[TowerTalk] Low Cost 20 Foot Mast

[Richard (Rick) Karlquist]

On 10/24/2020 1:59 PM, jimlux wrote:
> On 10/24/20 1:06 PM, Tony wrote:
>> 
> The key on stiffness is diameter - a 4" diameter thin wall tube is 
> enormously stiffer than a 2" diameter solid bar- because it goes as the 
> fourth power of radius.
> 
> Rick N6RK used 4" (?) aluminum irrigation tubing for verticals.  You 
> might be able to find it used ("Rain for Rent", for instance).
> 

Actually, the stiffness is proportional to the difference
between the OD to the 4th power and the ID to the 4th power.
For a constant wall thickness, this means the the
stiffness is proportional to the mean diameter cubed.

Rain for Rent now only carries aluminum tubing at the Fresno
store, AFAIK.  They never carried used tubing that I know of.

Any attachment to the tubing has to be in the form of a
sleeve that wraps around it.  A U-clamp will simply collapse
the tubing.

The verticals I have made out of irrigation tubing have mostly
been guyed.  But I have made some that were only 30 feet high.
But even those, didn't have anything on top.  For EME, you would
need to use a falling derrick to erect it.

I don't know if there is any wiggle room in "I can't anchor
guy wires to the ground", but my experience is that guyed
masts are much easier/cheaper,stronger, etc than self supporting
ones.  Most people underestimate the difficulty of the latter.

Rick N6RK