[TowerTalk] Rohn RSL tower - slightly off topic

Steve Maki lists at oakcom.org
Thu Jun 6 16:30:19 EDT 2019

Seems like if the wind is in-line with the booms, there will be a small 
amount of torque even if the antennas are perfectly wind balanced (if 
they share the same side of the mast).

And that small torque will be somewhat canceled if they are on opposite 
sides of the mast.

-Steve K8LX

On 6/6/2019 4:11 PM, George Dubovsky wrote:

> I'm with you, Chuck. The torque is additive regardless of which side of the
> mast the antenna(s) are on.

> On Thu, Jun 6, 2019 at 1:32 PM Chuck Dietz <w5prchuck at gmail.com> wrote:
>> 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.

>> 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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