John & Jim are absolutely correct.
Compared to a 2" OD 0.375" wall mast, the stress developed for a given
loading from increasing mast diameter / reduced wall thickness is as
follows:
2.5" OD, .375" wall: 61%
2.5" OD, .250" wall: 78%
3" OD, .375" wall: 39%
3" OD, .250" wall: 52%
The 3" OD mast with .250" wall almost doubles the safe "payload" compared to
a 2" OD mast with .375" wall.
Matt
KM5VI
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson
Sent: Wednesday, February 26, 2014 12:36 PM
To: towertalk@contesting.com
Subject: [TowerTalk] FW: Mast Wall Thickness
Date: Wed, 26 Feb 2014 10:37:31 -0500
From: john@kk9a.com
To: towertalk@contesting.com
Subject: Re: [TowerTalk] FW: Mast Wall Thickness
## IMO, whoever standardized a two inch mast was a complete idiot.
A 3 inch mast with a .25 inch wall weighs the same 7 lbs per foot as
a 2 inch mast with a .375 inch wall. The difference in strength is
HUGE in favour of the 3 inch mast. Since they both weigh the same..they
also both cost the same. Even a 2.875 mast with a .25 wall...made from 87
ksi
DOM tubing is ONE HELLUVA lot stronger than a 2.0 mast with a .375
wall...and made from
107 ksi chromolly tubing.
...
## Just use the free ARRL mast software. Then you can put any diameter
mast and and wall thickness you want.
You can also enter any yield strength u want. Then enter how much mast
above the top of the tower...
and where the various yagis are placed on the mast. It spits out the exact
mph where it will break.
## the strongest mast, bar none I heard about.. used a 3 inch mast with a
.375 wall....... made from 120 ksi chromolly.
Jim VE7RF
I have not used a 2" mast in years. At P40A I had two Yaesu G-2800DXA
rotators and my 2 1/2" aluminum mast fit into their clamp perfectly. My
prop pitch rotators have 3" masts. I am sure that other rotators also accept
larger masts.
John KK9A
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