After various test during the last few years, we’ve found that sail repair tapes have proven durable for minor reinforcements and repairing worn spots in sails, but for areas that are subject to higher strain—long tears that are perpendicular to the leach, for example—glues are a better choice (see “Sail Repair Part II, PS November 2018).
After adding a few new adhesives to the test, and leaving them exposed for two years, we’ve found a new winner. The repairs were never covered, so our two-year test equals about four years of exposure on the average boat.
POLYURETHANE SEALANTS (3M 5200, SIKA 291, LOCTITE PL S40)
Polyurethane adhesive sealants are proven in sail repair, but cure time is long, they’re messy, and the repairs are stiff. UV can degrade the bond, so repairs to dark colored Sunbrella and other dark fabrics last longer.
Bottom line: Two years later our polyurethane repairs are stiff, but still holding. Recommended for thick fabrics and dark colors (~$2 per ounce).
G-FLEX
This all-purpose epoxy is strong and slightly flexible, but messy to work with and slow to cure. We used it for a large repair on a laminated jib, which lasted through one season and partially through the next when the G-flex patch began to peel off.
Bottom line: Two years later we’re not so impressed with G-flex as a sail repair adhesive ($13 per ounce).
DR. SAILS
A sail-specific flexible epoxy that cures quickly and does not overly stiffen the sail, Dr. Sails is the easiest adhesive to use in the field, and the results are strong and flexible. Within six months the Dr. Sails sample on our rack test had failed, presumably due to UV.
Bottom line: Dr. Sails is useful for mounting tell-tales and making small repairs that won’t see much sun. Recommended (~$30 per ounce).
METHYL METHACRYLATES (MMA)
Devcon Plastic Welder, also known as Plexus MA-300, is a versatile adhesive. Its biggest advantage is the fast cure. After 20 minutes we could handle the sail, with a full cure within a few hours. Unfortunately, it did not create a permanent bond in our sail repairs, peeling apart within four months.
Bottom line: Devcon can outperform G-Flex and conventional epoxies in fiberglass projects, but not as well with conventional Dacron sails (~$8 per ounce).
SHOE GOO II
A tough, flexible carboxylated styrene butadiene copolymer adhesive (SBR), Shoe-Goo II’s UV resistance is much better than epoxies and MMA, but not quite as good as polyurethane. Sandwiched between layers of sailcloth, it exceeded expectations, and at the end of the second year the seam is stronger than the sail cloth with reasonable flexibility. It is best applied by smearing a thin layer on both surfaces, press them together, pull them apart, and then pressing them back together.
Bottom line: This flexible adhesive cures overnight and creates a lasting repair. Best Choice (~$7 per ounce).
APPLICATION TIPS
Scrub the sail with soap and water and rinse well. Wipe with acetone if available (wear a respirator). If you’re repairing luff tape where you’ve used a lubricant, you’ll have to clean aggressively. You’ll only have to patch one side of the sail.
Tape the tear area together with sail tape to match edges and get the wrinkles out.
Cut a patch that overlaps about one inch beyond the tear on all sides. Lightly outline the bonding area on the sail with a pencil, and mask the surrounding area.
Lay the sail on a non-stick work surface and spread the adhesive very thinly on both surfaces. Rub down firmly with a credit card or hard plastic spreader.
Clamping is not generally required, but you will need to leave the sail alone until the patch is partially cured. Polyurethane adhesives (3M 5200, etc.) might need days to cure. Repairs with Dr. Sails are ready for service in 3–4 hours in warm weather. Shoe Goo II cures overnight.
These glues will usually last more than two years in opened and used condition, but we’ve carefully re-sealed each of them. If you keep opened polyurethanes in a refrigerator in a sealed bag, they can last as much as five years.
CONCLUSIONS
While none of these sail repair glues are perfect, we found a few common adhesives that will give multiple years of service. Sewing is normally the best practice, but laminate sails are often best repaired using glues, and old sails in general don’t like needle holes. Once you start patching sails, it’s time to start planning for replacement.
