Topbanders
Milan, OK1FM gave the very informative Lanex tables for comparison of Rope
materials.
One important thing was not however expressed clearly (did not find) in
those tables. That is the form of stress/strain curve. Ideal is Steel as its
Stretch at breaking point is very low.
Plastic Ropes in general are bad as they start stretching at very low stress
and at breaking strength point it might be 20%.
That is the reason why towers fall or bend in high wind.
Breaking strength of plastic rope must be oversized to limit the elongation
of rope at 'working strength' of guy wire.
Good material of 'standard' ropes is Polyester. Low elongation was also
mentioned in Lanex proshyre.
Bad is of course its high price.
Polyester rope firstly stretches in use but is quite stable after a couple
refixing rouds.
UV-stability is also very important if the antenna is build to stand for
years. Materials for professional fishing are good or should be good at
least.
I have used polyester in my 160 and 80m four square constructions and there
is nothing to complain after about 5 years.
73
Ilmo, OH2BO
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