Good morning.
Using a structural model has an advantage of being able to look at the
element and boom wind loads, plus the wind load and mast torque in 10 degree
increments. Most antennas have more element wind surface area than the boom.
Some have multiple times the boom wind surface. The maximum wind surface
area is usually between 25 and 50 degrees away from the boom center line.
The boom, of course, does not flex like the elements. Element flex will
unload much of the force. The advantage of pointing the boom into the wind
is that the elements are symmetrical to the boom. This makes the force
equal (assuming the wind is the same on both halves of the elements) and
theoretically no toqrue to the mast/rotator/tower. The typical boom has some
offset to the mast, so it will impart torque on the mast/rotator/tower. This
offset will make the antenna hunt into the wind. A fin can be effectively
placed on the boom to equalize the wind load. Have used them for about 12
years and they are amazing. I use clear polycarbonate sheet.
Have a good day and 73,
Tom, N6BT
Force 12 Antennas and Systems
(Home Page http://www.QTH.com/force12 )
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
|