Agreed on the wind loading with elements retracted. I was only referencing
interaction between antennas. With the tapes homed, the antenna is
essentially invisible to the other antennas on the tower.
Also, lowering a tower is a great way to increase wind loading. However, if
you need to get a building permit, the load is measured with the tower at
full extension by most municipalities. I've had the same discussion at
various times, and the building codes look at worst case scenarios for
safety considerations.
73
Lou, W0FK
Message: 5
Date: Tue, 17 Mar 2020 13:42:39 -0400
From: "Art Greenberg" <art@artg.tv>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] TowerTalk Digest, Vol 207, Issue 17 / Yagi
Stacking Order
Message-ID: <73ed2eef-e546-4022-8fed-c63d89a32476@www.fastmail.com>
Content-Type: text/plain;charset=utf-8
On Tue, Mar 17, 2020, at 13:14, Lou Laderman wrote:
> All things being equal, and putting your SteppIR in the middle may be
> best as you can home 5e elements and make it ?invisible?.
Homing the elements only retracts the conductive ribbon. The fiberglass
element tubes are fixed length, so the wind load does not change. The weight
distribution probably changes only minimally.
I'm aware that I'd be committing an engineering no-no by stacking two 6
square foot antennas on this tower. The wind load spec is 12 square feet at
100mph in a gust (I don't recall if its 3 or 6 seconds). Of course, that's
for the entire wind load just a short distance above the top plate, as
another respondent pointed out. If I do this, I'd be committing myself to
lower the tower when its not in use to avoid the possibility of it being
impacted by strong winds.
Art
WA2LLN
art@artg.tv
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|