Instructables

Step 6: Rappel Down

Picture of Rappel Down
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This is where prussiks are (kind of) awesome!

All you have to do is squeeze the prussik knot, and it loosens and you can slide down the rope!

The downside is that you have to successfully do this to two knots at once;
fortunately, if you screw up, you just come to a halt on the rope.

You can also control your descent rate by how much you grip the knot,
which controls the friction between the rope and the knot.

I'm squeezing pretty hard, and making the accompanying face to show what it's like to loosen two four-turn prussiks enough to get it to slide. It worked well enough to prove the theory, but I abandoned the prussiks in favor of using an 8 for the rappelling.
 
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backstab3 years ago
Isn't this how to climb a rope with prussiks?
mahyongg4 years ago
Hey *, cool instructable! On this point tough, I agree to disagree too - one of the sacrosanct rules of ropework (or climbing or whereever you might be suspended above ground in reasonable heights to break your something when you fall back down to ma earth) is to never have rope slide over other rope (braid, sling, cord) while one is loaded with you or other weight - the reason being, not only is it gonna melt and the prussik slides (like in this case) but it will likely cut through entirely quite quickly. When using a prussik as a backup for rappeling, it is basically unloaded so thats OK (you just push it further with your hand so it doesnt thighten). Like desciribed here, you would make the prussik take serious friction which will be transformed to heat pretty quick. Ok for 4 meters maybe.. but that fall is survivable too D8. Try this if you want to get a feel for this heat thing: get an 8 or other non-automatic rappeling device (ATC etc), check out how to do it (here?) and then after some tries go as fast as you can still control the descent speed and you feel is safe. Probably the first descent if its more than 5 meters will be enough though - the rappeling device, made from slick aluminum, is pretty hot to the touch! Thats why people often clip their 'biners in to the open end of the eight and never touch the eight themselves after rappeling, because you can burn your fingers.. Burning ropes is unlikely though, because aluminum distributes the heat quickly and it will never get THAT hot ( I know a guy who is an alpine climber who did scientifical tests on that, measuring rappel speed and temperature of different devices with different rope thicknesses - it never got too hot, kind of a myth that it could with a regular rappeling device used for climbing!) Now imagine the a) higher friction and b) less heat dissipation of climbing rope materials on each other. And the fact they're thermoplastics.. all of them. Ouch.. Stay safe, have fun and thanks for the great instructable! Jan
davejjj5 years ago
I STRONGLY disagree with this approach. You have inch-wormed your way up the rope and now you should inchworm your way back down. If you slide the prusik knots as described above they will generate a lot of heat AND THEY COULD EASILY MELT AND STOP GRIPPING ENTIRELY. YOU WILL THEN SLIDE DOWN AT A VERY HIGH SPEED!!!!
I have to agree. There's a reason why ATCs are made of metal. Bring one with you and use the prussik as a backup. If you don't have an ATC go for the munter hitch with a prussik backup. If none of those are an option inch down as recommended above. Prussiks are awesome!
k