Re: 60 foot fiberglass pole (Pole Strength)

[ARDUJENSKI]

SUGGESTION
 
Use of fiberglass poles for end supports WITHOUT GUYING would indicate a  
lack of understanding of strength and stiffness of an end loaded beam. Most  
people however do not deal with this type of engineering so a simpler approach  
may be warranted
 
As was presented about 6 weeks ago on QRP-L, there needs to be a deflection  
test applied for comparative technical details. A simple approach would  be:
 
1. Mount pole horizontally about 4 ft above ground
2. Add with to the tip in 1/2 lb amounts and measure deflection
3. Record results for comparison
 
By knowing the load you will place on the mast tip you can know what the  
deflection will be beforehand. If unacceptable you can look at another support  
or check to see if guying would remedy the problem.
 
To simulate guying, you take the horizontal pole and move a support along  
the horizontal pole to check if this remedies the deflection problem.
 
If you guy at say the 20ft point, depending upon the pole design you may  
also need to guy every 10ft for heavier loading
 
NOW you can approach the question of what will be an  adequate SUPPORT in a
more professional manner.
 
For guying I generally use cheap Phillip screwdrivers as anchor points for  
my masts pushed in at a 45 degree angle.
 
Alan  KB7MBI
Woodinville, WA


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[Ron D'Eau Claire-2]

I've used 50 foot steel push-up masts which are arguably much stiffer than
the fiberglass. Even so, I'd never consider using one as a center or end
support without lots of guys.

If the mast is used at the center of an inverted V, I might leave the top 5
or 10 feet free-standing (except for the support the antenna wire itself
provides) with at least two sets of three guys below that, spaced at
120-degree intervals. For an end support, I'd use the same guy sets plus two
additional guys attached to the very top spaced 120 degrees relative to the
antenna wire to handle the horizontal load of the antenna itself.

It's not just wind loading on the pole or the weight of the wire. The system
must handle the shock loads of the weight of the antenna and feedline
dancing in the wind as well. If it's a permanent or semi-permanent
installation, remember you must design for the worst-case winds, not what
you typically see.

If you don't have room all the way around the pole for those guys, you're
probably much too close to the neighbor's yard. I recommend never raising a
pole higher than the distance from the pole to your property line. It's one
thing to put a hole in your roof if you misjudged the guy requirements; it's
a whole different issue if the hole is in your neighbor's roof, or your
neighbor...

Ron AC7AC

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