[TowerTalk] boom-to-mast slippage

[stan]

Hello Reid,

For my older sattelite boom I used the KLM fiberglass 1.5" OD boom.
Upon their suggestion I added 6" of 1" OD solid fiberglass dowel into
the boom ends. I also added  the stick-on traction pads like you may add
to the forward parts of stairs to add traction. This stuff is sold by the
foot
at hardware stores. Cut a length equal to the circumference of the boom,
remove the stick back backing and apply at the boom ends where
the antenna clamps will be placed. I prefer the gritty traction stick ons
and not the rubbery ones. adding the solid dowel allows more
compressive force with the u-bolts.

KLM sells the 1" OD dowel and the traction pads...
I would prefer the solid fiberglass dowel over the wood.
Fiberglass compresses less, and the wood, if not treated will
absorb water and may rot.

An additional move is to add about a 8" fiberglass dowell to the
center of the KLM boom so you can crank down harder on the
el rotator to boom clamps. Should not be too hard to push the
8" dowell down to the middle or to the location of the el rotator
clamps if you balance your boom.


On my latest satellite boom I used the split M2 type using 2.0" OD
1/4" wall fiberglass. a 1.5" OD solid aluminum peice is fastened to
the Yaesu elevation rotator and the 2 boom peices fit over the
exposed ends of the solid aluminum peice, coming thru the el rotator.
I did not use a dowel inside the fiberglas ends, but I did use the
traction patches under the u-bolts.  No movement has been noticed to date.

I upgraded to the split fiberglass boom so I could add more antennas on it
like 2 x of the M2 35 el 23 cm and later for P3D, a 1' dish for 24 Ghz
and 10 Ghz downlinks. I also use a KLM 22 el 2M cross pol and a
CC 738 XP, 38 el cross pol on 70 cm.at the ends.
Of course, for either boom you must paint the fiberglass to prevent
UV deterioration and subsequent shedding of fiber material.
Gets awfully itchy when ya crawl over it.....

Stan, WA1ECF   Cape Cod, MA    FN41sr



MAERTZ, A REID wrote:

> Greetings:
>
> Although the situation I'm going to describe exists in a vhf/uhf
> application, but I believe it has HF applications also.
>
> Situation:  I have a pair of M^2 yagis on a KLM fiberglass crossboom
> (for elevation control).  The 2M boom is about 18 feet long, the 70 cm
> is about 9 feet long. I am unable to tighten the 2M U bolts to the
> fiberglass cross boom enough to prevent it from slipping and thus
> rotating (in the vertical plane) to where the two yagis are no longer
> parallel.
>
> I reinforced the fiberglass boom by inserting a small section of wooden
> dowel into the boom at the point where the U bolts clamp to allow me to
> apply more torque.  That reduced the slippage, but hasn't prevented it.
> I'm concerned that applying much more torque to the U bolts will
> break/crack the fiberglass.
>
> Is there another alternative available that would eliminate this
> slippage at the boom that's been applied by some of you with the VERY
> long element HF antennas?  I realize you aren't elevating them and
> they're balanced on the boom for the most part, but there are still
> those unbalanced vertical forces that you had to compensate for to
> eliminate this type of slippage
>
> Thanks in advance for any suggestions you can provide!
>
> 73, Reid
> W0FVR
>
> --
> FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
> Submissions:              towertalk@contesting.com
> Administrative requests:  towertalk-REQUEST@contesting.com
> Problems:                 owner-towertalk@contesting.com
> Search:                   http://www.contesting.com/km9p/search.htm





--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm