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I have recently set up wire rope to support my installation of retractable sail shades.

My setup is as follows:

  • I connected 2 ropes in parallel that run from the back of my house to fence posts. They are approximately 8m apart and are not tensioned.
  • Onto each rope I connected 3 rope grips and 3 steel rings approximately 1m apart
  • I then hook 3 ropes approx 7.5ish metres in parallel to the rings on the first 2 ropes.
  • A turnbuckle is on each of the 3 ropes which is then tightened up to bring the whole system into tension
  • I then attach 2 sail shades approx 3x5m using snap hooks
  • I then further tension the 3 ropes

I am finding that after a few days/a week the tension on the wire ropes reduces and everything begins to sag.

I have taken off the shade sales reduced the length of the 3 ropes, re-tensioned the rope again and re-hung the shade sails. However, this does not solve the issue for very long.

Can anyone suggest a way to stop this set up losing tension?

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isherwood
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James
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2 Answers2

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Assuming everything is rigid...

Then one thing to provide constant tension is to run a loop towards the ground and hang a mass from that loop, gravity works.

Another example is the mass used as a door closer, sometimes the mass is "hidden" in a tube to stop fingers getting trapped or pinched. Often the masses were adjustable especially for heavy barn doors so there was a long rod that the masses could be added to easily.

You might need to increase the mechanical advantage by using pulleys.

Be careful choosing the amount of mass and also if kids can use it as a swing.

Also to consider is a spring either in tension or compression. But for this use I think the mass is more visible in terms of safety.

See:

https://www.instructables.com/Counterweight-Door-Closer/

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jsotola
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Solar Mike
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Here's the thing...

To keep a non-rigid member flat it has to be under extreme tension. In fact, the tension required increases exponentially as you approach zero sag. Therefore, it's not a reasonable goal to expect flatness when attached to fairly flexible supports. (The comments are correct that your fence posts are not as stout as you first believed.)

Therefore, embrace the arc. Treat it as a suspension bridge, which you'll notice all have substantial sag for the reason stated above. Your tilting fence will thank you.

isherwood
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