Show me the 9:1
OK, I’m on a SAR team and need to know fancy systems, or I’m a river guide who might need to pull a wrapped raft off a midstream boulder, or I like to drive offroad and need to know how to pull my truck out of the ditch. I'm ready for the 9:1! How do I do it?
Well, if you’ve read this far, you're ready for the fancy stuff. A 9:1 is a compound system, with a 3:1 stacked on top of another 3:1. Remember, with a compound system, the forces of each section are multiplied together to get the final MA, so a 3:1 on a 3:1 gives you a 9:1.
Important: if you have a high mechanical advantage system, say 6:1 or 9:1, and you are REALLY pulling on it (several strong people) to move a serious load (stump, car in the ditch) you may be getting dangerously close to the safe working limit of some of your equipment, such as a pulley or carabiner.
If you’re in this situation and feel you need to apply more pulling force, it’s probably a good choice, provided you have the equipment, to set up a completely separate system, may be on a new anchor, and pull simultaneously on both systems.
Granted, recreational climbers should pretty much never find themselves in this situation, but if you’re pulling out a stump or your truck, keep this in mind.
Many people (like me!) find looking at a diagram of a 9:1 makes their head spin. But as we like to stay around here, it's a better show than a tell. When you see it demonstrated properly it's actually pretty simple. Here is a nice video that shows you how to do it.
And, if you're the diagram type, here’s a pretty slick example of a 9:1.
image: https://roperescuetraining.com/raising_5-to-1.php
