[TowerTalk] F12 C4XL Manual

Jim Thomson jim.thom at telus.net
Sun Apr 9 00:28:36 EDT 2017

Date: Sat, 8 Apr 2017 16:46:16 -0700
From: Gene K5GS <k5gs at arrl.net>
To: Richard Thorne <rthorne at rthorne.net>
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] F12 C4XL Manual

- Wind load: 9.8 Sq Ft at 23 degrees from boom center.
- Weight: 65 Pounds
- Turning Radius: 23.8 feet

This is for the version with the alum-a-wire 40m elements.  I have a 
paper copy of the manual if needed...

- Wind Load:    5.6 square feet at 21 degrees from boom center
- Weight:  32 pounds
- Turning Radius: 19.8 feet


##  Those must be antique specs, if they start quoting windload, with
the boom rotated  23 / 21 degs. 

##  These days its EITHER the windload of the boom  itself, or the windload
of the all the els..    Typ the total of all the els is greater than the boom, but not

##  later on, F12   used either the boom windload or the total  ele windload, whichever was greater. 
BUT they used the old EIA-222-C spec, and used the ....effective  windload, instead of the actual
projected windload.   IE:  10 square feet of projected windload of a cylinder =  6.7 square feet effective. 
To get the 6.7  back to 10.0  you have to take the 6.7  and multiply it by 1.5. 

All tower specs for windloading are based on the actual projected windload of a cylinder. 
The falacy here is that a given tower may be rated for say  20 square feet of projected area...
and joe ham comes along and thinks he can then load if up with 20 square feet of  F12 ants. 
20 sq feet of F12 ants is actually  30 sq feet of projected area..which is the industry standard. 
Presto, tower is now 50 % overloaded.   

Hygain, mosely and a few others, still uses the out of date 222-C spec for windloading.  
Optibeam, M2, and JK ants use the actual projected area in their wind load specs. 

Projected area  is just length X width of each ele section.   You can do this by hand, or do it on a spread sheet,
or use the DX engineering Yagi mechanical software, which will spit out the projected area of each ele, the total of
all the els, and also the boom.   Then you have the real windload. 

Jim   VE7RF

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