Wish i'd discovered this list(and very valuable resource)much earlier.
Anyway, how many of you have, in building or planning low towers, noted
that Rohn specifies Block no. 4A(Concrete Anchor Data)for all 25G tower
installations up thru 110 mph,
and to 100 ft. with 45G in 110 mph wind before they upgrade to 4B.
I realize that i've heard it said repeatedly over the years that Rohn is
very conservative in their rateings.I also realize that it can be very
dangerous to "second guess" Rohn, or to depart from their specs.without a
lot of knowledge.
It is easy to look at a 50 or 60 ft. 25G tower with 110 mph specs and draw
a conclusion that Block 3D or 3E would be totally adaquate for anchoring
purposes. My anchors are GAC25's which are only 5-1/2 feet long as opposed
to GAC30's which are 7 ft. long. Since i am digging these holes
with post hole diggers and a shovel, i don't relish digging the last 1 foot
of depth between 3 and 4 ft. or even to 3-1/2 feet deep. I'd even make a
concession and pour the concrete 1-1/2 feet deep which is 50 % deeper than
called for in Block 3D and more than 3E, knowing full well that there would
be less "earth cover".
Am i barking up the wrong tree here?
My antenna will be a Mosley TA33 jr. which is about 50% of the 110 mph
windloading.(I've already purchased it). Since it and many of the popular
antennas would self-destruct before 110 mph is reached, thus removing the
windloading or much of it from the top of the tower, i really am hardpressed
to believe that Block 4A is necessary in this instance.
Comments appreciated! Thanks es 73 de Roy Lincoln/WA4DOU/N.C.
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