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Re: [TowerTalk] unguyed with house bracket

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] unguyed with house bracket
From: "AD5VJ Bob" <rtnmi@sbcglobal.net>
Date: Thu, 15 Nov 2007 19:50:14 -0600
List-post: <mailto:towertalk@contesting.com>
No one has answered my question about the Mobile home

Can you bracket to the V at the side of a mobile home or will the mobile home 
hold it?

It is a rental and I have permission for antennas, but wouldn't want to pay for 
a new wall or anything :)

tnx Bob AD5VJ 

> -----Original Message-----
> From: towertalk-bounces@contesting.com 
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Jarvis
> Sent: Thursday, November 15, 2007 1:58 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] unguyed with house bracket
> 
> 
> Lest the critical info be lost, there was a post which 
> referred the Uninitiated to a QST article on how to 
> house-bracket correctly.
> 
> Fascia boards are trim, not structure.  You must tie into the 
> structure.
> 
> Using a 2x6 backing plate inside an attic sidewall  is preferred.
> But here's an alternative which has worked:
> 
> I did not have an attic, it was a flat-roofed house.  All I 
> could do Is lag screw into the roof joists  and the floor 
> joists between the first and second floors.  That gave me two 
> points of attachment.
> 
> My 'bracket' was constructed of 2x8's, 5' long, which spanned 
> 3 bays of Roof joists.  I used 1/2" x 12" lag screws into the 
> 2x12 roof joists, Carefully locating their centers, and 
> pre-drilling pilot holes, so nothing split.  There were 2 
> bolts at each of the 3 joists I intersected.  Each bolt was 
> rated for 2700 lbs extraction force, and considerably more in shear.
> 
> The tower was captured by a sandwich of 2x6"s which were 
> bolted to the 2x8 backing beams in question.  So, I had the 
> ability to withstand something
> >12,000 lbs pullout, and 24,000 lbs shear failure at each of the two
> brackets.  
> 
> In turn, I calculated the windload with ice, from the 
> antennas and tower, and determined that at 90mph, it should 
> be no more than around 5,000 lbs at the point of the upper 
> bracket.  With a more than 2x safety margin, I felt 
> reasonably comfortable.
> 
> Let me point out that there were critical measurements 
> involved, and that a borescope was used to look at each pilot 
> hole...and that each lag screw was installed, removed, the 
> hole inspected for structure, and reinstalled.
> You can't be casual about whether you've hit the beam or not, 
> in that situation.  
> 
> And NO, you can't rely on a double-wide at 10' to hold up a 
> tower at 40', with any kind of wind.  You don't have the 
> overbuilt structure that is common with site-built houses.
> 
> n2ea
> 
> 
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