[TowerTalk] Joining Boom Tubing

[john at kk9a.com]

Here is my previous response to your question:
http://lists.contesting.com/archives//html/Towertalk/2014-08/msg00428.html

I always use 12' long boom sections to minimize splices.

John KK9A


To:	towertalk at contesting.com
Subject:	[TowerTalk] Joining Boom Tubing
From:	"L L bahr " <pulsarxp at embarqmail.com>
Date:	Mon, 15 Sep 2014 02:02:12 -0400 (EDT)

I'm slowly building up a 40 meter Moxon Beam and the boom needs to be
somewhere
between 24 and 27 foot long depending on the article used to build it.  The
boom has me stuck.  As all of you know, most aluminum is sold in 6 foot
lengths
for shipping purposes.  That means the tubes need to be connected.  I'm at
the
point where I need to determine what I am going to use for boom material and
how to connect the segments.

I have some 2 1/2 inch aluminum tubing I bought surplus many years ago.  The
stuff has a wall thickness of around 1/16th inch thick and is hard aluminum,
probably 6061 alloy.  I've got plenty of it in 6 foot lengths.  It's gorgeous
looking tubing and I initially figured and wanted to use it for my boom
material.  However, I have been racking my brain out trying to figure out how
to join the sections.  (The inside diameter is around 2 3/8th inches ID.) I
tried 2 inch schedule 40 pipe and it is a tad too large in diameter to fit
into
this 2 1/2 inch OD tubing with an approximate 2-3/8 inch ID. (I thought maybe
sanding down some schedule 40 aluminum pipe but would I get it to really
work?)
 I thought maybe turning some oak down to a diameter to fit inside this
tubing,
 I have hunted high and low for some aluminum stock to either snuggly fit
inside or outside this pipe with no success.  If I buy 3 inch OD tubing, it
will have an ID of 2-3/4 inches.  I even thought of slicing the
 ends open in the form of a cross in some 3 inch tubing and then use hose
clamps to secure things, but then the pipe would only be tight on one end of
the joining pipe. I thought maybe of slicing the 3 inch pipe open along it's
length and then use hose clamps to pull it tight and together again around my
existing pipe.  The bottom line is I have not been able to figure out how to
use my tubing satisfactorily.  I'm now starting to think maybe my tubing
is not
the answer for my needed boom material.  That really seems like a big
waste as
I know if I bought this tubing new it would run big bucks.  A 40 meter
Moxon is
no small antenna so the boom material needs to be decent and adequate for my
purpose.

That said,  am I missing something here?  Anyone on here who could get me
on a
proper path?  I need to either find of way to use my existing 6 foot
lengths of
2-1/2 OD tubing with a 2-3/8th inch ID or move on to something else for the
boom. I'd sure appreciate hearing from you experts as my quandary has been
bugging me for weeks now. Right now I am just spinning my wheels going
nowhere.
 I might add, I do not have a machine shop at my QTH.  I thought I would try
one last time to figure out how to use my tubing before I give up on that
idea
by asking you guys for advice.  Any and all comments would really be
appreciated.

Lee, w0vt
Houston