Question then...how much additional strength, if any, is added to a 2"
mast that is filled with epoxy cement or similar substance that is
poured in and becomes solid or semi-solid such as spray foam insulation
that goes in as a liquid but hardens quickly to form millions of tiny
pheres?
I've used the spray foam in beam elements to dampen hormonic vibrations
and it has worked great...better than the old two feet of cotton rope
trick used in the HY-GAIN
203BAs, etc...
later,
dave
===============================================================
Dimitry, et al:
Just a quick comment, the ultimate strength of a mast is not
as simple as the cross sectional area times the yield strength.
The ultimate strength also depends on the shape of the masts cross
section. This factor is accounted for in what is called the section
modulus. This explains why a 2" O.D. mast with a .033" wall will
be just as strong as a 1" O.D. solid rod made from the same material.
The 1" rod has about 4 times the cross sectional area of the thin wall
pipe, but its section modulus is the same. The key is that the thin wall
pipe has its mass where it counts - away from the center axis. The
formulas
can be found in Leeson's "Physical Design of Yagi Antennas" or most
Static Engineering Mechanics text books.
73 de Mike, W4EF.........
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