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Re: [TowerTalk] "Roll your own" tower/mast.

To: "'Tower and HF antenna construction topics.'" <towertalk@contesting.com>
Subject: Re: [TowerTalk] "Roll your own" tower/mast.
From: "John E. Cleeve" <g3jvc@jcleeve.idps.co.uk>
Reply-to: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Sun, 24 Jan 2010 19:17:45 -0000
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hello jimlux, thank you for your response and suggestions. I will take all
your points into consideration, and I can confirm that access to the site is
clear, and any lifting problems can easily be resolved. Sincerely, John
G3JVC.


 
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of jimlux
Sent: 24 January 2010 18:21
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] "Roll your own" tower/mast.

John E. Cleeve wrote:
> Gentlemen,
> 
> I would be grateful for constructive comment on the following problem. I
am
> in the market for a couple of 100ft towers or masts, the problem is that
in
> the UK there are very few manufacturers or suppliers, and those that can
> supply new, usually import their wares from abroad. However, one quotation
I
> received from a UK manufacturer was for approximately 12000 GBP per mast
> (guyed), at the factory gate, carriage, guy anchorages and erection of the
> m

$20K plus!  clearly, you're paying a lot for the labor, since the metal 
cost is a tiny fraction of that.

What you get with a conventional lattice type tower is a tradeoff of 
lower mass for more labor to build it.  The lower mass buys you lower 
material cost (which is a tiny fraction of overall cost), but more 
importantly, the ability to erect a tall tower in pieces, by relatively 
few people.

However, think differently..
Are you mass constrained? Particularly for erection? Do you have room to 
assemble the entire mast on the ground before erection? Can you hire a 
100 ft crane for, say, GBP1000 that can lift a few tons to 60 feet? 
(assuming a slightly above midpoint "pick").



What about a suitable piece of iron/steel pipe (or, more properly, a 
series of pieces of pipe of decreasing diameter).  Or stacked telephone 
poles?


Yes, it's not what most hams use, because a 20 foot section of 6" 
diameter pipe weighs a LOT (about 600 lb).. you're hardly going to bring 
it home on the car top, or lift it up with a couple helpers and the "iwo 
jima" approach.  However, particularly if you can find a surplus source 
for the pipe. Scrap steel, is, I think, around $0.25/lb these days, so a 
20 foot length of 6" pipe with 1/2" wall is going to set you back around 
$150-200..   Call it a couple thousand dollars for 100 ft worth, by the 
time you fabricate it.

Actually, I'd be looking around for aluminum irrigation tubing in large 
diameters and use many tiers of guys. Around here, there's quite a bit 
of it available, but that's because there's significant agriculture (I 
live near the coastal plain in Southern California.. strawberry and sod 
capital of the world, I think).  I don't know if temporary irrigation is 
something that is common in the UK (given that water falls from the sky 
directly upon the plain beneath, and doesn't need to be carried for 
hundreds of miles from the source)

It's possible, although tricky, to erect something like this without a 
crane, but you're going to spend a lot of time and analysis figuring out 
how to lift it without it buckling, probably involving truss and cable 
stiffening.  Think of sailboat (or sailing ship) masts.

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