[TowerTalk] tower base concrete or not

[Bill Coleman]

On Sep 7, 2004, at 7:29 PM, roy.thistle at utoronto.ca wrote:

> 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.

Depending on where you place the brackets, and how much you have on the 
tower, you may or may not need to have the guy wires.

>  The tower is in
> 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.

Rohn 25?

> I have dug a 3 foot by 3 foot by 6 foot hole. The hole has been there 
> for
> about a month, and shows little sign of collapse.

If this is Rohn 25, that's a HUGE hole.

> 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.

Use concrete. Put about six inches of gravel in the bottom and stick 
the tower legs into it. This will allow any condensation to drain out 
of the tower legs in the bottom of the gravel.

You need to use concrete.

> I am asking
> 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.

They've been lucky. You want to do better than depend on luck.

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

3x3x6 is a lot of concrete - 2 yards. I suggest you get a concrete 
truck out there to pour it.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901