If the boom was a uniform cross section (it is) and had no other weight
loading (it does), I would truss it at the 2/3 point from the center. This
leaves all unsupported sections an equal length. Since you have extra
weight at the far end of the boom, I would move the guy out a little further
to compensate, and likely wind up at the 75% point. The whole point is to
have the forces as equally spread along the boom as possible.
Don
VE6JY
On Sun, Apr 26, 2009 at 12:16 AM, Rick Karlquist <richard@karlquist.com>wrote:
> WA3GIN wrote:
> > Thanks but I've had the dipole element up for over 5 years in King George
> > County...have had 31 trees blow over but the antenna is just fine so far.
> >
> > What about the boom question. Truss connection...all the to the end or
> > half
> > way...what do you think?
> >
> > The antenna is on a 110ft crank up. I have it nested at 65ft just below
> > the
> > wa3gin
>
> Nice data point on the irrigation tubing. I think I'll
> keep making antennas out of it :-) We had a bunch of trees
> blow down here 2 years ago ("50 year storm") and nothing
> happened to my various irrigation tubing structures.
>
> I have a MonstIR on a 106 ft tower. The MonstIR boom is guyed
> half way out. The MonstIR elements are considerably heavier than
> yours, and it sags a fair amount past the guy points. You
> won't have so much sag.
>
> The problem you can get into if you put the truss at the end of
> the boom is that the boom could get into an unstable equilibrium
> and curve upward to relieve the stress of the truss. This can be
> triggered by tilting the beam during installation. By having
> some boom beyond the truss, this is much less likely to happen.
>
> I vote for guying half way out.
>
> Rick N6RK
>
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