[TowerTalk] Boom sag on Cushcraft A4S

[Kevin]

My father has had an A4S up for nearly 25 years sans a boom truss.

We live in Iowa. We have real winter.

We haven't seen the kind of damage Grant is talking about. When it comes 
down for bi-annual maintenance we put a new coat of clear Krylon on the 
center insulator. I do agree with replacing the DE center tube with 
solid fiber glass rod. I built that beam in my fathers driveway and 
installed it before I ever had a license. The beam outlasted a roof 
tower of questionable manufacture and is now happy on 39' of Rohn 25 
tower and Yaesu G-800 installed on his flat garage roof.


On 10/6/2016 4:57 PM, Grant Saviers wrote:
> The boom is not particularly heavy duty IMO (I have 2x A4S).  If icing 
> is likely a Phillystran truss would be a sensible addition. Also it is 
> quite easy to deform the boom with the element clamps and since mine 
> are used in Field Days, taken apart and back together yearly,  I have 
> internally sleeved the boom at each element attach point.  A few 
> sleeves required significant "urging" to go in and copious amounts of 
> Penetrox since they were a bit deformed.
>
> Same for the u-bolt holes in the elements, an overly enthusiastic FD 
> assembler flattened the element.  Simple sleeving  and new holes 
> solved that problem after sawing out the center.
>
> The fiberglass driven element center insulator rots in a few years in 
> the sun, so a couple of coats of clear acrylic spray are longevity 
> inducing.  I replaced mine with solid FG rod rather than the factory 
> FG tube.
>
> Another weak spot is the element to boom clamps can splay out and 
> loosen, yielding tilted elements.  I made mine square in a vise and 
> used long SS 6-32 machine screws and nylock nuts side to side to keep 
> the ears from bending outward.  Not much space with the u-bolts but 
> they do fit.
>
> Amazingly, even in dry CA, I had a boom fill up with water - duh. 
> Quite a surprise when I loosened the boom to mast bolts.  So notch the 
> end caps on the elements and boom at the lowest point.  Large enough 
> so water gets out and small enough so hornets don't get in.
>
> Otherwise it is a good antenna, no trap problems at 1kw, decent 
> performance for boom length, etc.  Mine are original CC, I can't speak 
> to "value engineering improvements" by MFJ.
>
> Measure three times all dimensions before "up the tower".  It is 
> sensitive and nobody on the FD team ever got it right first try. (even 
> before the 807's).  Below 15' or so height swr measurements are useless.
>
> Grant KZ1W
>
>
> On 10/6/2016 14:25 PM, Bill DeVore wrote:
>> I’m getting ready to put up my first beam. I’ve noticed the ends of 
>> the boom on the A4S sag about 3-5 inches below the center point. 
>> Would making a truss out of a non stretching material such as 
>> phillystran be worth the effort or am I just being anal about it? The 
>> boom is not bent.
>>
>> Bill - W3PNM
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-- 
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


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