Home - Blog - 2017-10-21

Making Rope from Ethernet Cable

Introduction

xkcd is a popular internet comic.

Each xkcd comic has hidden title text.
Hover your cursor over the comic to see it.

The title text of xkcd 308
suggests making a climbing harness
out of Ethernet cable.

Whether or not this would work
is a subject of some debate.

I decided to find out myself:

Would Ethernet cable work well for climbing? [1]
by holding myself from a car lift [2]
with cat-5e Ethernet cable.

Click on any picture
to see the full-size version.

First Try - One Loop, Hold On


I tied the cable to the lift with two half-hitches
and tried to hold on to the dangling cable.

The knot slipped because Ethernet cable is smooth
and it is too stiff to tie tightly.
It was also hard to hold on to.


Tightening the knot
caused the cable to snap
when I tried to hang from it.

Second Try - Use Handle and Different Knot


The clove hitch is a gentler knot than two half-hitches. [3]
I used one to attach some bicycle handlebars,
and another to tie the cable to the car lift.


The cable broke where it wrapped around the car lift.
The rounded edge was digging in to the cable.

Third Try - Loop Over the Car Lift


I tried spreading the load
by tying both ends to the handlebars
and looping the cable over the car lift.

Now each half of the cable
only held half of my weight.


The cable broke in both places
where it wrapped around the lift.

Fourth Try - Make Rope

To stop the cable from breaking at the knots,
I made each end of my cable into rope.

How to Make Ethernet Cable Rope

You will need
one long piece of cable
and six shorter pieces.
These are your fibers.

To be able to make a clove hitch,
the short fibers should reach three times
around what you are tying the rope to.


Twist one short fiber around one end of the long fiber.
In the same direction, twist two short fibers together.
These are your yarns.


In the opposite direction,
twist the short yarn
around the the long yarn.

Twisting in opposite directions
makes the twists oppose each other,
so that the rope does not untwist.


You have now made rope
on one end of the long fiber.
Repeat on the other end.

Testing the Ethernet Cable Rope


I tried braiding one end of the rope.
It nearly broke at the unbradided end.
I then braided the other end into rope,
but did not take pictures after that. [4]

When I braided both ends into rope,
the cable did not break at the knots.

The one long fiber of Ethernet cable
was able to hold my weight,
even when I bounced a little.

Conclusion

Ethernet cable can hold the weight of a person
if have a gentle way of securing the ends.

However, Ethernet cable breaks easily
when wrapped or tied. [5]

No, Ethernet cable would not work well for climbing,
although it does have the strength to hold a person.

Notes

[1] In retrospect, this is not exactly what xkcd 308 proposes. In the future I will make a climbing harness.

[2] The car lift was just a convenient anchor to suspend myself from.

[3] The clove hitch only bends the cable around what you are tying it to, not around the cable itself.

[4] I regret not taking late-night pictures of the final parts of the experiment.

[5] I suspect that when the cable is bent, it flattens, and one wire rips at a time.

Edited 2018-10-24