3 to 4 feet of concrete should provide plenty of lateral support for a
clothesline.
However, having 12' of 4X4 above ground without the top anchored (as it
would be in, say, a deck support) should produce some interesting curves in
the post over time :-).

KW

"a" wrote in message news:8t7Fe.103514$wr.72546@clgrps12...
Apologies to Mr. Gabriel.

I'm installing a 4X4X16 pole for a clothesline. I'm down to about 3 feet
and I
hit solid rock. Not 'a' rock - just rock. I'll be using 10" sonotube (I
have 4'
of it) and concrete.

Any rules of thumb for how deep I *should* be for good lateral stability?
I can
obviously cut the pole shorter, but I'd like to have 10'-12' above ground
to be
somewhat level with the mounting point on the house.

a