The Viper 640 is a 2 to 4 person, high-performance sports boat. It is FUN, FAST, EASY and AFFORDABLE. The Viper makes high performance sailing available to everyone. The open transom bails water instantly, even in extreme conditions. The Viper is simple, clean, and effective, with no protruding hardware and everything placed for efficiency. The Viper is light enough to be towed behind a compact car and simple enough to be rigged and sailed in under a half hour. The boat can be launched from a hoist or ramp. The 640 is strict one-design with no changes permitted to the boat as supplied by the class approved builder. The only option is sails, supplied by class approved sailmakers and strictly controlled through class rules, which encourages the development of tuning techniques with the help of the best sailors and sailmakers.

Performance Characteristics
- Fine entry, long narrow bow and pronounced cross sectional flare in the midsection results in low drag.
- Bulb keel and wide flared beam at the cockpit provides superior stability and enables a powerful sail plan.
- The combination of fine entry, low drag, and powerful sail plan make the Viper superior in light air or chop.
- The Viper will start planing before any similar class (SB3, Open 5.70, K6, U20, Melges 20 & 24 etc).
- The wide cockpit, superior stability and a sturdy carbon mast make it fast and secure in big breeze.
- The hull shape means that the Viper does not go 'bow down' planing downwind at high speeds.

Jib Leads
The 2:1 ratchet-controlled jib sheet runs through Carbo T2s on the clew to low-profile pinstop cars for trim angle adjustments. In addition to moving the cars forward to round the foot of the jib, Viper sailors can also improve light-air performance by removing the top batten to keep the leech open.

Jib Halyard Fine-Tune
For cranking up the luff tension in fresh wind, the Viper's jib halyard is deflected through a 8:1 fine-tune. The double-ended system uses Micro Carbo Cams with X-Treme Angle fairleads, making it easy for the forward crew to adjust without leaving the rail.

Gnav strut
The Viper cockpit is very clean with a gnav in place of a traditional vang. The new 8:1 Harken gnav replaces the slider system with a captive bearing car designed for compression loads. The Harken HC8418 utility car removes most of the friction to make the system more powerful, reducing the need for a very high purchase, and making it far easier to use under load.