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Old 05-31-2000
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Brian Hancock is on a distinguished road
Mainsail Configurations and Fabrics

AirForce Sails Product Manager Brian Hancock continues his multi-part series on sails and sailmaking technology. (Review Part Three.)

 
The author's optimal configuration: "a large mainsail . . . and small, non-overlapping headsails," is evident aboard his own boat, above.
 
One of the most important things you should know about your mainsail is that it's the back of the main that works with your keel to provide lift when you are sailing to windward. This single fact will have a bearing on the shape and size of your sail, which in turn will influence the fabric and panel layout you choose. The back of the main becomes less important once you bear away, for then propulsion becomes more a factor of projected area than aerodynamic shape. But even cruising sailors who try their best to keep the wind at their back, need to go to windward on occasion. So if windward performance is what you want, then remember the roach. In this article we will take a brief look at sail plan configurations and how to achieve an optimum mainsail by choosing the appropriate size, fabric, and panel layouts.

For the last 10 years there has been a trend toward in-mast furling mainsails. It's impossible to argue against the convenience of push-button sailing and rolling the main into the mast to reduce sail is certainly a convenient way to go. The drawback is that for the main to roll away, you can't really have much sail area that extends beyond a straight line between the head and clew. It's true that you can gain a bit of area by having vertical battens (the kind often utilized in stowaway mains), but this is a token amount and hardly worth the aggravation of battens that roll up.

 
Days of Dacron meant cross-cut mainsails and miter-cut genoas, but newer materials provide a broad spectrum of options for the cruising sailor.
 

By extension, it can be argued that boats with rollaway mainsails do not have good windward performance, which in turn could lead to problems, especially if you are trying to sail off a lee shore. Now, I am not trying to be an alarmist (although last summer I did have a problem off the Azores Islands because of a sweeping current and a lack of pointing ability), but if you are looking at mainsail choices and considering sail plans, you might want to consider what I view to be an optimal configuration: a large mainsail with power in the back end, and small, non-overlapping headsails, each using the latest sail handling systems like batten-cars and lazyjacks to help with the main.

There are very few pure-cruising sailors who relish their time at sea and don't care how long it takes for them to get to the next port. The rest of us tweak and trim our sails to get better performance, hoping to save at least a few hours on each passage. We all look for and expect performance from our boats and it's the sail plan that provides it. Lighter, stronger, and more exotic fabrics are relatively new to the cruising market where DacronTM has long dominated, and there are good reasons for this. DacronTM is rugged and reliable, and despite stretching a little over time, it has proven to be the best fabric for those planning to go offshore. One drawback has been that as boats get bigger, the loads become greater, and the sails get heavier. But now, exotic materials are able to make sail handling easier, as well as making sails look better and last longer. The only problem that remains is that the profusion of choices complicates the sail-buying process and confuses sailors.

 
This laminated mainsail should provide several seasons of reliable performance.
 
As far as I am concerned, for cruising boats up to 50 feet in length, there are really only two, or possibly three, fabric choices. This is based upon my experience making many sails that have performed well over a wide range of conditions for many years. The aforementioned durable DacronTM is a staple in the sailmaking industry and it goes without saying that, you can't go wrong with DacronTM as a basic choice. For a more performance-minded sail, consider PentexTM or a polyester cruising laminate. We discussed the pluses of PentexTM in the first two articles in this series, and how the fibers are used in a laminated fabric (Review Part One or Part Two.). That fabric is then used to build radial sails. Your other choice is a laminated polyester. The engineering of this cruising laminate has been well proven over time and I have seen these kinds of sails in all parts of the world.

With polyester cruising laminate sails, the yarns are bundled together with gaps between the bundles. The bundles are then sandwiched between a MylarTM substrate and a light woven taffeta. The adhesive gets a good bond between the bundles and with the light taffetas for chafe protection and durability, the fabric lasts a long time and has a soft feel.

"If your sails call for the stretch resistance and weight savings of VectranTM, then an investment in this high-tech engineering is a reasonable way to spend your money."
This same engineering is used with different fibers for bigger boats where the loads are more demanding and tough, and light sails are in order. Instead of the bundles of polyester yarns, the fabrics are made with bundles of either SpectraTM or VectranTM. SpectraTM is the most common because of the rugged nature of this fiber, and because nothing beats it for initial stretch resistance. These sails are now seen the world over. In fact, on my own boat I have SpectraTM sails that are built this way and they have lasted through several years of unkind treatment. VectranTM is not as common and is generally manufactured on a semi-custom basis. The problem with VectranTM is that it does not like that one key ingredient common to all sailing—sunlight. Ultraviolet light degrades the fibers of almost any fabric, but if the fabric is engineered correctly, it can be made suitable for extreme sunlight exposure. In this case, VectranTM fibers are sandwiched between taffeta that has been treated with a UV inhibitor, a UV-resistant film, and even a UV-resistant adhesive.

If your sails call for the stretch resistance and weight savings of VectranTM, then an investment in this high-tech engineering is a reasonable way to spend your money. Some of these more "exotic" yarns are woven into panels rather than bundled in, and while this produces a rugged, reliable fabric, there is still the problem of "crimp" (see Part Two of this series for an explanation of crimp). As the crimp straightens out, the fabric stretches.

 
For a coastal cruising vessel like this multihull, it makes sense to have a mainsail built out of a rugged laminated sailcloth.
 

How you decide what fabric to choose will depend upon where and how you sail your boat. If you spend weekends daysailing the South Carolina coast, then DacronTM will probably be more than adequate. If you are headed for the Azores this summer and you want to make it a quick passage, then think about a rugged laminate. If you have a heavy displacement craft that loads up under sail, then consider a PentexTM or cruising laminate sail. For boats over 50 feet, a laminate is almost mandatory, and for the much bigger boats, an "exotic" laminate will serve you best.

With such well-advanced engineering, most sailmakers will have no problem building you any size or shape mainsail. Full-batten sails with lots of roach are becoming more common on cruising boats where performance is desirable. And where fabric was once a limitation, it's now an advantage. In the next article we will look at all the features that make your mainsail easier to trim and handle, and how you can incorporate them into a new sail. As I have already pointed out, it's called the mainsail because it is the main component in your sail inventory, so it's certainly worth getting it right. And doing so will make your sailing safer and more enjoyable.

In Part Five of his Sail Tech series, AirForce Sails Product Manager Brian Hancock will discuss the details of mainsail construction.

 

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