Can you rappel with 550 paracord?

Answer 1

Short answer, no.

Long answer is open to a bit of debate but most people will agree that it is a very dangerous idea.

550 paracord has a breaking strength of 550lbs (hence the name). Now while that may seem like a lot, being well over the average body weight, a lot more forces come into play while climbing, and especially rappelling. A proper, bounding rappel can easily generate 900lbs of force. It's all about F=MA, the force you put on the rope is equal to your weight x the speed that you're falling **

Now, in comparison, a proper climbing rope has a breaking strength of about 4500lbs.

You also have a lot of other factors to take into account. Such as a most knots in a rope can weaken that section by 30-50%. And paracord also isn't very good against abrasion - it's easy to cut and the friction can also heat it up and melt it pretty quickly. If you're trying to rappel down the side of a cliff, any section were the cord is rubbing onto the rock could dangerously weaken it. Also, given the small diameter, it would be next to impossible to hold onto. Even some of most skilled climbers have trouble holding onto 8mm rope and paracord is only half that.

Now in an emergency, it might be possible to use a single strand to climb down the side of a cliff or building, on a few conditions. It would have to be a really slow, careful 'walk' down. You'd have to try to grip the wall with your feet as much as possible, trying to put as much weight as you can onto the wall. Also, you'd have to try your hardest not to jerk around and put too much strain on the cord, and if you happened to slip or fall at all you could easily snap it.

You'd also have to find something to anchor the cord too which wouldn't put too much strain on that section, something you could tie a 'frictionless hitch' to would be good. Then you'd still have to find a good way to grip the rope and make some sort of harness, or at the very least find some padding. Being that thin, paracord can easily cut into you.

Remember that a parachute uses dozens of these cords, and climbing with just one makes a big difference.

Now all this assumes your using a single strand off course. Get enough of it, and you could rappel with just about anything. But at that rate you're better off using a proper climbing rope.

** There's some good math here on the matter:

http://www.daughtersoftiresias.org/bearwiki/Using_parachute_cord_to_abseil_down_a_cliff

EDIT: I don't really disagree to much with the above statement, but if you're in a fourth story of a building that is engulfed in flames and you have no other way out and the firemen aren't coming/coming soon enough, you go out that window. I'm 230 lbs., 6'5, and I tested mine by tying it around a rough tree into a huge loop using one foot, and just jumped up and down for a while to make sure. The paracord was slightly stretched. I would trust it in a bind from a reputable manufacturer, but as suggested, use ONLY in emergency.