I'm sure you'll get lots of comments on this, and I'm no structural
engineer, but here goes.
First, the rigid conduit is basically the same as water pipe, it is
malleable steel, i.e. it is soft.
Second, it is heavy. Yes it is schedule 40 and the wall thickness is
substantial, but with that thickness comes weight, which you don't want too
much of.
IMHO, without any real engineering facts to support it, just having used
miles of conduit in the field in my job, it's too heavy and soft for that
substantial height. I honestly think you will find steel tubing much better
for the solution. Unfortunately, the tubing is hard to find in sizes that
allow you to do what you are describing, but I would think 60' would be
achievable.
FWIW, you might consider schedule 40 plumbing pipe if you decide to try this
because you can get it in approximately 20' lengths which may provide some
benefit.
I use rigid for 10' masts on towers quite often, 2" or 3", but never any
longer than 10'
Of course, your individual mileage may vary.
73
N7HQR
> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Thin Air Communications
> Sent: Monday, January 09, 2006 2:33 PM
> To: towertalk@contesting.com
> Subject: [TowerTalk] TowerTalk Digest: Using Double Wall EMT for wire
> support
>
> Hello TTians
>
> I am considering using some thick wall (rigid) EMT for supports for an
> 800'
> wire loop skywire. I currently am using ornamental steel that extends to
> 50'. The steel has not yet collapsed but the masts have become bowed due
> to
> high winds and I don't have the real estate to guy it properly. So I am
> looking at thick wall EMT also known as rigid EMT. I have heard of people
> using this same stuff to 40' but I haven't heard of anyone going beyond
> that. Ideally for the topband I'd need to be quite tall with 100' as a
> minimum but I've already figured I'd have to settle for less.
>
> The pipe is galvanized steel and is twice the thickness of the ornamental
> steel I currently am using. The pipe slides into each other but not
> tightly
> so I'd have to shim then weld the mast together. The sizes that are
> available at my local big box home store are 2", 1-3/4, 1-1/2, 1, 3/4 and
> 1/2". I would be using 4 10' sections on the bottom with 2" then
> progressively step down for each additional 10'. I wouldn't use the 1/2"
> at
> all. So I should have 40' in 2" and 10' for each size there after. So
> 40+10+10+10+10 = 80' possible. So my dilemma is, is this stuff
> structurally
> sound enough to go to 80' I have doubts. I would weld all the joints. But
> what would you think to be reasonable maximum with this stuff? I have mast
> bases already set in the ground with a lot of concrete and the bases have
> a
> pivot point as well as an up and out tie point for using a come-a-long to
> winch the mast erect.
>
> The winds we get here can be substantial. The last 2 storms brought winds
> over 50mph sustained.
>
> Thanks!
>
> Michael J Wood
> KE7ENC
>
>
>
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