Zack, Tad,
I think the line that failed on my release is the same size as your last loop that engages the tow line on Zack's release.
I'm thinking that two knots came untied with the increased forces/tension.
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My Barnyard Theory Trade secret??
On -windy- days while on tow, the rope is at ~45* angle. When the vehicle slows or even stops, and you are still climbing, flight path has to be in an arc.
At the top of the tow/arc, if the spool is not turning, and you are still climbing, at some point you will be climbing/flying farther away from the vehicle/winch. Like going into orbit.
That would cause a spike in line tension. But then why won't the winch spool out? Unless the brake pressure has been increased to "slingshot" or "top off".
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Yes, other than my theory, lots of good info here. Thanks