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Author Topic: sectional mast raising technique?  (Read 1619 times)
AA3YV
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Posts: 16




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« on: October 07, 2007, 12:32:50 PM »

I just bought nine fiber glass mast sections (about 40 ft  total) at a hamfest.  Now I have a stupid question.  Is there a website or book with procedures on how to actually stand up and lower this kind of mast correctly?

I'd like to put a very light beam on top.

The whole mast is so wobbly even without the beam.  I tried to connect sections on the ground and then rise the whole structure but the mast bows too much in the middle when I try to do that.  I can't imagine putting any kind of weight on top of it. I'm completely clueless as you can see.  Any advice would be appreciated.
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K4ZN
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Posts: 26




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« Reply #1 on: October 07, 2007, 04:09:33 PM »

I have an aluminum section mast up in the back yard for about 9 months now. This project requires several people to help. A lot of planing goes a long way.

First: putting any kind of beam on top of a sectioned mast like this is going to be dicy.  A beam suggests that you will want to rotate it! My ALUMINUM sectioned mast is only holding up the peak of an inverted "V". The sectioned fiberglass poles from e-bay are really only designed to hold up camo netting for the military. Even the aluminum poles I have were marked as such when delivered. They are not desiged at all to be load bearing. When you put them together on the ground you have a long wiggly pole that you can not erect - it does not have enough strength to bear it's own weight until it is vertical and properly guyed.

What ever you put up has to be hoisted up after the pole is up and the guys adjusted to keep the pole plumb and straight. The load has to be kept very light.

As far as erecting the pole is concerned. Here is how I did it.

First measure, measure, measure, and plan. Yes, it is only a little 2" diameter pole, but anything falling from 40ft+ can kill someone.

Use a cinder block or even a scrap peice of pressure treated lumber as a base. When guys are tensioned and even wire antennas are up there is quite a bit of downward force on the tube. It will sink in the ground if you don't put something under it to spread out the force.

To tie off the guy lines I used 60" heavy duty steel fence post (not the stamped steel el-cheapos). I used a 2# hammer to pound these 48" into the ground. With the soil conditions I have (red clay) these will not come out with anything less than a back-hoe. It's not so bad pounding these in. No concrete was needed.

My three guy points are on a 21.5 ft radius from the base of the pole. I wanted a little more radius but I had site contraints. I have 12 sections of pole up in the air with a guy every 4 sections. If I had to do this over again I would put a guy every 3 sections. The reason is that this would put the point of maximum deflection stress between guy attachment points at the middle of a solid section rather than at a joint. If you plan to hoist anything of any substance up the pole I would definately place a guy at every third section.

Also, rig up two pulleys at the top just in case one rope breaks or slips out. The extra pulley and 100ft of rope is well worth the redundancy. This is not a rig that you want to take down and put back up very often.

For guy line I used a 3/8" double braid dacron rope with a black cover to be UV resistant. Just get a 1000' spool, you will use a good bit of it.

To attach rope to pole I did not use the disks that go between the joints like what they sell on ebay. I simply tied the rope to the pole. I used a 'hangman's noose' type knot. This keeps any knot induced strength reduction of the rope well removed from where the rope needs maximum strength.

Do a litte trig and calcuate the rope lengths and allow extra when pre-cutting the guys.

Getting the pole up is a four person job. I used myself and three teenage girls. No special tools are needed. But, you do need a piece of string and a fishing weight or plumb-bob.

The first 3 or 4 sections can be assembeled on the ground and stood up. one person at each of the three guy anchors can hold the uppermost guy lines. I rigged up short pieces of pvc pipe on the guy anchors to imitate a cleat (like the thing you use to tie off your boat or the rope at the bottom of a flag pole). I used some heavy duty wire ties to hold the pvc pipe against the BACK of the guy anchor. When the guy lines are tied off just make sure that all the loads are compressive against the steel. Do not rely on the strength of wire ties or plastic pipe to hold up your pole!

Now the fun begins.

The way to get the pole up in the air is: each helper has to feed out guy line as you lift the pole from the bottom and fit in the next pole section from the bottom. I helps to have another helper hand you the pole sections, or have a way to have them vertical and ready to go. As the pole goes up it gets heavier. Remember to lift with the knees. The helpers quickly learn how to feed out the line.

Be patient and careful.

After several sections are up it is time to get out the string and weight. Walk out away from the pole and hold you plumb line at arms length. Check the pole against the plumb line. Give the helpers instructions to get the pole vertical. Then walk back to the pole, turn 90 degrees and march out again and check. You really do not want to get the pole bent too far as it goes up.

At some point the helpers have to handle two guy lines. If you have a total of four sets of guy lines you might have to have some more helpers or people who can handle three at a time. My experience is that the last (lowest) set of guys can be left slack until the whole pole is up.

Once the pole is up adjusting the guys is a one person job - no helpers needed.

The whole thing is rather wobbly until it is up and the guys are properly tied off. No tie off tools are needed. Just get the ropes hand tight. Dacron rope does not strech much. It does strech some. After a day or so some retensioning is needed.

My pole simply sets on an 8"x8" piece of pressure treated wood. It has no anchor. It has not 'walked' from center at all. Once the guys are tensioned the pole may expand in sunlight and contact in the cool of the night. Mine does. I recommed not setting the guy tension after sundown or in the early morning before sunrise. Things may seem a little loose in the cool, but tighten up in the sun. As long as the pole doesn't move too much in the wind it will be OK.

I calculated all the forces for my installation. I designed everything with a 400% safety factor in an 80mph wind. We never had an 80mph wind until after I put the pole up. Shingles came off the house, but the pole did not even need a guy retensioning after the storm.

I did break down and buy some real cleats from WalMart to tie off the antenna hoisting ropes. If you are going to hoist anything more than a wire antenna you will need something more than the few screws I have in a wooden base to tie off the hoisting ropes.

Please spend some time with paper and pencil and plan and measure. I believe I got my pole up with all guys and pulleys and hardware (and pole) for about $250.00 or $300.00.

Note: in my juridiction anything that does not have a 'permanent foundation' (meaning concrete) is 'temporary'. I have a 44ft pole in the yard that required no permits, inspections, etc. because it is temporary. And, indeed, the whole thing could be taken down. With less substantial guy anchors it could be set up for field day. It just needs a crew. Me and a few scouts can take the thing down and put it in the trunk of a small car. Can't do that with a tower. But a beam on top of one of these poles?!?!? I have some serious reservations. Be safe.
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AA3YV
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Posts: 16




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« Reply #2 on: October 07, 2007, 06:28:09 PM »

Thanks so much for a detailed description.  I see now the key point is that this mast should be raised by keeping vertical and adding sections at the bottom.  

My setup will be very temporary for a weekend contest so I probably can get by with less than 400% reserve as long as weather forecast is good.  

I did some more research and found an interesting method WW5AA uses with a 5 foot base and bungee cords as guys to keep the mast straight.  And it sounded he did it alone. See http://www.eham.net/forums/post/TowerTalk/11871
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WW5AA
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Posts: 2088




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« Reply #3 on: October 08, 2007, 08:23:26 AM »

Yup, works like a champ....I can take mine down and put it back up alone. 70' with a doublet on top and an 80 meter dipole cross ways for the top guys. I use hose clamps at the section coupling for added strength. With proper guying I would think that a small beam, especially for temporary use would work well. Good luck.

73, Lindy
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AA3YV
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Posts: 16




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« Reply #4 on: October 08, 2007, 10:39:54 AM »

Hi Lindy,

do you mind sharing some details or a sketch on how you did this base from 2x4s?  I'm really making baby steps here Smiley.  Also for the beam I probably won't try to go very high, may stop at 25 or 30 feet.

Vasiliy
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N6QL
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Posts: 31


WWW

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« Reply #5 on: October 08, 2007, 11:17:31 AM »

I put up a 30'  aluminum pipe mast with a SteppIR dipole on it with just me and my wife. It isn't free standing though as I used a sturdy fence to steady it while I added sections from the bottom. I plan to make it free standing (except for guys) in the middle of my yard soon though and I will use four helpers to hold the guys while I add sections form the bottom. One thing I disagree with is  the comment about "hoisting" the antenna to the top once the mast is up. I'm not really sure how you do that but I feel that adds way too much complication. If the antenna is too big to "push" it up as you add sections to the bottom then it is probably too big of an antenna to use on this type of mast.

Lastly, I would say that unless you bought the super thick walled fiberglass mast (that's rated for as much weight as the aluminum masts) then, as point out previously, it's really only safe to use it to hold up the center of a dipole.

73 Ron N6QL
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WW5AA
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« Reply #6 on: October 08, 2007, 01:38:00 PM »

Vasiliy,

A diagram is on its way to your email on QRZ.

73, de Lindy
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AA3YV
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Posts: 16




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« Reply #7 on: October 08, 2007, 02:20:58 PM »

Thanks all for great help. Lindy I got your pdf file! Will post a picture when I'm done Smiley
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