Gliding lecture slides

Thanks for the comments.

You wouldn't believe how much time I spent on the first few slides of the
Lift / Drag lecture, the bit covering how a wing generates lift, to try to
make them benign with respect to controversy but still say something
useful and meaningful.

Kevin, when I get a chance I will go back and review the streamline and
force diagrams on pages 7 and 8 of the Lift / Drag lecture. It does look
like they might be slightly erroneous, but I just want to check back
through the literature and dig out some experimental results before I make
any changes.

Bildan, with regard to yaw generating roll via dihedral effects I do
actually say that in the slide. However the section on the effects of the
controls is going to get a rework at some point. It's the only point in
all three lectures where the audience without fail zones out on you and
looses interest. So I need to think up some way of making it more
interesting.

Regards,

Richard

Mike the Strike wrote:
On Apr 15, 5:14 pm, brian whatcott wrote:
Mike the Strike wrote:
You might want to check on the accuracy of the oft-repeated /myth/ that
wings develop lift because of the pressure difference between the
upper and lower surfaces. My understanding of the physics is that
this component is negligible compared to the second mechanism you
mention of the downward deflection of the airflow.
If you think I am mistaken, then please explain how symmetrical
airfoils develop lift!
Mike
Amusing how partisans grow zealous for their chosen explanation! :-)

Brian W

Actually, we physicists get annoyed when people get the science wrong.

Mike


Hehe....good one, Mike! :-)

Brian W

On Apr 16, 5:10*am, (Richard Lancaster)
wrote:
Thanks for the comments.

You wouldn't believe how much time I spent on the first few slides of the
Lift / Drag lecture, the bit covering how a wing generates lift, to try to
make them benign with respect to controversy but still say something
useful and meaningful.

Kevin, when I get a chance I will go back and review the streamline and
force diagrams on pages 7 and 8 of the Lift / Drag lecture. *It does look
like they might be slightly erroneous, but I just want to check back
through the literature and dig out some experimental results before I make
any changes.

Bildan, with regard to yaw generating roll via dihedral effects I do
actually say that in the slide. *However the section on the effects of the
controls is going to get a rework at some point. *It's the only point in
all three lectures where the audience without fail zones out on you and
looses interest. *So I need to think up some way of making it more
interesting.

Regards,

Richard

You're right, I seem to have missed the section on yaw to roll due to
dihedral. I apologize.

Just a thought. This isn't exactly fair - it's clear you spent a lot
of effort on the graphics - but just repeating the same graphics style
with minor changes with different text can be boring. There's an easy
way to illustrate slides and get more color and realism by using a
flight simulator like Condor. I think Uros would grant you the right
to use the graphics if you give full credit.

The flight sim technique is to set up a situation you want to
illustrate and pause the simulator at just the right moment. Select
the outside view you like then take a JPEG screenshot. The resulting
JPEG file can then be edited with a graphics or photo-editor to add
additional graphics or text. The result can be quite pleasing.

On Apr 15, 9:20*pm, Mike the Strike wrote:
On Apr 15, 5:14*pm, brian whatcott wrote:

Mike the Strike wrote:
You might want to check on the accuracy of the oft-repeated /myth/ that
wings develop lift because of the pressure difference between the
upper and lower surfaces. *My understanding of the physics is that
this component is negligible compared to the second mechanism you
mention of the downward deflection of the airflow.

If you think I am mistaken, then please explain how symmetrical
airfoils develop lift!

Mike

Amusing how partisans grow zealous for their chosen explanation! :-)

Brian W

Actually, we physicists get annoyed when people get the science wrong.

Mike

Mike,

You might want to check your own physics, before making comments like
this.
Because us aerodynamicists get annoyed when people get the science
wrong :-)

Symetrical airfoils work the same way asymetric foils work. The air
is pushing up on the bottom, stronger than the air is pushing down on
the top. If the pressure was the same on the top and bottom surfaces,
there would be no lift.

Please, don't confuse pressure differential with the incorrect "equal
transit time" theory.

I have lost my favorite link to a well presented and complete theory
of lift, so I can't post it here. But the short version is:

angle of attack makes the air flow change direction
that change of direction makes
air pressure rise on the bottom ( but not by much )
air pressure drop on the bottom ( most of the change)

And it all happens because of the Kutta Condtion.
http://en.wikipedia.org/wiki/Kutta_condition

If you are going to berate people for their own incorrect knowledge,
you should be able to improve on that knowledge.

The original posters slides look like a pretty good explanantion. I
think that it is more information than a pilot really needs, but some
people won't relax and actually learn until they think they understand
"why" it works.

Todd Smith
Masters of Science Aerospace Engineering 1990

On Apr 16, 1:18*pm, toad wrote:

If you are going to berate people for their own incorrect knowledge,
you should be able to improve on that knowledge.



The only flight theory that most pilots need to know is that sustained
flight requires a continuous supply of money.

It is easy to prove that when the supply of money is exhausted flight
is no longer possible.

Andy

toad wrote:

The original posters slides look like a pretty good explanation. I
think that it is more information than a pilot really needs, but
some people won't relax and actually learn until they think they
understand "why" it works.

That's probably the best reason I've heard for teaching pilots about
aerodynamics.

Despite my deep interest in aerodynamics, my observation and experience
is knowing the aerodynamics doesn't seem to be an asset to flying
correctly, and that it is really all about keeping the airspeed up and
horizon in the correct place on the canopy. When I fly, thoughts of AOA
and pressure distributions are not flitting through my mind, and things
happen too fast to be deriving your next action from first principles.

You definitely want the designer of your glider to understand
aerodynamics, but the pilot - completely optional!

--

Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

On Apr 16, 4:17*pm, Eric Greenwell wrote:
toad wrote:
*The original posters slides look like a pretty good explanation. I
*think that it is more information than a pilot really needs, but
*some people won't relax and actually learn until they think they
*understand "why" it works.

That's probably the best reason I've heard for teaching pilots about
aerodynamics.

Despite my deep interest in aerodynamics, my observation and experience
is knowing the aerodynamics doesn't seem to be an asset to flying
correctly, and that it is really all about keeping the airspeed up and
horizon in the correct place on the canopy. When I fly, thoughts of AOA
and pressure distributions are not flitting through my mind, and things
happen too fast to be deriving your next action from first principles.

You definitely want the designer of your glider to understand
aerodynamics, but the pilot - completely optional!

--

Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz


I found the following website to be somewhat easy to understand and
extremely interesting, especially the last 1/2. The videos of lift and
pressure on a wing also good.

http://knol.google.com/k/why-it-is-possible-to-fly#

Brian

On Apr 17, 10:14*am, brianDG303 wrote:

I found the following website to be somewhat easy to understand and
extremely interesting, especially the last 1/2. The videos of lift and
pressure on a wing also good.

http://knol.google.com/k/why-it-is-possible-to-fly#

Brian

If that website is easy to understand, I'm stupid. I'll spend more
time researching their topic, but from a quick scan it looks pretty
confusing.

Todd

On Apr 17, 8:16*am, toad wrote:
On Apr 17, 10:14*am, brianDG303 wrote:



I found the following website to be somewhat easy to understand and
extremely interesting, especially the last 1/2. The videos of lift and
pressure on a wing also good.

http://knol.google.com/k/why-it-is-possible-to-fly#

Brian

If that website is easy to understand, I'm stupid. *I'll spend more
time researching their topic, but from a quick scan it looks pretty
confusing.

Todd

Todd,
I was pretty confused by much of what was posted but started to get a
clue when I researched the whole Kutta Condition thing, which was from
your post. THAT made sense to me, and led to the site I referred to
which starts off disorganized but gets better I think, anyway it
worked for me so I posted it. Perhaps my sense of understanding is
just a more complex form of confusion. Anyway the movies of lift on an
airfoil at different airflow speeds are pretty.

Brian

brianDG303 wrote:
On Apr 16, 4:17 pm, Eric Greenwell wrote:
toad wrote:
The original posters slides look like a pretty good explanation. I
think that it is more information than a pilot really needs, but
some people won't relax and actually learn until they think they
understand "why" it works. /snip/
You definitely want the designer of your glider to understand
aerodynamics, but the pilot - completely optional!

Eric Greenwell - Washington State, USA (netto to net to email me)


I found the following website to be somewhat easy to understand and
extremely interesting, especially the last 1/2. The videos of lift and
pressure on a wing also good.

http://knol.google.com/k/why-it-is-possible-to-fly#

Brian


I read this URL with interest.
While it is not a laughable piece about "I'm a physicist so I must be
right", it does suggest that they have their explanation right, and
everyone; Newton, Kutta, Bernouli, Uncle Tom Cobley an' all, have it
wrong. In a word, they exaggerate the value of their approach.
Still, it is interesting and helpful, in my view.

Brian W