There is a difference if the antenna is mounted horizontally or vertically. Horizontal has a lesser sq. ft. area than vertical where all the elements are exposed in a vertical plane. Just a thought.
Horizontal exposure for a 3-element beam: ---------------
Vertical exposure for a 3-element beam:
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Sorry for the low res graphics, but I hope it gets the idea across.
Windload specs are not different from horz to vert. Leverage on the supporting mast will differ but that is torque and not wind loading. You are assuming that with the horz antenna that not all of the elements catch the wind as if the leading element was blocking the wind from the other elements.. In the case of a horz antenna all the elements and the boom present the same surface area to the wind as it does if it were vertical. Furthermore if the vert beam is rotated directly into the wind it would present the same profile as a horz antenna also rotated into the wind. Vertical beams do require a stronger support mast but again, that is due to bending forces on the mast which is usually longer for a vert antenna in order to have the elements clear the tower if a tower is used, as well as the longer elements extending upwards. A horz antenna mounted at the same height as the top of the elements of a vert antenna would have similar bending moments on the mast. There is a big difference in a horz yagis wind profile depending which way it is pointed just like a vert yagi. The worst possible way is positioned 45 degrees to the wind. Manufacturers spec windloading in two ways actually. One is surface area expressed as sq. ft. and the other is in ft./lb. at a specified wind speed which is the rotational torque applied to the mast and rotator system.
Here is a cut and past from the Force 12 website that talks about wind load.
WIND LOAD is the worst-case wind resistance for the antenna. Using the latest structural analysis, the wind load is either the total element wind load OR the boom windload, whichever is the larger resistance to the wind. Most beams have more element than boom wind load. The figure specified is the effective area, which is the projected area of the elements or boom, multiplied by 2/3 for a cylindrical surface.
ROTATING RADIUS is the dimension taken from the mast mounting location to the farthest elemen
t tip. This is the maximum clearance needed from the support to the tip. Twice this figure is the total diameter circle that the antenna will cover on one rotation.
MAST TORQUE is calculated at 70 mph (20 pounds per square foot wind pressure). It is the amount of “twist” exerted on the tower and rotator in 70 mph winds in the worst-case wind attack angle. The antenna (or stack of antennas) might still want to align one way or the other to the wind. This is because an antenna will usually have more windload in the element or boom plane. Most antennas have more element wind load. This being the case, the additional of an 80 or 40 meter dipole parallel to the boom will minimally increase the wind load on the tower. The added dipole tends to make the entire installation more neutral in the wind, since the boom (plane) wind load has been increased and is now closer to the element load.
