Seems to me that the gist of all this is that those of us who live in
Florida or
on the Gulf coast can't have an antenna larger than a rubber duckie on
top
of any reasonably tall tower. I see all these ads for towers with X
number
of square feet of antenna at 50 mph! What a joke. My unguyed, house
bracketed, 40 foot Rohn 25 has been up for the last 20+ years. I don't
have a permit, (A bad idea, I agree) and it's made it through Andrew and
a
couple of lesser hurricanes. When I looked at the Rohn catalogue when I
bought the tower, I realized that getting it approved would be
impossible, so
I didn't try. What's a feller to do?? I sympathize with anyone trying
to put up
any kind of stick here or wherever the county wind figure is 110 or
higher.
Gil
W4PJI
On Mon, 15 Jan 2001 14:31:14 EST K7LXC@aol.com writes:
> In a message dated 1/15/01 10:02:26 AM Pacific Standard Time,
> aa4lr@arrl.net
> writes:
>
> > Do you want to do it "right" or "good enough"? Your source is
> correct
> > that Rohn tower sections are actually stronger than their
> published
> > figures. The design rules are likely to be 200-300% over the
> rated loads.
>
> I don't think that's right. The figures I've seen are 30-50%.
> The problem
> is that wind pressures do not go up linearly - the pressures go up
> geometrically. You run out of engineering overhead real quick if
> your tower
> takes a gust higher than your design windspeed. For instance, a wind
> 71 MPH
> exerts windpressure of 20 PSF; a gust at 87 MPH has a force of 30
> PSF - a 50%
> increase for a 16 MPH increase in windspeed.
>
> The LXC Prime Directive still applies - DO what the manufacturer
> says.
>
> Cheers, Steve K7LXC
> Tower Tech
>
> --
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>
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