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MattR

Rope size for monkey bridge

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Any opinions on rope size for the main rope of a monkey bridge. We have 1/2". Was wondering if 3/4 or 1" would be better. It's probably harder to tie but I was going to put an eye splice in the end and use a come-a-long to tighten it. We're thinking 20-30' for the span between the frames.

 

A website I found https://scoutpioneering.com/2012/12/27/double-a-frame-monkey-bridge/said 1/2 or 3/4.

Edited by MattR

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3/4 will work, but as an uncoordinated kid, I always felt more stable on a 1" rope. A splice sounds like a great way to increase stability.

 

1/2" Might not withstand the tension in a 30' span.

 

Has anybody modified the monkey bridge design with Kevlar, a.k.a. slack line?

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I like the website you reference.  That said, I have never seen a working Monkey bridge (county fair with public guided over it? Camporee? ) with a less than 7/8 or 1 inch manila hawser on the foot rope.  This is expensive stuff and needs to be taken care of each up and down, but it would, I think, give more confidence in the construction.  1/2 inch for the hand ropes and ties.  I especially like the double a-frame supports.  And the ring tackles for tightening.  

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Not that this is news, but new rope is stronger than used rope.  The local FD gives us rope annually that's fine for non-life-at-stake applications, but too old/used for their standards.

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3/4 will work, but as an uncoordinated kid, I always felt more stable on a 1" rope. A splice sounds like a great way to increase stability.

 

1/2" Might not withstand the tension in a 30' span.

 

Has anybody modified the monkey bridge design with Kevlar, a.k.a. slack line?

That's a great idea. Cheaper. Includes a tightener. Much easier to sell to the scouts. Easier to walk on. We can use it as a regular slackline at another event.

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The difference in rope is very telling. Manila will stretch some , but not as much as nylon/poly.   I tried to move a big rock with a block and tackle using Plymouth Goldline, and I just watched in amazement as the rope stretched and stretched and stretched but the rock did not move!  I doubled the length of the rope, and it did not fail!   Finally the rock moved, but wow....

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There's a story behind the expression used when someone was complaining about something, "You'd complain if you were hung with a new rope."

 

The executioner would "condition" the rope before the execution by hanging heavy bags of sand for a long period of time.  The rope was manila.  A new rope would have too much elasticity in it and the person would bounce around on the end of the rope as if they were "dancing".  Not a pretty sight.  So all the elasticity of a new rope was taken out of it before use.

 

Isn't that a bit of pleasant cocktail conversation you'd want to slip in sometime in the evening?

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