6.25 m |
|---|---|
| LWL | 17.50 ft5.33 m |
| Beam | 7.00 ft2.13 m |
| Draft (max) | 4.00 ft1.22 m |
| Displacement | 1,250 lb567 kg |
| Ballast | 400 lb181 kg |
| Sail Area | 193 ft²17.9 m² |
Design ratios
Computed from the specs above using the standard formulas. Try the sailboat calculators with your own numbers.
SA / Displacement 26.61 Performance / racer — powered up
Ballast / Displacement 32.0 % Higher = stiffer / more sail-carrying power
Displacement / Length 104 Light
Comfort Ratio 7.9 Racing / light coastal
Capsize Screening 2.60 Better suited to coastal use (> 2.0)
Hull Speed 5.6 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
$11,000 typical range $9,000 – $13,000
⚠ 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.
