[TowerTalk] windload - how much is too much?

[K7LXC]

In a message dated 98-03-06 12:18:03 EST, brunet@us.ibm.com writes:

> How do you determine how much windload is acceptable for a tower, e.g. a 65'
>  Rohn 45 guyed at 25', 45' and 65'?  

    You mean besides having a copy of the Rohn book? Well, none actually.
TOWER TECH has them for five bucks. It's one of the most valuable things you
can have for planning tower systems.

      First things first. Williamson County is a 70 MPH wind zone which is the
lowest value they give. You need to use that as the minimum wind force when
planning and building your system.

>Some example configurations being
>  considered with various windloads are
>      F12 C3+EF240230 -- 14.8
>      F12 5BA+EF240230 -- 17.4
>      TH11+EF240230 -- 18.9
>  Are any of these getting too high?  We can get some very strong bursts here
> in
>  Austin when fronts come through.

     Sixty feet of 45G @ 70 MPH will handle 24.7 square feet of antenna load. 
>  
>  Another consideration is putting the higher freq antennas at 65' and the
30/
> 40
>  up around 100'.  Does this change the analysis?

     No. The antenna load can be distributed anywhere on the tower. Ordinarily
it shows up as head-load (on the top of the tower).

     Get the Rohn catalog, hang out on TowerTalk for awhile, look through the
TowerTalk archives (http://www.contesting.com/_towertalk/), get a TOWER TECH
catalog that has some good reprints that are available and start doing your
homework. We all had to start somewhere. The good news is that TowerTalk and
other resources are available nowadays. 

73 and GL,  Steve  K7LXC     

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