Ben Cantrick (mackys) wrote,
Ben Cantrick
mackys

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The Zeppelin bend, or How to jailbreak with a rope made from bedsheets.

Someone over at the Mythbusters Fanclub forums posted about whether it'd be practical to escape from jail with a rope made from bedsheets. I figure absolutely. The interesting question to me was, how do you most efficiently tie the sheets together, while wasting the least length? (Insert "Well, that certainly sounds kinky to me!" joke here.)

My first impulse was to just say screw it, and use square knots to tie everything together. As it turns out, this is almost the worst possible way to do things! Every knot weakens the rope its tied in to some extent. Better knots only weaken the rope's strength to 70-80% of normal breaking strength. The square knot (more generally known as the reef knot), as it turns out, weakens whatever you tie it in to less than half (usually about 47%) of its normal strength!


For the uninitiated, knots that are used to tie two ropes together are called "bends." Wikipedia has a list of bends. I also found this table of knot strengths on the excellent Layhands knots site.

After a day or two of thinking, I came up with some attributes that would be optimal for jail-break knots:

  • Easy to learn, remember and tie - even under stress or in the dark
  • Strong, as not just your escape but also your life may depend on it
  • Resistant to coming undone when jerked or snapped
  • Wastes a minimum of length in the knot


And for the "anchor knot" that secures the top end of the rope to your bedpost or window bars, there were two additional criteria:

  • Must be tieable with only one end of the rope available, because the rope may be very long, or already out the window
  • Must be tieable around an enclosed post, you can't just make a loop and hope there'll be something to throw it over


For joining rope segements, the Zeppelin bend wins hands down:

- Really simple, really easy and fast to tie
- Wastes very little length at the loose ends
- Quite strong (75-80% efficiency)

If you can remember "b over q" then you can tie a Zeppelin in less than five seconds - faster with practice. The only competition here is the Alpine Butterfly Bend, but that wastes more length and is slower to tie and harder to remember. Other contenders are significantly less strong (Fisherman's) or waste much more rope (Double Dragon). It's arguable that the Ashley bend is as good as the Zep, but I think the Ashley would be harder to tie in the dark.

The winner for the anchor knot is also pretty clear, it's the Adjustable Grip hitch:

- Pretty easy to tie and remember (much easier than any of the competition)
- Quite strong (again, quoted at 80% efficiency)
- Any extra length in the loop around the post will slip out and become extra length in the main rope

There were many contenders here, but the combination of strength, ease of tying, and the ability to slip extra loop length out to the main line bring this guy clearly above all other contenders. Trying an Alpine Butterfly or especially a Double Dragon around a post is less than simple in the light, and will be very difficult do under stress in the dark. The double figure eight is very strong and easy to tie, but also uses a lot of rope. Various other hitches are significantly less strong, waste more rope, are prone to loosening under jerks, or all three of the above! Traditionalists will say the Bowline is superior, but it's both weaker and it doesn't allow the loop to shrink and recover that length into the main rope.

So there you have it. If you ever have to escape from jail, remember this post. ;]


FWIW, if you aren't in a time pressed, stressed, or otherwise emergency situation, the best of breed knots seem to be:

- The Alpine Butterfly, both loop and bend
- The Double Dragon loop
and
- The Zeppelin bend


Even if you have no interest in knots at all, I encourage everyone to take a glance at The Zeppelin bend. It's the simplest, strongest, most elegant, most useful knot I've ever seen. It'll take you fifteen seconds to learn it, and then you'll forever know the best way to tie two ropes together.
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