On Wednesday, April 6, 2016 at 6:35:43 AM UTC+3, Bill T wrote:
Tom, we get our rope from an industrial supplier of safety and climbing equipment, the rope has to meet specs.
The 1/4 inch 3 ply twisted poly meets specs for FAA weak link requirements for most gliders. The Janus C requires a stronger weak link, so we use 5/8 ind dia for that. We also use 5/8 inch for auto tow. We could use 5/8 for aero tow, but it does not stand up very well to the abuse.

Does any glider truly *require* a stronger rope? PTT should never be an emergency situation.

Gliding New Zealand specifies a 750 kgf weak link for all gliders, but I think all clubs I've flown at use a rope of the correct strength without any weak link. The rope gets replaced when it looks worn. I've seen a few old ropes break at initial towplane acceleration but breaks in mid air are very rare.

http://gliding.co.nz/sites/gliding.c...s/AC3-02v5.pdf