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Author Topic: use pvc pipe for 35' mast  (Read 7161 times)
KE5HTB
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Posts: 15




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« on: August 07, 2010, 07:43:11 AM »

i am thinking of using 3" pipe at base, 2" center and 1 1/2 on top to try and get to 30-35foot ranges. of course all guy wires also installed. would have min. 3 wires for guy's.

MY ? is I live in S. TX and I am concerned about the summer heat and the pipe maybe start to melt kinda or bend due to the heat.
I am building 2 of these maybe 3 for wire antennas to get them up in air.
simple 80m dipole maybe a fan dipole for 80-20m setups.

has anyone used PVC pipe and if so tips ideas or is it not really worth my time and efforts and save up more $$ and get alum poles and be done with it. I am very much limited on funds as I am a disabled ham.

thanks for ANY tips ideas or suggestions for maybe other ideas to get me on the air better then I am now.

ke5htb
fred
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WX4O
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Posts: 98




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« Reply #1 on: August 07, 2010, 08:31:24 AM »

I have a 30 or 35' PVC mast. I used a schedule 40, 5'' piece for the base, then smaller towards the top.
I don't use any guys, but it's bolted to the eaves at about 10'. Been up for about 4 years w/o problems.

John/WX4O
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AH6RR
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Posts: 803




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« Reply #2 on: August 07, 2010, 08:40:33 AM »

Aloha Fred,

 If you use PVC you will need to stiffen it up a bunch by using larger pipe or by inserting wood into to it ABS might work a tad bit better but it is black so it will need to be painted to keep the direct off of it. So why not build it out of wood since it will be guyed? I was born and raised in Corpus Christi and between the wind and heat of South Texas you will see the PVC in the size you want to use on the ground in no time, or better yet find some used metal push-up poles. Finding 30 to 35 foot trees in next to impossible down there. Contact some of the local clubs maybe someone has or knows of push-up poles.

73
Roland AH6RR ex N5JKJ
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KB1LKR
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Posts: 1899




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« Reply #3 on: August 07, 2010, 09:20:42 AM »

PVC (or even ABS) isn't the material you want to use for anything that long, unless you go MUCH larger in diameter, it lacks stiffness, and may have UV resistance issues too, leading to embrittllement.
 Fiberglass, aluminum or galvanized steel tubing (not solid) would be far better choices.

A wood structure, like those shown on OLD (e.g. 1946) ARRL Handbooks, would work, but may not be economical these days compared to the '30's to '50's.

If you're going to stiffen it w/wood internally you may as well save some money and just use the wood, skipping the PVC but for perhaps for a cap over the top end.
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WB6BYU
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« Reply #4 on: August 07, 2010, 09:56:27 AM »

Quote from: KE5HTB
...I am concerned about the summer heat and the pipe maybe start to melt kinda or bend due to the heat...

PVC pipe is going to bend regardless of the heat (unless it gets very cold, in which case it shatters instead.)
One problem is that different manufacturers use varying amounts of UV inhibitor in their PVC formulas, so you
really can't count on the long term performance of such a mast until you've tried it.  (And the next one may
not be the same.)

I've tried PVC for shorter masts and found it has a poor weight/strength ratio.  ABS is lighter and stiffer, but
still will bend (and take a set) if there is too much tension on it.  I've heard of folks using 40' of 4" PVC with
two sets of guys and watching it bend 90 degrees in a storm, but I haven't quite figured out how to get such
a long mast vertical if there is any weight at the top.

My advice would be to start with one mast and consider it an expendable experiment.


Irrigation pipe typically comes in 40' lengths - you might see if a local aluminum scrap/recycling place has some
lengths that got run over by a tractor near one end.
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AH6RR
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« Reply #5 on: August 07, 2010, 12:07:11 PM »

Quote from: KE5HTB
...I am concerned about the summer heat and the pipe maybe start to melt kinda or bend due to the heat...

PVC pipe is going to bend regardless of the heat (unless it gets very cold, in which case it shatters instead.)
One problem is that different manufacturers use varying amounts of UV inhibitor in their PVC formulas, so you
really can't count on the long term performance of such a mast until you've tried it.  (And the next one may
not be the same.)

I've tried PVC for shorter masts and found it has a poor weight/strength ratio.  ABS is lighter and stiffer, but
still will bend (and take a set) if there is too much tension on it.  I've heard of folks using 40' of 4" PVC with
two sets of guys and watching it bend 90 degrees in a storm, but I haven't quite figured out how to get such
a long mast vertical if there is any weight at the top.

My advice would be to start with one mast and consider it an expendable experiment.


Irrigation pipe typically comes in 40' lengths - you might see if a local aluminum scrap/recycling place has some
lengths that got run over by a tractor near one end.

Since you are in the Beeville area there are lots of farmers there see if any of them has any 3" Irrigation pipe that they are not using they would be perfect for what you want. Or you could get hurricane fence top rail pipe and put them together to get the length you want but it l in diameter it is only 1.25 inches so you would need more guy wires than the irrigation  will need.
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N4HAL
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Posts: 53




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« Reply #6 on: August 07, 2010, 03:02:38 PM »

Think if you use the plastic electrical conduit (grey), instead of the standard pvc water pipe
(white) you'll find it more temperature and uv resistant. Just a thought.

Bill KJ4RDQ
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K5LXP
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Posts: 4438


WWW

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« Reply #7 on: August 07, 2010, 04:29:05 PM »

Fence rail might get you that high relatively cheaply, and would be plenty strong for a light load like wire antennas on top.


Mark K5LXP
Albuquerque, NM
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N0OKS
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Posts: 115




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« Reply #8 on: August 07, 2010, 06:36:17 PM »

I have a 20 foot piece of white, 2 inch diameter, schedule 40 PVC tube that has been sitting with one end on the floor and the other supported about 4 feet high. It sags about a foot, end to end. I just looked at it and it has taken a set in just a few months.

I also have some gray, schedule 80, 2 inch diameter PVC tube for use as a conduit and I can barely get it to flex.

I was going to use some PVC to put up a Field Day dipole and I can see the schedule 80 tube is much preferable. I think that even with a bunch of folks holding guy ropes that the schedule 40 tube might be too flexible to put up. I am thinking 80 feet of the schedule 80 stuff with some suitable joints for a really knock out 80 meter dipole.

Mark, NØOKS
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KE3WD
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Posts: 5694




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« Reply #9 on: August 07, 2010, 06:39:43 PM »

Consider also your liability when erecting antennas. 

I doubt if the use of PVC, ABS nor the electrical conduit would pass a serious engineering evaluation for such structures. 

On the other hand, the common wooden telephone pole can be erected "trench style" and makes a very sturdy antenna platform. 

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KE5HTB
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Posts: 15




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« Reply #10 on: August 08, 2010, 02:23:03 AM »

thanks for all the help. I have decided to wait on PVC or any kinda save the money and go pipes and get it done right. I hate to spend the money now just to have to spend more later to replace the pvc when it breaks.

I borrowed a pushup pole for now and will use it till I save my money up for my own proper setups for my dipoles mainly.

thanks everyone for your answers. it helped me decide what to do in the end.


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KE3WD
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« Reply #11 on: August 08, 2010, 07:32:12 AM »

Wise decision.

Have fun and 73
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KI4SDY
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Posts: 1452




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« Reply #12 on: August 08, 2010, 03:33:18 PM »

Just use electrical conduit tubing and stainless steel U bolts. You can get it in the diameters that you want and telescope it up to 60' guyed with no problem. It will run you about the same price as PVC, but it is much stronger and less likely to bend. I have been using it for years and all of mine has stayed up through several hurricanes and many tornados. Grin
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KE4DRN
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Posts: 3710




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« Reply #13 on: August 09, 2010, 06:59:21 PM »

hi,

take a look at these military fiberglass mast sections,
they take primer and paint great.

on ebay, top seller  auction # 220650496744

http://myworld.ebay.com/hoosier-man/

Just bought my second set.

73 james
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NA0AA
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Posts: 1043




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« Reply #14 on: August 10, 2010, 07:44:28 AM »

I've been beating myself about the head and shoulders for a decent 30' mast.

I've settled on Rigid steel conduit -it's got threaded couplers on the ends, and the 1.25" seems reasonably durable.  But it's about $3/foot.

IF I could get them, I'd use the Rohn/Laird/Cushcraft push-up masts but while they supposedly still make them, obtaining them is difficult since they are far too long to ship UPS so they are expensive to get delivered.

I doubt that PVC will give you any sort of long term durability - I know of a guy who used 'em for a 4-square and they were almost pointing to the horizon....bent over.

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