[TowerTalk] RE: Strongest mast material

[K2we@aol.com]

I too must ask what antennas are you going to install and what kind of a 
tower will this go on. 

22' of mast above the tower with only 2' inside is asking for trouble.

I have an LM-470D tower made by Tri-Ex. In the fine print, the tower company 
states that the tower can hold no more than 300 lbs Dead weight. That's the 
total weight of the antennas, mast and rotor.

Several years ago when I re-cabled the tower, I installed an 18' piece of 
1/2" wall aluminum mast. I have 6' in the tower and 12' above the thrust 
bearing.
I installed a Cushcraft 402CD at the top of the mast and a Mosley 4 element 
monobander for 20 meters (36' boom and a weight of almost 100 lbs) just above 
the bearing. This package stayed up during some of the worst storms we ever 
had. 

I have a friend who has a stack of Telrex monobanders (5 on ten,5 on 15 and 6 
on 20 meters) on a US tower 89' heavy duty tower. He has 22' of very heavy 
chromolly mast (it took 3 of us to lift it!!) sticking out above the bearing. 
In 50 MPH winds, the mast bent in the 1' area between the bearing and the 20 
meter beam. We had to use a bucket truck to remove the 3 yagi's and then 
remove the mast and have it cut before reinstalling. This time the 20 meter 
beam is sitting 2" above the bearing.

I would think this out, Is it worth putting so much weight on the tower and 
installing so much mast above the bearing??  

I can see you spending a lot of time on the mast keeping everything 
operational.

73  Steve/K2WE


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