[TowerTalk] Rohn RSL tower - slightly off topic

john at kk9a.com john at kk9a.com
Thu Jun 6 19:18:52 EDT 2019

I missed the torque part however I wish someone could explain this in simple terms.


John KK9A



From: Byron Tatum [mailto:bjtatum1 at att.net] 
Sent: Thursday, June 06, 2019 23:03
To: towertalk at contesting.com; john at kk9a.com
Subject: Re: [TowerTalk] Rohn RSL tower - slightly off topic


I believe that Steve K7LXC is referring to the torque load on the mast and not the wind load, per se.

Byron W5FH


On ‎Thursday‎, ‎June‎ ‎6‎, ‎2019‎ ‎05‎:‎45‎:‎55‎ ‎PM‎ ‎CDT, john at kk9a.com <john at kk9a.com> wrote: 



I wish that I understood how mounting antennas on opposite sides of the mast

cancels their wind load.


Also I am not sure how well a single tribander will work at 115 ft high

whenever the sunspots return and 10m opens.


John KK9A



k7lxc wrote:


>  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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