Turtle Cove Dock Swing STEM Project

I'm hopeful CZcams will turn on my comments soon. They apparently thought I'd made these videos for children, and were concerned about inappropriate comments.
This is the technical engineering documentation of my efforts to design, analyze, and build a safe rope swing on my dock. I hope to make a short video of the grandkids using it soon.
I made a couple of minor mistakes. I guess I'm getting old. Let me know if you see any major errors. Thanks