Author Topic: Fiberglass Mounting Pole?  (Read 966 times)

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Offline ARAMP1

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Fiberglass Mounting Pole?
« on: June 21, 2021, 10:06:29 AM »
I recently purchased a Davis Pro2 that I'm planning on mounting on my roof. 

I'm considering using these fiberglass pole sections and epoxying them together...

https://www.ebay.com/itm/233660298681?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I really don't have a good way to ground anything.  I'm worried about lightning strikes.  Will the fiberglass be strong enough to hold up to wind?  Thoughts?

Offline Aardvark

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Re: Fiberglass Mounting Pole?
« Reply #1 on: June 21, 2021, 10:22:28 AM »
I doubt it will work.  Use a steel pole or one of those mounting poles that Davis offers or similar.  Fiber glass will snap.  Wouldn't worry about lightening hitting your pole.  Why are you mounting the unit on the roof in the first place,  I can see putting up the wind portion of the unit there, but not the rest.  radiation off the roof will screw with your temp/humidity.  And you will have to climb up there to clean out your rain bucket of debris , unless you like doing that stuff.  If you want to ground it, run a copper wired that is attached to the pole, to a grounding stake in the ground.

Offline ARAMP1

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Re: Fiberglass Mounting Pole?
« Reply #2 on: June 21, 2021, 10:40:45 AM »
I have a lot of trees on the property and really no clear space to mount the anemometer.  I've thought about running the rain gauge/temp sensor at another location on the ground which is probably ideal. 

Offline doubleohwhatever

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Re: Fiberglass Mounting Pole?
« Reply #3 on: June 21, 2021, 01:20:48 PM »
Fiberglass is stronger than most realize and at that thickness I highly doubt you have to worry about it snapping.

We've also found that four inch schedule 80 pipe makes for a solid mast. In areas with heavy winds, we'll fill it with concrete. If we need it to be freestanding, we'll concrete a six inch piece in the ground. Since it's pipe, adapters for various sizes are readily available. 24' is the highest we've gone with a six inch piece as the base in the ground and the whole thing filled with concrete.

Offline Aardvark

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Re: Fiberglass Mounting Pole?
« Reply #4 on: June 21, 2021, 02:19:04 PM »
Oh my,  you have choices to make.   I am closing out my two cents worth of advice here.   By the way , if Zeus toss a bolt of lightening your way,  fiber glass filled with gold won't save your station.  The trick is not to irritate Zeus.   

Bye, bye

Offline havtrail

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Re: Fiberglass Mounting Pole?
« Reply #5 on: June 21, 2021, 05:27:59 PM »
Aardvark's other piece of advice, which you should follow no matter what type of pole you use, is to mount just the anemometer up high, and keep the rest of the unit down at an easier-to-maintain level. The different sensors have different recommended heights and siting.

Rich K.
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Offline 92merc

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Re: Fiberglass Mounting Pole?
« Reply #6 on: June 22, 2021, 09:22:29 AM »
Personally, I used sections of top rain from chain link fencing.  I pounded a chunk into the ground.  I think it was around 4 foot.  That should ground the setup.  Then I ran a couple of pieces until those went about a foot over the peak of my house.  That piece is tied to the facia board on my roof with metal strap and screws.  I put some weather stripping around it to isolate any noise from the house.

Then the last piece is about 12 ft tall.  So that piece I can remove if I go on the roof.  I have a remote anemometer transmitter as my setup for this.  So the box is at head height so I can easily replace the battery.

I also filled the lower section with sand.  Upper section I used spray foam to "plug" the bottom.  Then filled that with sand as well.  That stops a lot of the pole moving around in the wind.  Not totally.  But a good deal.

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Offline davidmc36

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Re: Fiberglass Mounting Pole?
« Reply #7 on: June 22, 2021, 03:23:59 PM »
Nice Beemers lol

Offline 92merc

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Re: Fiberglass Mounting Pole?
« Reply #8 on: June 22, 2021, 03:45:56 PM »
Wife and I will be riding those Beemers out to Great Falls Montana tomorrow.  Put on 550 miles each way to the BMW Motorcycle owners rally.  Should be fine.  Hope the weather cooperates.
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Offline safuser

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Re: Fiberglass Mounting Pole?
« Reply #9 on: June 22, 2021, 04:03:07 PM »
Will soon be mounting one of these onto a piling on our dock to host the anemometer.  They come in multiple lengths.  Going to cut off the ends and put an end cap over.

Grainger #485C53

https://www.grainger.com/product/NUPLA-Pike-Pole-485C53?internalSearchTerm=Pike+Pole%2C++10+ft+Handle+Length%2C++Steel+Head+Material%2C++Butt+Handle+Design&suggestConfigId=8&searchBar=true&opr=THKS


Offline Jim_49

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Re: Fiberglass Mounting Pole?
« Reply #10 on: June 26, 2021, 03:05:07 PM »
Your pole is a cantilever beam turned on end.  You can assume a uniformly loaded beam.  The end deflection of a uniformly loaded circular cantilever beam is:

d= (qL^4)/8EI

Where:  d = deflection
             q = load per unit length or wind load
             L = Length of pole
             E = modulus of elasticity
             I = second moment of area (or moment of inertia) = (D1^4 - D2^4)pi/64  Where: D1 = outside diameter and D2 = inside diameter

Deflection increases with an increase in load, or wind speed and air density.
Deflection increases with the fourth power of the length.
Deflection decreases with the fourth power of the diameter.
Deflection decreases with a higher modulus of elasticity.

Modulus of elasticity needs to be calculated in your case because your pole is a composite.  You'll need to find out about the fiber material, the resin, how the fibers were laid, etc.  You can google modulus of elasticity for fiber glass.

Google wind load to determine how to calculate it.  Also be aware that wind velocity increases with altitude.  In other words the wind load will increase as you go up the pole.  Averaging it should get you close but the deflection calculation will not be exact.

You also need to use the weight of the thing sitting on top of the pole but in this case the anemometer weighs almost nothing so you can ignore it.

I used beam calculators on the web.  The above information gives you a little better understanding of the effects of the different elements affecting deflection.

The breaking point is something that I haven't researched.

I did all of this with the help of a civil engineer that designed free standing parking lot light poles.  A lot of integration is involved.  I wanted a free standing mast for my VP2 anemometer.  I'm going to use a telescoping flag pole with the base buried in the ground.  This way I can collapse the pole to service the anemometer.

As for grounding you need to research grounding antennas.  There is a bunch of information in the National Electric Code but they sometimes use confusing terminology.  You also need to review your local codes.  I talked with a tv antenna installer.  He said that most people who install their own antennas don't bother with grounding and don't have any problems with lightning.  I also have a friend who had an antenna in his attic.  In one particular storm the lightning wanted his antenna so it went right through the roof and got it.  There was a 6 foot hole in his roof and nothing remaining of the antenna.

This is probably more information than you wanted but I found that there is no easy answer for deflection of a tall freestanding pole.

 

anything