Tests of Zeppelin vs Double Fisherman's bends?

John RB

New Member
Location
Eastern
Is anyone aware of strength/efficiency tests of a Zeppelin Bend vs Double Fisherman's? Yeah, I know, prussik loops shouldn't need to be untied, but I have a legit reason to do so on occasion, and breaking a double fish is awful, like ending a bad relationship... Yes, i know a stopper knot can be tied but i actually want to know the strength of the naked bend. I bet the strength is the same or close.
 

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John RB

New Member
Location
Eastern

Time stamps are in description.
Many thanks for posting that. So 3267 lbf for Zeppelin vs 4100ish for Double Fisherman's in this test... not an insignificant difference but stronger than figure 8.... and my selfish question is if a 7mm prussik loop closed with Zeppelin is safe for half of my weight, in a doubled rope system. I have stoppers too but just had a setup reviewed by others and those in Europe were calling the Zeppelin appropriate for rigging only. I have marked some of mine and executed a lot of climbs, but no falls, and they're solid and not budging a bit.
 

agent_smith

Active Member
Location
Townsville
Hello John RB,
If you would like to dive into deep technical detail about the 'Zeppelin bend' - I recommend that you visit this website:
Link: http://www.paci.com.au/knots.php (knot bio at #6 in the table).

I would comment that MBS yield point of a knot (ie strength) is entirely irrelevant. There is no load that a tree climber can generate while using PPE for positioning or during mobility in the tree canopy (or even a fall) that will reach the MBS yield point of a knot.
Unfortunately, most knot testers are fixated on the MBS yield point of a knot - rather than examining other qualities (such as; resistance to jamming, amount of rope required to form the knot, whether the knot is 'TIB', 'EEL', stable and secure in various loading profiles, effect of cutting one of the eyes (for example cutting one eye of a #1085 double Figure 8 while under load and observing what happens), etc.

The notional concept of 'efficiency' is frequently misunderstood to mean MBS yield (ie strength).
In actual fact, the metrics for knot 'efficiency' are as follows:
[ ] amount of rope required to form the knot (a zeppelin bend consumes less rope than #1415 Double Fishermans)
[ ] jam resistance (the zeppelin bend is jam proof...there is no known load that will induce jamming)
[ ] footprint
[ ] stability (under various loading profiles)
[ ] security (which includes resistance to slack shaking and cyclic loading)
[ ] whether the knot is 'TIB' (Tiable In the Bight) - ie, the knot can be tied and untied without access to either end
[ ] whether the knot is 'EEL' (either end loadable)
[ ] in the case of 'bends'; stability and security when different cord diameters are joined (eg 8.0mm joined to 11.0mm diameter rope)

Note that 'strength' is absent from the above metrics.
 

John RB

New Member
Location
Eastern
Ok, I am an engineer by career and so i GREATLY appreciate the level of detail in your response. Thank you. The attribute you mentioned about being TIB ... this was the subject of my thread here just a week ago (Single Guy Seeking Sexy Friction Hitch), where i am looking for a TIB Friction Hitch that could compare to the Michoacan tied with a cord. I am buying the beer if you have one for me. Thx again.
 

CjM

Active Member
Location
Asheville
A little bulky with cord perhaps, but have you tried a water knot (overhand retrace)? I've had them totally fused in webbing, and rolled the knot between my sneaker and a car mat with great success
 

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