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 Sailormagazine 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.
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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