[TowerTalk] Rohn RSL tower - slightly off topic

[Chuck Dietz]

Maybe I’m dense, but I don’t see how this does anything (much). If the back of both antennas has a larger wind area than the front, the torque on the mast is going to twist the mast in the same direction no matter to which side it is attached.

Chuck W5PR

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From: k7lxc--- via TowerTalk
Sent: Thursday, June 6, 2019 11:38 AM
To: towertalk at contesting.com; bjtatum1 at att.net
Subject: Re: [TowerTalk] Rohn RSL tower - slightly off topic


>  Hello-? ? I was at a friend's QTH recently viewing his new Rohn RSL100L10, a 100' self supporter put together with 10' sections R-10H through R-1. It is rated for 25 ft/2 wind load at 90 MPH, dropping back to 11 ft2 at 100 MPH. We were discussing his planned installation of a KT-36 and M2 3 ele 40 meter yagi. He wishes to have the KT-36 about 15' above the tower top plate with the 40 meter yagi approx. 1' or 2' above tower top. Both antennas are fairly close in weight (approx. 95#), boom length (36') and wind load (10 ft2). ? I wanted to get opinions of folks experienced with large antennas and self supporting towers if this planned installation is OK for this tower.
Hiya, Byron --
    The proposed configuration sounds good to me but I'm not offering an answer to your question. What I am offering is a tower technique that I highly recommend.

    Install the antennas on opposite sides of the mast. That way many of the wind vectors cancel each other out. This was determined by Dick Weber, K5IU, a PE and the article appeared in QEX years ago. Anything you can do to reduce the wind induced torque on a mast is a good thing. Did I mention this is highly recommended?
Cheers.Steve    K7LXCTOWER TECH   

   
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