K5IU's last sentence, last paragraph. Did vigorous discussion follow and
did any of the antenna manufacturers acknowledge (or not) the work and
adopt it (or not) or just continue to use the same old methodology?
Don W7WLL
On 9/3/2019 5:16 PM, Steve Maki wrote:
K6MR was kind enough to send me an article by K5IU that sheds some
light on this issue. It's not intuitive (at least for me), but when
you look at his drawings of the vectors and accept the formulas, you
can see that the boom does NOT go in-line with the wind even in the
case of a one element yagi with the element at one end of the boom.
K5IU shows, in the course of debunking commonly accepted methods of
determining wind area of a yagi, that when you have crossed tubes, the
minimum wind force occurs when NONE of the tubes are either in-line
with or perpendicular with the wind. It doesn't matter how the
elements are distributed. Only the relative areas of the boom vs the
elements. If the areas are the same, than minimum wind force occurs at
45° offset. If one or the other has more area, than it's some other
angle, but always oblique from the wind direction.
By extension (my take from the article) is that if allowed to, the
assembly WILL rotate to the minimum wind force position. It may be
that the torque for a given wind speed is not all that great, but the
torque must be there.
So it still seems to me that the assertion that yagis are
automatically torque balanced just by mounting them at the boom center
is not true.
I hope Dick Weber won't mind if I post a url to his article.
https://app.box.com/s/40l9icahrtlpqoyd0zppp9vdxn5ck1xc
-Steve K8LX
On 9/3/2019 10:59 AM, dj7ww@t-online.de wrote:
No, the wind aerea at the boom side with the element on is much
larger then on the opposite side and turns the boom into the
direction of the wind, always!
73
Peter
-----Original-Nachricht-----
Betreff: Re: [TowerTalk] High VSWR
Datum: 2019-09-03T14:21:19+0200
Von: "Steve Maki" <lists@oakcom.org>
An: "towertalk" <towertalk@contesting.com>
I can't wrap my head around this.
Yes, the element is "torque balanced" at it's own center, but at the
boom center? I think not.
-Steve K8LX
On 09/02/19 12:41 PM, Jim Thomson wrote:
## vane NOT required if boom mounted at center. Counterweight
IS required....at light end.
## Longer eles... and number of eles has nothing to do with
with it. Each ele is symetrical...so the eles are already
tq balanced . If wind hits the eles at an angle...... and
viewed from above... left side of eles bends CW.....
meanwhile right side of ele bends CCW...... they cancel
out...... or vice versa. The eles are still tq balanced.
## I tried this experiment. 40 ft boom..... mounted at
exact center of boom....to mast. Only ONE 20m ELE USED...THE
REF..... mounted of course, at extreme end of boom. no
counterweight used for this test. No coax, no rotor.
Does not rotate, nor ....weathervane, etc. Stays put,
regardless of windspeed, or where boom was oriented by hand.
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