In a message dated 96-12-19 18:17:22 EST, you write:
>I am also trying to study the tower literature for an installation
>next year. I have had a comment that at least one manufacturer
>(is it Tri-ex?) states that their crank-up sections are specially
>strengthened in the area of the overlap.
>In this case the tower is weakened if the owner lowers it half-way
>down, under storm conditions?
The forces on a crankup are obviously at their maximum when the tower
is fully extended. Having the overlap areas beefed up is a good thing to do
since most hams load their towers to the max and leave them extended. When
the tower is lowered, the overall forces are reduced because there is less
surface area exposed and there is less moment of force on it. If you have a
tower with a load that exceeds the wind speed rating, you can lower the
tower an amount (that you have to determine) until you reach a height that is
safe for that wind load and speed.
73, Steve K7LXC
TOWER TECH -- professional tower supplies and services for amateurs
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