Viper 640
Rondar Raceboats · designed by Brian Bennett · 1996
keelboatBermuda rigUnited States
The Viper 640 is a 21-foot bermuda rig sailboat designed by Brian Bennett and built by Rondar Raceboats, first launched in 1996.
General
| Builder | Rondar Raceboats |
|---|---|
| Designer | Brian Bennett |
| Years built | 1996 |
| Hull type | keelboat |
| Rig type | Bermuda rig |
| Construction | fiberglass |
| Origin | United States |
Dimensions
| LOA | 21.08 ft6.43 m |
|---|---|
| LWL | 19.08 ft5.82 m |
| Beam | 8.17 ft2.49 m |
| Draft (max) | 4.49 ft1.37 m |
| Displacement | 750 lb340 kg |
| Ballast | 262 lb119 kg |
| Sail Area | 211 ft²19.6 m² |
Design ratios
Computed from the specs above using the standard formulas. Try the sailboat calculators with your own numbers.
SA / Displacement 40.90 Performance / racer — powered up
Ballast / Displacement 34.9 % Higher = stiffer / more sail-carrying power
Displacement / Length 48 Ultralight
Comfort Ratio 3.6 Racing / light coastal
Capsize Screening 3.60 Better suited to coastal use (> 2.0)
Hull Speed 5.9 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
$15,000 typical range $12,000 – $18,000
⚠ 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.
