Please don't try to do that as you have described it. The tower,
if it doesn't bend in the middle, will have stresses placed on it
well over its design ratings.
I put up the first 80' of my Rohn 55 by lifting it from flat on the
ground to its prepared base by lifting it with a helicopter. Before
doing so, I calculated the stresses involved and concluded that even
Rohn 55 would be overstressed if picked up 80' from the end. As I
recall, I put the lift sling at about 50' from the ground end, so
that there would not be more than 50' of unsupported tower. That was
well within the design criteria and it went up without a hitch (the
NCDXF has a video tape of the full tower installation you can borrow
if it interests you).
My suggestion would be to have the crane pick the tower just above
the mid point, lift it up slightly, then set it down gently, letting
it lay over while the ground end is loosely secured. Please control
the ground end of the tower at a safe distance with several people
and long ropes. I hate to think what a 100' tower could do to
someone trying to control it by hanging on to it.
73, Jay O'Brien
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