[Towertalk] installing tall masts

[n4kg@juno.com]

>From your description, I *assume* your 24 ft mast
that resides above the mast for your 15M beam
is THIN  WALL  ALUMINUM (a fact you neglected to state)
and NOT a THICK WALL STEEL MAST.

FWIW, we use the opposite approach at Field Day,
inserting 20 ft  1-1/4 inch masts for our 80M antennas
*inside* the short masts for the 20M and 15M antennas.

Tom  N4KG

On Wed, 16 Oct 2002 03:12:55 +0000 Dan Robbins <kl7y@alaska.net> writes:
> My 160m inverted vee hangs from the top of a 24' mast.  The latter 
> sits
> on top of a 125' 25G tower.  There is a mast (from rotator) sticking 
> up
> about 5' through the thrust bearing on top.  A Hy-Gain 155CA beam is 
> on
> that mast, just above the thrust bearing.  The 24' mast rests on the
> Hy-Gain boom to mast bracket and is sleeved over the rotator mast 
> for
> about 4 feet. (The 24' mast does not go into the tower.) To install
> that, not only did the entire 24' mast have to clear the top of the
> tower, but it had to go 5 feet higher to clear the rotating mast 
> that it
> had to slide over.  No problem for a regular 12' Rohn gin pole....
> 
> All you need is a counter weight.  With a counterweight and a 25' 
> rope
> dangling from the bottom of the 24' mast, I was able to tie the gin 
> pole
> rope only 6' from the bottom of the 24' mast.  There was 18' of
> free-swinging aluminum mast above the gin pole rope tie-off, 6 feet 
> of
> mast below, 25' of rope hanging down and then a hefty counterweight. 
> 
> With that set up there was no way the mast is going to point any 
> other
> direction than straight up.  It was actually pretty easy to do and I 
> did
> the same procedure when I had to remove/re-install the mast for
> maintenance on the pulley at top.  The only real problem was my 
> ground
> person who whined about hauling up the heavy counterweight.  Of 
> course,
> I had to stand on top of the thrust bearing plate (or the boom) to 
> reach
> that high, but that's why I buy flat tops instead of taper tops.
> Personally, installing this mast feels a lot safer than wobbling 
> around
> on 2 or 3 unguyed sticks of 25G while the section with the guy wires
> comes up the side.  Of course, we checked out all the weight and 
> balance
> several times before hoisting the thing up.
> 
> For those interested, the 24' mast is not secured.  The 5' of mast
> inside holds it upright and the weight of the inverted vee keeps it
> pressing down on the boom to mast mount.  The 24' mast will 
> ocassionally
> wind up a half turn of top rope as the rotator turns, but any breeze
> unwinds it right away and there has never been a problem there.  The
> mast is wearing down a bit, and also eating into the boom to mast
> mount.  But it has been up there for at least 15 years and the wear 
> is
> maybe 1/8" on the mast and less on the mount. I will wear out before 
> it
> does.  Getting the 160m antenna up above the beam and away from all 
> the
> metal of the tower and guy wires really seemed to help the signal 
> more
> than expected from just an increase in height. 
> 
> 
> Dan KL7Y
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