Quote Originally Posted by Knotty View Post
The reason for the 1000#+ rating is you still need to account for dynamic (shock) loads and have some safety factor.
And don't forget that knots, biners, splices, and the like can reduce line strength by 50%.

Figuring the physics of effective forces and effective strengths on every angle and every part of a rigging system can not be determined without some brain power and study. Thus the rule of thumb where human safety is involved, of 10-to-1. Or if using Amsteel whoopie slings, 5-to-1 (because Samson Amsteel ratings already take into account the splices.

Rain Man