Gary,
Before erecting my HG52SS, the HyGain parts lady (forgot her name) sent me a
copy (unsigned) of their stress calcs. I recommend this highly for your
HG-54HD! It looks to me that they used varying wind loads depending on the
height, then developed the shear and bending stresses from those, for each
section of tower. The loads used for the HG52SS (ref.: UBC20...I assume a
'Uniform Building Code' spec.) were 15 PSF from zero to 30 ft., 20 PSF from
20 to 50 ft., and 25 over 50 ft. this is for a tower spec'ed for 9 SQ. FT.
at 50 MPH. Your HG-54HD, from their catalog, is for 16 SQ. FT. but at 60
MPH., so I would expect your windloads to be greater.
BTW, the antenna was sized, for these calcs., at only ONE square foot! They
appear to do the basic stress calcs assuming this, then back the allowable
antenna areas out from the calculated margins above the UBC requirements.
(Am I reading this right, stress guys?)
Anyway, Gary, they seem to acknowledge varying wind strengths with height.
Looks like they've already accounted for wind breaks, etc. wihin the Uniform
Building Code. Get the document if you can...but BEWARE...it won't always
reflect a typical amateur application. It will make you (and your building
inspector) feel good about your installation, if installed by the book. And
it will provide lots of good info (19 pages worth) like cable threading,
dimensions of the concrete base weldment (should you ever need to move this
tower, and don't have a spare), and more.
Good Luck! Mine went up as advertised, but I worried like hell over it until
it was vertical! Yes, K7LXC, it's FINALLY UP!
Chuck, N4NM
----- Original Message -----
From: Gary McDuffie, Sr. <mcduffie@scottsbluff.net>
To: <towertalk@contesting.com>
Sent: Sunday, April 11, 1999 11:10 PM
Subject: [TowerTalk] Tower windload with trees blocking
>
> I'm curious about the good or bad effect of uneven wind load on a tower
> and its wind rating. When I read a wind load rating, I assume that the
> manufacturer assumes the load will be applied nearly equally from top to
> bottom. Now, what about reality? What is the effect of protecting the
> bottom 3/4 of the tower with wind breaks, etc? What happens when most
> of the load is applied to "only" the yagi and the top of the (HG-54HD)
> tower?
>
> Gary - AGØN
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