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[TowerTalk] HF beam against the wind.

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Subject: [TowerTalk] HF beam against the wind.
From: (Jerry K. Liley)
Date: Thu, 13 Nov 1997 12:15:59 -0600
One more stab at this subject.......

Since the beginning of this discussion,  it seems to me,   there should
been a separation between PROTECTING your tower / mast  from stress,
 OR  protecting your beam from stress.

If it is your beam that you are trying to protect,  then that needs to be
into;   protecting the ELEMENTS or protecting the BOOM.

If allowing the beam to freewheel in the rotor clamp finds the point at
there is the least resistance,    then that direction would place the
least stress
on the tower.    

 That may not be good for the beam elements.    The elements are the
 weakest part of the beam and will bend with the wind pressure.      I 
have had them take the shape of a swept wing fighter plane.    I have
never had
the boom do that.   (it is possible tho).      Now if you have been
following me
you would think that I am saying to turn the boom ACROSS the path of the
wind.     That is not always the best either.

Let me tell you a story of fact.     I had a full sized three element 40
meter beam
at 100'.    The boom was 48' of 3" x 1/4" wall guyed with two Phillystran
runs to 
each end of the boom  (separated by 45 degrees).    I was not concerned
with the
boom failing.     The elements were 70' long (aprox) and were 1-1/8" at
the tip.
They were vertically guyed from the  boom but NOT  horizontally guyed
from the
side.    In other words I   WAS  concerned with swept-wing failure.    I
that I would turn the boom ACROSS the wind in storm conditions and hope
that the boom would not fail.    This placed the ends of the elements
into the wind.     During a storm the ends of all three elements in the
of the wind were lifted up over the boom and dropped on the other side of

If you are one of the persons wanting to decide which way to park your
beam in
a big blow,   maybe this story above gives you an idea of what could
First:       Decide if you want to protect the tower at the expense of
the beam.  
Second:      If you want to save your beam you must decide if the
elements will become a victim to "SWEPT-WING" syndrome when parked 
ACROSS the wind...
Or if your boom will become swept-wing if you turn   IT   across the
Or if the tips of the elements will be taken up over the boom and broken
if you turn the boom ACROSS the wind.

Personally,  I turn 20 meter beams and smaller,  INTO,  the wind;    30
and larger   ACROSS   the wind.     My element failure probably was
caused by
some UP-DRAFT in the storm that came through here.  (tornadoes are common
in Missouri and some are up in the air and not on the ground)     My
are not  a primary concern to me.    I think they are overkill (Rohn 55).

Good luck with your decision.    Nothing is foolproof.    Mother Nature
tear it down under the right conditions.    Do your best  and take your

73,  Jerry Liley,  K0GUG,   Holts Summit,  MO

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