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From Knacke (6-84), "all lines and tapes are [traditionally] measured under a preload. A preload of about 1% of the ultimate material strength is required to align all fibers in the woven or braided material before the individual fibers are stretched." Furthermore, "[it] is practical to let all fabrics relax for a short period after rewinding from the storage spool before measuring the material."
Vent
Using a vent helps stabilize a parachute and eases construction.
Terminology
take-up: the shortening of two pieces of fabric around the seam. Ideal parachute design takes this into account.
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