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Viper 640
Designer: Brian Bennett  ·  Builder: Viper Boats (Usa)/Rondar  ·  First built: 1996
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About the Viper 640

Designed for pure performance and competitive racing, the Viper 640 has earned a strong reputation as one of the most exciting one-design sports boats on the water today. Built for a crew of three, this sleek planing hull delivers an exhilarating sailing experience that appeals to experienced racers looking for a fast, responsive, and highly competitive platform. The Viper 640 is particularly well suited to inshore and coastal racing, where its agility and speed-focused design can be fully exploited. Its relatively simple rig and manageable size make it accessible enough for a small but skilled crew, while still offering the kind of intense, high-performance sailing that keeps seasoned racers coming back. The boat is known for being physically demanding in a rewarding way, rewarding good technique and sharp tactical decisions. With an active class association and a dedicated racing community, the Viper 640 benefits from strong fleet presence at regattas across North America and beyond. For sailors seeking a boat that prioritizes speed, competition, and fun over comfort or cruising capability, the Viper 640 is a compelling and well-regarded choice.

Core Dimensions
LOA (Length Overall) 21.08 ft / 6.43 m
LWL (Waterline Length) 19.08 ft / 5.82 m
Beam 8.17 ft / 2.49 m
Max Draft 4.83 ft / 1.47 m
Min Draft 1.83 ft / 0.56 m
Displacement 700.00 lb / 318 kg
Ballast 185.00 lb / 84 kg
Sail Area (Reported) 252.00 ft² / 23.41 m²
Design & Construction
Hull Type Lifting Keel
Rigging Type Fractional Sloop
Construction FG
Designer Brian Bennett
Builder Viper Boats (USA)/Rondar
First Built 1996
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Performance Ratios
PHRF Rating PHRF (Performance Handicap Racing Fleet) is a national racing handicap measured in seconds per nautical mile. Lower values indicate faster boats. Ratings are sourced from US Sailing's national database (median across 60+ regional fleets).
Under 0 — Ultralight racer0–90 — Performance racer90–150 — Cruiser/racer150–210 — Typical cruiserOver 210 — Heavy/slow cruiser
 99
SA/Displacement Sail Area to Displacement ratio measures how much sail power a boat has relative to its weight. Higher values mean more performance and speed.
Under 14 — Heavy cruiser, slow14–18 — Cruising sailboat18–22 — Cruiser/racerOver 22 — Performance racer
 51.22
Comfort Ratio Ted Brewer's Comfort Ratio predicts how comfortable a boat will feel in offshore conditions. Higher values mean a steadier, more comfortable motion in a seaway.
Under 20 — Uncomfortably rough20–30 — Acceptable coastal30–40 — Good offshore comfortOver 40 — Very comfortable offshore
 3.35
Capsize Screening Formula The USHS Capsize Screening Formula estimates offshore capsize risk. Lower is safer — values under 2.0 are considered acceptable for offshore sailing.
Under 2.0 — Safe for offshore2.0–2.2 — Borderline offshoreOver 2.2 — Coastal use recommended
 3.68
Hull Speed Hull Speed is the theoretical maximum speed of a displacement hull, calculated from waterline length. Most cruising sailboats reach this speed in moderate conditions. 5.85
S# (Speed Number) The Speed Number (S#) is a quick performance index. Higher values indicate a faster, more powerful design relative to its size.
Under 3.0 — Slow cruiser3.0–5.0 — Average cruiser5.0–7.0 — Performance cruiserOver 7.0 — Racer
 10.03
Pounds/Inch Immersion Pounds per Inch Immersion (PPI) tells you how much weight is needed to sink the boat one inch. Useful for calculating how additional gear and stores affect waterline. 556.99
Rig Dimensions
I (Foretriangle Height) 21.67
J (Foretriangle Base) 8.33
P (Mainsail Luff) 25.62
E (Mainsail Foot) 10.0
SA Fore 90.26
SA Main 128.1
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