Hi Tom,
The 15.2 sq ft at 70 MPH specified by Rohn is in addition to:
- 8 square feet for three side arms (General Note 4), and
- the wind load of 2 coaxial feedlines on each face (General note 5)
You probably won't use side arms, and if you attach your feedlines to the legs
that windload is significantly reduced too.
Your 80-90 MPH wind zone is an entirely different issue...
73
Frank
W3LPL
---- Original message ----
>Date: Mon, 14 Sep 2009 07:49:36 -0400
>From: "Tommy" <aldermant@windstream.net>
>Subject: [TowerTalk] 45G Wind Load
>To: <towertalk@contesting.com>
>
>According to my Rohn manual, if I understand the drawings correct, the
>maximum wind load for a 70' 45G tower is 15.2 sq.ft. Can someone please
>confirm for me that this is correct? The reason I'm concerned (this will be
>my first tower) is I see pictures of contest stations with five or six
>pretty big yagi's on Rohn 45G towers which I think must really be exceeding
>the wind load spec.? I am planning on (following the Rohn recommendations
>for tower installation) installing two OptiBeam yagi's, the 40m 2-el and the
>tribander 16-el, which have a combined wind load of 19.4 sq.ft.
>
>
>
>I live in the south part of Georgia where the A58.1-1982 ANS shows my area
>between the 80 and 90 MPH wind speed zones.
>
>
>
>Understanding (somewhat) the 'safety factor' included in engineering tower
>design, am I putting my tower/yagi system at great risk with a wind load
>that is 4.2 sq.ft. over recommended specs.?
>
>
>
>Thanks for any comments.
>
>
>
>Tom - W4BQF
>
>
>
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|