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Thanks, once again, to UK Sailmakers, in this issue we bring you the low-down on mainsails.
There is occasionally some confusion with respect to mainsail area. Most sailmakers compute mainsail area as though the sail were a right triangle with three straight edges.
With this method, area = the luff x 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 of the 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.
Properly made mainsails 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
The Shelf-Foot and Loose-Foot constructions are options that allow the addition of a substantial degree of extra fullness in the lower portion of the mainsail, in order to improve racing performance on reaches and runs. In very light air, the improved performance is achieved even to windward.
The extra fullness is removed by tightening the outhaul. When the outhaul is eased, the sail maintains an airfoil shape down to the boom.
With the Shelf-Foot option, a light piece of material connects the sail to the boom. With the outhaul eased, the connecting material unfolds and forms a shelf between the bottom of the main and the boom. When the outhaul is pulled tight, the shelf closes up and lays against the side of the boom.
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 just as strong as the attachment of the foot to the boom.
Many boats are switching to Loose-Footed mainsails because they are easier to bend on and to remove from the boom. They are also less expensive.
Reefs
Mainsail reefs are used to de-power 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.
The Fully Battened Main
A mainsail with full-length battens, meaning that the battens extend all the way across the sail from leech to
luff, has 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. Full-length battens induce a smooth airfoil shape to the sail, which improves performance in all conditions. In light air the fully battened holds a smooth airfoil shape instead of sagging like a wrinkled bed sheet.
The fully battened mainsail won’t 'slat' as the boat rolls in the waves nor, in heavy air, will it flog when the sheet is eased out to reduce heeling. The fully battened main does not flail and snap when de-powered and 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, making more of the sail area useful.
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.
For more information about sails, why not visit the UK Sailmaker website
at http://www.uksailmakers.com
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 Three of the sails aboard our boat bear the red crown that distinguishes them as Elvström sails.
Paul Elvström has always been known as a man who refuses to compromise. He started out in a small shop and has, over the years expanded into a business that spans five continents and uses the ultimate in sail-making technology.
Elvström has been instrumental in the development of some of that equipment - the longest and widest computer-controlled laser cutter in the world of sailmaking, for example. The 3.000 m² sail loft at Aabenraa, Denmark, keeps 70 specially trained people in employment, serving clients from the cruising and racing communities.
Of the more than two million sails that Elvström have produced so far, our three have certainly proved their worth as cruising sails in a wide range of conditions. It must be said that none of
the sails we own are made using the very latest techniques, they are all fairly old but, as they are still giving good service, they will continue to have a place in our cruising sail plan.
As far as we know, Elvström are still producing top quality sails for
sailors who expect a lot from their equipment and, no, we are not being
paid or rewarded in any way for carrying this article. All three of our
sails were purchased from other vessels and had been used before we
acquired them. From being held as spares they have become our favourites.
Quality that carries over like that deserves compliments.
For more information about new sails,
Elvström Sails are at:
Uglekaer 1
DK 6200 Aabenraa
Denmark
Telephone: +45 7362 4800
Fax: +45 7362 4819
Website: http://www.elvstromsails.com
e-m@il: elvstrom@elvstromsails.com
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