A lot of different knots have a breaking strength in the 80% region.
The figure 50% is very conservative. I have used the bowline knot
finished with a stopper knot for securing rope around a thimble.
There may be better knots for this application but this works for me.
Doug/VA5DX
A method I've used is to carefully cut the rope with scissors and heat
seal the end with a blow torch. Then the rope is fitted around a
thimble (is this what you mean by a D ring?) and 'whipped' into place.
( I need to be careful here, because some of the subtle differences
between English English and American English can cause confusion)
Whipping consists of wrapping the rope aound the thimble and laying
the open end against the fixed end. Then a smaller cord is used to
wrap tightly around both. Done properly, this is very strong.
A rule of thumb is that a knot has 50% of the strength of the rope,
while a well done splice has about 75 to 80% of the strength of the
rope. My experience is that the most strain appears on the rope during
erection: obviously, the greater the guy tension for any reason, the
greater the compressive force on the mast. So you can get the
situation where the mast buckles before the guys break.
73
Peter G3RZP
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