After recent torrential rain and unprecedented flood event, I went in to a local river canyon to inspect and assess crucial anchor stations.
An abalakov thread joined by a zeppelin bend suffered intense buffeting and water pressure.
Refer to attached photo.
The cord is 8.0mm diameter Sterling high strength (15kN rated).
The zeppelin bend was tied with identical tail lengths.
I was the original installer.
The flood event took out a national highway road bridge, scoured away all vegetation/trees on the river banks, altered the river banks, cut power to local communities, destroyed roads (massive landslides), and cut a crucial water supply pipeline, etc.
The zeppelin bend survived intact (with minimal tail slippage).
The cord suffered extensive damage (refer to photo).
The metal chain link is for threading a rope (for abseiling) - and this link was severely buffeted by hydraulic water pressure.
Basically, any attached hardware oscillates wildly in the strong flow of water - it is a 'point mass' that vibrates and flails wildly.
NOTE: An abalakov thread (in this example) is 2 intersecting holes drilled into hard rock, allowing a cord to be threaded through.
Historically, abalakov threads were used in mountaineering (in solid ice).
The idea for its use in canyon environments is to avoid the use of permanent bolts (ie less invasive to the environment).
Commentary
This flood event is the 'ultimate test' for a joining knot (ie 'bend').
I would surmise that a Double Fishermans bend (Ashley #1415) would also have survived.
(#1415 is an inter-penetrating bend that is a very secure, but highly vulnerable to jamming).
The zeppelin bend is a non-jamming bend based on inter-linked overhand knots.
The fact that the zeppelin bend did not shake loose and had minimal tail slippage is very interesting.
It is the non-jamming class of joining knots that is of interest here, and this shows that a zeppelin bend
is secure and stable.
Note that the cord in the photo is not 'dyneema' - ie there is no mechanical reason for knot to slip apart
and fail due to the inherent nature of the cord material. Dyneema is known to cause security issues
for hand tied knots.
