[TowerTalk] RE: Am I about to screw up?

[K7LXC at aol.com]

In a message dated 8/18/03 8:18:50 PM Pacific Daylight Time, 
k4mir at comcast.net writes:

> I thought that I had a current Rohn catalog, but it turns out to be
>  around 1997 vintage.  Great.

    Actually the drawings haven't changed in years (decades in most cases!) 
so a 1997 version is current.
>   
>  I am in the process of installing a Rohn 25G bracketed tower of about 60
>  feet.  It will be bracketed against my house at around 23 and again at
>  43 feet (yes, I have a tall house).
>   
>  However, the base section concerns me.  I purchased a short base section
>  (SB25G) which is 3'4" and was going to use this as my base section.  Is
>  this a problem?  I didn't have a drawing for it, so I used drawing
>  number A871298r1 and modified it for the short section instead of the
>  five foot section.    That means instead of the hole being 4 feet deep,
>  it is 36 inches deep, including the 6 inches of gravel for the drainage.
>  The soil is solid georgia clay.  
>   
>  I was all set to pour concrete today...have the tower plumbed (I think)
>  and leveled and decided I'd better check with someone who knows.  Has
>  anyone used this setup before?
>   
    The aforementioned drawing is for a drilled pier but reflects the other 
configurations; i.e. 4-foot deep hole.

    Is a 3-foot hole a problem? No. The purpose of the base of a guyed or 
housebracketed tower is to keep the tower from sinking in the ground. With your 
relatively small tower and subsequent relatively small tower/wind forces, it's 
not going to exert enough downward compression force on the base to worry 
about. 

    The tower specs fall into the "one-size-fits-all" plus a good-sized 
safety fudge factor. In other words they use the same base spec for towers up to 
190' so you can see the spec is pretty much overkill for a 60-footer. 

    Also it's interesting that they specify a 4-foot hole and the short base 
is only 3' long - hi.

    GL on your new installation.  

Cheers,
Steve    K7LXC
TOWER TECH -
Professional tower services for commercial and amateur