I was recently introduced to the concept of line stretch as a reason to recalibrate the line lengths.
Being a 100kg kiter, in 8 months it was explained that the front lines can stretch considerably. This is like negative depower, so to adjust for the same conditions, I'd have to pull in depower to offset the amount of stretch.
Here's where it gets complicated, at some stage most people would say: too much information!
Lines are formed of a braid.
The fibres in a braid don't only point one way, they weave back and forth past the other fibres.
Can you see where we are going with this yet?
If the fibres all lined up in parallel they would separate, catch on things and break off, any salt crystals, sand, pollen or other contamination would fatten them but they would still be the same length and you'd need special laboratory equipment to find a difference in length between not contaminated and after contamination.
But that's NOT the sort of lines we use! The weaving back and forth past all the other fibres locks fibres in after several cm so that individual breakages in different places don't each subtract from the total strength, only the worst damage counts.
But this does something else too, because the braiding means that the fibres are constantly at angles away from the actual line's axis, any contamination actually affects the line's length by forcing the fibres to go around all these little mini obstacle courses.
So lines can stretch under loading, weaken through UV exposure, over-capacity loadings, chemical contamination, abrasion.
And shorten through contamination and absorption of any chemical that fattens the fibres!
If you have any Chemical spills near you.... read up on your fibre's absorption characteristics for the released chemical! Or at the very least, measure your dry line length for a fixed pull on some fishing scales and try again dry after your next kite sessions.
Here's some further discussion of it: http://www.wetestkites.com/2016/10/14/s ... ite-lines/
Some people have over the years told me that I over-think things but honestly, I'll be thinking about something completely different moments after posting this!