In general, the greater the complexity - the greater chance for errors. When working with significant forces as described above, set-up errors can cause a rope to snap or send an attachment like a carabineer or pulley flying like a bullet. Getting hit by a snapped line or carabineer can cause serious injury. You really need to evaluate the strength of your rope and anchors to ensure nothing can break.

The Z Drag isn't something we practice very much so it can take some time to figure out. It also takes time to locate and set-up suitable anchors for this system. Add additional time for safety dampers and brakes and 20 - 30 minutes can go by very quickly. Compare this to simpler methods like the Armstrong method, vector pull, and simple turning - all of which are safer and much faster.

For these reasons, avoid heavy mechanical advantage systems when rescuing a pinned boater. Often time is of the essence for a trapped paddler. If possible, extract the boater and deal with boat recovery when everyone has had a chance to rest.

Water exerts a great deal of force on objects. The following chart is from River Rescue, 4th Edition - Les Bechdel & Slim Ray:

The force increases in proportion to the square of the water velocity. Water is heavy as well, it weighs 62.4 lbs per cubic foot (or 8.35 lbs/gal). Figure an average kayak holds 75 gallons without air bags, the total weight is: (75 * 8.35) + 40 (average kayak weight) or 666 Pounds. Now you can understand why we insist on paddlers installing air bags in their boats.

As you can see, these numbers add up quickly. If you are paddling in a small party like 3/4 boaters, you will may need some form of leverage to extract a pinned boat.

For many, this is the most interesting and fun part of the SWR course. Unfortunately, it can also be the most dangerous. For the most part, mechanical advantage techniques are used to unpin boats or rafts - not people. This is a good thing since you can and should take time to plan your strategy. Always remember the KISS approach and attempt the least complex methods like direct tugging first. On many boating runs, you can get assistance from boaters in other parties for the Armstrong (10 Boy Scouts) method. True mechanical advantage systems like the Z Drag or Pig Rig should wait until the other, less complicated approaches have been exhausted and you simply lack adequate manpower.