[Antennas] Mast design equations & rules of thumb?

[JAKidz]

Greetings:
	I'd like to build a tip up, free-standing 1/4 wave 40m vertical,
base at 11 feet, out of small town available materials (e.g., chain link
fence rail, electrical conduit, water pipe). No guys (small lot with a
bunch of house stuff in the way) so support has to be close to the base.
Due to CC&R's, I have to tip it up for use and down the rest of the time
so wind loading would be moderate at most. What diameter and wall
thickness does the base need to be to withstand repeated bending from
being pushed up but not overkill? Only one old guy is the pushup force
so it can't be 34 feet of 3 inch water pipe on top of the 11 foot base.
I'm guessing that for less weight but adequate rigidity, it is best to
have reduced cross-sections with height but how many and how long for
each is optimum? I figure a Radio Shack steel CB whip can top it off.
Any good thumb rules or design equations for such things? As fence rails
and metal electrical conduit come in a variety of wall thicknesses, I'd
like to run the numbers for some confidence that the thing isn't like to
make a big dent in my noggin or my roof.

	Thanks and 73,
John, K7JG.