"A much better and more accurate discussion of mast forces is in Dave
Leeson's, ex-W6QHS, W6NL, book "Physical
Design of Yagi Antennas". It's out of print but you can probably find
a copy somewhere. It's got LOTS of interesting information about lots
of tower and antenna system topics.
For those interested "Physical Design of Yagi Antennas" is available
on Amazon.com. I just purchased it today at around $20
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