Author Topic: Reliable eye knot that is simultaneously PET and TIB?  (Read 868 times)

RGB

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Reliable eye knot that is simultaneously PET and TIB?
« on: September 23, 2018, 06:45:03 AM »
Does anyone know of a reliable eye knot that is simultaneously post eye tiable (PET) and tiable in the bight (TIB), other than variations in the lock on the bowline version shown in the first image below (made with S chirality on this occasion)?

I think bowlines can not generally be tied in the bight through a tarp grommet or around a post (at least not without passing the bight around the entire tarp or the entire planet in which the post is embedded, which is impractical).

There is a practical reason to ask this: for emergency roof repairs, tarps are commonly rigged using lines tied at the corner grommets by a bowline, and reeved with half-hitches through the side grommets for strength. Then the corners can be anchored (tied down) with lines of the required length (each connected by a bowline through the bowlines). Maybe the second photo below will be better than my words. This gives a very strong rig, but on a large tarp the rigging lines are long, so threading a bowline on a corner near the centre of a line is slower than desired. Tying these corners by an eye knot on the bight could be an important time saver. But the knot must be easily tied through a tarp corner grommet. Ideally it should also resist intermittent tail loading at 90 degrees. After all, we are talking about the corner of a tarp on a roof during a storm.

This bowline does not need any lock if the 3rd eye is made about the same size as the other two and the anchor line mentioned above is passed through all three eyes, though this may be error-prone (3rd and 4th pictures below, made with Z chirality). I could not find this form in ABOK, but it is shown by it is shown by Svensson (1940) as Fig 51, Day (1947-1986) as 67E, and Warner (1992; where it is called the triple bowline) as 435. Although Day secures the tail (for a triple end loop in 67F), I think it is either-end loadable when tied in the bight, as pictured below.

I am aware of methods that use a slipped hitch (ABOK 1873) or a karabiner toggle (ABOK 1867), but they are not secure with tail loading and/or consume extra equipment.

Any suggestions?
« Last Edit: September 24, 2018, 07:17:20 AM by RGB »

siriuso

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #1 on: September 23, 2018, 10:19:49 AM »
Hi RGB,

I prefer Alpine Butterfly Loop, it is TIB and PET.

Happy Knotting
yChan
« Last Edit: September 23, 2018, 10:21:09 AM by siriuso »

roo

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #2 on: September 23, 2018, 05:20:21 PM »
I'm a little surprised at the amount of work being done to apparently reinforce the tarp.  Maybe a sturdier tarp is in order. 

Also, keep in mind that force takes the path of greatest stiffness.   Many of those reinforcements may remain slack during wind load, depending on how things are tied down, leaving the fabric of the tarp to take full load.  I'm not entirely clear on the details of the use, but it does seem like things could be simplified.
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RGB

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #3 on: September 24, 2018, 07:14:22 AM »
Thanks Siriuso and Roo,

I know how to tie an alpine butterfly in the bight (TIB), and how to reweave it through a grommet (PET), but I can not do these things simultaneously. Is it possible?

I think the alpine butterfly is the best of the solutions that involve tying a TIB eye knot then feeding the bight through the grommet and securing it by connecting the tie-down line by a bowline through the reeved bight. A picture is shown below. Tying this way (by reeving a TIB bight through the corner grommet) has the disadvantage that the bight can be pulled out until the tie-down rope is attached, but many tarp grommets are barely wide enough for two rope diameters, which provides enough security for the reeved alpine butterfly bight until the tie-down rope can be attached. If the tarp rings or grommets are too large to provide this temporary security for the reeved bight of an alpine butterfly, it may be achieved by tying an overhand knot after reeving a bight of sufficient length.

Rigging a tarp this way is a bit of work, but the result lasts much longer on a roof during a storm than any tarp that is merely tied down from the corners. The 'first responders' who do this work like to get it right the first time rather than have to come back during a severe weather event, so they go to the extra trouble. Of course anything that speeds it up with equal security is likely to be welcome.


« Last Edit: September 24, 2018, 07:19:11 AM by RGB »

siriuso

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #4 on: September 24, 2018, 09:41:29 AM »
Hi RGB,

You may use a carabiner clamped to the loop of the Alpine Butterfly Loop after the loop is inserted through the grommet. This carabiner acts as a stopper to prevent the loop from slipping out. Then by finishing the tie-down rope, the carabiner can be removed or kept as stopper before dismantling.

yChan

RGB

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #5 on: September 24, 2018, 10:51:59 AM »
Thanks Siriuso,

As mentioned in the OP, I am looking for a method that does not require additional hardware like carabiners to be left on the roof.

On reflection, the method I use to tie an alpine butterfly with its bight around a post or grommet (slide below) requires either a thumb knot in the standing part before reeving, or later use of the standing end to form a thumb knot: so the method I know is not PET (as defined in Mark Gommers' Analysis of Bowlines). It does permit tying through a grommet, but not (I think) tying through a grommet while tying in the bight. It can be used as mentioned (and pictured) above, with the disadvantage mentioned above, as an excellent tri-loaded eye knot when passing an entire bight through a grommet.

By the way, the drawing of the 'evil imposter' in the slide below is from Roo! I do not think the 'evil imposter' can result if you pass the wend through the original R space to make the second (interlocking) thumb knot, in step 4 of the slide. Other mistakes are possible, but in my experience any mistake results in a knot that 'looks wrong'.

Roo, sorry the tarp quality probably is not visible at the resolution needed for the OP. These tarps are a fair way along the price/quality curve. They have side grommets through reinforced hems, a line inside the hem around the entire circumference, and a reasonably large plastic reinforcement that is stitched and riveted over each corner. Still, they last longer under adverse conditions when rigged as described, so the 'responders' are trained to use them that way.

I appreciate the input.
« Last Edit: September 24, 2018, 10:53:03 AM by RGB »

siriuso

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #6 on: September 25, 2018, 04:42:21 PM »
Hi RGB,

Further re my post. Instead of using the carabiner as a stopper, I will tie a Harness Loop as a stopper and it has an eye/loop for the tie-down rope.

yChan
« Last Edit: September 25, 2018, 04:43:51 PM by siriuso »

Dan_Lehman

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #7 on: September 26, 2018, 09:14:09 PM »
Hi RGB,

I prefer Alpine Butterfly Loop, it is TIB and PET.

Happy Knotting
yChan
? Not PET, it's interlocked overhands after all!

But maybe you meant what I see as the only decent
solution, to tie the butterfly loosely and with an ample eye
that is reeved through the grommet,
inserted through the knot's center,
and then knotted with an overhand stopper
(conceivably, a mere slip knot will do --just the
one side stoppered, i.e.!).  This compound knot
seems pretty robust to me,
with through loading and loading qua eye knot
from either side.

Or, as I think is told above, simply use the stopper
in the eye to secure the line to the grommet.


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RGB

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #8 on: September 27, 2018, 11:43:24 PM »
Thanks all, very helpful.

Twine

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #9 on: October 08, 2018, 05:26:58 AM »
Any suggestions?

Sorry about this late answer. Since the grommets are wide enough for a double line I suggest the following method:  Fold your line and use it as though it was just a single line. Hitch this (pretend) single line to the grommet using a buntline hitch. If you expect you might need to untie the hitch after use you better use a lobster buoy hitch instead to avoid jamming. After tying this hitch you will find that the tail end of your pretend single line is actually a nice loop which you can use to tie other stuff to.
"Simplicity is the ultimate sophistication" - Leonardo da Vinci

agent_smith

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Re: Reliable eye knot that is simultaneously PET and TIB?
« Reply #10 on: October 15, 2018, 12:16:05 AM »
Quote
But maybe you meant what I see as the only decent
solution, to tie the butterfly loosely and with an ample eye
that is reeved through the grommet,
inserted through the knot's center,
and then knotted with an overhand stopper
(conceivably, a mere slip knot will do --just the
one side stoppered, i.e.!).  This compound knot
seems pretty robust to me,
with through loading and loading qua eye knot
from either side.

I concur with Dan Lehman.
Use #1053 Butterfly eye knots.
The eye (which is enlarged) is fed through the eyelet/grommet.
It is then a simple matter is tying an overhand knot or a slipped overhand knot to act as a 'stopper'.

The Butterfly knots can be finely adjusted to achieve the correct tension/length - which will then aid in holding down the tarp over the roof.
Wind gusts can create a vortex effect which causes the tarp to lift off the roof and flap wildly. So you want to get the adjustment right to retard this effect.

This system also meets the KISS principle (Keep it Simple and Safe).

It sounds like this is an SES (State Emergency Service) type of job for wind damaged roofs in Australia?
If it is 'SES' - these types of agencies are notoriously bogged down with archaic procedures and techniques that date back to the age of dinosaurs. To introduce new techniques/procedures is to open pandoras box. In this case, using just one knot (ie #1053 Butterfly) to accomplish the task should be appealing to decision makers who famously hate and/or fear the concept of 'change'.
« Last Edit: October 15, 2018, 12:17:29 AM by agent_smith »