[TowerTalk] How to get another 10' in height? Add a mast or add another section?

[john@kk9a.com]

The 80 percent guy anchor radius is just a guideline, it can be less if properly engineered.  The bigger problem may be with the rotating rings.  I believe that most rotating tower component manufactures recommend a guy radius of 100 percent.  This puts less stress on the bearings and also allows more room for the antennas to turn

John KK9A

To:  TowerTalk <towertalk at contesting.com> 
Subject:  [TowerTalk] How to get another 10' in height? Add a mast or add another section? 
From:  John W <xnewyorka at hotmail.com> 
Reply-to:  xnewyorka at hotmail.com 
Date:  Mon, 9 Jan 2012 20:23:17 -0800 

If I have a Rohn 45G tower of a given height, let's say 90', guyed per the Rohn 
book, and rotating from the base, hosting several side-mounted yagis for 10m 
(3), 15m (2), and 20m (1), and I want to add another antenna up at 100' (a 
small 40m 2L) that also rotates with the tower, which one is the safer/better 
installation:  adding a mast that protrudes 10' above the top of the tower (and 
for some distance down into the tower), or adding another 10' section and 
sidemounting the new antenna at the top of it?

This is a theoretical question, because I haven't built the tower yet, but I 
plan to.  

The first reply many might have is probably: Why don't you just build it to 
100' per the book, instead of 90'?
The answer to that is that I don't have enough real estate to put guy anchors 
80' from the base, I only have 72' available.

Also, I have not even seen hardware that allows adding a FIXED mast at the top 
of a Rohn tower - sort of like a thrust bearing that can't turn. How is this 
typically done?

Thanks & 73,

John
W2ID