On Sun, 25 Jan 2004 11:33:38 -0500, "Ralph Mowery"
wrote:


Yea, allow about 6 to 10 yards of concrete for starters.
Not sure how big of a hole that would take right off in dimensions.

That's in the ballpark of a small concrete house foundation, isn't it?

That would be 162 cu ft (for 6 yards of concrete) or
10 x 10 x 1.6 ft, or
6 x 6 x 4.5 ft.

For reference, 10 yards is the typical capacity of a cement mixer
truck.

For any project, you need to look at the total cost of installation
and all components, not just the primary component.


I figure I have as much invested in concrete as I do in the tower and
mine is guyed. http://www.rogerhalstead.com/ham_files/tower.htm

As you have shown there are many ways to pour the material . I am sure the
tower maker has their recommendations. I doubt it would do much good to
have it only 1.5 feet deep and 10 feet wide. I would think it would be

Although it's not normally recommended to go that way, the weight is
the stabilizing factor to be considered.

poured in more of a cubic form but deeper than it is wide. Also there is

A cube is normally fine, but still, there are zoning restrictions and
the engineering standards by which to abide. With ROHN they come
right out and give you the specs.

Disclaimer: Do not use my calculations for anything other than an
examples. Refer to the specific pages in the ROHN catalog for actual
requirements.

Going over the catalog they list the base for a free standing ROHN
45-G as requiring 4.1 yards of concrete. That makes the assumption
the builder will strictly adherer to the ROHN Specs and maximum wind
loading. Based on the 45 G specs the concrete base will be 5'3" on a
side, or for a ball park figure that is 27.5 sq ft. A cubic yard is 3
X 3 X 3 or 27 cubic feet. Sooo... we can figure *roughly* with a base
of those dimensions, each foot of depth equals one yard of concrete.
Then the base would be 4 feet deep and 5' 3" square.
BUT the 45 G is limited to only 11.4 sq ft of wind load at 45 feet
when free standing with a 70 MPH wind limitation and no ice.
(certainly they do have a healthy safety factor built into those
calculations.

Using the same calculations for a 65-G results in 8.9 cubic yards of
concrete and *roughly* 65 feet for an 11 sq ft wind load at 70 MPH and
no ice. This tower base is 7' 9" square, or 60 cubic feet for each
foot of depth. That is 2.2 cubic yards. So, 8.0/2.2 surprise 4 feet
deep again.

It turns out, in my guyed installation I also happened to have about 9
yards of concrete. 1.5 yards at the base and the rest evenly divided
between the guy anchors. I used slightly more concrete than required
in the base.

On thing emphasized by ROHN is there will be *no* welding of the
reinforcements/rerod in the concrete. All the reinforcements are free
floating. They have a whole set of specifications on those as well.

all the rebar to install correctly and if it is like some Rohn tower there
is a specification of some rocks and sand at the bottom of the hole.

6 inches of compacted sand and gravel for a drainage bed.

There is also a specification as to the soil in the sides of the hole
and requires soil samples to verify the soil is strong enough to meet
their specs. Otherwise more concrete is required and I don't have the
figures for that.

Towers are not somthing youjust stick up and hope for the best.


At least nothing more than a small TV antenna tower installation.
This is probably the main reason the insurance companies don't want to
see towers bracketed to the end of a house, or to the eves. My
insurance carrier was willing to insure mine as long as there was no
direct connection to the house. (coax doesn't count)

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com