Be forewarned…I tend to get wordy…
After hearing several tales of boats rescued from pins by use of a z-drag, and then hearing the recount of a member of our new club having both her and her boat pinned in a logjam (they got her out quickly, but almost dislocated her shoulders in doing so–large guy walked out on the jam and lifted her vertically) and hearing about how hard of a time they had getting the boat out, I decided to set up a drag system for myself. Never having the opportunity to see one in action before, I had to do some online research to figure it out. Turns out it’s a basic pulley system that I’ve used before in a physics course.
Made a trip to the hardware store tonight and bought all the components. Decided to build mine using 100’ of 3/8" braided poly line, tensile strength over 1,000 lb (I’ve used this same line to pull my 5,800 lb truck up the driveway…just to see if I could) Since this will be a permanant setup, I’m not going to mess with tying an autoblock or clipping ‘biners on the line–I’ve got two pulleys that are also going to serve (via locking d-rings) as the connections to the boat and anchor. Since the rivers around here that we paddle rarely have anything upstream of a jam that could be used as an anchor, I also got 50’ of 1/8" braided steel cable, and bound loops into the ends of the cable. This is to stretch possibly across the river and serve as a ‘floating’ anchor point. However, I do recall from my past physics courses that this increases the stress on the cable exponentially. This could also be used to extend an anchor point from upstream if needed.
Everything I bought for the setup has a minimum safe working load of at least 200 lbs force, and with the factor of safety they build into that, it should all be good to at least 3-4x that.
Hopefully I won’t ever need to use the setup, but after hearing the stories of members of my club goin over dams and gettin caught in strainers, I’m not goin back out with them without it…
Be forewarned…I tend to get wordy…
Probably more important than the equipment alone though is to take some lessons in swift water rescue. Knowledge of what to avoid (or have folks in a group avoid) plus knowledge of how to get someone out in a jam are good things.
So far, I have taken just basic SWR but at some point I need to take an advance course which involves unpinning boats and people. There is one coming up with Charlie Wallbridge who wrote a book on the subject. Unfortunately it falls on a weekend that I can’t make.
Your line is not strong enough
I don't want to discourage you but rescue work is serious stuff. Poly rope is for tieing things down or holding boats to the dock it does not have what it takes for a serious rescue system. Typical Z drag line is half inch kermantel and rated at over 9000 lbs, pulleys are over 6000 lb. and one inch webbing rated at over 4000 lbs. carabiners too must be safety rated. It's OK to be safety minded but the forces of moving water need to be taken into account. In the water huge amounts of stress will be loaded on the system. A badly designed system could be more dangerous in the water than the pin itself. Many rescuers have died entraped in there own lines. There are Z drag kits on the market, they are not cheap and usually sold to fire department rescue teams. Or you may have a local paddling club that practices rescue. I would do more homework and reading.
Echoing what has been already said, make sure you use the proper gear for the “real thing” otherwise you stand the chance of making matters worse. Now for the positive side of things. Practicing and familiarizing yourself with the methods and quirks of rescue systems is invaluable. Try on lots of various angles and loads (keeping them in the safe working range of course) and just remember don’t designate that decorative tulip tree in the yard as the object to be pulled clear out of the ground. (Sorry Mom!)
Have fun, be safe and see you on the water,
I think your rig
is too light for recovery work. The line is rated at tensile strength of 1000lbs--ok that is maybe a working load of 200lbs--not nearly enough. Plus--everytime you put a knot in the line you reduce the working load. 1/8" cable--not heavy enough, especially if you plan on stringing it across a river. Your vector loads are going to add up pretty quickly plus if something suddenly moves you are going to have shock loads to deal with.
Remember--this is for SAFETY. You have to be sure every component of your system will not fail. Are your biners rated biners--or are they from the hardware store? Are your blocks rated?? What are you using for your prussiks?
There is a reason a good Z line system isn't cheap. Quality really counts here.
I have seen what a line can do to person if it parts under extreme loads--You don't want any part of that. That 1/8" cable could remove an arm or leg if it snaps, the line could easily cause serious lacerations. I would re-think your design.
Part of the reason I posted that was to get a feel for the adequacy of the setup. Some of the load ratings mentioned earier make me question if those setups were maybe designed for pulling larger boats out, or maybe in higher-current situations than I’m dealing with. But, that could very well also be my lack of experience talking. Most of the rivers around here flow at about 5 mph, plus or minus a few, and tend to be 30’ wide or better, with average depths in the 6’-10’ range.
Yes, I am familiar with rope/cable failures, I’ve been present for several of them and know what areas to avoid around a line under tension, but explaining it to bystanders isn’t always easy.
Guess some more homework is in order…maybe I was mistaken, looks like I built a bear rope last night… And, I would gladly take a water rescue course if there was ever one offered in my area, but I’ve never heard of any around here. Not exactly the whitewater capital of the world…
You can look at it this way…
A 16’ canoe sitting on dry ground filled up with water already exceeds the weight limit of your rope. Add swift moving water to the problem and you can see where I’m going. Two feet of fast moving water can move a truck.