One of the things to remember about FD is it is a *temporary* operation
so we don't use the kinds of installations we'd use for something
permanent, BUT we still can't sacrifice safety. However to me that is
not installing for 100 MPH survival or even 70. I consider any one who
stays out there in the tents when the wind gets much over 40 to be nuts
any way. <:-))
I may be going against some of the conventional wisdom, but I do have a
lot of experience with this type of tower arrangement.
My only comment with Nylon rope is don't use it for guying in situations
like this or for the only guys. (I've used it to guy an AV640 on top of
a 40' tower" but that is quite different than guying the tower) Braided
Poly rope which is actually cheaper in some instances is stronger, or
can be stronger. 3/16" is about 600# test. 5/16" is 800# and 3/8" is
about a 1000# and has very little stretch. My personal preference would
be galvanized wire rope, or the 3/16" Phillystran. Just remember that
wire rope varies widely in strength and quality. A 40' tower with a
TA-33 doesn't present a large wind load (over turning moment) even with
40 - 50 MPH winds at least when all else is taken into consideration.
As to Manila rope, the only rope of this kind I'd ever use would be new
and of at least 3/8" or preferably 1/2". As has been mentioned, it ages
and can deteriorate rapidly. I've used large Manila rope in farming
operations and have had several close calls. I always treat it as if it
is going to break. Taking that approach I've never been hurt using it.
OTOH I've seen large Manila ropes break under less load than they were
normally subject. They can make a great slingshot!
The tower base: normally serves to keep the tower from sinking in the
ground or as an anchor point that won't slide out from under it and
*normally* adds little to the over turning strength presented to the
tower by the guys. Again with small loads (short towers and small
antennas) this usually isn't much of a problem. 25G is not considered
self supporting and certainly not 40' of it so the purpose of the base
is again to just hold the tower in place. The flat, hinged baseplate
(BPH25G) certainly needs something to hold it in place. For temporary
setups my choice would be either the drive in base (SDB25G) or the
drive in rods (DR25G), but you do have to remain conscious of what's
under the surface and athletic fields may have all kinds of things "down
As to the guy anchors, I've used standard, drive in fence posts although
they should have additional flat plates welded on the part going into
the dirt and be driven in deeper than normal. The guy lines should
attach at ground level with the post driven in perpendicular to the guy
line. Note, if some one does use fence posts like this they can be
*dangerous* objects you can walk into and get hurt seriously. I had a
couple in the yard temporarily. They had foam rubber wrapped around the
tops to about 2" thickness and that was wrapped with bright Yellow tape
At FD we've used the standard "screw anchor" just like they use for
tying down airplanes. They are 18 to 24" long and look like a cork screw
with a triangular handle. These are strong enough to hold a tower like
you describe *IF* the soil is strong enough. Here the soils is at least
as important as the anchor. I've used 3' pieces of 3/4" pipe to screw
them in and a 4' piece to get them out, but this was in clay. In sand or
light soil they'd be next to useless. NOTE like many other things the
quality and strength of these screw anchors varies widely and is
probably proportional to the price.
Another important point about the soil is what happens when it gets wet?
Good old fashioned clay only gets gooey at the surface while clay or
sand loam may turn to goo with very little strength far enough down to
affect the integrity of the anchor.
Sooo... For me, I'd make up a set of drive in rods for the tower base
along with a template to keep them aligned and they are a bear to align.
I'd also make up a set of drive rods with flat plates for guy anchors
along with a tool to go over the end so they can be driven without
damage. Depending on the soil 2 to 2 1/2' penetration would be plenty.
In some cases you'd need 4'. I'd also make up either pre cut wire rope
or Phillystran guys with turn buckles. I'd not worry about the steel
ends we normally use for permanent installations, but don't build a camp
fire next to one. Phyllistran is expensive, but the 3/16" is 1200#
test, it's light, and easy to handle. OTOH you do have to use cable
clamps on it and can easily damage the cable with improper installation.
To me, Tower height, plus 50% is normally sufficient safe distance, but
it depends on what you put on the tower. Let common sense be your guide.
Roger (K8RI - ARRL Life Member)
N833R (World's oldest Debonair)
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