Tnx for the various input much apprfciated. This mast is for a friend for the
following application. I have sent him all the feedback from u folks:
"125 MPH version of the M2 log periodic for 10-30 MHZ and a heavy duty 7
element 6 meter yagi from Directive Systems on it (not on the website). Both
antennas have truss supports so I need some vertical space for each. I am at
an elevation of 160' ASL and on the salt water (edit: he is in coastal
Maine ,tough winters). On the water so there is constant wind and the
likelihood of ice loading as well in the winter. "
73. Steve. K1PEK
Steve Davis
Senior RF Cable Design Engr.
& Founder
DAVIS RF Co. a division of
Orion Wire Co., Inc.
Tel: 978-369-1738
ALSO: Davis Rope & Cable Assembly Co., LLC:
Design Engrs, Distribution
> On Sep 15, 2015, at 12:00 PM, towertalk-request@contesting.com wrote:
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> Today's Topics:
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> 1. Looking for good source of 20 ft mast (Jim Thomson)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 15 Sep 2015 00:37:03 -0700
> From: "Jim Thomson" <jim.thom@telus.net>
> To: <towertalk@contesting.com>
> Subject: [TowerTalk] Looking for good source of 20 ft mast
> Message-ID: <B775B429A6144E73B14E0E76B965B28F@JimPC>
> Content-Type: text/plain; charset="utf-8"
>
> Date: Mon, 14 Sep 2015 13:33:37 -0400
> From: Stephen Davis <sdavis@davisrf.com>
> To: "towertalk@contesting.com" <towertalk@contesting.com>
> Subject: [TowerTalk] Looking for good source of 20 ft mast
>
> Hello all
>
> Specs : 20 ft. 2" O.D. .50" wall chrome moly
>
> Yep, .5 " !
>
> Tnx a lot. 73. Steve. K1PEK
>
> Steve Davis
> Senior RF Cable Design Engr.
> & Founder
> DAVIS RF Co. a division of
> Orion Wire Co., Inc.
> Tel: 978-369-1738
> ALSO: Davis Rope & Cable Assembly Co., LLC:
> Design Engrs, Distribution
>
> # A 2.875 or 3 inch OD cm mast with just a .25 wall is one helluva lot
> stronger
> vs a 2 inch mast with a .375 wall......yet they all weigh the same....and
> cost the same !
> You can see all of that on the arrl mast software at a glance. Huge
> difference in strength.
>
> ## as soon as u exceed .25 wall, you are essentially wasting your time and
> $$. At that point,
> the OD needs to be increased. A 2 inch mast with a .5 wall will only be a
> tiny bit stronger than
> a .375 wall. A 2 inch solid mast will gain you nothing....but weight + $$.
>
> ## in my case, the HDX-689 was all setup for a 2 inch OD mast so I was
> screwed. My only option
> was to use a 2 inch x .375 wall CM mast. Another option if u are stuck with
> a 2? OD mast is to
> insert a 2nd tube inside the 1st one, close fit...then weld the base.
>
> ## for folks that actually have a choice of mast OD, always use a 3 inch OD,
> 4130 CM mast...or a 2.875
> inch OD DOM mast....and both in .25 wall.
> DX eng sells the 3 x .25 CM masts. Array solutions sells the 2.875 x .25
> DOM masts.
>
> ## Dunno which idiot decided to standardize a 2 inch od mast for ham radio
> use, but it was fubar.
> I have been collecting bent and broken mast pix since 1977..think its now up
> to 36 or 37. Removing
> mast bent at a 90 deg..with yagis still on it is beyond extremely
> dangerous. In many cases, a crane
> cant be used, or will not fit the space, to get at them. Then what ? Ever
> see one fall and slice the guy wires below it.
> Then the tower comes crashing down.
>
> ## use the freebie ARRL mast software to plan your install....and also
> allow for future expansion.
> Sure, a 2 inch od x .25 wall CM or DOM mast sounds wonderful, till u find
> its maxed out when u go to stack
> your shiny new 40m yagi parked right at the top. If a single yagi is
> mounted within a few feet of the top of the
> tower, anything will work, including plane jane 35 ksi water pipe, in sched
> 40 or sched 80. Again the software
> will tell u at a glance if its even doable for XXX windspeed.
>
> ## IMO, the mast is the most important thing up there. It has to be the
> strongest component in the mix. A mast
> failure should not even be a remote possibility. But if you are stuck
> with a 2 inch od mast, your only option is DOM, and if that?s
> not up to the task, then CM. If CM in .25 isnt up to the task, then
> thicker wall CM, like .375 or perhaps .5 thick is an option.
>
> ## hams have been cheaping out on masts since day 1...and are still doing it
> to this day. Better to pay once, cry once, and buy the
> real deal..and have it hot dipped galvanized too. Use the dx eng handy cap
> for the very top, to keep water out of the inside.
> I kicked myself many times for not buying a good mast 35 yrs ago...when they
> were a lot cheaper. A good mast will easily last a lifetime,
> and have good re-sale value. Section modulus x yield strength = max
> bending moment. Bigger OD + thinner wall results in a bigger section modulus
> vs smaller diam + thicker wall.
>
> sri for the riot act.
>
>
>
>
>
> ------------------------------
>
> Subject: Digest Footer
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> ------------------------------
>
> End of TowerTalk Digest, Vol 153, Issue 42
> ******************************************
>
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