Before you begin sewing sails, you must choose the proper needles and thread for the job. Needles that are not appropriate for sewing sails may break or bend as you work and cause damage to the sail cloth. The wrong thread might compromise the sewn sail cloth's durability and cause premature wearing.
If you're planning on machine sewing your sail, look for size 16 needles. This needle size is ideal for medium to heavy weight fabrics, including sail cloth. In addition to looking for a size 16 needle, choose a standard sharp point needle. Regular sharp point needles work well on sail cloth's woven fabric.
Look for heavy-duty threads with which to sew your sails. Heavy-duty threads come in variety of materials, including polyester, cotton-wrapped polyester or cotton. Heavy-duty threads are slightly thicker (typically size 40) than standard sewing threads and they feature a coarser surface. The thicker thread will stand up to stress and strain that wind can put on the stitches.
Sewing sails by hand requires a few more specialised materials than machine sewing. Rather than simply looking for a needle that can sew through heavy fabrics, you should look for a sailmaker's triangular shank needle. These needles differ from standard needles, which have rounded shanks and pointed tips, in their triangle-shaped shanks.
Once you find a sail needle, you need to pick to appropriate size. You can do most of your sewing with size 16 sail needles. But if you need to sew through multiple layers of fabric, you'll need a larger-size needle. In addition to selecting a sail needle, you'll need a 4-inch scratch awl to perforate your sailcloth before you sew it.
Threads coated in wax are ideal for sewing sails by hand; you can purchase already-waxed cotton or you can simply run your thread through a block of beeswax to sufficiently coat it. Waxed thread will move smoothly through your sewing holes and keep the thread from tangling as you work.
When sewing sails by hand, you'll typically use a thicker thread than you would on the sewing machine. However, if you decide to sew your sail with synthetic sail twine, you can use a lighter weight than if you were sewing with its cotton counterpart.