Tandem-wing Airplanes

"Morgans" wrote in
:


wrote
I suppose I missed the point. But it disturbs me that Ken
agrees with me. Either he's right for once or I'm way off base.

The fact that he makes this determination based on his observation of
model
planes further reinforces his lack of real and tangible knowledge of
the subject at hand.

And anyway, even a stopped clock is right once (or twice) per day.

I would be disturbed, too. Don't take it too hard, though. It was a
lucky guess.



He's wrong, oh so wrong in this case as well.


Bertie

"Dan Luke" wrote in news:13qf47hr26ig515
@news.supernews.com:


"Bertie the Bunyip" wrote:

Ken agrees with you.

Eeewww!

Usenet cooties!




I know, it's got to be every poster's worst nightmare.

I think there may be a recovey group for this somewhere.



Bertie

"Bertie the Bunyip" wrote

He's wrong, oh so wrong in this case as well.

I'm not surprised at that, either. He had not been right about anything,
that I had noticed.

To tell the truth, (no surprise) I have not been reading this thread for
content. I've mainly just been skipping to the next message without really
reading them, to get them marked off as read.
--
Jim in NC

"Morgans" wrote in
:


"Bertie the Bunyip" wrote

He's wrong, oh so wrong in this case as well.

I'm not surprised at that, either. He had not been right about
anything,
that I had noticed.

To tell the truth, (no surprise) I have not been reading this thread
for content. I've mainly just been skipping to the next message
without really reading them, to get them marked off as read.

well, it must be at least a bit interesting for an experimenter. The rocket
man posted som salient stuff there and understanding the relationship
between CG and the aerodynamic center is a very useful thing for a builder.
Not strictly neccesary, of course, but definitely nice to know. Less so for
a pilot...

Bertie

"Bertie the Bunyip" wrote

well, it must be at least a bit interesting for an experimenter. The
rocket
man posted som salient stuff there and understanding the relationship
between CG and the aerodynamic center is a very useful thing for a
builder.
Not strictly neccesary, of course, but definitely nice to know. Less so
for
a pilot...

I feel I have a good grip on the relationship between CG an AC for
conventional planforms. I have no interest in canards or tandem lifting
wings.

I did pay a bit more attention to a few of the posts, though, and his being
some of them.
--
Jim in NC

On Feb 4, 3:04 pm, "Morgans" wrote:
"Bertie the Bunyip" wrote

He's wrong, oh so wrong in this case as well.

I'm not surprised at that, either. He had not been right about anything,
that I had noticed.

To tell the truth, (no surprise) I have not been reading this thread for
content. I've mainly just been skipping to the next message without really
reading them, to get them marked off as read.
--
Jim in NC

C&B!!!!!!!!

"Ken S. Tucker" wrote in
:

On Feb 4, 3:04 pm, "Morgans" wrote:
"Bertie the Bunyip" wrote

He's wrong, oh so wrong in this case as well.

I'm not surprised at that, either. He had not been right about
anything,
that I had noticed.

To tell the truth, (no surprise) I have not been reading this thread
for content. I've mainly just been skipping to the next message
without really reading them, to get them marked off as read.
--
Jim in NC

C&B!!!!!!!!

J&B!!!!!!!


Bertie

"Morgans" wrote

I feel I have a good grip on the relationship between CG an AC for
conventional planforms. I have no interest in canards or tandem lifting
wings.

I did pay a bit more attention to a few of the posts, though, and his
being some of them.
I did not look at the link he provided, the first time. I went back, and
checked it out.

Most is pretty straight forward aerodynamic stuff that a person that has
done some reading on the subject will already know. It was a pretty good
site, though. Good read for a person that has not done that much reading on
aerodynamic stability.
--
Jim in NC

"Morgans" wrote in
:


"Bertie the Bunyip" wrote

well, it must be at least a bit interesting for an experimenter. The
rocket
man posted som salient stuff there and understanding the relationship
between CG and the aerodynamic center is a very useful thing for a
builder.
Not strictly neccesary, of course, but definitely nice to know. Less
so for
a pilot...

I feel I have a good grip on the relationship between CG an AC for
conventional planforms. I have no interest in canards or tandem
lifting wings.

I did pay a bit more attention to a few of the posts, though, and his
being some of them.


Well, it's relevant to conventional airplanes in an indirect sort of way,
which is my point. If you truly understand the principles involved, you
then thoroughly understand enough to trim your homebuilt. My own airplane
is notorious for needing stab adjustments after the first flight. A real
PITA since the stab is welded into position ( I plan to make mine
adjustable with shims) Now, the stab on my airplane has a negative
incidence, while the top wing is set at zero and the bottom is set at plus
2 degrees. Doesn't seem to add up, does it? The stab is flat plate, BTW.
So, waht's all that about?



Bertie

wrote in message ...
On Feb 3, 9:05 pm, "Marc J. Zeitlin"
wrote:

Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
behind the main wing AC. There are many aircraft that when flown at
rear CG positions and low speeds will have the tail producing lift.
Gliders, in particular. Off the top of my head, I don't know of any
in particular, although I remember being told that a C-172 will have
an upforce on the tail at low speeds and rear CG. Can't cite it, though.

Even with the CG at its most aft position, a 172's AC is still
behind the CG. CG range is typically 25-33% of MAC, while AC is around
40%.


The web site I indicated:

http://www.av8n.com/how/htm/aoastab.html

explains all this.

That's a good site that I've used for more than four years. I
think we're talking about two different things here and there's a
misunderstanding that leads to argument.
I find a fairly widely-held opinion that the aft CG can be
(legally) at or behind AC. This isn't true for any "modern"
lightplane. FAR 23.173 requires that the airplane return to trimmed
speed after being slowed or accelerated using pitch inputs only and
releasing them; this won't happen in a CG-behind-AC situation. As the
wing slows its AC moves forward due to the breakup of the boundary

layer toward the trailing edge, the CG therefore ends up even farther
behind the AC, the situation gets worse as the nose rises with the

****The CG is in front of the AC****

forward-moving AC, and it eventually stalls. This is what I meant by
the illegality of a lifting tail.
Here's an example of some common miperceptions:
http://answers.yahoo.com/question/in...9225927AAfYZDU
Even the first answer, the one the voters liked, says that the CG is
12" ahead of the AC even in the most-aft position, This is extreme;
it's a lot less than that, but it's still forward. Other posters think
that with the CG at the aft position the tail must produce lift.

Dan