Slack line training

[lpskier]

We want to install a slack line at our ski site. Installation will not involve the use of trees since we really don’t have any we can use. I plan to set pressure treated 4x4s in the ground set in concrete. It looks like a typical line is 45 feet long so I guess the posts should be about 40 feet apart. For safety, I’d like the line about 24-30 inches off the ground. So here are my questions:

1. Is two feet in the ground for every foot above the ground enough for the posts? Or is that ratio overkill?

2. If I have say 30 inches of post showing above ground with the slack line attached at the top, will a 4x4 be sturdy enough the resist the tension of the line, or is 6x6 the better way to go.

3. Any suggestions on the best slack line product? This will not need to be portable but should be UV resistant.

4. How much sag should I expect over a 40 foot span? Am I starting too low with a 30 inch post?

5. What am I overlooking?

 

Thanks!

[ToddF]

I would go with 6x6. There is a lot of tension being put on those posts

I use a 2" ratchet strap 27 feet long. You can get longer straps but they work pretty good and are cheap 30-80 dollars

If you eyebolt through the post you can put a couple of eye bolts at different heights that way you can go higher when you are feeling confident and put some more slack in when you are really feeling it

 

Look across and not at your feet

[dchristman]

Here's a useful site with info on setting up without trees. It shows posts with dimensions and using A frames with ground anchors.

[ozski]

Put one up in my back yard last year, great for balance and core strength. I use it almost daily and its a lot like slalom skiing, some days your on and some days it does not come together for no apparent reason.

[BobF]

Love slacklining! A-frames with ground anchors may be the best way to go if you're not using trees or some other sturdy vertical attachment. I remember looking up some calculations regarding how much additional tension a bird puts on a wire when it lands. It's a lot.

[oldjeep]

X2 on just buying 2" ratchet strap. The gibbon slack line we have is nothing more than that. If it were me I would cement in some steel pipe rather than treated wood in concrete.