Sails are damaged a number of ways. They will chafe when allowed to rub continuously against something.

Ultraviolet radiation weakens sail fabric slowly over time, and can cause failure when sails are placed under heavy working loads. Likewise, dirt and salt trapped within the fabric causes damage and degrades the sail.

The leading cause of torn sails, however, is unequal or over-tensioning of the sail. This is seen when one section of a sail is tensioned far in excess of other, adjacent areas. Extreme outhaul tension, especially with laxity at the leech and luff, can cause long, sail-wrecking tears along the foot of the main.

It is important to stop using any damaged sail immediately, especially in heavy wind. The weakened area is far more likely to worsen, and repairs are easier when the defect is minor. Lower or reef a mainsail so that the damaged area is taken out of service. Lower a jib and haul in a spinnaker when defects are spotted; even small punctures or tears.

Before beginning the repair, find the cause of the damage. Notice the area of damage-high-stress or low stress, hardware attachment point, chafe, etc. This determines the type of repair, which must aim at preventing future damage.

After the repair is done, it is sometimes necessary to protect the affected part of the sail while it's in use. As an example, after stitching a horizontal tear below the first reef point of the mainsail, hoist the sail and tension the first reef line just enough to minimize pressure on the repair area until permanent repairs are made.

Most sail repairs at sea, especially in low-tension areas, consist of covering both sides of the damaged area with adhesive Dacron tape or nylon sail tape for spinnakers. Most sailmakers recommend at least 2-inch wide sections of tape for best results. Tape doesn't adhere to wet, salty or dirty material, so begin by rinsing the affected area and then drying. If drying is difficult, apply rubbing alcohol and dry again. Any loose filaments of thread or tattered sail will diminish holding of the tape, and should be removed with scissors or a hot knife.

Sail tape alone may be adequate in some cases for an emergency, but stitching is far more reliable. Duct tape is even less desirable, and many sailmakers will hesitate to repair sails if you've used duct tape. Contact cement may make a strong repair, but the segments of sail must be aligned exactly right because of the instant bonding nature of the compounds. Sail repairs are easier when the sail is removed from service and taken to a suitable work area out of the wind and with a flat surface.

To repair small holes or tears, cut two sections of sail tape large enough to cover the defect and overlap the area by at least two inches on all sides. Oppose the adjacent sections of the sail exactly to avoid wrinkles and an improper patch job. Ask a shipmate to assist by holding the area while the patch is positioned.

Place the first section over the defect. Then, while holding it in position, slowly remove the plastic backing from one end of the tape to expose the sticky surface. While the backing is peeled away, press the tape into position. Next, turn the sail over and repeat the procedure on the other side. Once both sections of sail tape are on, press them down and rub firmly for a secure repair. If the tear is in a low-tension segment of the sail, this method may be enough to repair the sail. Stitching, however, will be needed for larger tears and those in load-bearing areas like along the foot and leech.

Large holes or tears can be a more challenging fix. If the tear is straight with no jagged edges, sail tape placed on both sides should be strengthened with stitching. The area of tape overlap should also be at least three inches on all sides for more strength. For jagged tears, it's best to replace the torn section of sail with a piece of new fabric.

Bring the sides of the tear into direct opposition, inserting pins if needed to hold the segments in place. Remove the paper backing from one side of double-sided tape, and adhere it around the tear edges on one side of the sail. Align the tape either parallel or perpendicular to the cloth weave direction. Now, begin removing the affected area by cutting the sail inside the tape area. Use either scissors or a hot knife to obtain sharp sail edges.

Lay repair cloth over the sail tape that surrounds the tear and trace over the outside edges with a pencil. Cut the cloth at the pencil line and, after removing the backing paper from the tape strips, lay it over the tear. Firmly press the sail down against the tape until all edges are adhered and the repair material is perfectly flat against the sail. Now sew the repair section into position at the outside edge.

To do this, use a white, Dacron/polyester thread for the repair; it lasts longer than dark thread, is UV-resistant, and the end can be terminated by melting instead of being knotted. Always use a triangular-shaped rather than round sewing needle; the hole it makes is less likely to tear. Hand stitch by using a zigzag pattern- ///// -which spreads out the "pull" and stretches as needed. Push the needle through the new fabric and through the original sail. Subsequent stitches are placed at 4mm to 5mm intervals along the repair. Pull the thread taut at each step, but not so tight as to crimp the sail material. Continue this along the whole side of the repair.

Now stitch backwards in the opposite direction, using the needle holes just made, to complete the pattern. Each stitch is pulled taut as before. Terminate the stitching by tying the two ends of thread together and melt them to form a more permanent closure. Use the same pattern along all sides until the repair is completed. If the repair is in a high-chafe area, cover the stitching with sail tape for extra protection.

Stitching along seams will be raised above the sailcloth, and is therefore more exposed to chafe and deteriorates more quickly than the cloth. Eventually, even the best seaming can wear out and allow the seam to part. For repair of worn or torn seams, it is important to oppose the sections of sail perfectly and stitch the sail back together. The existing needle holes simplify alignment, but always use glue, such as Seamstik or a glue-stick from any office supply store, to adhere the two segments together before stitching.

Spinnakers will often develop small punctures or tears, but no matter how minor, immediate repair is necessary to prevent very serious rips. Anyone who has seen a spinnaker explode understands how a tiny puncture can lead to destruction of the sail. Your sail repair kit should include a supply of "dots," round sections of sail repair tape. These are perfect to use on these small tears.

Larger tears can also be repaired with nylon sail tape alone, without stitching, on spinnakers. Clean the edges of opposing sections of frayed thread, bring the edges together, and place pre-cut sail tape along one side. Repeat the process on the other side to complete the repair.

These procedures on the water are meant to be only temporary, used to make the sail serviceable until landfall. Any sail that has been damaged and repaired at sea should be taken to a loft for permanent repair.

Recommended sail repair kit contents
n Sailor's palm
n Sewing needles of assorted sizes; straight and curved
n UV-resistant thread: V92
n Waxed nylon thread
n Seamstick tape, 1/2-inch
n Seizing wire, stainless, 1/16-inch
n Adhesive Dacron tape of various sizes
n Spinnaker "dots"
n Seamstik glue or glue stick
n One-inch tubular webbing
n Shears, bent blade
n Awl
n Seam rippers
n Wire cutters
n Hot knife