[TowerTalk] Low Cost 20 Foot Mast

[Mark - N5OT]

What a great thread.  Thanks for all the wisdom about multiple things.

73 - Mark N5OT


On 10/25/2020 10:16 PM, Richard (Rick) Karlquist wrote:
>
>
> On 10/25/2020 7:53 AM, Grant Saviers wrote:
>> Another thing to note is that irrigation tubing comes in several wall 
>> thicknesses.
>
> It possibly could, but I haven't had much
> luck actually finding thickwall tubing.
>
>>
>> One gotcha I experienced was metal fatigue, since aluminum has no 
>> "infinite fatigue life" stress threshold like steel.  My 80m vertical 
>> sections harmonically coupled between guys and fractured at the 
>> highest stress point. (guys were at couplings) So guys need to be 
>> spaced unevenly to reduce vibration mode coupling.
>>
>> Grant KZ1W
>>
>
> I spent years building 90 foot verticals consisting
> three thirty foot pipes, of diameter 4", 3", and 2".
> The top 2" section would always eventually buckle
> for no apparent reason.  It was clearly fatigue.
> It turned out after a lot of trial and error that
> the vertical needed to be guyed at 30, 60, 75, and
> 90 feet.  It didn't need to be guyed at 15 or 45 feet.
> The 75 foot guys were the critical ones when it came
> to the fatigue failure.
>
> Once I figured this out, the vertical always stayed up.
>
> Rick N6RK
>
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