This bulletin has been compiled in order that both our own
personnel and those of our customers can better understand
exactly what to expect from ropes which have been
spliced, knotted or hitched.
All of the efficiencies listed herein either correspond with or
take precedence over previously published figures.
Efficiency of Splices
Before discussing individual splices it should first be understood
that we have traditionally based our published rope
strengths on tests using an eye splice at both ends. When
tested, the ropes invariably part at the splice.
This may seem conservative, on our part, since a straight,
unspliced line will have greater strength. However, it is hard
to conceive of an actual “in use” application where sufficient
force can be applied to reach the breaking point without
some sort of splice, knot or hitch being utilized. Occasionally,
where small ropes may be tested by securing both
ends with several turns around a post or cleat, break
strengths at slightly higher than eye-spliced results may
sometimes be achieved.
As you will see, in certain cases, obtainable splice efficiencies
may sometimes suggest the desirability of using a
slightly smaller diameter continuous length of line for a larger
diameter which must be long or short spliced.
Instructions for making the various splices are shown in specific
brochures and booklets, which deal with the proper use
The test data were compiled using rope constructed of Nylon,
Dacron, Polypropylene, Manila and P/D combinations.
Percentage of efficiency varies little for ropes of dissimilar
compositions used in the same type of splice.
Three Strand Construction
As previously noted, our published strengths are based upon
tests in which the rope is Eye Spliced at both ends. Therefore
we can, for comparison purposes, consider this splice
to be 100% efficient.
Besides being more closely related to actual field use this
splice is most convenient for test purposes since it offers
the longest method of attachment.
It should be noted that only Eye Splice, either with or without
a thimble should be seized with marline or wrapped with
tape for longer wear. When using a thimble for an Eye Splice
with synthetic fiber rope it is advisable to use an eared
thimble for greater security.
The Short Splice, which is used to join two ends, is essentially
same as the Eye Splice. If the splicer uses the same
number of tucks back in each direction and tapers the splice
in a manner similar to the Eye Splice, the efficiency, of the
Short Splice will be very close to that of the Eye Splice (See
Figure 1). The only disadvantage to the Short Splice is that
it greatly increases the diameter of the rope at that point so
that it may not pass through rings or over sheaves.
You will note in Figure 1, that Long Splices do not afford the
strength of the Short Splice. However the Long Splice causes
a smaller increase in diameter. Properly tucked and well
pounded down the Long Splice will often run satisfactorily
If ordered from our mills, care must be taken in terminology
to avoid confusion with the Long Blind Splice, listed below.
In the Long Splice, strands are not divided, but are tucked
back over and under in both directions.
Long Blind Splice.
Sometimes called the “Transmission Splice”, the Long Blind
Splice sacrifices a great deal of strength in order to preserve
a constant bulge-free diameter.
The mating strands are divided in half and recombined. This
introduces points of seriously reduced strength. The Long
Blind Splice should never be used except where the reduced
strength is acceptable.
|Knot or Hitch Efficiencies|
|Knot or Hitch||Percent of|
over 5/8" dia. ring
over 4" dia. post
|Two Half Hitches|
over 5/8" dia. ring
over 4" dia. post
|Square Knot ||43-47%**|
|Sheet Bend ||48-58%*|
|Fisherman's Knot ||50-58%|
|Carrick Bend ||55-60%|