Hello everyone, I was wondering if anyone can enlighten me as to the specific definition of what it means when a knot jams. I remember reading about it here some time ago, but have failed to find the post in a search. My foggy memory recalls something to the effect of a jammed knot not being able to be untied by the hands after it has been placed under a strain that would be half of its MBS. Am I even close here? Thank you for your considerations.
Wow, how synchronous: I just opened Mark’s paper on the Rigger’s Bend, and it seems he has answered my question. Sorry for jumping the gun!
There’s some flexibility in the term, but a jammed knot is knot that difficult or even virtually impossible to untie. How much strain is required depends on the rope (material, construction, age, etc.), lubrication, and other minor factors such as vibration.
Are you referring to this (footnote #25) ::
This author differentiates [i]initial[/i] jamming threshold from [i]maximal [/i]jamming state. A knot that its initial jamming state [sic] cannot be untied by hand and human finger strength alone. Maximal jamming refers to a state where tools are required to loosen and untie the knot --and during this effort, damage to rope fibres is likely to occur.(Note exchange of "threshold" & "state" re "initial" jamming.)
One should of course realize that one person’s “jammed”
per the above definition might not be another’s --their
loosening abilities might differ, along with technique.
And as Roo notes, there are many factors that contribute
to a knot being hard to loosen.
Also, Mark’s insistence on finding a “threshold” for jamming
and dismissing knots that jam say at 50% of break strength
runs counter to common ideas that knot behavior should be
considered at normal working loads --not test-bed exceptions!
One might take another sense of “jammed” : that of being
what I call “slack-secure” (resisting loosening via shaking, etc.).
I’ve discovered some bowline variations that can be “jammed”
in this sense and hope for slack-security thus,
in contrast to the mirrored bowline which gets slack-security
from an abundance of material in close quarters, resisting
movement to loosen; the zeppelin end-2-end joint is another knot
that has this secure-when-unjammed aspect.
–dl*
First off, thank you Roo for your response. It seems that there is no official definition or litmus test (as of this time) for what is referred to as “jammed” outside of difficulty in undoing, or not being able to untie the knot in question altogether. Obviously there are numerous factors to consider within this scope. In short, your insight clarified things for me.
Thank you Mr. Lehman for your insights as well. Yes, footnote #25 was where I discovered what I had been querying about, as well as in the discussion from May 8th of this year referencing the Rigger’s bend paper. The ripostes between you and Mark are always enlightening as well. There is a kind of dialectic that goes on between both of your reserves of knowledge in knot lore and experience, such that you seem to challenge one another and keep the debate fresh. I assume that the ostensible vitriolic temperament of your exchanges is more playful than serious, but I’d just like to say that the work and research you all do (and this includes Roo and others) is inspiring and important.
Cheers,
Seth
Just out of curiosity, which versions of the bowline are you referring to regarding slack-security?