[TowerTalk] concrete bases for freestanding towers

[K8RI on TT]

On 5/15/2011 3:03 AM, John Lemay wrote:
> This thread about towers which are bracketed to the house, and also guyed is
> very worrying to me. I'm a charted engineer, and I can see considerable
> difficulty in deciding how the various forces are distributed between the
> house bracket and the guys.

It's certainly not a trivial matter for anything other than a small 
tower and very small antenna.
The tower height above the bracket is limited to some where around the 
the normal free standing height, which for guyed towers such as the 25G 
and 45G, is not much.
Walls tend to move in the wind. Towers do as well, with added leverage.  
The attach point needs to be reinforced to spread the force out across 
many studs in the wall. Add to that, walls are not really strong in the 
horizontal plane, perpendicular to the wall, so the wall itself may 
require reinforcement. Then if the tower is only capable of 30 feet self 
supporting and it's bracketed at 10 feet you only gain about 10 feet if 
everything works out correctly.  But even a 45G has a very limited wind 
load for a very short tower in the self supporting configuration.

As was mentioned, a properly guyed 45G would probably be doing more to 
support the wall than the wall to support the 45G.

The article that was in QST covered this in detail, but I do not 
remember the month or year.

73

Roger (K8RI)

> John G4ZTR
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of K8RI on TT
> Sent: 15 May 2011 06:14
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] concrete bases for freestanding towers
>
> On 5/14/2011 11:59 PM, EZ Rhino wrote:
>> Frankly I've never understood why a house bracket is either needed or a
> good idea.  If the tower is guyed above the bracket, there is no reason to
> have it because it isn't adding anything to the system (assuming guying at
> the proper intervals, etc).  The only reason I can see to have one is in
> steadying the lower sections as the tower is constructed (in place of
> temporary guys).
> I believe the recommendation is to not bracket guyed towers.  The house
> probably moves more than the tower.  Go up on top of a home on a windy
> day. go over by the chimney and watch the flashing between the roof and
> chimney flex.
>
> 73
>
> Roger (K8RI)
>> Chris
>> KF7P
>>
>>
>>
>>
>>
>>
>> On May 14, 2011, at 19:50 , W2RU - Bud Hippisley wrote:
>>
>>
>> On May 14, 2011, at 9:29 PM, WA8JXM wrote:
>>
>>> My concern with attaching a tower to the house is that if the tower moves
> back and forth just a slight bit in the wind, will that eventually loosen
> the framing on the house?
>> Goodness!  What are you guys _putting_ on your house-bracketed towers?
>>
>> Why would wind on a thin-member lattice tower and cylindrical-element
> antennas create more disturbance to framing than wind on a solid wall?
>> Bud, W2RU
>>
>>
>>
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