Depending on where you live, to be really safe, add another0.5 " or so to
the mast diameter for ice, although you're probably not likely to get ice
and high wind at the same time.
I've had "good luck" (after lots of calculation) with 2"dia x 0.25 wall
seemless steel tubing, with large LP a foot or two above the top thrust
Gene / W2LU
----- Original Message -----
From: "Jim Thomson" <Jim.firstname.lastname@example.org>
Sent: Friday, March 19, 2010 1:29 AM
Subject: [TowerTalk] 2" OD pipe.. again
> Date: Thu, 18 Mar 2010 19:12:25 -0400
> From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
> Subject: Re: [TowerTalk] 2" O.D. Pipe???
> Stan Stockton wrote:
>> Just my opinion.... 1.5 inch schedule 40 may be fine if you have some
>> big tribander or 35 foot monobnder and it is mounted right above the
>> top bearing. If you are stacking antennas on the mast, forget it.
> http://www.rogerhalstead.com/ham_files/Tower29.htm shows a tribander at
> 100', 7L 6-meter Yagi at 115 and a 14' cross boom at 130' holding a pair
> of 11L on 440 and pair of 12L 144. That all on 2" schedule 40 but it's
> structural steel. It's a bit flexible with the top looking like a blue
> gill rod that just tied into a big Bass, but it's withstood over 70 mph
> winds and many occasions.
> ## sched 40 pipe doesn't come in a 2.0" OD. It's is 1.9" OD,
> with a .145" wall.
> ## You mean to tell us that you have 30' [thirty feet] of mast,
> sticking out the top of the tower ??? Do you ever get ice...
> or ice + wind ?
> I'm going to a heavier wall DOM so it doesn't beat the antennas to
> death, but strength wise it seems to have been more than sufficient.
> OTOH it's not ordinary schedule 40 pipe which is relatively soft and
> easily bent.
> ## Regular sched 40 pipe would have been toast, long b4 now.
> ## 1026 DOM comes in 60 ksi, to as high as 90 ksi.
> ## IMO... for ants mounted way up a mast, you had better [A] run the
> numbers through the spread sheet.. and [B] make sure the mast you buy
> has paper work with it. Inform your steel supplier, that it's a legal
> issue... and guess who's liable? As far as wind speeds go.... unless
> have a wireless wind speed indicator, at the top of the tower, you are
> guessing. If it's 56 mph at grnd level, it could easily be 70 mph at
> top of the tower. Talk to anybody who has a wireless wind speed
> at both the top of the tower.. and also at the 15' level. You will get
> ## all of this mast issue is really a no- brainer. Stuff the numbers
> into the
> spread sheet, and see what spits out.
> ## estimate the max wind speed gusts for your area.... then add a MIN
> of 25% " to the speed [and pref a lot higher... like 30-50%]. Then
> the correct mast. These 1 in a 100 yr wind storms are too plentiful
> these days
> and ditto with ice storms, seismic events, and heavy rains. WX patterns
> changing.. for the worse. OK, so you buy a mast that's overkill, so what?
> Ham's spend $12K on a xcvr, without blinking an eye. When you get the
> crane bill, to remove the destroyed ant's, coax, etc... the pricey mast
> will look cheap.
> later....... Jim VE7RF
> Roger (K8RI)
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