[TowerTalk] Yagi torque balance

[jimlux]

On 9/3/19 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
> 



an excellent article..

Although, the reference to drag coefficients from that Eiffel guy... 
Yeah he designed built freestanding towers and kit churches, but his 
aerodynamic work was done *after* he built the tower. In fact, he used 
the tower to drop stuff from to measure the drag properties.