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Ed Jensen wrote:
> I have always used windload forces to calculate safe mast and tower
> loading. If I understand the recent postings correctly, it appears to
> me that the new specs from Hygain result in lower calculated windload
> forces for their beams than before. They included the boom in the old
> effective area figure but now say to use only the element or boom
> figure, whichever is larger. For example, the old effective area of a
> TH7 was 9.4 sq ft. Now, applying a .66 shape factor to the new
> element flat area spec of 11.5 sq ft, the effective wind area of 7.6
> sq. ft. That's quite a reduction! No wonder I have never bent a mast
> or tower hi! Have I got this right?
Hi Ed,
Yes you do have it right.
Referring to my 8/16/98 post on Antenna Area Spec's:
The old method used by Hygain and many of us produced an antenna area
larger than the boom or elements areas alone. All of the Hygain antenna
areas have been reduced, when making a complete comparison! The apparent
increase is due to the change from the old shape factored area to the
new non-factored (projected) area.
The projected area of the "old" Hygain 9.4 SqFt would be 14.1 SqFt today
with the new suggested standard.
Maybe this will prevent some from shooting their towers and antennas, or
taking them down on Saturday.
73, Kurt
YagiStress - The Ultimate Software for Yagi Mechanical Design
Visit http://www.freeyellow.com/members3/yagistress
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Ed Jensen wrote:
<BLOCKQUOTE TYPE=CITE><FONT COLOR="#000000"><FONT SIZE=-1>I have always
used windload forces to calculate safe mast and tower
loading.</FONT></FONT> <FONT COLOR="#000000"><FONT SIZE=-1>If
I understand the recent postings correctly, it appears to me that the new
specs from Hygain result in lower calculated windload forces for their
beams than before. They included the boom in the old effective area
figure but now say to use only the element or boom figure, whichever is
larger.</FONT></FONT> <FONT COLOR="#000000"><FONT SIZE=-1>For example,
the old effective area of a TH7 was 9.4 sq ft. Now, applying a .66
shape factor to the new element flat area spec of 11.5 sq ft, the effective
wind area of 7.6 sq. ft. That's quite a reduction! No wonder
I have never bent a mast or tower hi!</FONT></FONT> <FONT SIZE=-1>Have
I got this right?</FONT></BLOCKQUOTE>
Hi Ed,
<BR>Yes you do have it right.
<BR>Referring to my 8/16/98 post on Antenna Area Spec's:
<BR>The old method used by Hygain and many of us produced an antenna area
larger than the boom or elements areas alone. All of the Hygain antenna
areas have been reduced, when making a complete comparison! The apparent
increase is due to the change from the old shape factored area to the new
non-factored (projected) area.
<BR>The projected area of the "old" Hygain 9.4 SqFt would be 14.1 SqFt
today with the new suggested standard.
<BR>Maybe this will prevent some from shooting their towers and antennas,
or taking them down on Saturday.
<P>73, Kurt
<BR>
<P>YagiStress - The Ultimate Software for Yagi Mechanical Design
<BR>Visit <A
HREF="http://www.freeyellow.com/members3/yagistress";>http://www.freeyellow.com/members3/yagistress</A>
<BR>
</BODY>
</HTML>
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