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[Towertalk] Towers in Hurricanes

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Subject: [Towertalk] Towers in Hurricanes
From: (W0UN--John Brosnahan)
Date: Wed, 28 Aug 2002 06:09:54 -0400
>P.S.  W0UN probably remembers the state of shock we were in right
>after this happened since he came over to hold our hands!

I sure do recall the mess.   I just came over to see if Bill needed to
cover the hole in his roof and was surprised at just how big the
chimney was and how it fell anyway.  I could understand it if it
was a tall skinny chimney, but this thing was massive!  I think the
thing that impressed me the most was the fact that none of the
rafters failed at the joints that were held together with the plates with
all of those "fingers" that are pressed into the wood.   The wood itself
failed in many places--but none of the plate connections failed.

N0RR lost his 3L 40M Telrex within a few weeks of installing it--all six
half-elements broke at the same spot--4 or 5 feet out from the boom.
Clearly the weak point.  But he proceeded to design some really stout
beams to withstand the 100-140 mph winds that he got quite often.
It certainly is possible to make towers and antennas for 150 mph winds--
but there is very little market for such expensive antennas.

Many of the commercial antennas that have had reputations of failing--
such as the 4L 40M KLM Yagis actually had other design problems that
caused the most common failures, rather than issues with the strengths
of the aluminum.  I put up a stack of two of the 4L 40s and they never failed
through almost 10 years of winds.  Although my winds in CO were on the
plains and rarely exceeded 70 mph.  They just blew all winter long.  The
weather at my CO QTH was more like Cheyenne, WY than Denver, CO
even though we were closer to Denver.  In the case of the KLMs there
are a couple of simple mods I made that greatly improved their survivability.
If anyone has an interest I can respond off-line with the info.

Many of the ham towers that I have seen that have failed, have done so
because of compromises made at some point in the system, rather than
from structural failure of the tower itself.

Do the engineering and the towers and antennas will survive ALMOST anything.

John   W0UN

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