This is called a roving 4:1, which is an internal 4:1 system and all the rave with a certain ilk of provider. But without the pulleys you lose 40% per caribiner / contact point, so with 3 contact points that's really a maximum of 2.8:1. Plus the roving 4:1 means you need to feed the end of the throwbag through the grab loop, which is kinda mad, as it's both rope hungry and it would mean getting to the boat that is pinned in the first place and returning to shore to start the rescue. Your possible exception of dangling a weighted line of a bridge, to thread the rope through, clearly worked in that situation, but experience would suggest it's a very rare option.Mark Dixon wrote:I used a figure of 8 on doubled up end of my throwline as when I was fishing for Sams boat over the side of Newbridge I couldnt see thegrab handle with the bag in the way, so used the other end. That way I could attach the clip 15ft below me.
I havent a photo but will try and sort one out sometime, but I'll explain and maybe you might understand it.
1. put end of throwline through rescue pt.
2. attach sling to tree with caribiner on
3.feed end of rope through caribiner.
4.feed end of rope through caribiner on end of throw line.
5. pull towards tree.
6. When bag reaches convenient place keeping all tight pull main line up while bag goes back towards boat.
7. pull towards tree until boat free or where you want it to be
This is identical to having bag attached to boat, caribiner / sling at tree then prussic/caribiner and pulley to create mechanical advantage.
Tried and tested by top level 5 coach and works a treat. Hope this helps.
Beyond the realms of a small group of diehard BCU WWS&R Provider's, the classic roving 4:1 is not at all used. Mainly because, within this grouping, they were determined to have a mechanical advantage system that does not use prusiks & pulleys on the Basic WWS&R course. In most boat pinning, you would try to get a rope attached to the boat, and pull, and then try a vector pull. After which you are highly unlikely to venture back out to the boat, to un clip the throwbag to then feed it through the caribiner and throw the throw bag back ashore, it's pretty impractical, time consuming and there are better more effective options. Other options where you could use an internal 4:1 system, is where you simply loop the rope several times around the spine of the bank end binder after attaching the line to the boat. And then set up a PigRig as above, simple.
Most river professionals the world over prefer external systems to internal ones though, simply because you can attach another line ti the pinned boat/raft, and set your initial rigging on that, without losing the tension from the first rigging set up.