[TowerTalk] Cut off extra 7 ft of mast or leave it?

[David Winarsky]

Hi Jim and others,

Thanks again for the input. The tower is a Tashjian LM-354HD and the mast is a Tashjian AD-200EH. The mast is 2” OD by .25” wall. It looks like it is galvanized steel. 

I’m going to go with the below setup. I’ll send pics when it’s up!  I got the Steppir assembled yesterday, so next step with be putting the Jk401 together and the assembling all on the tower. 

David K6ZD
 

> On Nov 24, 2020, at 09:41, Jim Thomson <jim.thom at telus.net> wrote:
> 
> Date: Sun, 22 Nov 2020 18:39:24 -0800
> From: David Winarsky <david at winarsky.com>
> To: TowerTalk at contesting.com
> Subject: [TowerTalk] Cut off extra 7 ft of mast or leave it?
> 
> <Im putting up my first tower, a LM-354HDSP with a Steppir DB11 and a JK 40 meter horizontal dipole, both in the same mast. I have a 20 ft 2 in OD mast from Tashjian and am wondering whether I should cut off the unused length or leave it?  
> 
> <Karl at Tashjian suggested I install the rotator plate 3 ft below the top of the tower and the DB11 2 ft above the top, with the JK40 8 ft above that (10 ft from the top of the tower). That will leave 7 ft of the mast unused. 
> 
> <Do you folks recommend I leave the extra 7ft of the mast in place or cut it off?
> 
> <Appreciate the input and any other comments or suggestions on my plan. 
> 
> <73,
> <David K6ZD
> 
> ##  what kind of mast ?   what is the OD ?   wall  thickness ?   KSI  strength of mast.   aluminum or steel.  is it  chromolly  or  dom, or plane jane  35 ksi ? 
> Knowing that, simple software calcs to provide  bending  moment where  mast enters the tower.
> I would put the rotor plate down six to  eight  feet.   That reduces the stress  on the top of the tower... by a bunch.   Leaving 14 foot  above the top of the tower.  Ok, then put the 40m rotary dipole at the top, or close to the  top.
> Align the  40m rotary dipole  so its  inline with the steppir  boom.  Then just do mental math..and  either  add or subtract  90 degs  from your  rotor indicator dial. 
> Depending on snow and ice, and length of the 40m  rotary dipole,  you might require a non conductive overhead truss  line on the 40m dipole, hence mounting the
> 40m dipole 3-4 feet below top of mast.  Remember to cap off the  top of the mast.  DXE sells  caps.  Then no water  running down the inside of the mast. 
> 
> Jim   VE7RF
> 
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