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[TowerTalk] HF beam against the wind.

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Subject: [TowerTalk] HF beam against the wind.
From: (Roger L. Elowitz)
Date: Sun, 09 Nov 1997 22:42:15 -0500
Hi Charles... and the TowerTalk gang,

Thanks for your thoughtful comments. I guess the fact of the matter
is... that I simply don't have enough real understanding of all the
parameters operating here. 

The fact that a beam "naturally" seeks the wind by turning the
directors in that direction [upwind] somehow doesn't convince me that

A windmill that doesn't turn itself into the wind... doesn't work! It's
designed to do exactly that..turn into the wind.  Only in that
direction will the wind exert the forces necessary to spin the blades

A beam is generally not intentionally designed (I don't think) to turn
into the wind. If it does.... it's because it just so happens to
balance the turning forces that way. That's not exactly the same thing
as taking the position of the least total stress [wind load] which, in
my humble estimation, is a worthwhile goal. Directors broadside to the
on-rushing wind may then end up as being the position of least stress
on the rotor brake... but what about the wind load on the tower as a

Or, as Matt Trott--K7BG points out, vibration problems due to elements
facing the wind are easily corrected by changing the beam's direction
perpendicular to the wind and letting the boom take the blow. That
seems a worthwhile thing to do.

Naturally this begs the question... do beams have more than one wind
load specification?  Most of the time I believe we only see one
spec.... which I'll go out on a limb and ASSUME is the one measured
when the elements are broadside to the wind.  But, if you park the beam
perpendicular to the wind.... is not the wind load REDUCED because so
much less tubing surface is being impinged upon by the on-rushing air?

Now it has been pointed out that in many instances this orientation
places greater stress on the boom... and this may very well be so...
but.... the question being begged here is whether the wind load of the
total beam is less and therefore the load on the tower lessened?  

So, in contention here are two simple wind loading numbers and it
should be possible to calculate the results of each and reach a valid
conclusion as to which way the manufacturer recommends it being parked
for each and every beam. [Why do I have a nagging suspicion that
manufacturers would rather avoid this discussion entirely? Liability

Possibly you could be right that the longer boom, asymmetrical element
type of beams should be left or rather 'parked' to seek the prevailing
wind... but I would really like to see the numbers.  This is a question
PHYSICS CAN ANSWER... but like so many things about this wonderful
hobby... the answer will always get bogged down in "testimonial"
experience ...that only clouds the issue.

Can anyone address this issue with number specifics rather than...
"this is what I do... or didn't do and look what happened."  Please,
please.. don't get me wrong.  I AM NOT DISCOUNTING PERSONAL EXPERIENCE!
 It is usually valid and reasonable.  I'm just looking for some
numerical justification to all that wonderful experience.  Thanks.

[And YES! I am capable of some good thoughts (I hope) without stupid
jokes....which I dearly love too!]

Roger, K2JAS
Morganville, NJ
It's in most any Atlas... look it up.
Not a bad place to live... when I'm out of town!
It would be a much nicer place... without my neighbors.

At 02:19 AM 11/10/97 +0000, you wrote:
>Glad to talk to you.  My opinion is based on locking the HyGain rotor
>controll with the brake off and then watching the beam in the wind.
And I
>had a TA-33 during one of these tests som years ago.  If a windmill turns
>into the wind due to least resistance going that way, why not a beam.
>beams always turn themselves director first, with the director pointing
>right into the wind.  If something is wrong with this analogy, then the
>whole thing is into doubt.  If analogy is ok, then point into the wind as
>I do.  de K4VUD
Roger, K2JAS
Morganville, NJ
Just about half-way between NYC and Philly!

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