[VHFcontesting] Masting . . .

[Ron Hooper]

I have a reinforced 2 element 40 meter Crushcraft mounted 15 feet above the 
top of a tower on 1.5 inch schedule 40 water pipe which has been in place 10 
years now. I have also seen the same type pipe bend with a M2, 7 element 6 
meter beam the same distance out of the tower in less than a year. The way 
to keep the water pipe from bending is to insert a 1.250 stick of square 
tubing inside the water pipe. The square shape in the round tube makes it 
extremely strong, probably better than the HSS tubing. The tubing fits tight 
and many need to be dressed with a grinder or plan to use a big hammer to 
get it inside. Sure it is heavy but so is going with a larger diameter pipe. 
On 21 foot water pipe I usually use about 15 feet of tubing inside starting 
at the rotor.

Ron W4WA



----- Original Message ----- 
From: "Fred Lass" <felasstic at yahoo.com>
To: <vhfcontesting at contesting.com>
Sent: Saturday, October 29, 2005 4:57 PM
Subject: Re: [VHFcontesting] Masting . . .


> Note that water pipe has a rated yeild strength of 30,000 PSI.  Most mast 
> materials are rated at 80,000 PSI.
>
> When you buy pipe, 2 inch pipe is 2 3/8" OD; 1.5" pipe is 1.9" OD wall 
> thickness of .145, but 2" tubing is really 2" OD.
> So, in round numbers, a real 2" mast with .25" wall is ten times as strong 
> as a 1.5" schedule 40 pipe.
> Normal wall thickness of pipe is schedule 40, thicker wall is schedule 80.
>
> So, pipe is fine for small antennas that are not too far above the top of 
> the tower.  That's why you often see 6 meter antennas lowest on the mast. 
> For stacking 6 meter beams, a real mast is necessary.
>
> My friend Saul, K2XA, didn't believe me and bought a 1.5" schedule 80 pipe 
> and mounted a 6 element 10 meter beam 20' above the top of the tower.  I 
> refused to install it for him, so he did it himself.  It bent in a 50 MPH 
> wind.  Removing the bent mast was the hardest tower job that I ever did.
>
> 73,  Fred K2TR
>
>
> "S.J.Swanson" <swanson at ticon.net> wrote:KC8QVO, Steve said:
>
> " . . . Also, what does everyone recommend as a mast? Array Solutions 
> sells some REALLY NICE PE certified masts, but they are VERY expensive. I 
> was thinking about going to the plumbing supply store and getting a 2" 
> galvanized steel pipe. . . . "
>
> In a direct communication to Steve I had suggested 2 inch o.d. galvanized 
> pipe which is 1.5 i.d. inch water pipe. The 2 inch nominal is actually 1 
> and 7/16 inches which means that the walls are 1/4 inch or 7/32 inches. 
> The stuff is bullet proof and a 15 foot spliced piece with two VHF and two 
> HF beams survived a wind event that pulled my tower away from the house 
> and twisted the two lower sections of tower. The antennas, top two 
> sections of tower and the mast are still pristine and in use.
>
> I use this pipe because 26 years ago, HyGain used it as their "gold 
> standard" when describing the process for shimming a mast in the Ham IV 
> rotator. I do not use the new stuff --I priced it today, it is $33.00 per 
> 10 foot section. I go to a salvage yard and get used 1.5 inch pipe. It may 
> have rust on the inside but I have found that pipe with no external 
> pitting or rust is as strong as new and only runs 40 cents per foot. It is 
> sold by the pound at the junk dealer.
>
> When it is necessary to splice in order to get a desired length, I take 
> the pipe to a hardware store and have them extend the threads beyond the 
> standard for a water seal. This in conjunction with a standard coupling 
> gives plenty of purchase to give a strong joint. Once assembled I drill 
> through the coupling and pipe and install tension pins (roll pins) to 
> prevent the joint from unscrewing. (It did happen once!)
>
> The down side is that the stuff is heavy. However, I have a Glen Martin 
> Hazer on each of my towers and I am working from a roof top or from the 
> ground. Easy enough to use a block and tackle on the tower to lift the 
> mast above the Hazer and lower it into the bearing. Of course once it is 
> in place, weight is a non issue.
>
> 73, Sherm KB9Q, (EN52vv)
>
> swanson-KB9Q at ticon.net
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