Chris,

My cantilever would be fine if the horizontal member was attached
half way up the vertical member,



Based on what?


Based on the fact that the deflection would then be symmetrical about
the horizontal member, so the root of the cantilever would not be rotated.

Not good enough.


It is not so much a matter of accurate and inaccurate, it is about
right and wrong.


So what's right then? In my opinion engineering is all about accuracy.

No - engineering is more about managing inaccuracy. Before you can
learn to do that, you must become proficient with the type of problem
solving that appears in undergraduate texts.


My first model may have been fairly inaccurate,

tactOff
Chris, it was nonsense.
/tactOff


but that's the way it
goes: you build one model, think about it and discuss it, then build a
better one.

Not in this case. You clearly lack understanding of the basics that go
into such a model.



What about the vertical component of the tension in the beam FBD on
the left?

We can't include it as we know nothing about the kinds of joints Steve
intends to employ in the structure. I assumed that there are pin joints
at each end of the beam because this makes the structure statically
determinate. We know so little about the structure that this is only
assumption one can make. Granted, I did not draw a pin joint. That was
an honest mistake.

Again, nonsense. You called it a tension member, hence you were assuming
frictionless pins and negligable weight. Otherwise known as a two force
member, and it's item one in any engineering statics course.


I don't have a formula for this case.



Sorry, somebody has to say it: if you need a "formula" for something
like that, then you should not be giving advice on structural mechanics.


In which case, why are there big books of formulae published for
structural engineers to use? Like Roark's formula book which Ned
mentioned? Probably I could have figured out the formula from first
principles if I'd chosen to spend an hour or two on it,

Time wasted if the FBD is incorrect.


but I didn't
want to. Structural engineers don't begin all their calculations from
scratch.

Clearly the tables exist (I consult them at times myself), and they
exist to save time, not to escape learning. My statement stands.



So okay, I am not a structural engineer. I'm someone who took a few
structural engineering courses a while back.

If you still have interest, get a Schaum's outline on statics and start
solving problems. It will eventually come back to you.


But I'm the only one who
actually tried to help Steve in the first place. Others then joined the
discussion, which I feel is a good thing if everyone remains reasonable,
but now it seems some traditional Usenet insults are being thrown in.

And no one here has yet claimed to be a professional structural engineer...

Wisely so. A pro won't touch something like this - responsibility w/o
compensation. Some time ago, a poster suggested that the OP needs to
find a structural engineer, which was very good advice.

Bill