In a message dated 2/13/2007 1:59:35 A.M. Greenwich Standard Time,
Cqtestk4xs writes:
In a message dated 2/13/2007 1:47:20 A.M. Greenwich Standard Time,
bmaser@tampabay.rr.com writes:
Rohn claims that you can use 65 up to 60 feet with 70mph winds
with ±5 sqft of surface area, if you have the proper foundation.
Actually, according to my Rohn book for 70 MPH and Rohn unguyed is 18.4 sq
ft. I would never want to put up a tower with specs only at 70 MPH. Even out
in KH6 where the codes are pretty relaxed, it is 80 MPH. As with all
self-supported towers, one must consider the size of the base to counter the
overturning momentum. The base of the Rohn 65 is only about 4 x 4 x 4. That
ain't
much!
Most of the self supporting towers at 60 feet made to hold that 18 sq ft
require a hole around 5-6 feet deep and around 5-6 yards of concrete.
Rohn towers are not made to be self-supporting towers and the bases in the
book are not designed as such. Although they function quite well as self
supporters, the builder must use due care and keep in mind the extra concrete
that
must be added to compensate for using them that way.
As far as the shakey factor, we all have different pucker factors. I would
not be comfortable at 70 or 80 feet of 65. YMMV.
Bill K4XS
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