[TowerTalk] Tower foundations

[Cqtestk4xs at aol.com]

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 at 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