Recommend that you consider chain link fence "top rail" instead
of EMT. Get the "1 7/8 inch" OD variety. It is the same
diameter as "1 1/2 inch" water pipe. It is actually intended
to be structural. There is also a "1 3/8 inch" OD variety than
you can telescope. It is the same diameter as "1 inch"
water pipe.
Rick N6RK
On 1/1/2020 8:13 AM, Gedas wrote:
HNY to all !
I cannot think of a better time to start a new 40m phased vertical
project then the dead of winter with snow on the ground (as usual I
could not get to it during the summer or fall).
Anyway, I have drawn up two possibilities for a pair of 33' self
supporting verticals. Both start out with a 10' length of EMT but one
choice starts out with a larger dia then the other before I switch over
to tapering aluminum sections.
A) Starts out with a 10' length of 1-1/4" EMT followed by tapering 5'
sections of aluminum tubing (4' long exposed, 1' inside the previous
lower section) until the very top length section which will be 3/4" OD
dia. These will be standard DX engineering aluminum tubes.
B) Starts out with a 10' length of 1-1/2" EMT, then a 5' length of
1-1/4" dia of EMT (4' long exposed, 1' inside the previous section of
EMT) then followed by tapering 5' sections of aluminum tubing as above.
The only difference being this choice would end up using 1" aluminum
tubing as the very top piece.
So the obvious difference between the two are that choice A) uses just
one length of thinner EMT and overall thinner aluminum tubing sections
to the top while choice B) uses 2 lengths of larger dia EMT and then
larger dia aluminum tubing to the very top.
I do not have the software to analyze choice A) vs. choice B) in a high
wind situation. I am uncertain if the stronger, larger dia tubing with
it's higher wind load will be a plus or a minus in the end to it's
overall strength. Any thoughts or comments on which one will survive
better during heavy wind conditions? TU
Gedas, W8BYA
Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
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