Author Topic: Best anchor knot for a tree  (Read 9486 times)

sinthome

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Best anchor knot for a tree
« on: October 24, 2011, 07:57:17 PM »
I had the following situation arise the other day and I have been pondering what the best knot would have been-- a ridgeline securing a tarp about 15' high in a large diameter tree. The rope was pulled taut and then handed downwards to anchor it around the trunk. After tightly wrapping the rope a couple times, running diagonally down the trunk, I realized there is not much rope left and I will have to tie it off to itself as efficiently as possible. I drew a picture. It was kinda awkward since the wraps were still fairly high in the air and there was little of a tail left. It was also a time-conscious situation and I just needed to tie it off quickly. Best knot for this?

knot4u

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Re: Best anchor knot for a tree
« Reply #1 on: October 24, 2011, 09:20:28 PM »
Hi and welcome, there are many solutions.  I'd probably go with something else than what you have in your pic.  Based on your description, I'm assuming you have a ladder or something that allows you to get to the 15' mark safely.  I'm also assuming there's no strong branch to support the rope in the vertical direction.

In that case, you could tie a Trucker Hitch to tension the rope.  End the Trucker Hitch with Round Turns around the tree, and Two/Three Half Hitches around the tensioned rope.  Alternatively, if you can get enough tension without the Trucker Hitch (it sounds like you can), then go directly into tying Round Turns around the tree, and Two/Three Half Hitches around the tensioned rope.

Here we have Two Round Turns and Three Half Hitches:
« Last Edit: October 25, 2011, 04:01:01 AM by knot4u »

roo

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Re: Best anchor knot for a tree
« Reply #2 on: October 25, 2011, 12:03:02 AM »
I had the following situation arise the other day and I have been pondering what the best knot would have been-- a ridgeline securing a tarp about 15' high in a large diameter tree. The rope was pulled taut and then handed downwards to anchor it around the trunk. After tightly wrapping the rope a couple times, running diagonally down the trunk, I realized there is not much rope left and I will have to tie it off to itself as efficiently as possible. I drew a picture. It was kinda awkward since the wraps were still fairly high in the air and there was little of a tail left. It was also a time-conscious situation and I just needed to tie it off quickly. Best knot for this?

I'm afraid I would have chosen an entirely different set-up.   I don't think you'll be happy with the results of tying off at the bottom of that spiral, hoping that the tension of the last loop will dig into the bark of the tree enough to prevent the loop from twisting around the tree from the tarp weight or tension.

Enough turns and aggressive enough bark might allow you to get away with it, but you don't have many turns, and who knows if you'll always have rough or smooth tree bark.

Then, you have the additional problem of the top of the rope sliding down to slacken the helix. 
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sinthome

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Re: Best anchor knot for a tree
« Reply #3 on: October 25, 2011, 04:34:26 AM »
Haha, I knew you would cheat.  ;) The person in the tree had climbed there and was losing their balance, passed me the rope with only one half wrap around the tree, fifteen feet up. We didn't have time to do it right, unfortunately. After they passed me the rope, I was able to pull it taut and walk around the tree for a couple wraps, but then I got stuck on how to secure it with such a short tail. Assuming I can't tie back onto the main line and I have to just anchor to the lowest wrap.. what knot is the best assurance against slipping and seizing? The tree was a large old growth cedar.. I was pretty confident that the wraps would hold the tension.

knot4u

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Re: Best anchor knot for a tree
« Reply #4 on: October 25, 2011, 05:20:17 AM »
Instead of the spiral, I would tie a Marline Hitch http://www.seascout.org/about/program/knots/marline.html down the tree.  I would then secure the working end to the tree with a Strangle Hitch.  If I didn't have enough rope for the Marline Hitch, I would go straight into tying the Strangle Hitch.  Slip it if you can.

Let's back up.  What does the part near the 15' mark look like?  Does the rope just spiral down from 15' as shown in your pic?  If so, then I would NOT expect this to hold.  The guy up at 15' should at least tie a few Round Turns up there around the tree.  Tell the guy to climb the tree again and start over with solutions from my previous post.  :D
« Last Edit: October 25, 2011, 08:14:17 AM by knot4u »

alpineer

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Re: Best anchor knot for a tree
« Reply #5 on: October 25, 2011, 07:32:33 AM »
A Timber Hitch would answer your question. 

knot4u

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Re: Best anchor knot for a tree
« Reply #6 on: October 25, 2011, 08:15:06 AM »
I don't see how a Timber Hitch at the end would keep all the tension.

alpineer

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Re: Best anchor knot for a tree
« Reply #7 on: October 25, 2011, 08:42:52 AM »
You're correct. No knot will keep tension in the O.P.'s setup due to the widespread spacing of the spirals. The O.P.'s originally stated circumstances do not allow us the option of your more appropriate solution. By Timber Hitch I meant simply to wrap the rope end several times around the lowest possible part of the spiral (without the rope end taking the "U" turn around the Standing Part, of course). I use the term "Timber Hitch" rather loosely. :)
 
« Last Edit: October 25, 2011, 10:02:35 AM by alpineer »

sinthome

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Re: Best anchor knot for a tree
« Reply #8 on: October 26, 2011, 12:07:16 AM »
Thanks for the input, all. For what it's worth, the line did stay taut and secure for the duration that it was up there (5 days). The way i tied it off was just to pass the tail under the last warp and tie a couple half hitches in it. I think that semi-timber hitch would have worked pretty well, too.

knot4u

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Re: Best anchor knot for a tree
« Reply #9 on: October 26, 2011, 06:32:44 PM »
It's funny how rope can behave differently on a relatively large object with lots of friction.  The system you tied is "not supposed" to hold.  I recreated your system using 550 paracord on a tree having a diameter of about 4 inches.  As expected, the system did not hold when I applied a downward force and shaking to simulate a tarp.  On a slicker pole, don't even think about it.

A "Semi-Timber Hitch" (as named above) is a tangle that most little kids would naturally tie.  In fact, I recall tying this tangle when I was a kid and knew nothing about knots.  Again, I could not get this tangle to hold on the relatively small tree.  A Strangle Hitch is better there, but a Strangle Hitch was apparently unnecessary on a relatively large tree with lots of friction.  By the way, a regular Timber Hitch (ABOK #1665) to finish the end of a tensioned rope is ass-backwards, just for future reference.

An analogy here is a binder.  Some binders that hold on small objects don't hold on relatively huge objects, or vice versa.  Some binders that hold on convex objects don't hold on square objects, etc.  That's why it's important to practice tying knots in a variety of scenarios.

Don't take my word for any of this.  Test the knots yourself.  You're going to be the one tying your knots.  ;)
« Last Edit: October 26, 2011, 10:25:19 PM by knot4u »

DDK

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Re: Best anchor knot for a tree
« Reply #10 on: October 26, 2011, 09:18:55 PM »
Starting with the spiral configuration, two half-hitches would seem reasonable.  When hanging bear bags (think heavy) for the night, I used a Kellick hitch (half hitches or marline hitch, and then a timber hitch).

BTW, some tips, if hanging something heavy between trees well above your head, place your rope 5 to 10 feet (more if spacing of trees is large) higher than you want your item (usually placed by throwing the end of the rope tied to a rock over a limb).  A higher placement will dramatically decrease the tension you will need to exert to lift and anchor.  For those who remember their physics, yep, its that tangent of the angle trig thing which makes getting that last bit of height impossible (tension needed approaches infinity).  If you want to go pro, a pulley tied in the rope where you want your item and where the pulley has been prethreaded with a second rope for the lifting of the item makes hanging heavy items a snap.  Secure the main line, hoist your load, tie off the load line (and its reusable for multiple nights/meals etc!)

DDK