Integrity of the zinc-concrete-air interface is critical to long term tower
durability. If poor construction techniques allow the interface to become a
zinc-concrete-water interface -- or much worse, a zinc-concrete-mud interface
-- the tower is doomed to premature failure through electro-chemical corrosion
of the tower steel at the interface with the concrete foundation.
Careful attention to this interface is extremely important when the tower
foundation is being finished. Although rain will come into contact with the
zinc-concrete-air interface, a properly finished foundation will quickly drain
water away from the interface. Its also very important to ensure that there
are no voids in the concrete in which water will pond adjacent to the tower
legs.
The Tower foundation should be finished 4-6 inches above grade level to ensure
that surface water, mud and debris cannot collect on the foundation and the
zinc-concrete-air interface. Remove any collected debris from the foundation
during your annual tower inspection.
73!
Frank
W3LPL
---- Original message ----
>Date: Tue, 1 Aug 2006 07:41:58 -0700
>From: "JC Smith" <jc-smith@comcast.net>
>Subject: Re: [TowerTalk] 80' tower in SF Bay area (update)
>To: "'KA9OFM John Garrett'" <ka9ofm@gmail.com>, <K7LXC@aol.com>,
><towertalk@contesting.com>
>
>Hi John,
>
>Yes, my plans call for ~6" above the soil level. I'm on a slight slope
>(3" - 4" fall over the 9' the hole covers) and I've been pondering whether
>to just do the top of the pier parallel to the ground or do it horizontal
>with a crown in the center. I'm thinking it will look a little a little
>more professional if it's horizontal so I'll probably do that (with the
>crown). That's how I did my other tower and the water runs off great.
>
>I don't have the bottom section of the tower yet, and it's very heavy anyway
>(279 lbs.) and would be difficult to work with while leveling the base.
>Also, it's not a parallel-sided tower so I have to use a different technique
>to get the base level and plumb. I'm practicing with the base outside the
>hole right now, to develop the best technique and a jig to do it once I get
>in the hole with the rebar, etc. I also got some hints from the
>manufacturer on how to do all that. I must admit, this is the scariest part
>of the project (to me anyway)... a lot scarier even than working 80' above
>the ground to install the antennas. You only get one shot at pouring the
>base.
>
>Thanks for your advice.
>
>73 - JC, K0HPS
>
>
>-----Original Message-----
>From: towertalk-bounces@contesting.com
>[mailto:towertalk-bounces@contesting.com]On Behalf Of KA9OFM John Garrett
>Sent: Monday, July 31, 2006 10:29 PM
>To: jc-smith@comcast.net; K7LXC@aol.com; towertalk@contesting.com
>Subject: Re: [TowerTalk] 80' tower in SF Bay area (update)
>
>One final suggestion - Make your tower base a few inches higher than the
>surrounding earth. I always make my pours 4 inches higher. This will allow
>water to run off the base during a rain instead of possibly standing on the
>base. Which would eventually allow rust to begin. You can even put a slight
>angle on the base top so water runs off rapidly, but if you do that then
>don't overdo the angle of the top of the base as only 1 or 2 degrees is
>necessary.
>
>>73
>John, KA9OFM
>
>
>On 7/31/06, K7LXC@aol.com <K7LXC@aol.com> wrote:
>>
>>
>> In a message dated 7/31/2006 11:20:47 A.M. Pacific Daylight Time,
>> john@iguanavilla.com writes:
>>
>> > I'm guessing that the earth was already disturbed from installing the
>> 9 ft
>> square x 1 1/2 ft. thick footing that the manufacture (AN Wireless)
>> recommends.
>>
>>
>> Well, sort of. The undisturbed part is the sides. Obviously the
>> dirt
>> you dig out is disturbed but since it doesn't have anything to do with
>> the
>> base installation, it's a non-issue.
>>
>> Cheers,
>> Steve K7LXC
>> TOWER TECH -
>> Professional tower services for hams
>> Cell: 206-890-4188
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
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