Ripstop nylon is a synthetic fabric woven in three dimensions to make it resistant to tears. It was developed during World War II as an alternative to silk for parachutes. Today, ripstop nylon is still used for parachutes as well as boat sails, hot air balloons, kites, flags, banners and in numerous pieces of backpacking and camping equipment, such as tents and sleeping bags. Ripstop nylon is slick and strong, and if you already know how to sew, you already know most of what you need to know to properly sew this fabric.
You can sew this fabric with a basic sewing machine, but since ripstop nylon is slippery, a "walking foot" is a good accessory to have. A walking foot moves the top layer of the fabric while the machine moves the bottom layer. Your machine should be able to make straight and zigzag stitches and move in reverse. Keep the fabric tight by pulling the fabric on both sides of the needle instead of trying to pull the fabric through. Never pin ripstop nylon. Use a glue stick to fasten seams instead.
American sewing machine needles come in sizes from #8, which is the lightest, to #19, which is the heaviest. Use a #12 or #14 needle with ripstop nylon. Don't worry about poking too large a hole. The single most important factor in sewing this fabric is keeping it tight as you sew. Also, remember that tension can be hard on thin needles. Because the fabric is tough, you should never sew with a dull needle. Dull needles make a snapping sound as they penetrate the fabric. Bent needles are worse than dull ones as they drop stitches.
Never use cotton thread to sew ripstop nylon. Use commercial quality, 100 percent nylon or 100 percent polyester thread. Polyester is a little softer than nylon. The diameter and weight of the thread depends on what you are sewing. The two standard thread sizing systems you are likely to encounter are called "denier" and "tex." The latter expresses the weight of 1,000 meters of thread in grams. Denier weighs 9,000 meters of thread instead. Kite-makers use thread that is 300 denier, or about 33 tex. Parachutes are sewn with thread that is about three times heavier than that. Use about eight stitches per inch when you sew ripstop nylon.
The edges of ripstop will quickly fray unless they are either hemmed or heat-sealed. There are two ways to cut the fabric. Ripstop is usually cold-cut with a sewing tool called a rotary cutter. These cutters are used with a mat and a straightedge; any cold-cut you make will have to be hemmed. This fabric can also be "hot-cut" with a wood-burning tool or a solder iron. Ripstop nylon must be hot-cut on a large sheet of glass. Never use plastics like Plexiglas instead of glass because the heating tool will fuse the fabric to the plastic.