Airborne Textiles
Uniform shrinkage just lowers the pilot. It is the difference between front and rear that quietly re-trims the wing.
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Trim rotation caused by differential line shrinkage
A rigid two-point rotation about the mean chord is assumed, which is a considerable simplification of a wing whose profile is held by many cascades at once — real line trim maps are measured line by line against the manufacturer's table, and that measurement is what a trim check consists of. The linear lift slope is only valid well below stall and says nothing about the behaviour that actually matters here, which is how much collapse margin has been lost. Lines can also lengthen rather than shrink, and sheathed and unsheathed lines age differently within the same set. **This is a decision-support estimate only.** Paraglider line trim is airworthiness-critical: have the wing checked and re-trimmed by a qualified service centre against the manufacturer's data.
Paraglider Line Shrinkage & Aerodynamic Trim Distortion — free, with the formula and a worked example, at Textile School.