How does stitch length affect parachute seam strength and fabric performance?

• A. Longer stitches may reduce strength; shorter stitches increase strength but risk fabric damage; set per Navy standards.
• B. Stitch length has no impact on seam strength.
• C. Longer stitches always increase fabric durability.
• D. Shorter stitches always damage the fabric.

Answer: (A)

Stitch length controls how often the thread grips the fabric along the seam and how the load is distributed when the parachute is under tension. Shorter stitches provide more anchors, so the load is shared by more points and the seam tends to be stronger. Longer stitches leave fewer anchors, letting the seam pull apart more easily under stress, which weakens it. But stitching too densely can create excessive needle holes in the fabric, risking damage to the parachute material and reducing its fatigue life. Because parachute fabrics and their seams must meet stringent safety standards, the correct practice is to set stitch length according to Navy standards, which balance seam strength with fabric integrity.