[TowerTalk] Trees as anchors and guy dynamics

[Bill Putney]

I'm putting up a 50' Rohn 25 tower. The tower is anchored in concrete at the
base (36" dia X 5' deep with rebar) and braced with a house bracket at 10'
above ground.

This tower replaces a 40' crank-up tower (with a house bracket at 10') that the
previous owner of our house had erected. The old tower was "guyed" by one piece
of aluminum clothes line wire and an inverted V made from 12 ga hard drawn
copper. To give this arrangement it's due, it survived on the site with a
tri-band beam (~4 sq' of wind load) for 10 or more years.

Rohn suggests that my new 50' tower have 2 sets of guys made of material with
an ultimate breaking strength of 4000 pounds. The initial guy loading suggested
is 400 pounds. Do I need two sets or can I count the base for guying as the
house bracket? Rohn suggests one set of guys for a 40' tower.

The antenna loads will be roughly the same as the old tower. The site doesn't
lend it self to symmetric guy placement. To get the 120 degree guy spacing and
not end up in the middle of living spaces outside I have one guy at 70%, one at
120% and one at 140% (of the tower height out from the base). Are there any
good tables to give the suggested initial loading for guys set at varying
angles? I suppose it's a matter of doing the vector math to exert equal force
in the horizontal plane for each guy(?).

The guy that is out 70% of the tower height out from the base lands at the edge
of the house. I've installed a forged eye bolt that is well anchored into the
house. The other two guys fall at the base of some ~45' (36" dia.) pine trees.
Does anyone have any experience guying to trees? How do I anchor to the trees
without compromising the survival of the trees? Is it a bad idea to guy to
trees?

- Bill

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