[TowerTalk] Yagi torque balance

[Don]

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 at 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 at oakcom.org>
>> An: "towertalk" <towertalk at 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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