[TowerTalk] Guy Wire Formula?

[Roger (K8RI)]

Bill MacLane wrote:
> Alain,
> I forgot to mention that you could guy 30 ft. out from the base if you want.
>
> Also, if you buy dacron rope in 500 ft. spools one spool will make a complete set of guys for one mast.  You still need a halyard.
>
> Finally, to figure the guy length it isthe square root of the height of the anchor squared plus the distance from the base to the anchor squared.  I think that is what you intended to write.  However I don't know how to make the formula in email.
>
> 73,
> Bill
> AI4WM
>
> Alain Michel <opalockamishabob at yahoo.com> wrote: Hello All!
>
> I am in the process of erecting a 40'+ mast to support the feedpoint of my G5RV. I was initially planning 3 wires [Dacron rope] at each level. Should I use 4?
>
> Using A2+B2=C2, how far out from the bottom of the mast should the guys be fastened to the ground? I plan on guying the mast at the 20', 30' and 39' levels.
>
>   
Writing that formula out a^2 + b^2 = c^2

where a = altitude or height of anchor on pole
           b=base or distance from pole to anchor point
and     c =guy length

Square and square root are usually written out "^2" and "sqr"
so if we take the square root (sqr) of both sides we have

    sqr(a^2 + b^2) = c for the guy length.
If your algebra is a bit rusty do the stuff inside the parenthesis first.

If you want the base length "b", or distance from the pole to the anchor 
point:
Then subtract a^2 from both sides to get:
b^2 = c^2 - a^2 or b = sqr(c^2 - a^2)

Links to lengths have already been listed, but for the do it yourselfers 
you can also figure the lengths for given angles using trig although for 
guy angles of 45, 30, and 60 degrees there are short cuts. The shortest 
is throw out the 60 degrees although that might be kind of handy for a 
bottom set of guys.
For 45 degrees the height and base are the same.  The 30, 60, 90 
triangle is a special case that looks a little more confusing so I'll 
skip it unless some one wants it.

The trig is easy (if you know, or knew trig), otherwise we don't have 
the time or room on the reflector as trig is a whole semester.<:-)) OTOH 
you can get by with only sin, cos, and tan for working with towers and 
guys IF you really feel the need to do the calculations<:-)).

73

Roger (K8RI)
>
> All suggestions will be most gratefully received!
>
> 73,
>
> Alan...KI6HPO
>
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> 73,
> Bill
> AI4WM
>        
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