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Doyle Downwind

Doyle Spinnaker Design

Engineering downwind sails that blend durability and performance - not only in straight line but also be forgiving to trim in changing wind angles - is a challenge and art. Doyle Sailmakers central design team consists of highly qualified sailors who each bring different strengths to the team. Richard Bouzaid, the leading designer within the group, heads the innovation and research for the Doyle Design team. Knowledge gained from years of racing and cruising coupled with advanced CFD development allows Doyle’s designers to accurately model downwind sails and produce efficient designs that are carefully matched to individual boats. Specifics such as projected wind range, crossover charts and specifics of an individual sail can be modeled and predicted prior to the sail even being fitted to the boat – ensuring trouble free sailing.

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Selecting the Proper Spinnaker Material

Materials have a big effect on the performance of downwind sails, and given the range of apparent wind speeds that the sails can see can have a big effect on the life of the sail. Most spinnakers, asymmetricals included, are built from nylon-based fabrics. These materials are light and range from .5 oz through to 2.2 oz. While nylon-based materials are relatively stretchy - which allows them to flap and be taken in relatively high wind speeds, overloading these materials does cause them to become more porous and reduces their strength considerably. Most people will admit to being caught over range with a spinnaker up or in a big broach with the spinnaker flapping and the boat on its side. Most people will also be surprised that the sail didn't break at that time, and then some time later while sailing along in nice conditions the sail breaks for what seems to be no reason at all.

A basic guide for wind strengths for different materials that will keep the sails out of the dangerous overloading range is below. Note that these are apparent wind speeds, not true wind speeds, and are for average size boats. Also, these apparent wind speeds should be lowered if the sail is old or has been overloaded in the past.

  • .5oz cloth up to 10 knots AWS
  • .75oz cloth up to 14 knots AWS
  • 1.5oz cloth up to 18 knots AWS
  • 2.2 oz cloth up to 21 knots AWS

While nylon is a good material for asymmetrical spinnakers, other fabrics have more recently been developed for closer reaching designs that overcome the problem of the stretch and overloading of nylon. As the sails become smaller and flatter for sailing at closer angles, the yacht's stability has typically been the limiting factor and nylon sails have historically been strong enough. Now, with many of the more modern racing yachts with either water ballast or canting keels that have high stability and can carry reaching asymmetrical sails in much higher winds and at much higher boat speeds, alternative higher strength materials have been developed. Fabrics utilizing Polyester, Spectra, Kevlar, and carbon fiber are becoming common for high performance race yachts that carry only asymmetrical spinnakers. While these fabrics are considerably more expensive than nylon materials, they are much stronger and lower stretch for the same weight.