Originally Posted by glenn
Putting more stress on the end points assumes the end points are fixed. In this case the swimmer is not. With someone moving downstream constantly adjusting the vector angle the swimmer and anchor will actually be under less load than without the vector.
Adding a vector pull will definitely add mor pull on the anchor, fixed or not. The hip belayer is now holding the swimmer and part of the vector puller. The swimmer if being subjected to the force of the downstream flow of water regardless unless the anchor/belayer moves downstream with the swimmer.
Having a second line on the swimmer will alleviate some of the force acting on the belayer if the second line is slightly upstream of the swimmer. If he is downstream if the swimmer he is now pulling on the anchor and the swimmer which would be counter productive.
I'm going to try each method on Thursday at the river and I'll report back if I find a significant difference. Wish I had inline force measuring devices (I'm sure there's a technical term) to get some quantitative data...
3:1 setups are great for many uses but from talking to rescue instructors and professionals and reading online forums they seem to be used less and less for unpinning crafts (east coast seems to be ahead of the curve on this one). The angle of pull is much more important than the amount of force exerted.
Thanks for keeping the discussion going...