[Towertalk] crankup v. fixed

[jljarvis]

Chaque un a son gout.  But it seems neither side in this
debate is listening to the other.  Hopefully this sheds
more light than heat.  

A properly guyed tower will withstand hurricane force
winds.  There are many, many broadcast towers which fit 
this description. W1CW has such a structure in Florida;
dual-guyed anti-torque provisions.  His son did a paper 
on it at Dayton, a few years ago. It exceeds most amateur 
installations for robustness.  He also has fall room, 
in the event that the system fails. 

A properly maintained crankup tower...particularly where you
don't have 100% setback...is a perfectly viable alternative,
even in hurricane force winds.  Without a doubt, being able
to lower the structure reduces the potential for lightning
strikes, provides added robustness, and makes it easier to
work on.  Properly maintained is the key.  Cables, sheaves
and axle bolts need routine inspection.  And lube.  

>From first-hand experience, crankups are best USED, rather
than left in one position.  This provides the opportunity to
inspect and lube things, as the structure goes up or down.  

There is one major safety issue:  DO NOT EVER, EVER, PLACE
HANDS OR FEET INSIDE THE TOWER STRUCTURE UNLESS IT IS FULLY
BLOCKED WITH STEEL STOPS.  I have seen wood 2x3's sheared by 
falling tower sections.  I have seen the damage caused by a minor
shift of a winch, pinching a hand in the structure. (Not mine,
and it wouldn't have happened, had I been there.  But it
happened to a close friend.)  

Crankups are costly, for high structures.  As a result, 
most of these will top out in the 60-70  foot vicinity.
Fine for casual use on 20 and above...inadequate if you
want big iron, up high.

There was a comment relating the strength of a tower to
the strength of the frame in a double-wide.  The tower is
many times stronger.  Windload is a lot less, too, even
for tubular towers.  

As for Hurricane Andrew; I've been on sailboats with 100 kts
across the deck, and wished I were anywhere but!  There 
are still questions about the maximum sustained winds in that 
storm, because the anemometers came apart. Few antennas would 
survive 175mph winds.  Hurricanes are usually small enough
storms and slow enough that you can outrun 'em.  Design the
antennas for the 100mph the code reqires.  Count on losing
'em in a big one.  Watch from a distance.

n2ea