Without a doubt, the number one feature cruising sailors look for in sails is durability. Yet durability is one of the least quantified elements in sail performance. Predicting durability is a tough challenge because sails are subjected to so many different forms of abuse, from mother nature and from their owners. Nonetheless, the most common question we hear from cruising sailors is "How long will my sails last?" Here, we'll try to provide some answers.

Perhaps the most significant contributor to the lifespan of a sail is sailcloth. In racing sails it can mean the difference between winning and losing. In cruising sails it can mean as much or more. Racing sailcloth has undergone a revolution over the last 10 ­ 15 years. Cruising sailcloth has as well, taking the best ideas developed for racing and adapting them for a different task. Today's cruising sail has a lot more racing heritage than most cruisers realize!

There are two basic types of sailcloth for cruising; lightweight fabrics for downwind sails such as GENNAKERS and spinnakers, and stronger fabrics for mains and headsails. This latter group comes in three basic forms:

· traditional woven polyester
· laminated polyester (with Mylar)
· high­performance laminates (Spectra/Dyneema)

Traditional woven polyesters
Woven polyester has been the world's standard sailcloth for working sails since the early 50s when it replaced cotton. It is commonly called Dacron after the trade name that yarn supplier Dupont calls its polyester yarn. There is a wide range of polyester fabric available in the commercial sailcloth market ranging from "bed sheet" quality to tightly woven, high performance versions. The sailmaker typically chooses the cloth for his design, however "quality" grades have some common features:

1. Tight weave. The tightest weaves are achieved on classic shuttle looms rather than high­speed "modern" looms. High­strength weave design relies on tightness to
maximize performance.
2. Quality Yarn. Not all polyester yarn is created equal. The highest rated polyester yarn is high­tenacity genuine Dupont Dacron@.
3. Finish. A quality polyester fabric should be finished with only a modest resin level applied with a high pressure calender operation.

Today, quality woven polyesters are the longest lasting sail fabrics made.

Laminated Fabrics
The next class of sailcloth for working sails are laminates of polyester cloth and Mylar film. For cruising, it's best if the polyester cloth is light weight and laminated on both sides with the Mylar out of sight and protected in the center. With proper bonding these laminates can last almost as long as a top quality woven Dacron while offering lower weight and stretch. They are particularly well suited to overlapping roller furling genoas because their strong warp adapts well to radial panel layouts.

Spectra™/Dyneema™
Maximum performance cruising sails are most often laminates made with with super strong, low stretch Spectra or Dyneema yarns. These highly processed polyethylene super­fibers cut sail weight by 25% or more while offering lower stretch, higher strength, excellent UV resistance and durability. Spectra/Dyneema laminates are a favorite of marathon multihull racers because they combine near­Grand Prix performance with exceptional long­term durability and UV resistance.
North is currently developing Spectra/Dyneema and polyester versions of its patented 3DL one­piece molded sails for cruising sailors.

Downwind sail fabrics

For lightweight downwind sails such as spinnakers and GENNAKERS, the most common material used is the familiar rip­stop nylon similar to the cloth used for parachutes.
It comes in a variety of colors and is very strong and tear resistant considering its minimal weight. Another option to nylon is a fabric made with small diameter polyester yarns. It offers lower stretch and better UV resistance than nylon, but costs more to produce. Its appearance is virtually the same.
Quality lightweight nylon and polyester fabrics are tough, durable, and have excellent breaking strength.

The longevity question

Here comes the challenging part. First of all, the best way to measure sail longevity is not in years of ownership, but in hours of use. Racers log hours on their sails to track the aerodynamic life of their sails (how long the designed shape will last)...cruisers should do the same. How many hours should you expect out of a cruising sail? Here are some examples:

· Most charter fleets expect 2 ­ 3 years of use from basic Dacron sails, which translates to about 1500 ­ 2500 hours of varied duty, typically including a high flogging quotient. Charter sails used 2,000 hours or more are typically considered "shot."

An important point: There is a big difference between a sails "ultimate life"-when it starts to fall apart-and its "performance life" ­ when it loses its shape to a point that it could benefit from recutting or replacement for optimum performance. Performance life is always shorter than ultimate life.

· The record­setting ocean multihull Commodore Explorer (see feature on page 26) used her FullBatten Spectra/Dyneema mainsail for 80 days, 24 hours a day, for 1,920 hard hours of use, and the sail still had more performance life left.

If you assume a typical sailing season might be 30 days sailing 5 hours per day for a total of 150 hours, you might calculate that an average cruising sailor can expect 10 + years of use out of a quality Dacron cruising sail.

From here, there are other factors to take into account:

Quality. We've all seen sails with 50 ­ 100 hours of use that are a mass of wrinkles, even with careful use. Low quality cloth may look comparable to "the good stuff" at first, but will break down much faster. Seams stitched properly with UV resistant thread, well designed patches and batten pockets, chafe protection, leech and foot cords...all affect sail longevity.

Maintenance. Small problems left unattended become big ones later. Regular service helps sails last longer, just as it does with your automobile's engine. (For advice on sail care & maintenance see page 8 of this Guide.)

Unusual conditions. If you sail in southern latitudes and don't cover your sails, UV degradation can be significantly accelerated. Leaving a sail up and flogging in a squall for 30 minutes can equal 50 hours of "normal" sailing. Consistently flying a sail over its designed wind range can also age a sail well before its time.

The life expectancy of a well­maintained airplane engine is about 1,800 hours. For an automobile engine...2,000 + hours. Many cruising sailors will probably be surprised to know that the life expectancy of their "wind engine" is in the same league.

Peter Mahr is President of North Cloth.
Photo at top and above right by Ned Rabinowdz