Vector Pull Math for Whitewater Rescue

[@noelfruchtenicht2345]

Great stuff. It explains why the rock climbers that would come out to guide school were always so anal about the angle of the self equalizing anchor we would practice on D-rings for pulling a boat off a wrap.

[@kastnk]

Great video! Another thing to keep in mind when applying vector pull onto an already tensioned line (ie. with a 3:1) is the consideration of the rule of 12. Big difference if the 3:1 was tensioned with 1 or 3 people and then doing the vector pull on top of that. Hopefully the prussik would slip before anything else unexpected occurs.

[@DaxTheMagnificent]

I love that you did the Math. Very helpful to think of it in those hard number terms, and the difference between real world and ideal scenarios

[@msilva3084]

Doing a vector pull on a line that's already under tension. As in it's already being pulled normally, or with a MA pulley rig. Would minimize stretch and keep it at a low angle, but I definitely don't want to be the person pulling in the middle of a system already under high tension. I don't want to be in the middle of everything if something breaks. I've seen it done that way once to get a way overloaded boat unstuck, and afterwards everybody had the same thought. "That was way too sketchy, let's never do that again." And even then, the vector pull wasn't super helpful because as soon as the boat moved a few inches it stopped being low angle and wasn't effective.

[@GearGarageTV]

Yes to all of that

[@tedanderson463]

In the lineman's handbook..... I understand there's a diagram like that.... and it says that a man can pull 1500 lb.... For short distances then he needs to retighten his rope..... There's a type of Hauser line that tugboats use that they advertise stretches very little.... I'm just throwing a few things out that I've heard from engineers and looking in my tipler physics book and such..... And talking to people that work for the pud. IE people that work on telephone poles cross-country feeder lines... You know guys that work at the power company..... When they are apprentices this is the type of stuff they teach em. The diagram in the tiplers physics book.... Says that the rope..... that the rope better be able to hold 12 or 1500 lb... Here's the thing.... If somebody is trying to rescue somebody they have a whole bunch of adrenaline built up they've got tons of extra strength now.... Anyway a man who is amped up is going to be able to pull one hell of a lot more than 100 lb.... Not to disagree on anything that you said. I read a story problem in that book (physics book) and it gave the exact amount it said how strong was the rope have to be if it was exerted 150 lb... I think it said 1345 lb

[@GearGarageTV]

1 kN is a lot for one person to pull. 1 kN is 224 lbs.

[@pathickey2553]

Great video. In his swiftwater rescue class, Lee Baker taught us to use a vector pull to get some extra mechanical advantage after tensioning the line up with a simple progress capture or a z rig. I believe tensioning the line will take a lot of the stretch out of the line, especially with the polypropylene throw bag ropes which stretch far more than a static line. One thing I don’t know is what sort of stress strain behavior these static lines have - is that 2% elongation quote the total stretch at max working load? If you load it up with three people using a z rig, then one person vector pulls, how much stretch is that vector pull creating? My gut says less than 2%. Maybe you can follow up with a video where you rig it between some trees and show us the stretch and angles that result from real world ropes. And once upon a time you had a load cell, right?

[@GearGarageTV]

The stress-strain is not linear and different for every rope. I've done the experiment you've mentioned with the load cells and the result is what you'd expect based on the math. When I have some free time I'll try and make a video about that.

[@brotheroftheboys]

I got as far as ferry angle