Thanks but I've had the dipole element up for over 5 years in King George
County...have had 31 trees blow over but the antenna is just fine so far.
What about the boom question. Truss connection...all the to the end or half
way...what do you think?
The antenna is on a 110ft crank up. I have it nested at 65ft just below the
tree tops...seems ok...50 miles south of DC we don't get much ice. I will
be guying the elements half way out which should benefit the 2" tubing.
73,
dave
wa3gin
----- Original Message -----
From: "Rick Karlquist" <richard@karlquist.com>
To: <donovanf@starpower.net>
Cc: <towertalk@contesting.com>
Sent: Saturday, April 25, 2009 6:27 PM
Subject: Re: [TowerTalk] 40m BEAM BOOM
> donovanf@starpower.net wrote:
>
>> It sounds like you're planning on full sized 40 meter elements, they will
>> be about 75 feet long with your severe taper. Irrigation tubing only has
>> only 0.040 inch wall, I expect it to fail in the first strong breeze.
>>
>> Its surprising that you plan to use such a strong boom, an excellent
>> choice for this large antennam, but you plan unreasonably thin wall
>> elements that would be marginal even for a 20 meter Yagi.
>> W3LPL
>
> Actually, irrigation tubing is at least 0.050 inch and heavier grades
> are available. I have made 30 foot unguyed verticals out of it that
> survived very high winds (>70 MPH). I'm think your Yagi plan
> might be OK, as long as you are not going to experience ice or
> hurricanes. The rating is 28,000 PSI, you can calculate the
> wind survival using the usual tools. The main issue with thin wall
> tubing is to avoid mounting it in such a way as to encourage buckling.
>
> Rick N6RK
>
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