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[TowerTalk] Phillystran and cable clamps

To: <towertalk@contesting.com>
Subject: [TowerTalk] Phillystran and cable clamps
From: DAVED@ctilidar.com (Dave D'Epagnier)
Date: Thu, 17 Dec 1998 07:49:32 -0700
Bill,
the force due to wind on a surface is:

f = A*(0.5p)*V^2*Cd

where:  f = force (lbs)
        A = area of surface (ft^2)
        0.5p = 0.001188 (slug/ft^3)
        V^2 (V squared) = wind velocity (ft/sec)
        Cd = drag coeficient = 1 to 1.28 (unitless)

have fun.

Dave
AB0GJ

> ----------
> From:         WBH3@daimlerchrysler.com[SMTP:WBH3@daimlerchrysler.com]
> Sent:         Thursday, December 17, 1998 7:05 AM
> To:   k7lxc@aol.com
> Cc:   towertalk@contesting.com
> Subject:      [TowerTalk] Phillystran and cable clamps
> 
> 
> 
> 
> Steve:
> 
> I am somewhat concerned over your comments, ref: item 5 below, where
> you
> say that "cable clamps and Phillystran do not mix"!!
> 
> I recently put up a 15 foot Create tower on top of my house and have a
> KT34-XA  on top of it.  Gerald at  Texas Towers told me that the
> smallest
> Phillystran (1200 lb. test) would be sufficient to hold this in 70
> mph
> wind.  Further, Texas Towers' catalog says to use 4 cable clamps with
> the
> smallest Phillystran and preform grips with all other sizes.
> 
> The "local tower guru" only used 3 clamps, and said  I didn't need 4
> anyway
> when he helped me put up the antenna  Steve, could you elaborate a
> little
> on your comment?  Am I at risk with only 3 clamps, considering the
> square
> footage of tower and antenna?  (Tower is rated at 23 sq. ft. @ 90
> mph).
> Also...I don't understand the statement 23 sq. ft. @ 90 mph......what
> does
> it mean?  How do you calculate what the windload is at 70 mph if its
> 23 @
> 90 mph?
> 
> To me a more definitive number is how many  pounds of wind force are
> trying
> to push the antenna and tower over.  If I know how many pounds of
> force are
> pushing then I can calculate the vector forces vertically and then
> determine how much strength I need for the guy material.  (Assuming
> that
> the pounds of force are horizontally  pushing on the assembly).  I
> realize
> that this can get very complicated since we need to know the angles
> the guy
> wires make with the horizontal, etc.  How do I calculate the force on
> my 9
> sq. ft. of antenna at 70 mph?  Someone told me it was 9 times 70 =
> 630
> pounds.
> 
> Although I am an Electrical Engineer, I don't want a detailed
> mathematical
> formula, just a rough rule of thumb.  Well, I guess that is enough
> questions for now (I have lots more...hi).
> 
> Thanks, Steve
> 
> Bill Haselmire  WX8S
> wbh3@daimlerchrysler.com
> 
> 
> 
> 
> 
> 
> 
> K7LXC@aol.com on 12/15/98 09:33:56 AM
>                                                               
>                                                               
>                                                               
>  To:      mlowell@noclant.navy.mil, towertalk@contesting.com  
>                                                               
>  cc:                                                          
>                                                               
>                                                               
>                                                               
>  Subject: Re: [TowerTalk] thimble size                        
>                                                               
> 
> 
> 
> 
> 
> 
> 
> 
> 5/16" EHS     1/2" thimble
> >  >
> >  >3) If 4000lb Phillystran is used  with Preform Grips, the thimble
> is
> >  >7/16".
> 
>       This is correct but you're not using Phillystran.
> >  >
> >  >4) If 6700lb Phillystran is used with Preformed Grips, the thimble
> is
> >  >1/2".
> 
>        This is also correct but you're still not using Phillystran.
> >  >
> >  >5) If Phillystran is used with cable clamps (highly not
> recommended)
> use
> >  >one size smaller than above.
> 
>       Cable clamps and Phillystran do not mix anymore.
> >  >
> >  >In all cases the heavy duty version of the thimble is used.
>        Use the 1/2" ones as per above.
> 
> Cheers,   Steve    K7LXC
> Tower Tech
> Champion Radio Products
> 
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> 
> 
> 
> 
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