Monday, June 7, 2010

How to Build a Slackline

 
 

Sent to you by Ignacio via Google Reader:

 
 

via How to of the Day on 6/7/10

Maybe you've tried a friend's slackline, or read the How to Walk a Slackline featured article, and now you're keen to figure out how you can build one on your own. This article will show you how to build your own slackline, using a couple of trees, some ordinary climbing gear, simple knots, and a carabiner pulley system to tighten the line. The end result is a fusion between a tightrope and a trampoline--a bouncy, highly-tensioned, single-line playground that you can carry around in a stuff sack. Once you learn the steps and gather your supplies, you can set this up in just five minutes.

Steps

  1. Gather your supplies. Slacklines are typically built from 1" (25mm) tubular webbing, although other materials can be used. A typical setup includes:
    • 50 feet (15 meters) (or more) of webbing for the main line
    • 2 pieces of 10-15 foot (3-4.5 meter) lengths of 1" (25mm) tubular webbing for the anchors
    • 5 carabiners (climbing-strength, oval-shaped)
    • 2 pieces of carpet, cardboard or other sturdy material for protecting the tree anchors.
  2. Select the anchor points. A good length for beginners is about 15-20 feet between anchors. Find an area clear of sharp objects--smooth grassy areas are ideal. Shorter spans are easier to learn on than longer spans and allow for a lower line.
  3. Build the anchors. Choose anchors capable of holding about 500-1000 pounds (226 kg-453 kg) of lateral force: medium-to-large trees, cemented poles, truck hitches, eye-bolts, etc. When using trees for anchors, make sure to protect the trees by padding the area of contact with carpet or other sturdy material. Wrap the loop of webbing around the first anchor about 2-3 feet (60-90cm) off the ground for a 15-20 foot (4.5-6 meters) length. Attach a carabiner to the two ends. Repeat for the second anchor using two carabiners instead of one.
  4. Attach the line to the first anchor. Connect the webbing to the carabiner on the first anchor with any secure knot. Or, if you're good with knots tie a munter hitch[1] with a half-hitch backup to make it easy to untie when disassembling.
  5. Attach the other end of the line to two carabiners. Tie two carabiners to the line about 80% of the way to the second anchor. Use a clove hitch here or two half-hitches. This makes untying easier and helps keep the line flat.
  6. Build a 'primitive' pulley system tied off with half hitches[2] or a clever friction knot[3] to secure the line. Then, pass the line through the first carabiner attached to the anchor, then through the first carabiner on the line end.
    • Repeat for the third and fourth carabiners on the anchor and line. You should have a zig-zag pattern connecting the carabiners--the "pulley".
    • Pull tightly, using about 50-100lbs (or more) of pulling force.
    • Grab the lines in the pulley with one hand and tie off the loose end with three half-hitches. Alternately, use a tightening system that comes with a specialty slackline kit.
  7. Tighten your line. You can experiment with tying the line very taut or moderately taut. If the line is too loose, it will lose many of its dynamic qualities and sag excessively. Make sure, however, that the line is tight enough so that it will not touch the ground at any point along your path over it.

Video

Tips

  • Buy more webbing than you need for the span between anchors. Although, you may only want a slackline that's 20 feet long, you'll need about 20 more feet to operate the pulley system.
  • Use different colored webbing for the anchors and main line. This makes it easy to sort out your supplies when setting up the slackline.
  • Get more leverage when tightening the line by wrapping the webbing around a sturdy stick. As the distances increase, you'll need more leverage to tighten the line. Tie the webbing to a stick with a clove hitch and several wraps around the pulling end of the webbing to get a better grip on the line.
  • Piggy-back pulley systems to maximize tightening for long lines. Instead of pulling directly on the webbing used for tightening, run this webbing through another pulley system attached to another nearby anchor. Ideally, the other anchor is in line with your line. Although somewhat complicated, this will provide an enormous amount of leverage, for those extra long lines.
  • Combine pulling strength with two or three friends. Get a friend or two to help pull the line with you. If using a stick with a clove hitch, you can each pull on a side of the stick. Careful not to wrap the webbing around your fingers.
  • Buy a commercial tightening system. If you want a fast and easy method for setting up a slackline, consider investing in kit. Several manufacturers offer professional tightening systems and complete slackline kits.[4] Expect to pay about US$100-$200, depending on the model.

Warnings

  • Slacklines generate enormous forces on the anchors when weighted. Carefully choose anchors that can withstand up to 1000 pounds of force.
  • Do not use webbings or carabiners for climbing after they have been tensioned in a slackline.

Things You'll Need

  • Two anchor points
  • 50 feet (15 meters) of 1" (25mm) tubular webbing for a 25-foot (7.5 meters) main line with pulley system
  • 2, 10-15 foot (4.5-6 meters) pieces of 1" (25mm) tubular webbing tied into loops for the anchors
  • 2 medium to large trees or other anchors
  • Padding to protect the trees
  • 5 carabiners

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