*** French Prussick Knot ***

Subject:    the "French Prusik"
  Date:     26 Oct 96 02:41:33 EDT
  From:     "Kenneth N. Laidlaw" <73542.3361@CompuServe.COM>
    To:     Search and Rescue - List <SAR-L@islandnet.com>
    CC:     BAMRU <bamru@hpasdd.mayfield.hp.com>


I have noticed postings here and on another list related to the "French
Prusik".  I have some background on this hitch. I first learned about it
from a gentleman from Wales who came to a NASAR conference a number of
years ago and called it a "dog-n-tails". I began using it specifically
as a haul line connection as it seemed to be similar in behavior to a
Prusik hitch and was steeped in tradition, dating back to the Battle of
Trafalgar, a British naval victory in 1805.

The rope size was not critical. but I used a 2 m. piece of 8 mm. Mammut
that allowed it, when doubled, to be laced tightly around the 11 mm.
main line with fourteen crosses, also by tradition. I whipped the free
ends together with a short piece of cord. An immediate disadvantage was
the length of the contact area with the main line. Its use was popular
with everyone who saw it work.

During an informal testing sequence another disadvantage became apparent
in the haul line application. With a slow pull by a haul team the hitch
did not slip when the dynamometer indicated 16.45 kN (3,700 lb.) which
was the maximum force the haul team could apply. In this experience the
first four crosses were pulled out, the last four crosses were still
loose, and the middle six crosses were glazed into the sheath of the
main line.

For the application as a contact for a haul system it would be a safer
practice to use a connection that will slip at a known point. A three
wrap Prusik is better for this application, as it will usually start
to slip when a force of about 7 kN is applied. If it does slip, it is
a warning to determine why, before damage is done to the litter or the
patient. This hitch is an excellent choice, however, for use whenever
a loop must be created along a main-line somewhere. An in-line
figure-eight or a butterfly knot will weaken the main-line but this
hitch will not.

This hitch is referenced in pre-WW II U.S. Navy seaman's manuals as a
"rat tail hitch" and is well known and used in the oil fields of the
western United States. In discussions with mountain rescue personnel in
both Scotland and the Free State of Ireland this past summer they
indicated that this hitch is frequ\ently used for mid-line connections.

Knowledge of the "rat tail hitch" makes it an excellent tool for self
rescue applications as it can be made from a piece of rope cut from the
end of the main line. It would be inappropriate to refer to the "rat
tail hitch" as a "French Prusik" since its traditional origin involved
a defeat for the French navy in 1805.

   Kenneth N. Laidlaw


Subject:    Re: the "French Prusik"
  Date:     Sat, 26 Oct 1996 13:07:30 +0100 (BST)
  From:     Gerry Butler <gbutler@tcd.ie>
    To:     sar-l@islandnet.com


In the Dublin Wicklow MR Team we use the hitch described for tensioning
cableways (high-lines) and for some hauling. However, the number of
crosses can vary above a minimum of eight. The lower number will have a
lower slip tension and will not cause the problem discussed in the
original posting.

The hitch is called "dogging the rope" here.

The "French Prussik" is a different hitch. A normal prussik loop,
extended into a long flat loop, is wrapped like a coil of paired rope
around the rope to which the hitch is to be applied. Both ends of the
loop are brought together and a karabiner clipped through to which any
connection is made. This is a useful rapidly applied hitch, which is
easier to release under load than the normal prussik.

In our team we use the french prussik on an abseil(rappel) rope below
the descender and clipped to the harness leg loop. Holding a hand just
above the french prussik allows a normal abseil descent but releasing it
allows the person to hang on the abseil rope with free hands. The weight
is bourne on the descender, not the prussik so the holding power of the
prussik needs only be sufficient to stop the rope from slipping through
the descender. About three turns is usually enough, so use a short
prussik loop to start with.

Gerry

PS, the name of the country is the Republic of Ireland, not the Free
State of Ireland.

Dr Gerry Butler (gbutler@tcd.ie)
TELTEC Radio Propagation Group
Electronics Dept, Trinity College Dublin, Ireland
Dublin+Wicklow Mountain Rescue, EMT-D, EI0CH

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