[TowerTalk] Need help with tower info

[Jeff DePolo]

> General TIA wind
> ratings for the county are 80mph, with "special areas" - and 
> of course I am
> in one of those special areas which has ratings of 110mph.

Which TIA-222 standard are you required to adhere to by your AHJ?

> Right off the bat I excluded putting up a Rohn 25G, opting 
> instead for a 45G
> - but then a buddy of mine said that he would go for a 55g.

A 45GSR (solid-rod) will provide appreciably more capacity (38.3 sq ft, 110
MPH rev G) than a 55G hollow-leg.

> I intend on putting up a big M2 or Mosley multi-bander (15sqft) and a 40
meter three element (20 sqft).

Both at the top?

> Are the specs WAY too conservative or should I put up a really HUGE tower
to accommodate what I want to do?

When you get up to 110 or 130 MPH wind ratings, the max loading for the
"catalog" designs drops a LOT as you found out...

My advice would be to have Rohn do the design.  Don't get hung up on the
catalog designs.  They can/will engineer the tower design for your loads,
including varying the diameter/tension/height/radii of the guys, adding
additional structural members and/or customizing sections that would
otherwise be over-stressed, provide recommendations on load placement (you
will likely be better off with one antenna a little down from the top on a
ring rotor), etc..  For a fairly straightforward design with only a few
loads like you are describing, the design may cost $1500 as a guess; money
well spent in my opinion.  Depending on the total cost of the order, the
design fees may be applied toward the purchase price.  You'll end up with
stamped drawings, foundation/anchor design (may or may not require a geotech
study), detailed structural analysis, etc. which you may need anyway for
permits.  You'll sleep well at night, and should anything ever happen (God
forbid), the liklihood of any challenge by your insurance carrier will be
greatly minimized.

					--- Jeff WN3A


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