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Viper 640 Sails - North Sails is the leader in one design sailmaking. On this page, you will find information about our complete line of Viper 640 sail models, Viper 640 tuning advice and Viper 640 news and results from the race course.

North Sails continues to lead the way in Viper 640 sail development and product features. Our Viper team has focused our product line on creating the fastest sails using the best materials and design features to enhance performance and durability. The North Viper main and jib are constructed using Pentex fabric which, in concert with our radial panel construction, has proven to provide the best durability as well as superior shape holding which equates to faster, more durable sails.

Viper M-7 Mainsail

The Viper 640 M-7 mainsail has been designed to take advantage of a tuning system that emphasizes simplicity while optimizing speed! . This shape enables you to chock the mast in light air to induce the proper amount of headstay sag while enabling you to block the mast back and tension the lowers in fresher breezes to straighten the headstay and allow optimal use of vang sheeting. Our design has other new features as well including optimizing the batten positions of the full length battens enabling us to maximize the size of the sail at the measured girth points as well as relocating the jib leech window for better viewing of the jib leech telltale for both helmsman and trimmer.

Mainsails include:

  • Trim stripes
  • Sail numbers
  • Insignia
  • Vision window
  • Jib leech window
  • Sail bag

How to tension battens?

For prices and more information contact our Viper Experts or your

Viper J-4 Jib

The North Viper 640 jib has been changed as well. To start we have lowered the jib clew so that the jib lead adjustment is more effective and each change has a distinct effect on enhancing performance. Also, our jib features a full-length top batten which helps the top of the sail twist more effectively which allows more control with the jib sheet and the ability to trim harder! Combine all this with a design that features a fuller entry, flatter leech and a maximum length tapered bottom batten as well as additional panels in the head which assist in adding durability to the sails shape and you have a proven performance leader.

Jibs include:

  • Pentex load bearing fabric with radial construction for superior durability
  • Trim stripes
  • 2:1 Clew blocks
  • Luff telltales
  • Leech telltales
  • Sail bag

For prices and more information contact our Viper Experts or your

Viper Asymmetrical Spinnaker

The North Viper 640 spinnaker has been designed utilizing the knowledge we have gained on making championship winning sails for a variety of sportboats. Our first project was to maximize the size of our design which, in doing so, makes our sail class maximum size. Our next goal was to create a design that would twist and rotate better so that we could sail lower angles while sailing the same speed or faster. Our Viper 640 spinnaker enables you to do just that. Maximum size, lower and faster. The perfect Viper 640 spinnaker.

For prices and more information contact our Viper Experts or your

Tuning your Viper 640 for Speed

>> Download the North Viper 640 Tuning Guide Updated!

>> Download the NEW Viper Quick Guide

For more information on Viper sails, contact the North Viper experts.

Sail Numbers & Letters

300mm (12”) Sail Letters & Numbers

Please contact your local North Loft or Agent to make your order or for further details.

Contact the Viper Experts:
Ruairidh Scott
+44 (0)1329 443 430 Work
Paul Young
+44 (0) 1380 831138 Work
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