A Mainsail for all Seasons

A head-to-foot look at the sail we depend on most

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Standard battens on a 42-foot Alden Nordfarer add support to the leech and a fraction of roach.©billy Black

Perhaps more than any other sail in our inventory, the mainsail deserves careful consideration, whether you’re selecting a new sail or maintaining or improving the one you already have. The type of mainsail and options you choose will depend on not only your rig and vessel but also the type of sailing you do. As cruising sailors, we generally want durable, long-lasting mainsails that will perform well in a wide variety of conditions and are easy for the crew to handle and maintain.

The useful life span of a mainsail is largely dependent upon the strength and stability (ability to retain shape) of the sailcloth and its resistance to chafe and the sun’s ultraviolet rays. Workmanship at the sail’s seams, corners, and edges and the quality of hardware also play key roles in its durability. While furling mainsails have their adherents, I’ll focus on the more common traditional mainsail that’s flaked or furled on top of the boom when not in use. Many of the details I’ll discuss apply equally to both types.

Sailcloth woven from polyester, such as Dupont’s Dacron, is remarkably seaworthy and an excellent choice for mainsails on most cruising boats under 60 feet. Premium Dacron is the designation given by most sailcloth manufacturers to their finest woven polyester. Because of its many tightly woven, low-stretch, fine-denier yarns, this sailcloth has better, more durable stability. Lesser-quality Dacron, which is more loosely woven of coarser yarns, relies more on its resin finish for stability, often yielding stiff, less manageable sailcloth. As the resin coating breaks down, this cheaper sailcloth will soften over time, and your sail will assume the undesirable shape of a shower cap.

To test the condition of your sail’s fabric, first muster the courage to push the tip of a number 14 sailmaker’s needle through a worn part of the mainsail, then pull it firmly in all directions. If the needle easily tears the cloth, the fabric isn’t worth repairing. You can test the thread by firmly rubbing the edge of a coin over a length of stitching. If the thread is brittle and breaks, it’s time to restitch the seams. Extra-wide seams offer an advantage since the new stitches can go between the original rows rather than on top of them. To further reduce the possibility of perforating seams, zigzag or triple-step stitching is preferable to straight stitching.

Batten Options
When buying or retrofitting a cruising mainsail, the issue of battens is bound to arise. The main purpose of these relatively narrow struts is to support roach, the sail area that lies outside a straight line drawn from the head to clew. Usually installed parallel to the foot or perpendicular to the leech at four or more evenly spaced intervals, battens must be at least three times as long as the roach they support. A mainsail is generally categorized according to the kind of battens it uses: full battens, standard battens, or no battens. Some sailmakers offer a compromise, with a combination of standard and full battens.

Full battens: On a fully battened mainsail, the battens extend from the luff to the leech so they can project a great deal of roach. More important, full battens help maintain a more aerodynamic cross-sectional shape, and they hold this shape for the life of the sail. By dampening the mainsail’s motion, full battens minimize the noise and debilitating effects of leech flutter and sail flogging. They also allow you to more effectively use excessive twist to depower the main, and they can aid in reefing and flaking the sail.

Now, for the drawbacks. Battens and the pockets that hold them are the source of most mainsail repairs. They can chafe, hang up, or destroy themselves on rigging. Battens complicate transporting or stowing the sail. They want to jump out of their pockets at the most untimely moments. Flat battens and stoutly constructed platform pockets (pockets that isolate the batten from the sail with an extra layer of Dacron fabric) will minimize these tendencies, but the greatest concern with full-length battens is the compression loading that concentrates at the luff. This force leads to chafe along the luff and on the batten pocket’s leading edge. Even worse, the compression loads make it difficult to raise, lower, or reef the mainsail. A seaworthy batten-end receptacle solves these problems. A good batten-end receptacle secures the batten in the pocket, protects the luff from chafe, and has an articulating, integrally attached sail slide. The receptacle is even better if it allows you to tension the battens. Properly installed full-length battens add significantly to the mainsail’s cost, and although they’ll provide a longer-lasting efficient sail shape, they won’t necessarily extend the sail’s overall life. Barring accidents, it’s sun exposure that will ultimately destroy the sail.

If you have a high-aspect mainsail (one fitting a tall mast and a short boom), roach will add vital sail area and improve efficiency, and you’ll need battens to support it. Larger mainsails will benefit most from full-length battens since they must endure higher loads and they take more time to raise, reef, and strike, which leaves them more prone to flogging.

Standard battens: The shorter standard battens project only partially from the leech toward the luff. The standard-batten mainsail is usually less chafe prone and easier to raise, reef, and lower than a fully battened mainsail. It’s certainly easier to stow. A standard-batten mainsail has a conservative amount of roach (e.g., 14 inches on a 40-foot leech) and costs significantly less than a fully battened main. It is, in many ways, easier to trim. However, in its declining years, a sail with standard battens will suffer from unsightly and performance-compromising leech gutter, formed when the mainsail’s leech hinges at the batten pockets’ inboard ends. This unhappy shape change is exacerbated in a high-aspect mainsail because its loads are concentrated along the leech. Standard battens have a penchant for poking through their pockets.

Sailors with sloops or cutters smaller than 35 feet (or larger boats with split rigs) can be completely satisfied with the performance of a standard-batten mainsail; indeed, coastal and offshore cruisers with far larger vessels have also had success with this time-tested type of mainsail.

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| ©Billy Black|

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| In-mast furling precludes the use of battens in the sail of this Beneteau Oceanis 370.* * *|

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No battens: A battenless mainsail eliminates the nuisances associated with battens and is less costly to build. A battenless mainsail (sometimes called a roachless main) can be made new or recut from a main with standard or full-length battens. But in a high-aspect battenless mainsail, cloth fatigue inevitably manifests as an inefficient cupped leech. As the sail ages, the fullness of the sail will migrate aft, making it less efficient to windward and more difficult to ensure proper trim.

If you plan on circumnavigating the five great capes with a low-aspect (short) rig and you don’t mind sacrificing a few ounces of performance for the sake of self-sufficiency, simplicity, economy, and ultimate durability, a battenless mainsail may be your best choice.

Cringles and Nettles
Once you determine batten style, you can settle on the number and position of reef rows. A row of reefs allows you to reduce the mainsail's size when the wind pipes up. Each row consists of a secondary tack and clew (often referred to as reef cringles) and intermediate reef points. To pull down and make fast the secondary tack and clew to the boom, reefing tackle is rove through the reef cringles. After the reef tack is secured, the clew reefing tackle must pull the clew reef cringle down to the boom and outhaul it aft toward the end of the boom. If the reefed sail isn't outhauled, the sail will be too full. This will induce excessive heeling and leeway when working to weather and is less effective at reducing boat speed off the wind. Once you make fast the reef tack and clew cringles, it's prudent to tie a backup line or webbing strop through the cringles and around the boom. You can then loosely secure the bunt of the sail using the reef nettles, or reef tie lines, that are rove through the reef points; this will keep loose sail from catching wind and water or obscuring visibility from the helm. To minimize the shock loads on the reef points, you should tie the nettles only around the bunt of the sail, not the boom.

A mainsail’s reef rows typically are spaced relatively evenly and roughly parallel to the foot of the sail at a workable distance from any battens. A common first-reef position reduces a mainsail’s size by 20 percent. A second reef generally shaves off 40 percent. Cruisers venturing offshore may choose to have deeper reefs or to add a third row. Although three sets of reef points can create a spaghetti factory at the mast or cockpit, a third reef offers more options for balancing the headsails or keeping a tender boat on an even keel. Regardless of how small your mainsail may be reefed, it’s still prudent to carry a trysail when bluewater sailing. A trysail serves as both a storm sail and a backup mainsail, albeit less than a third of the mainsail’s size.

Capable Corners
The mainsail's corners are subject to dramatic loads. Accordingly, high-quality, non-corrosive hardware of appropriate size and strength must be set into stout reinforcing patches at the head, tack, and clew as well as at the reef tacks and clews. Reinforcing patches consisting of several layers of sailcloth in weight equal to or greater than the sail fabric should extend generously into the body of the sail. The length of the reinforcing patch should be 12 to 15 percent of the side of the sail that it supports. (For example, a 40-foot leech might have a 6-foot-long clew patch.)

You have various hardware options at the corners, including external rings (D-rings, maxi-rings, and others), integral rings (either hand sewn or hydraulically pressed), and headboards. An external ring is secured with multiple webbing strainers and hand stitching; if sized properly, an external ring is suitable for any primary corner, particularly if it must fit into a narrow or short shackle, or fitting. External rings are easy for a sailor to replace by hand at sea and present little chafe concern. Integral rings are commonly used at the primary corners or for reef cringles. Hydraulically pressed rings here are stronger under a steady load than a hand-worked ring, but they don’t have as flexible a bearing surface and aren’t as easy to replace. Either is suitable for a cruising sail, but beware of older pressed rings made of dissimilar metals, an arrangement that invites corrosion. The reef clew cringle of a battenless or standard-batten mainsail is an ideal location for a hand-sewn ring because it will endure a lot of flutter and flogging over the course of its life. That same sail would be well served by hydraulically pressed tack and clew rings that are held captive under load by unyielding stainless-steel tack and outhaul fittings.

An anodized aluminum headboard is appropriate for a standard or fully battened mainsail, helping to support the roach at the head and to provide a secure attachment point for the halyard. Use the forward headboard hole to hoist the mainsail if its halyard is rove through a masthead sheave; use the aft headboard hole if the main halyard block is hung abaft the mast on the masthead crane.

Webbing strainers--straps that are folded in half and sewn from corner hardware into the body of the sail--can be used at any corner. Thick, hand-sewn leather is second to none for protecting corners from chafe; it’s the most durable material and easiest to replace. If your reef tack attaches to a reef hook, a short length of webbing rove through an integral tack ring and attached to a stainless-steel round ring makes reefing easier. Beware of tack rings with webbing sewn on only one side of the sail. These can easily tear out.

Tracks and Slides
A cruising mainsail's slides hold the luff to the mast; they should be durable, well secured, and able to move smoothly up and down the mast track. They should be approximately 2 feet apart and doubled at the head. Whenever possible, you should use the best and strongest slide available, particularly at the head and above each reef tack, where loads are highest. Ultra-high-molecular-weight (UHMW) plastic internal slides are stronger and create less friction than their common and less expensive white plastic counterparts, and they don't gall or corrode inside an aluminum mast track like stainless-steel or bronze slides can. An external-style stainless-steel mast track (often found on a wooden mast) requires a robust external bronze or stainless-steel slide that fits around the track. These slides work beautifully if the track is clean and fair, though they'll bind if the track's joints aren't aligned. Grooved mast tracks for a racing mainsail's boltrope will also fit slug slides on a cruising sail, but raising and lowering these sails can be truly aggravating. This track and slide arrangement doesn't belong with fully battened mainsails.

Sail slides on a voyaging mainsail should attach to either hand-sewn or hydraulically pressed rings along the luff. Avoid using common spur grommets in highly loaded areas near the head and just above reef cringles. The best way to attach luff slides is with a webbing seizing, a narrow length of webbing wrapped several times around the bail of the slide, through the luff grommet, and hand-sewn in place. Compared with the alternatives--plastic or stainless-steel shackles--webbing better absorbs shock loads and won’t chafe the luff or wear through the bail of the slide.

Along the Boom
The foot of a cruising mainsail can be either loose (attached to the boom at only the clew and tack) or attached along the length of the boom. A loose-footed sail simplifies trimming and achieving ideal shape. It also makes proper reefing easier, allowing you to quickly secure the bunt of the sail by tying it around the foot of the sail, not around the boom. The drawbacks of a loose-footed main are higher loads on the outhaul car and more chafe on the mainsail's foot. If a mainsail isn't loose-footed, it should have foot slides seized with webbing to stout rings spaced every 14 to 18 inches along the boom. A foot that's attached directly to the boom by means of a boltrope through a groove will chafe where the boltrope enters and exits the boom, and you'll have no way to tie reef nettles without going around the boom. Such an arrangement also poses problems if you choose to dead-end reef tackle around the boom.

A cruising mainsail is asked to perform on all points of sail, in almost all wind speeds, and in a challenging variety of sea states--and it’s expected to do so for many years across thousands of nautical miles. The combination of durable, high-quality cloth and hardware with time-honored construction details are only part of the equation. The other part--proper sailhandling--is up to you.

Sailmaker Carol Hasse is a Cruising World Boat of the Year judge and the owner of Hasse and Co., Port Townsend Sails(360-385-1640, www.porttownsendsails.com) in Port Townsend, Washington.