Yes, you're right. I hadn't considered guying just the lower section.
You could do that, but it wouldn't add capacity.
I'm a fan of these tubular crankups, except for the fact that their
are relatively low. So long as you don't have to meet a 90mph wind
you can use them for small antennas.
On May 7, 2008, at 10:32 PM, Jim Lux wrote:
> jim Jarvis wrote:
>> Ignoring, for the moment, the prime directive, let's look at
>> what you're doing if you guy a crankup tower.
>> The lateral forces on the tower, which cause it to flex and shed
>> load, are transferred to
>> the guys, and to the vertical structure itself. With a crankup,
>> that means to the hoist cable!
>> The cable is not specified for anything more than lifting the
>> weight of the tube, with some
>> safety margin.
> Except if you just guy the bottom section. I'm assuming that the
> lowest tube has plenty of compression strength. I'm not sure this
> buys you much (I suppose you could get away with a smaller (or
> almost no) base, since it doesn't have to take the overturning
> I've seen this strategy used with things like tower trailers.
> Solves the problem of keeping the whole thing reasonably upright,
> without adding load to the hoist cable.
> Jim, W6RMK
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