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Chapter
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There is occasionally some confusion with respect to mainsail area. Most sailmakers, including us, compute mainsail area as if the sail were a right triangle with three straight edges. With this method, area equals the luff times the foot divided by two. Most mainsails are, in fact, somewhat larger than that by reason of the extra area at the leech, called roach, which falls outside the straight line triangle. The promotional material distributed by boat builders and dealers sometimes includes this extra area as part of mainsail area. If they’re using the same luff and foot dimensions, they’re talking about the same sail in spite of the different figure for area. When we make mainsails, we’ll include as much roach, not only on the leech, but also on the luff and foot, as is practical and proper for the particular sail. Shelf Foot and Loose Foot |
| Loose-Foot construction does away with the shelf material. The sail is only attached to the boom at the tack and clew. This attachment method is equally as strong as that of the foot attached to the boom. Many boats are switching to Loose-Footed mains because they make it easier to bend on your mainsail and to remove the sail from the boom — and it's less expensive. | |
| Reefs Mainsail reefs are used to depower a boat in strong winds. Reefing makes the mainsail smaller. Each row of reefs consists of a heavily reinforced patch with a grommet at the luff for the tack horn and a grommet at the leech for the reefing outhaul. Between the reefed tack and clew may be a row of evenly spaced smaller grommets (called reef diamonds) to provide a means of gathering up and tying off the excess sail. This row of holes is omitted in the case of a flattening reef because there is not enough excess material to worry about. The number of area-reducing reefs varies with the size and anticipated use of the sail. |
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The Batmain We use the term Batmain to describe a mainsail with full-length battens, meaning the battens extend all the way across the sail from leech to luff. Full-length battens have many virtues for cruising sailors including better shape holding ability, longer life and easier handling. The sails last longer because the full-length battens prevent flogging — the violent snapping back and forth that happens when you're tacking, reefing, hoisting or lowering your sail. As conventional sails flog, the sailcloth breaks down, especially at the front end of the battens where the leech of the sail “hinges” back and forth. Flogging is the prime culprit in sail wear-and-tear. The full-length battens induce a smooth airfoil shape to the sail, which improves performance in all conditions. In light air the Batmain holds a smooth airfoil shape instead of sagging like a wrinkled bed sheet. |
| Also, the Batmain won’t slat as the boat rolls in the waves. In heavy air the Batmain doesn’t flog when the sheet is eased out to reduce heeling. The Batmain does not flail and snap when depowered, the silence is a pleasant surprise. Full-length battens also restrict the draft of the sail from moving aft in heavy air when sailing upwind. Downwind, the full-length battens hold out the leech of the main giving you more pro-jected sail area. | |
| All major rating rules, IMS, MORC, and PHRF permit sails with full-length battens with no rating change at all. If your current main is in good condition, its life can be extended by adding full-length battens. | |
| The Powerhead Main 
The Powerhead main is our long-life racing design. Whether you are buying
a Tape-Drive, Tri-Radial or Cross-Cut main, the Powerhead’s full-length
top batten gives you many of the durability benefits of a full-batten
main (UK’s Batmain), while offering performance benefits. The Powerhead
gives you more control over the shape of your main, especially the draft's
depth and fore-and-aft positioning because the full length battens prevent
the sail from changing shape much. The Powerhead is easier to trim than
a full-batten main since the leading edge of the sail is free to luff.
And the Powerhead is a lighter sail than a Batmain since it uses shorter
battens and no special luff hardware. |
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| The long top batten stabilizes the highly loaded head area, and stabilizes the leech allowing UK to build a maximum-roach sail that gives you more sail area. The full-length top batten also increases longevity by dampening the damaging effects of luffing and by preventing the draft of the sail from moving aft over the years. | |
| Along with the full-length top batten, Powerheads feature the new longer-length battens in the lower positions. The longer battens support the leech better and eliminate a hard ridge that sometimes develops at the inboard end of the battens as sails age. Powerheads that are used with lazy jacks or the Dutchman ® flaking system can have the bottom batten full-length to help catch the sail better as it comes down. | |