[TowerTalk] FW: supporting a 40 meter rotatable dipole with trusses

[N1BUG]

Terry,

That would be a lot closer to how I am building mine. After
telescoping, typically 1' per joint, I have 6' 2" x .120 wall, 5'
1.75" x .120 wall, 6' 1.5" x .120 wall (they were 7' sections). The
boom truss is attached 16' out on each side from center, or 1'
inward from the end of the 1.5" .120 wall tube. At the end of the
1.5" it then steps down to 1.125" (sleeved with a short section of
1.25" so it will fit snugly in the 1.5"), then tapers to .625" at
the tips.

For the center insulator I have a 4' length of 1.75" x .25 wall
sleeved with 4' of 1.25" x .125 wall fiberglass U-bolted to the boom
to mast plate. I am now worried that this fiberglass will not be
strong enough with the single overhead truss! Although I would have
preferred to keep it simple I think I am going to add two side
trusses in addition to the overhead. Hopefully this will survive but
we shall see.

In my case I am going to suspend a 30 meter element one foot below
using smaller, lighter tubing. It doesn't need to be as strong since
it will not be self supporting. Hopefully the 30m element won't add
enough weight and wind load to destroy the whole thing.

I can't do anything until the weather cools down so mine isn't going
to be finished for a while.

Paul N1BUG


On 08/15/2018 03:59 PM, terry burge wrote:
> Hello again,
> 
> Checking my stock of parts I find I have (2) 2" X 6' X 0.120" Thick wall aluminum; (2 or more) 1.750" X 6' X 0.120" TW AL; (2) 1.500" X 6' X 0.120" TW AL. The reason I did not build the antenna with this larger stuff was finding some kind of insulating boom-to-mount at a reasonable cost. I do also have DXE fiberglass tubing (1) 2" X 8'; (2) 1.5" X 8'. Then some smaller pieces. Making the B-to-M clamp will be the biggest problem but there is a place in town I found I could possibly come up with some aluminum plates to do the job. I would like to use two plates and make a pivot joint so the dipole can be rotated down to reach the resonance adjustment slip joint or coil/tap/whatever. 
> 
> Terry
> KI7M