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Thread: Load sharing anchors

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    Forum Member Fairfield's Avatar
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    Default Load sharing anchors

    There are many ways of going about making them. Some are right and some are wrong for what the job may entail. So, for what your team sees for the most part what is your go to setup? Mind you, I don't just mean load sharing due to the fact that one anchor does not seem strong enough. You may have a point that you need to center up on and that is why you are using more then one anchor point.

    For me, it does depend on the job. For the most part though I like to use a nine to one point then center it up with a butterfly. If the point from the anchor to the knot is not far (in means of making a good inner angle) I like the double eared eight ( due to ease of adjusting it to the load direction). I will use the the self adjusting load sharing anchor when I have to but don't like it much due to its binding and unexpected releasing while under load. For me those are the main go to setups, whats up your sleeves?


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    There's a fantastic two point adjustable anchor taught by RTR that uses the Portuguese bowline. It's used for positioning the focal point between two bombproof anchors.

    Too complicated to describe with words...will try to find a photo.

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    Quote Originally Posted by servantleader View Post
    There's a fantastic two point adjustable anchor taught by RTR that uses the Portuguese bowline. It's used for positioning the focal point between two bombproof anchors.

    Too complicated to describe with words...will try to find a photo.
    And if the 2 or more anchors are marginal, you can do basically the same thing, except with yet another of the many variations within the Bowline family of knots.

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    Forum Member Fairfield's Avatar
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    Not a big fan of it due to a few reasons but the Spanish Bowline can also be an option. It sucks though.

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    The adjustability of the Portuguese bowline makes it better than the Spanish bowline IMHO. Adjusting the length of one of the bights is almost always necessary. Double loop figure 8s (the double eared bight Fairfield notes) are also very useful in creating basic multi-point anchors.

    I have found self-equalizing anchors aren't as smooth in adjusting in real life vs. theory once loaded, but YMMV. I recall some research showing that pre-equalization is generally preferred since it reduced issues with shockloading and anchor extension.

    There was some detailed analysis done of multi-point systems a few years ago that was presented at ITRS. I'll see if I can find the link and share it.

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    Forum Member MichaelXYZ's Avatar
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    Quote Originally Posted by MtnRsq View Post
    There was some detailed analysis done of multi-point systems a few years ago that was presented at ITRS. I'll see if I can find the link and share it.
    Was this what you were looking for?
    http://www.itrsonline.org/PapersFold..._ITRSPaper.pdf

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    Quote Originally Posted by MichaelXYZ View Post
    Was this what you were looking for?
    http://www.itrsonline.org/PapersFold..._ITRSPaper.pdf
    I had forgotten about the paper John and Bruce did. Good reminder.

    The one I was thinking of was the one Beverly and Attaway did in '05. The paper wasn't linked from the ITRS site but I was able to pull it up from the MRA site. It is a bit techy

    http://www.mra.org/images/stories/me...zedanchors.pdf

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    Forum Member Fairfield's Avatar
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    I like the S.E.A when rock climbing and very very few industrial/rescue setups. Although the majority of the rigging I do personally has a set point prior to the edge or the ascent, making the S.E.A pointless in some ways more of a danger of shock loading. My big issue is when a program pushes one way over the other for every setup, instead of teaching when to look at one as better then the other for each situation.

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    Multi-point anchors are only needed when a single anchor point will not hold the load. In the industrial environment this is usually a non issue as there are typically many strong anchor points available. In a wilderness environment the issue of anchors is more of a concern, even then a well constructed 1-1-1 picket system is a good option. Now for climbers, that is an area I know nothing about.

    In the end, we choose something that is safe, effective, and gets the job done.
    Last edited by MichaelXYZ; 11-27-2013 at 01:49 AM.

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    Forum Member Fairfield's Avatar
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    Michael, Don't be to sure about not needing a multi point anchor often in the industrial world. I have been to a hand full of factories and refineries that had been around for 100 years or more and had some horrible infrastructure to anchor to (although at one point was meant to hold a building up). Also keep in mind, you may not need it so much for the reason of a weak anchor point. You may be using it to center one point up. If this was the case you still should know good basics of load sharing and the angles within the anchor due to strain on the anchor material ie; sling, rope, webbing.

    Oh, wanted to go back on the Spanish Bowline comment I had made. I do use it but find that others have a hard time remembering how to tie it. So when they do it looks like it is right but then will slip out when loaded. So that makes me nervous. I guess like any other knot though, if you cant tie it right it will fail.
    Last edited by Fairfield; 11-27-2013 at 07:54 AM.

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    Quote Originally Posted by Fairfield View Post
    <<on the Spanish Bowline comment I had made. I do use it but find that others have a hard time remembering how to tie it. So when they do it looks like it is right but then will slip out when loaded. So that makes me nervous. I guess like any other knot though, if you cant tie it right it will fail.
    Again, so many variations within the bowline family to choose from for a multi-leg anchor. Although a Spanish bowline would be toward the bottom of the list. I might use it to manage ropes with separation during rigging- lowering/raising the lines- but otherwise would pick another. Bowline variations in the cranial tool box is a huge value for rigging.

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    Quote Originally Posted by MichaelXYZ View Post
    Multi-point anchors are only needed when a single anchor point will not hold the load. In the industrial environment this is usually a non issue as there are typically many strong anchor points available. In a wilderness environment the issue of anchors is more of a concern, even then a well constructed 1-1-1 picket system is a good option. Now for climbers, that is an area I know nothing about.

    In the end, we choose something that is safe, effective, and gets the job done.
    Pickets definitely work although the added weight of pickets plus 'sledges is a bummer. The BFR/BFT anchors are preferred but we had a post-wildland fire area where all the normal anchors were suspect. Rock pro was also suspect due to the high heat leading to scaling issues. Pickets were the go to option and we used them several times operationally.

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    Forum Member Fairfield's Avatar
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    For the guys that use the Portuguese bowline, what advantage do you view it having over the double eared eight?

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    Just for giggles, I decided to put together a static simulation using vrigger. See image below. What I see is that the 3 point distribution does a good job of distributing the load equally. I moved the angles around between anchors and the distribution remained fairly even among the three anchors. Now in the event of a failure of one leg, the distribution converges on the center most line.
    Playing around with 2 point distribution angles really impacts load distribution, far more than in the 3 point system.

    Conclusion:
    For load distribution, the 3 point anchor affords less worry where angles are concerned. If the 2 point system is to be used, critical angles greatly influence load distribution. A 3 point system alleviates many of the pitfalls of a 2 point system.


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    Quote Originally Posted by Fairfield View Post
    For the guys that use the Portuguese bowline, what advantage do you view it having over the double eared eight?
    First and foremost... Happy Thanksgiving to everyone! Have a safe holiday.

    Re: the question on advantages, I have found the Portuguese bowline lends itself to quick and easy loop size adjustment vs. the double-8. Both certainly work and it is largely a matter of preference IMHO.

    I have no empirical evidence but have noticed a tendency for rescuers to be either bowline-centric or figure eight-centric and default to the familiar outside of training.

    vRigger is a cool tool and is useful for modeling all kinds of systems. Both Steve Achelis and Tom Moyer are long time mountain search and rescue guys. Waaaay off topic for Firehouse.com, but Steve has an outstanding site (http://beaconreviews.com/transceivers/) re: avalanche beacons. Cuts through all the marketing hype and hits the +/-'s of a key piece of equipment you hope to never need.
    Fairfield likes this.

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