I can find tubing with a .120" wall, and I can find it with .058" wall.

For a short run (just a few feet), would there be any significant
difference in bending resistance between a length of the thick wall stuff
and one made from two nested thin wall lengths?

Weight's not an issue, nor is price.

--
Bert Hyman W0RSB St. Paul, MN

On 06 Feb 2011 15:58:26 GMT, Bert Hyman wrote:

For a short run (just a few feet), would there be any significant
difference in bending resistance between a length of the thick wall stuff
and one made from two nested thin wall lengths?

Hi Bert,

Probably not, but what is on either side of this "short run" that
loads this run with stress?

Is this a vertical run, or horizontal run?

73's
Richard Clark, KB7QHC

In Richard Clark
wrote:

On 06 Feb 2011 15:58:26 GMT, Bert Hyman wrote:

For a short run (just a few feet), would there be any significant
difference in bending resistance between a length of the thick wall
stuff and one made from two nested thin wall lengths?

Hi Bert,

Probably not, but what is on either side of this "short run" that
loads this run with stress?

The rest of my antenna :-) About 25 feet of more aluminum.

It's actually a Hy-Gain AV-640, and the base tube is made of two nested
pieces of .058" tubing, but it's only a foot long, and I'm considering
some mounting options that would require a longer section that I'd have
to make out of stuff I can buy easily.

Is this a vertical run, or horizontal run?

It's vertical.

--
Bert Hyman W0RSB St. Paul, MN

On 06 Feb 2011 18:01:47 GMT, Bert Hyman wrote:

Probably not, but what is on either side of this "short run" that
loads this run with stress?

The rest of my antenna :-) About 25 feet of more aluminum.

It's actually a Hy-Gain AV-640, and the base tube is made of two nested
pieces of .058" tubing, but it's only a foot long, and I'm considering
some mounting options that would require a longer section that I'd have
to make out of stuff I can buy easily.

Hi Bert,

So it is at the point of maximum leverage - something to consider. As
it is vertical, then wind forces will be magnified at this point.
However, it seems you are doubling the length of what would have been
there anyway.

It still seems robust.

73's
Richard Clark, KB7QHC

On Feb 6, 2:01*pm, Bert Hyman wrote:
ichard Clark

wrote:
On 06 Feb 2011 15:58:26 GMT, Bert Hyman wrote:

For a short run (just a few feet), would there be any significant
difference in bending resistance between a length of the thick wall
stuff and one made from two nested thin wall lengths?

Hi Bert,

Probably not, but what is on either side of this "short run" that
loads this run with stress?

The rest of my antenna :-) About 25 feet of more aluminum.

It's actually a Hy-Gain AV-640, and the base tube is made of two nested
pieces of .058" tubing, but it's only a foot long, and I'm considering
some mounting options that would require a longer section that I'd have
to make out of stuff I can buy easily.

Is this a vertical run, or horizontal run?

It's vertical.

--
Bert Hyman * * *W0RSB * St. Paul, MN *

Hi Bert, I had a similar issue, filled the center of the tubing with
hardwood dowl. The rod I used was for a curtain or closet. I survived
a hurricane and a tornado that took off a good part of my roof. Not
only does it add strength but it keeps the aluminum from collapsing.


Jimmie


Jimmie

On Feb 6, 7:58*am, Bert Hyman wrote:
I can find tubing with a .120" wall, and I can find it with .058" wall.

For a short run (just a few feet), would there be any significant
difference in bending resistance between a length of the thick wall stuff
and one made from two nested thin wall lengths?

Weight's not an issue, nor is price.

--
Bert Hyman * * *W0RSB * St. Paul, MN *

It would depend on how you did the nesting. If there's an
interference fit, then it's pretty much one piece of metal.
If it's not, and they can bend independently, you need to figure out
how the loads distribute between the pieces.

On 6 feb, 16:58, Bert Hyman wrote:
I can find tubing with a .120" wall, and I can find it with .058" wall.

For a short run (just a few feet), would there be any significant
difference in bending resistance between a length of the thick wall stuff
and one made from two nested thin wall lengths?

Weight's not an issue, nor is price.

--
Bert Hyman * * *W0RSB * St. Paul, MN *


Hello Bert,

If I understand you well, the current tube is a nested construction
(one foot). Considering the overall length of the antenna (25 feet),
the bending moment will slightly increase when changing from 1 to
about 2 feet.

If you believe that there will be more clearance between the two tubes
(w.r.t. the current nested tubes), you may fill the clearance with
epoxy resin. This will reduce the risk on buckling significantly.

Best regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me in most cases