Author Topic: best advice for towing  (Read 18589 times)

Hereward

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best advice for towing
« on: January 15, 2010, 07:45:02 PM »
Hi,

my first post!

As a Landorver driver rescuing vehicles has been a frequent recent activity. In general we use pre-made strops and shackles BUT sometimes we need to use ropes where it is difficult to attach with a shackle.

So the obvious question: what knots should be used with what type of rope. Obviously the knot (should) be easy to tie and undo. Also what is the effect of the type of knot on the strength of the rope. A bit of elasticity helps in towing, the attachment point can be broad or narrow.

And by comparison how do these knots compare with an eye-splice?

Many thanks for all your help.

roo

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Re: best advice for towing
« Reply #1 on: January 15, 2010, 09:29:11 PM »
As a Landorver driver rescuing vehicles has been a frequent recent activity. In general we use pre-made strops and shackles BUT sometimes we need to use ropes where it is difficult to attach with a shackle.

So the obvious question: what knots should be used with what type of rope. Obviously the knot (should) be easy to tie and undo. Also what is the effect of the type of knot on the strength of the rope. A bit of elasticity helps in towing, the attachment point can be broad or narrow.

And by comparison how do these knots compare with an eye-splice?

Welcome!

As you seem to know, just about any bend (for making a large circle), loop, or hitch form that is easy to untie will be what you want.  Towing typically doesn't require a lot of resistance to loose flogging (security).

Here are some semi-random ones:
http://notableknotindex.webs.com/Zeppelin.html
http://notableknotindex.webs.com/bowline.html
http://notableknotindex.webs.com/sailorhitches.html
http://notableknotindex.webs.com/pilehitch.html
http://notableknotindex.webs.com/timberhitch.html

I doubt you'll know the precise load in the line, so just size your rope (I'd choose nylon) comparable to large tow strap capacity.  Knots or any curvature (from anchor points, terrain) in the line may reduce strength by up to roughly 50%.

You can use an eye-splice if you want, if your rope is splicable, and if you know that you can flip your eye splice over a hook.  Aside from the time and skill it requires, it tends to concentrate wear in one spot.   It may be stronger than many knotted options, but if you're using properly-sized rope, that will not even be an issue.
« Last Edit: January 15, 2010, 09:38:02 PM by roo »
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Hereward

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Re: best advice for towing
« Reply #2 on: January 15, 2010, 10:30:12 PM »
Cheers.
I have always used a bowline  but add a halfhitch round the loop as on one occaision the short end pulled through. I had always found it worked well. But one of my fellows derided it as unsuitable. Hence the question.

My question on the eyesplice is : is it stronger than say a bowline? When I use a pre-made loop I use a strop rather than a rope. But I have never learned to make a good job of a splice. Maybe I should try.

roo

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Re: best advice for towing
« Reply #3 on: January 15, 2010, 11:21:35 PM »

My question on the eyesplice is : is it stronger than say a bowline? When I use a pre-made loop I use a strop rather than a rope. But I have never learned to make a good job of a splice. Maybe I should try.

An eye splice is stronger than a bowline, but if you're breaking rope, you grossly undersized your rope.  A tow rope getting dragged across an obstacle will also reduce the rope strength more than an eye splice, temporarily.   Tow rope is something that deserves to have a significant factor of safety. 

I tend to avoid eye splices if I use the rope for more than one purpose.  I hate to have an unused loop dragging around snagging things.   It sounds like you might have to get inventive with your rope in the envisioned field of use. 
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DerekSmith

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Re: best advice for towing
« Reply #4 on: January 16, 2010, 10:20:57 AM »
Hi Hereward,

Yes, knots weaken rope.

The answer then is - Don't use knots.  Or at least, if you have to then don't put all the load on them.

Enough cryptic.  Just learn one knot - the B&Q knot (AKA Rosendahl, Zeppelin) - why ?  because it is reasonably strong, very secure, but most importantly, I have never been able to load it sufficiently to make it jam - even with cold wet fingers it is the perfect gentleman to untie.

Now to taking the load away from the knot.

Pass the rope through (around) the load tow point, back to your vehicle and around (through) your tow point.  Then join the two ends together with the B&Q knot.  Don't worry if you don't have access to both ends, the knot is usually shown being tied using the ends, but you can just as easily tie the knot using bights or just tuck a slip loop through to lock up the knot.

The vehicles are now connected with two lengths of rope, only one of which has a weakening knot in it.

If the towing points are reasonably slick, and if your rope is say 8mm nylon (it has excellent elasticity for towing), each length will only be taking half the load.  With a typical breaking strain of 1.3 tonnes, and say a 50% weakening from the B&Q knot, then you will be able to make a 1.3 tonne haul by the time the B&Q is at risk of failing.

Want even more pulling force with the same rope and still only one B&Q knot?

Middle your rope and take the mid bight to the load, through (or around) the hitch point and back to your vehicle, drop the bight loop over your tow hitch.  Now back at your vehicle, join the two ends using a B&Q, making the rope into a large single loop which has been threaded through your load.  Drop the second loop end you have just made by joining the ends over your tow hitch and you now have four lengths of rope between you and the load and only one knot.  The load in each rope is quartered and so you should theoretically be able to apply 2.6 tonnes of haul before you put the B&Q in danger.

Finally, you could have done this without putting any knots under serious load.

Take the loop to the load and back to your vehicle, dropping it over the tow hitch as before.  Now take the ends and make two round turns around the tow hitch and tie then out with a half hitch.  Very little of the load will have made it to the half hitch and only intact (i.e. unknotted) rope will have been taking the load - nearly 5 tonnes breaking strain haul from a little 8mm nylon rope...

Happy hauling, and see how many people you can pass the B&Q on to - it is a great little knot.

Derek

Corrected re Hunters bend pointed out by DL
« Last Edit: January 18, 2010, 12:33:54 AM by DerekSmith »

sharky

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Re: best advice for towing
« Reply #5 on: January 16, 2010, 10:26:27 AM »
Just came back in off the water, and I'm a little scatterbrained at the moment, but get some 24-32mm 8 strand nylon rope. It's pretty easy to splice the ends, and is good for 20- 25 tons. It ties and holds knots well, and you can store it by stacking instead of looping or flaking. If you are going to be treating it roughly, such as dragging it on concrete and so forth, get some cheap polyethylene rope and do a french whip over the 8 strand as a chafe guard. You can make the chafe guard as long as you need it to be, and the french whip will allow the rope to maintain flexibility during use and storage. Hope this helps...
Sharky

Fairlead

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Re: best advice for towing
« Reply #6 on: January 17, 2010, 05:32:01 PM »
Derick,
Once again you have jumped in with both feet without reading the question and come up with a heap of useless advice.
Hereward is talking about hauling/recovering off-road vehicles - to which none of your answers are suitable.
Hereward,
there are some good offroad sites with excellent advice on the use of ropes for recovery - most favouring the 8 strand multiplait and of late the use of Soft Shackles instead of metal ones. 

Gordon

Dan_Lehman

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Re: best advice for towing
« Reply #7 on: January 17, 2010, 08:03:42 PM »
Quote
generally use strops, but sometimes we user ropes where it is difficult to attach with a shackle

But might this rope use be supplemental, serving merely to attach
stuck vehicle to shackled strop?  -- to make a bridle, as it were.

You have a broad range of possible materials.  Elastic ones have the asserted
benefit of sustaining tension w/o careful matching of towing to towed vehicle
speeds -- i.e., of stretching and having that energy stored in the rope.  This
is also a potential hazard, as a snapped attachment can send things flying.
(I distinctly recall one anecdote of a strop breaking off a trail-hitch ball and
delivering it INTO the stuck vehicles now-silenced engine!)  Low-stretch
materials (strops by constuction tend to be lower than ...) such as HMPE
rope have less recoil, and immediate transfer of force.

So, how the rope is to be employed will suggest which knots to use.
In short, though, the bowline, if applicable, should be fine AND able
to be made a tad stronger & more secure by tucking the tail back
through the central nipping loop, which should also help preclude
capsizing.  A similar structure can effect a bending of end-to-end:
in one side of the to-be-formed ring of rope make the nipping loop,
and then "tie a bowline" with each end, in opposite directions
(which means that the knot makes a sort of bow -- eyes to
either side of it, in effect).

As Roo suggests, questions of strength should be handled by using
amply strong material, not tip-toeing hundreds of pounds force below
some perceived load threshold.  Splices indeed can/should be stronger
than knots.  (But re this, it was comical to read a Practical Sailor
magazine article in which some reputed rigging firm's experts with
hi-mod ropes had eyes pull out before a to-be-tested bowline broke(!),
which, wasn't at much force.)  Splices are usually more economical
in material consumed, and then in structure to handle (no knob);
but they are also permanent (practically).  Suit your needs.

Quote
the B&Q knot (AKA Rosendahl, Zeppelin or Hunters bend)

I have a good idea what Rosendahl's Zeppelin bend and (Smith)Hunter's bends
are like -- and they are NOT "aka", except in error.  "B&Q" I take is a moniker
offered to suggest the geometry of the former.  SmitHunter's, btw, can jam.

It sounds as though you might have sufficient connections to acquire some
discarded rope, such as from SAR or caving groups.  I'd think that some
not-in-bad-shape 11mm low-elongation ("static") caving/rescue rope,
coupled with 1" tubular nylon webbing put around the rope for either
full-sheath redundancy or just here-&-there chafe guards would serve
well, used esp. in some doubled (load-sharing) manner.  Similarly, some
discarded other beefy line as one might get from the docks.  The smaller
stuff though might work best in making attachments (with some sort of
chain or hardware against harmfully-edged metal parts) beneath a vehicle.
The sort or protection suggested by Sharky with a flattening form of
polyethylene/polypropylene rope can be helpful, too -- one can see this
(just simple wrapping, all I've noticed) on commercial-fishing gear.


And, hey, come back with some further reports, and maybe some photos
of cordage in use!

--dl*
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DerekSmith

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Re: best advice for towing
« Reply #8 on: January 18, 2010, 12:36:18 AM »

I have a good idea what Rosendahl's Zeppelin bend and (Smith)Hunter's bends
are like -- and they are NOT "aka", except in error. 

--dl*
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And the error was mine - thanks Dan - post corrected.

Derek

squarerigger

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Re: best advice for towing
« Reply #9 on: January 18, 2010, 04:01:30 AM »
Absent some definite research results (i.e. proof with a note of the research conducted to derive this statement) that a bowline is made "a tad" stronger by adding structure to it, I think it behooves us not to recommend such a maneuver without further explanation, preferably accompanied by a photograph.

Quote
In short, though, the bowline, if applicable, should be fine AND able
to be made a tad stronger & more secure by tucking the tail back
through the central nipping loop, which should also help preclude
capsizing.

This does not seem like replicable instruction and, with a knot that, when poorly tied is capable of capsize and release (particularly with HMPE), it seems improper to discuss or recommend use of such a weak structure to be used in towing.  About security there can be little doubt - almost anything you do with the tail on a bowline will improve its (the knot's) security.  To suggest it will also make it a tad stronger (i.e. able to take a higher load without failure) flies in the face of logic.  I would like to know how this happens (makes it a tad stronger) and how does it help preclude (i.e. stop or prevent) capsizing?  Your explanation of these events is most welcome Dan.

SR
PS  Derek - could you please explain where to find the B & Q knot - it does not show up in a Google search - did I miss it somewhere here?

Sweeney

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Re: best advice for towing
« Reply #10 on: January 18, 2010, 11:35:38 AM »
For what it's worth I would use the Rosendahl/Zeppelin as a loop knot rather than a bowline. It is not difficult to tie with a little practice (and the bend can be tied by the same method though it is easy to tie SmitHunter's by mistake).

Barry

DerekSmith

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Re: best advice for towing
« Reply #11 on: January 18, 2010, 02:13:45 PM »
snip...
PS  Derek - could you please explain where to find the B & Q knot - it does not show up in a Google search - did I miss it somewhere here?

'B&Q' or more correctly 'b and q' from the easy to remember tying method. In the UK we have the large chain store B&Q with the tag line "You can do it if you 'B' and 'Q' it", so kids find it very easy to remember this knot by calling it the B&Q knot. http://en.wikipedia.org/wiki/Zeppelin_bend

Also sometimes called 'Fishes' or '69' for ease of remembering http://www.survivaltopics.com/survival/how-to-make-a-zeppelin-bend-knot/

If I teach kids the Zeppelin bend, I can virtually guarantee they will forget it.  Where I have taught them and called it the B&Q knot, I see it being used all over the place.

Derek

Sweeney

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Re: best advice for towing
« Reply #12 on: January 18, 2010, 02:53:04 PM »
The loop version can be tied as in this video clip:

http://www.youtube.com/watch?v=ocoUUu1E520

The bend can also be tied in the same way though it's not as easy as the "B&Q" method.

Barry

SS369

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Re: best advice for towing
« Reply #13 on: January 18, 2010, 03:50:01 PM »
Although I am not recommending its use I'll share a recent personal experience.
I had to pull a small tractor up a slippery slope of soggy mud and grass. With no traction for the tractor to bite I resorted to towing from the top of the incline (no lower access or egress available) with my 4 wheel drive truck.

I didn't have a suitable length of tow chain so I used an arborist's bull rope. Being old-ish and stiff I made a long continuous loop of it using the Zeppelin bend, but I took the working end and made a second pass through the loops that would then tighten down on the increased bulk.
I took a smaller cord and cinched with frapping/lashing, the larger right behind the ball hitch to aid it staying there during the slack moments. The other end was just looped around the front (smooth edged) bumper before the bend was tied.
I left the bend tails long and at the end of the task I had no problem untying and the knot did not slip, even with the multiple jerking and slacking that is inevitable with towing.

I personally think that the use of over sized to-the-task rope be used regardless.

Just a personal experience.....

SS

Dan_Lehman

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Re: best advice for towing
« Reply #14 on: January 18, 2010, 08:37:42 PM »
Absent some definite research results (i.e. proof with a note of the research conducted to derive this statement) that ...

Goodness.  One cannot get out of bed, by this criterion!
Nobody has this, much, for anything knotting.

Quote
[this statement that] a bowline is made "a tad" stronger by adding structure to it, I think it behooves us
not to recommend such a maneuver without further explanation, preferably accompanied by a photograph.

Attempting to rise above the level of behooved animals,
there has been some ("a tad bit of", one might say) testing re this,
presented on this very forum -- to wit:  http://igkt.net/sm/index.php?topic=1239.30
There have been images --sketches & photos-- as well.  I'll attach one previously
presented photo (which is easier for me to fine in my computer than
in the forum, alas) here (oh, maybe a duo).

Quote
In short, though, the bowline, ... // when poorly tied is capable of capsize and release (particularly with HMPE),

Any research results showing this?
I speculated that it might be so, but then saw video of rather
different (and astounding) behavior -- steady slippage under load.
In its great INelasticity, HMPE cordage lacks one attribute that I surmise
enables the deformation making capsizing more likely.


Quote
it seems improper to discuss or recommend use of such a weak structure to be used in towing.
About security there can be little doubt - almost anything you do with the tail on a bowline will improve its (the knot's) security.
To suggest it will also make it a tad stronger (i.e. able to take a higher load without failure) flies in the face of logic.
I would like to know how this happens (makes it a tad stronger) and how does it help preclude (i.e. stop or prevent) capsizing?

And I'd like to know what logic it is that "it flies in the face of" !?
-- and how the bowline came to be "such a weak structure" in our scheme of things?

My reasoning is repeated and simple:  you have increased the material around
which the heavily loaded (100%) line bends into the knot by 50% (2, +1).
Now, the exact orientation of this triple-diameter mass I think also influences
curvature and thus strength.  It might also make it easier for the SPart to slip
slide around the mass, collapsing the eye, as was seen in the Brion Toss videos
-- but note that that came with (1) very slippery cord (HMPE 12-strand) AND
a most accommodating low-friction & broad diameter object (metal ring 15x? diameter).

An admittedly weak, suggestive confirmation of this strength gain came
in Agent_Smith's testing, reported in this thread, which page I've linked
to has my summary of results:  http://igkt.net/sm/index.php?topic=1239.30

-- yes, a most paltry case of a few tests' average, for a slight difference
(really, even IF this difference were fully acceptable --and I mean that in this
limited testing it cannot be--, it's not much to write home about).

So, again to this forum are photos of versions of what I've generally called
"Janus Bowlines" -- because they are two-faced, in that the knot is symmetric
("the same coming as going", so to speak) in topology (but not loading).
I prefer to begin with the tail-on-outside bowline, which I think gives a
nicer geometry to the tucked strands.  The collar made around the
eye legs with the tail should be drawn up more tightly than that around
the SPart, to enhance slack-security.

--dl*
====

Quote
'B&Q' or more correctly 'b and q' from the easy to remember tying method. In the UK
we have the large chain store B&Q with the tag line "You can do it if you 'B' and 'Q

In the southern hemisphere,
or, at least, so I hear,
you're more likely to see
things done p & d
(and for making fast you'll do
this knot tying PDQ!)

-- Anon. II