Re: [TowerTalk] tower base concrete or not

["Tower (K8RI)" <tower@rogerhalstead.com>]

It depends on where you live, the climate, the soil, and maybe local 
regulations.


> I am installing a 40 foot tower. It will not be self supporting. It will
> be bracketed to the roof/wall, and I will use guy wires. The tower is in

How high to the bracket?  If the house is sturdy and the bracket close to 20 
feet off the ground the end of the house will be taking most of the load and 
to me that would be a good reason for guying.

> 10 foot sections, and is about 50 pounds per section. It looks similar to
> TV type tower; but, it is more reinforced with cross-braces, and is
> heavier.
>
> I have dug a 3 foot by 3 foot by 6 foot hole. The hole has been there for

That's 2 yards of concrete to fill that hole and we bring the concrete at 
least 2 inches above the surface as well as crowning it.

> about a month, and shows little sign of collapse. The soil seems firm and
> compacts well.

That is the size I'm using for my 100 foot 45G.  Come to think of it, it's 
larger than my base which is only 5' deep. Then again I used a round hole, 
3' in diameter, by 5' deep.

> I was wondering the following, after having read many of the posts on
> installing towers, and visiting some web sites.
>
> Do I need to use concrete? Can I just drop 4 to 5 feet of the bottom
> section of the tower in the hole and back-fill with gravel. I am asking

There are two camps on this.
In the central Michigan area, I'd guess most of the towers of 50 feet or 
less with nothing larger than a small tri-bander are guyed with dirt bases. 
(Probably 80% at least within a 40 mile radius of me).  Although I'd not 
recomend them to some one else, I've used dirt bases for short towers for 
years.  I'd certainly not hesitate to use on on a temporary 40 footer that 
was bracketed to the house.  Again I want to emphasize "In this area".

I gave away a "dirt base" that had been used at three different locations 
and had spent over 30 years in the ground.  It did not have any rust.  OTOH 
I have seen them that had only been in a few years that were no longer 
structuraly sound.

Even a "dirt base" needs proper drainage and all that I've seen had large 
flat plates on each side to give a large purchase on the soil.

I really wouldn't want to use a tower section as a dirt base.  I'd use one 
in concrete though as long as it was properly drained..

OTOH a tower section set in concrete without proper drainage is also asking 
for trouble.

> because I have seen many TV type towers (some over 30 feet high) installed
> with a roof or wall bracket, and the bottom section buried only about 18
> to 24 inches down in the ground. Some of these towers are holding a 12
> foot steel mast, and a yagi...some are holding a couple yagis and rotors.
> I have climbed many of them, until I realized how flimsy the installation
> was. Never the less, some of them have been up for almost 50 years.

The ones I had up were rock solid, but again if the installation is going to 
be in for the long haul I'd put crushed rock in the bottome of the hole, set 
the base in plumb and fill with concrete.
You have quite a bit of over kill with that big hole.

The concrete only does three things at the base of the tower.  It keeps it 
from sinking, It adds area to keep the base from shifting, or moving, and it 
protects the tower base (if properly done). It doesn't take a lot.  (It does 
not prevent the tower from tipping over<G>. To do that takes a pretty good 
chunk of concrete and a very strong tower.)

I have about a yard and a half at the tower base with over two yards holding 
each guy anchor.

> I think that there was a previous thread wondering about the amount of
> concrete that is required?

For a small tower, about 6 to 8 inches beyond the outside circumference of 
the tower, but again it depends on the soil.  The ROHN book shows the CB-1 
base which is 2' X 2' X 3' = 12 cubic feet, or a tad less than half a yard 
of concrete.  OTOH that is the smallest base they show and they use it on 
towers through 130 feet tall.  They also make a dirt base for the 25G 
(HGB25G), but again, I'd only want to use it on a short tower that was 
sturdily bracketed and/or well guyed.

Properly done there is nothing wrong with a dirt base when used under the 
proper conditions. If there was, ROHN would not have been making dirt bases 
for the 25G.
>
But again, I would not recommend one to some one else.
That would have to be their choice.
> r.
Remember there is nothing wrong with having more on the base that your need, 
but when the wind blows and the ice storms come (up here) you want a solid 
tower.  Then again, up here, that time of year the ground is one great big 
concrete block. <:-))


Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
> any questions and ask for Sherman, W2FLA.
>
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See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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