On Fri, 27 Aug 2010 08:54:39 -0700 (PDT), Tim Shoppa
wrote:

I've had a really nice 130-foot doublet fed by ladder line hanging
between two trees for the past three years.

It's hung using 3/16" black UV-resistant polyester rope in the trees,
and has a pulley and a 15-pound counterweight (plastic jug of sand)
for tensioning at one end.

It's held up remarkably well over those three years, but I had noticed
that the rope while still fundamentally flexible was kinda
"hardening".

Where it went through the tree branches there was remarkably little
wear over the three years. There was some black fluff where some
chafing had occured but it still was holding up nicely.

But I went ahead and replaced all the rope anyway. With the tennis
ball cannon I actually got the new rope hung a little bit higher than
the old rope.

Just by touch, the new rope feels flexible and supple, and I contrast
that with the old rope that isn't exactly "brittle" but does not feel
nearly as flexible. The new rope felt kinda like a towel just having
been washed and dried; the old rope felt kinda like a towel that had
been used to mop the garage floor and then left lying there to dry.
Maybe the feel was just grime and dirt that the rope had absorbed over
the years?

I fixed a couple of broken ladder line insulators, and inspected the
plastic end insulators too. The UV-rated polycarbonate that I had used
for the insulators seemed to be holding up fine, although it was no
longer crystal clear and had a good amount of grime and haze on it.
Certainly didn't feel "brittle" yet.

I did replace the plastic jug of sand that's used as the
counterweight. I had painted the jug brown and green to kinda blend in
with the trees but even despite the paint layer I was a little worried
about the plastic deteriorating there. On a previous antenna I had
used a 1 gallon plastic milk container to hold the sand and that
didn't even last a year before decaying. I'm using some darkroom
container jugs now, with some extra reinforcement rope through the
handle on the interior, and they seem to hold up OK.

Is three years a typical "good repair" replacement interval for ropes
in trees? I think it probably could've stayed up another 10 to tell
you the truth.

Re-hanging the antenna back up after replacing the rope felt so good.
It is beautiful to see it stretching from treetop to treetop one
hundred feet up.

Tim N3QE


Try this.

When you replace the rope, put up an extra length of rope with nothing
attached to it. I have a rope over the limbs to two trees; trees are
about 160 feet apart, which accommodates a 135-foot doublet fed with
open-wire line.

I installed, over each tree limb, next to the ropes that hold the
antenna, another rope that is simply a long loop -- goes from the
ground to the limb, over the limb, and back down to the ground.
There's no strain on this rope -- actually, two ropes, one over each
limb where the antenna is supported. That way, if the rope holding
the antenna breaks, I already have a spare rope installed -- just use
it to haul up a new antenna support rope -- no need to haul out the
slingshot.