> My company based in New Zealand is looking at designing a guyed tower for
> New Zealand conditions and using Dyneema ropes, with are made from
> "superstrong" polyethylene fibers. I'm interested in hearing from
> anyone who
> has used this material for guys. Also I'm particularly interested
Antenna guying is what is known as "corner case" in terms of application:
1. Because of wind loading, you need high strength vs diameter.
All the "miracle" ropes I've seen are only high strength per weight.
I see that Dyneema is the same diameter as steel for the same strength.
Thus the only important parameter defaults to cost per strength (see #3
below)
2. UV exposure is worse than perhaps any other use. I see that Dyneema
loses 1/3 of its strength in 2 years. Not clear what happens after that.
3. Cost is of the essence. We already have Phillystran. It seems to
be perfectly acceptable in nearly all respects. I can't imagine
using any substitute unless there was a substantial cost saving. Actually,
there's nothing wrong with steel in antenna applications where you
don't need nonconductive guys, and it's even cheaper.
4. A rope that didn't stretch much might be worth spending extra bucks
on. I couldn't find anything definitive about that on the web, except
weasel words about the fibers changing alignment with age.
For cost saving, there needs to be a high volume user of suitable rope
(not just the Dyneema fiber) to get the manufacturing cost down, and
there needs to be direct availability without going through middlemen
such as Yacht supplies dealers who are used to dealing with the moneybags
set. Dyneema seems to be too new to qualify.
Rick N6RK
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