[TowerTalk] Adding guys to self supporting towers

[Steve Dyer]

For the simple case, what about the added downward force on the lift 
cable(s)?
73,
Steve
W1SRD
> The topic of adding guys to self supporting towers has been
> discussed a number of times on this reflector, but I am
> still not clear on exactly why it supposedly won't work.
> If I have figured crrectly, the worse case compressive load
> on a leg at the bottom of a trianguler tower
> is equal to the product of the horizontal windloading
> at the top times the factor h/[w*sqrt(3)] where h is
> the height and w is the width of a face.
> For example, a 100 ft windload at the top of a 50 foot
> tower with 18 inch face will induce 1925 lbs of
> compressive force.  If a the tower is guyed at the top
> with the guys at 45 degree angles, the compressive
> force is simply equal to the horizontal wind load, or 100 lbs.
> Much less than the unguyed 1925 lbs.
>
> It seems to me the guyed tower is much stronger and could
> handle a considerably larger wind load based on this
> simple analysis.
>
> The only way I can see that this wouldn't work is if a
> larger antenna resulted in torque loads that the tower
> couldn't handle.  For example, the HDBX series, well known
> for its poor torque strength, would be a poor candidate
> for guying.  OTOH, a light weight tower with a large
> face width might be able to take a lot of torque.  To
> facilitate this, you might want to build the tower with
> less taper than it typically has in the self supporting
> configuration, or maybe no taper.   All of this depends
> on wind area and boom length.
>
> Comments?
>