[TowerTalk] Yagi Mechanical

[StellarCAT]

I've used it. My biggest complaint is it is awkward on how you build 
elements ... and the boom part is really lacking. For example the program 
should readily know where the COG is for the finished antenna... but instead 
you have to tell it where to 'start' (for the mast location) and then play 
with it again and again. I could find solutions all up and down - I'd rather 
an automatic first off calculation of the COG, easily done, tell me where it 
is and go from there.

Gary
K9RX



-----Original Message----- 
From: Jim Thomson
Sent: Thursday, March 30, 2017 1:20 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Yagi Mechanical

How many of you folks have used the latest software version of DX 
engineering... yagi mechanical ?
YM  spits out everything from windload of what ever you are modeling, to 
weight, to costs, total length,
res freq,  tq imbalance on a boom, how ot fix that issue, max wind speed, 
you name it.  Although a total of
6 x different wind specs can be used, upon talking to a few ant makers, they 
all use the.. no spec  option,
which is what you get in a wind tunnel. Its a bit more stringent than the 
222-C spec.

Its an eye opener to say the least, as you can juggle all sorts of tubing 
schedules around, up to 20 diameters,
changing OD, ID, changing to any wall thickness, and stuff like  adding 
inner re-enforcement liners.  Or doing different
splice techniques, like a plane swedge, or an inner sleeve, or an outer 
sleeve, or both.   This can be done on both the boom and any ele.

One caveat, they list  6063-T832 as  35 ksi yield strength, when it is 
actually 39 ksi.   6061-T6 is 40 ksi yield. Easily corrected,
as you can enter any number you want.

You can also add any amount of ice to the mix, then see the results asap, 
like how much wind it will handle, with XXX
ice on it.   Or see how much additional  sag occurs  with XXX ice.

Play around with it long enough, and you can readily either modify any 
existing design, beefing it up quite a bit, without
adding hardly any additional weight,  or  design an ele or boom from 
scratch.   It will show you where all the weak links in
the chain are.   It will also spit out sag at the boom or ele tips, and also 
the horizontal deflection of an ele or boom, when
either is broadside to the wind...and provide numbers for any wind speed you 
enter.   Or default to the max horz deflection
for an ele or boom, at V max..which is the max speed for an ele or boom. 
Will also show you the effects  of adding either
an overhead truss on a boom or ele...as far as reducing sag.... or show the 
effects on horz deflection, if side guying is used on a
boom or ele.  Or the effects of various length mounting plates..on either an 
ele..or boom.

An eye opener, when plugging in hb yagi designs from the 70s and 80s..and 
also stuff like old hy-gains and telrex and wilsons from years ago.
At the very least, it is cheap entertainment.  In a practical sense, places 
where I intended to re-enforce, I find out after using the software,
was a waste of effort, and bought me nothing. Meanwhile the software spat 
out where the real problem area actually was, which then makes
it easy to fix.

If designing from scratch, the idea is to design an ele , such that you get 
max bang for the buck, with the least windload and weight.
I designed and built a pair of  17.5 ft long T bar capacity hats..... b4 I 
bought the software, dumb move on my part.  With some minor
tweaking on the software,  I managed  to increase the wind survivability by 
a substantial amount, and only increasing weight by a
miniscule amount.. like just .4 lb per T bar.   My latest creation weighs 
exactly 2.5 lbs, and is good for 122 mph, and sags just 2 inches at the 
tips.
Using readily available tubing in 3 and 6 ft lengths, I also ended up 
wasting zero tubing in the process.  Software was cheap, runs on windows,
and they provide for automatic updates.   So far, so good.  What it wont do 
is factor in the weight from rivets, nuts + bolts, hose clamps etc, etc, so 
the total sag
number will be a hair more than what it depicts.

Jim   VE7RF