[TowerTalk] Is A Tower Weaker in Some Directions?

[Patrick Greenlee]

Norm, Bill is right but hasn't dropped the other shoe yet.  Will some 
mechanical engineer type please tell us which direction of lean is strongest 
in a triangular tower with X-braces or the typical zigzag bracing. Do you 
want a flat side toward the wind or the side opposite..  For reference lets 
assume one leg of the tower is toward the north.  Then one leg is at 120 
degrees and the other is 240 degrees.  Which wind direction(s) would be the 
most dangerous for the tower?

One would guess there are three directions of wind that hit the tower at its 
least strength and three where it is the strongest. The question is in the 
above example of a tower what would be the most dangerous wind ,one from the 
north, 120, or 240 degrees or would worst case(s) be 60, 180, or 300 
degrees?

If there is a substantial difference in max wind vs relative bearing of the 
wind then those with rotating triangular towers might want to be guided by 
this as regards where to leave the tower when not in use.  ...and the rest 
of us might wasn???t to consider this with respect to our triangular towers.

Oh woe is me... I have already committed 3 out of 4 towers to their final 
positions with no regard to wind direction.  I have 49 ft of Rohn 25 plus 
mast to erect and have not poured the foundation for the tilt base yet (whew 
just in time.)

Patrick
-----Original Message----- 
From: Bill Aycock
Sent: Sunday, October 05, 2014 11:45 AM
To: Cox, Norman R. ; towertalk at contesting.com
Subject: Re: [TowerTalk] Is A Tower Weaker in Some Directions?

Norm--
Be cautious about your assumptions. The direction of the strongest winds
does not correlate closely with the direction of the storm path. I one did a
study for a Rocket test site, (over 30 years ago) that showed (for that
site) that the strongest sustained wind was almost 90 degrees from the storm
path. The strongest winds are the result of rotation, not path.
You might consult your local Weather office for help.
Bill--W4BSG

-----Original Message----- 
From: Cox, Norman R.
Sent: Saturday, October 04, 2014 4:41 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Is A Tower Weaker in Some Directions?

Dear Group:

    I just joined Tower Talk -- I've read through the last 5 years of
archives and have certainly learned a lot I did not know.  What a resource!
I have a question:

    I have just ordered a US Towers HDX-555 tower. At my QTH, I have the
option of orienting the base plate in any direction I want to.  My question
is:  Are these 3-legged towers weaker (or stronger) in some directions than
others?  (I am not a structural engineer.)  The reason I ask is that most of
the violent storms that hit here usually come from the same direction.  Will
orienting the base plate in a certain direction make it any less vulnerable?

Thanks!
Norm
KE0ZT

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