What a valuable resource this reflector is!
Thank you all for the comments to my original post. Some brief explanations:
- I cannot consider using sections longer than 6ft because they have to be
transported air freight. Maybe you haven't noticed my callsign :))
- Exactly what Tom reported below happened to my previous attempt to
construct the verticals out of irrigation tubing. Maybe it's not the same
material as what can be found in US, my tubing is awfully thin and it
appears of being no more than rolled aluminium sheets. I have noticed strong
vibrations in the wind and eventually the verticals came down
- Finally I have ordered 4 18m fiberglass poles from Spiderbeam and now hope
for the best.
Thank you again for valuable support.
73 de Mike, YO3CTK
YR7M stationmaster
----- Original Message -----
From: "Tom McAlee" <tom@klient.com>
To: <towertalk@contesting.com>
Sent: Saturday, October 28, 2006 10:06 PM
Subject: Re: [TowerTalk] 80m vertical: reality check
>I have 2 full-size 80m verticals using tubing from Texas Towers. The
> current versions have been up for 1.5 years with no problems. But, they
> are
> the third version. The first 2 attempts didn't go so well!
>
> As they are now, they start at 2.125" and telescope to 1.25". They are 6'
> sections with several of the first 3 sizes doubled up. They are guyed at
> 5
> levels (every 12') with Phyllistran to posts 43' out, guys attached to the
> top of the posts that extend 3' out of the ground (makes mowing the yard
> easier)
>
> These verticals cannot be "walked up" as you would do with a smaller
> vertical. I used a 60' bucket truck to build them 12' at a time. I found
> a
> local sign company that charges $55/hour and it took about 1/2 hour per
> vertical.
>
> Mistakes made in the first two versions that were destroyed on windy days:
> - telescoping up to too small a size that couldn't withstand the vibration
> in the wind and broke off
> - not having enough guy levels (without enough of them, you can't tighten
> them much because tightening them will buckle the tubing without more guys
> below to prevent that)
> - not having the guys out far enough (tried to be cheap on the
> Phyllistran,
> bad idea)
>
> 73,
> Tom, NI1N
>
> ----- Original Message ----- > From: towertalk-bounces@contesting.com on
> behalf of Yo3ctk
>> Sent: Fri 27/10/2006 12:40
>> To: towertalk@contesting.com
>> Subject: [TowerTalk] 80m vertical: reality check
>>
>>
>>
>> I am trying to design an 80m lambda/4 vertical for a 4-square. My plan is
>> to use 6 ft sections of AL tubing, 0.058" wall, as advertised on Texas
>> Tower website:
>> http://www.texastowers.com/aluminum.htm
>>
>> Starting with biggest O.D of 2.125", twelve (12) more 6 ft sections of
>> progressively smaller O.D. will be telescoping with 1 ft overlap at each
>> joint. Joints will be fastened with AL rivets. The entire vertical will
>> have an (adjustable) height of 66 ft (20m) and a total weight of about 22
>> pounds (10 kg).
>>
>> Unfortunately I have no expertise in calculating if such a structure is
>> mechanically sound, hence following questions for the experts on the
>> list:
>>
>> 1. Is the vertical expected to break at the lower joints in stiff winds
>> (say no more than 65mi/100km/h)?
>> 2. Must the vertical be guyed? Where?
>> 3. Is it feasible to raise the vertical from the ground, by fixing the
>> largest section to the base and telescoping sections starting with the
>> smallest diameter, and riveting as we go?
>>
>> Thank you all for any comment.
>>
>> 73 de Mike, YO3CTK
>> YR7M stationmaster
>> _______________________________________________
>>
>>
>>
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>>
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>>
>>
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>
>
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>
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