In the June 2006 issue of Flying Magazine Page 101. Peter Garrison
wrote
another good information article called "Spin Doctors"

Its good information about Vortex Generators, that every builder pilot
should
get a copy and read.

He has been a editor for Flying Magazine for a very long time.
Peter is one of the best engineering, information editors in the Flying
Magazine.
His article, is always the first one I read.

Larry Fitzgerald

www.fitzair.net

can you suggest the point of the article... I've considered using them
on my to be completed homebuilt.. Is the article on-line somewhere?

The Point of the Article is to understand their use.

Peter makes these statements.
"Vortex generators seem like a discordant
element in aerodynamic design" and "violating the rule that smoothness
is
desirable above all things"

Think, very hard about his statements. I have agreed with the first one
for many years.
Vortex Generators are a correction, of a poor airfoil use, at a given
angle and air pressure
Ect.

The article is only in the magazine at a store or subscriber.
Make a copy at the library. While their, look at the back issues.
Peters articles are worth making copies of, for your personal library.

Larry Fitzgerald

www.fitzair.net

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TJ400 wrote:
> can you suggest the point of the article... I've considered using them
> on my to be completed homebuilt.. Is the article on-line somewhere?

I remember 20 or so years ago I asked some engineers from the Columbus
Ohio North American plant about vortex generators.
Their reply was that vortex generators are used to fix a problem with
the original design found after the aircraft entered service.

john smith wrote:
> I remember 20 or so years ago I asked some engineers from the Columbus
> Ohio North American plant about vortex generators.
> Their reply was that vortex generators are used to fix a problem with
> the original design found after the aircraft entered service.


VGs were traditionally used as a band aid to correct the effects of flow
separation, especially in supersonic flight, and usually just ahead of
control surfaces.

The use of VGs as a STOL device is more recent development when some
bright light discovered that they increased stalling AOA with almost no
increase in cruise drag. They have become a sort or poor man's LE
slat, giving 1/3 to 1/2 the AOA increase a slat gives, or about .3 to .5
increase in Clmax.

Garrison also had a great article once about how winglets work. It's
the only time I've seen them explained properly, in that they harness
energy in the wing tip circulation to create thrust that is surplus to
the winglet's drag when operating at high L/D, as airliners do when
cruising at 35000 ft. The simply create a lift vector that is angled
inboard and forward like the sail of a boat. Which is why they are
sometimes called "tip sails".

John

AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
whole sport aviation for some time and just trying to grasp it all over
again..

thanks..

AOA = Angle Of Attack
The angle with which the wing contacts the impinging air stream

L/D = Lift to Drag ratio
As AOA goes up, so does lift, but drag goes up too. Knowing what the L/D
curve looks like for a specific airfoil as AOA increases is an important
point in designing an aircraft to meet a stated mission.

Clmax = Maximum coefficient of lift
The AOA where the wings lift is maximum. Usually occurs at an AOA just
before stall.

L E Slats = Leading Edge Slats
http://www.liming.org/ch801/slathistory.html



"TJ400" > wrote in message
oups.com...
> AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
> whole sport aviation for some time and just trying to grasp it all over
> again..
>
> thanks..
>

What he said...

Ron Webb wrote:
> AOA = Angle Of Attack
> The angle with which the wing contacts the impinging air stream
>
> L/D = Lift to Drag ratio
> As AOA goes up, so does lift, but drag goes up too. Knowing what the L/D
> curve looks like for a specific airfoil as AOA increases is an important
> point in designing an aircraft to meet a stated mission.
>
> Clmax = Maximum coefficient of lift
> The AOA where the wings lift is maximum. Usually occurs at an AOA just
> before stall.
>
> L E Slats = Leading Edge Slats
> http://www.liming.org/ch801/slathistory.html
>
>
>
> "TJ400" > wrote in message
> oups.com...
>
>>AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
>>whole sport aviation for some time and just trying to grasp it all over
>>again..
>>
>>thanks..
>>
>
>
>

"TJ400" > wrote in message
oups.com...
> AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
> whole sport aviation for some time and just trying to grasp it all over
> again..
>
> thanks..

Try - http://www.risingup.com/fars/info/part1-2-FAR.shtml
--
Jim in NC

Morgans wrote:
> "TJ400" > wrote in message
> oups.com...
>
>>AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
>>whole sport aviation for some time and just trying to grasp it all over
>>again..
>>
>>thanks..

http://www.home.earthlink.net/~tp-1/a4412-a.jpg
http://www.home.earthlink.net/~tp-1/a4412-b.jpg

Earthlink is so messed up right now it's almost unusable.

I posted these two charts, but EL tells me the images cannot be viewed
because they contain errors.

WSFTP had no trouble showing them - so I dunno....

Two charts of airfoil performance data for the 4412.

Notice (I hope) that the flaps deployed curve is similar in shape as the
no-flaps curve, but a little taller and broader at the bottom.

Interpret that as Higher CL at any given AoA.

Power off, the wing will stall at some partiular AoA.

I usually look for that initially between 10 and 12 degrees (depending
on the airplane).

I've also noticed that many common airfoils actually have a
_lower_ stall AoA with flaps down!


Like in a 172, notice the way the nose comes down with flaps?

We are operating at a higher CL now and need LESS AoA to make
the same amount of lift. Has to do with the increase in Camber
with flaps down, I believe.

That indicates a NARROWER range of AoA (flaps down compared to flaps
up)- not higher!

Power ON will allow for higher AoA, and thus higher CL.

How much higher depends largely on how much power can be applied (while
maintaining control of the aircraft at extreme AoA!)

However, do consider the possible results of a super slow approach
speed. Gusts have a much more profound effect on the amount of lift
generated (or suddenly lost?).

As would an unexpected loss of power...

This is flying pretty close to the edge, kids.



Richard

wrote:
> The Point of the Article is to understand their use.
>
> Peter makes these statements.
> "Vortex generators seem like a discordant
> element in aerodynamic design" and "violating the rule that smoothness
> is
> desirable above all things"
>
> Think, very hard about his statements. I have agreed with the first one
> for many years.
> Vortex Generators are a correction, of a poor airfoil use, at a given
> angle and air pressure
>

ISTR hearing about someone with a Cherokee who used them to
reduce drag on his fuselage.

--

FF

cavelamb wrote:
some mindless drivel again...

>
>
> http://www.home.earthlink.net/~tp-1/a4412-a.jpg
> http://www.home.earthlink.net/~tp-1/a4412-b.jpg
>
Should be working well now.

(-a) shows section drag and moment plotted against section C Lift.

Note that teh moment curve is pretty flat, and has a negative value.
(pitches nose down?)

At the bottom of the page is the Legend.
Curves for 3, 6 and 9 mill Reynolds Number, and with split flaps.

(-b) is a handier form.
Section CL and Pitch moment are shown plotted agains Angle of Attack.

Note that the Flaps Down curve is Narrower and shihted to the left.
Interpret that aa a narrower AoA range, and at a lower AoA values,
but with higher CL/ (delta)Angle ?

(-c) if I had it handy, would be similar to -b, but details the section
Coefficient of Drag.

wrote:

> wrote:
>
>>The Point of the Article is to understand their use.
>>
>>Peter makes these statements.
>> "Vortex generators seem like a discordant
>>element in aerodynamic design" and "violating the rule that smoothness
>>is
>>desirable above all things"
>>
>>Think, very hard about his statements. I have agreed with the first one
>>for many years.
>>Vortex Generators are a correction, of a poor airfoil use, at a given
>>angle and air pressure
>>
>
>
> ISTR hearing about someone with a Cherokee who used them to
> reduce drag on his fuselage.
>

Three kinds of air flow.
Laminar, Turbulent and Separated.

Induced drag, that from generating lift, is hard to reduce significantly.

But dragging a bunch of small wakes is all parasitic drag.

Reattaching a separated wake should, in general, reduce patasitic drag,
and make the old sled that much faster...

cavelamb wrote:
> cavelamb wrote:
> some mindless drivel again...
>
> >
> >
> > http://www.home.earthlink.net/~tp-1/a4412-a.jpg
> > http://www.home.earthlink.net/~tp-1/a4412-b.jpg
> >
> Should be working well now.

It would work a damn sight better if the images had been created
as gifs or tifs. Then it might be possible to read the labels and
scales.

Jpeg is the worst possible common image format for line drawings
or text. Well, maybe second worst after mpeg...

Don't mean to single you out for this particular rant. Illegible
graphical information is legion on the web. It would seem that
most people posting such haven' t taken into consideration
that people seeing it may actually need to be able to read
the text.

--

FF

cavelamb wrote:
>
> ...
>
> Note that the Flaps Down curve is Narrower and shihted to the left.
> ...

Remind me to stand to the RIGHT of that plane when flaps
are down ...

--

FF

"cavelamb" > wrote in message
nk.net...
> Morgans wrote:
>> "TJ400" > wrote in message
>> oups.com...
>>
>>>AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
>>>whole sport aviation for some time and just trying to grasp it all over
snip

>
> I've also noticed that many common airfoils actually have a
> _lower_ stall AoA with flaps down!
>
>
> Like in a 172, notice the way the nose comes down with flaps?
>

When you lower the flaps, you change the angle of incidence. With a fuselage
that remained level during the change, you would have increased the AoA.

Al

wrote:
> cavelamb wrote:
>
>>cavelamb wrote:
>> some mindless drivel again...
>>
>> >
>> >
>> > http://www.home.earthlink.net/~tp-1/a4412-a.jpg
>> > http://www.home.earthlink.net/~tp-1/a4412-b.jpg
>> >
>>Should be working well now.
>
>
> It would work a damn sight better if the images had been created
> as gifs or tifs. Then it might be possible to read the labels and
> scales.
>
> Jpeg is the worst possible common image format for line drawings
> or text. Well, maybe second worst after mpeg...
>
> Don't mean to single you out for this particular rant. Illegible
> graphical information is legion on the web. It would seem that
> most people posting such haven' t taken into consideration
> that people seeing it may actually need to be able to read
> the text.
>

Point taken, of course.
Totally agree, Fred.
But that's all I got right now...

And I wasn't really trying to pull numbers off of them,
just the shapes of the curves - and how they shift.

Another thing about working with jpg...
Jpg LOSES picture information EACH TIME you SAVE it.

In house, I usually use PCX format.

but these were all I could find...


Rx

wrote:

> cavelamb wrote:
>
>>...
>>
>>Note that the Flaps Down curve is Narrower and shihted to the left.
>>...
>
>
> Remind me to stand to the RIGHT of that plane when flaps
> are down ...
>

The meds can sometimes be fun...

Al wrote:

> "cavelamb" > wrote in message
> nk.net...
>
>>Morgans wrote:
>>
>>>"TJ400" > wrote in message
oups.com...
>>>
>>>
>>>>AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
>>>>whole sport aviation for some time and just trying to grasp it all over
>
> snip
>
>
>>I've also noticed that many common airfoils actually have a
>>_lower_ stall AoA with flaps down!
>>
>>
>>Like in a 172, notice the way the nose comes down with flaps?
>>
>
>
> When you lower the flaps, you change the angle of incidence. With a fuselage
> that remained level during the change, you would have increased the AoA.
>
> Al
>
>
>
True, but we are more concerned with maintaining a given airspeed rather than
a level floor...

cavelamb wrote:
> Al wrote:
>
> > "cavelamb" > wrote in message
> > nk.net...
> >
> >>Morgans wrote:
> >>
> >>>"TJ400" > wrote in message
> oups.com...
> >>>
> >>>
> >>>>AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
> >>>>whole sport aviation for some time and just trying to grasp it all over
> >
> > snip
> >
> >
> >>I've also noticed that many common airfoils actually have a
> >>_lower_ stall AoA with flaps down!
> >>
> >>
> >>Like in a 172, notice the way the nose comes down with flaps?
> >>
> >
> >
> > When you lower the flaps, you change the angle of incidence. With a fuselage
> > that remained level during the change, you would have increased the AoA.
> >
> > Al
> >
> >
> >
> True, but we are more concerned with maintaining a given airspeed rather than
> a level floor...

Some pilots are also concerned about having a good view
of the runway.

--

FF

wrote:

> cavelamb wrote:
>
>>Al wrote:
>>
>>
>>>"cavelamb" > wrote in message
nk.net...
>>>
>>>
>>>>Morgans wrote:
>>>>
>>>>
>>>>>"TJ400" > wrote in message
oups.com...
>>>>>
>>>>>
>>>>>
>>>>>>AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
>>>>>>whole sport aviation for some time and just trying to grasp it all over
>>>
>>>snip
>>>
>>>
>>>
>>>>I've also noticed that many common airfoils actually have a
>>>>_lower_ stall AoA with flaps down!
>>>>
>>>>
>>>>Like in a 172, notice the way the nose comes down with flaps?
>>>>
>>>
>>>
>>>When you lower the flaps, you change the angle of incidence. With a fuselage
>>>that remained level during the change, you would have increased the AoA.
>>>
>>>Al
>>>
>>>
>>>
>>
>>True, but we are more concerned with maintaining a given airspeed rather than
>>a level floor...
>
>
> Some pilots are also concerned about having a good view
> of the runway.
>


Yeah well, there are those kind of guys too...

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Try PNG. None of the limitations of gif, decent lossless compression,
and no artifacts like jpeg when displaying line drawings.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)

iD8DBQFEgFZvpxCQXwV2bJARAqJBAKCSYZnG3L/N5WAseL3fBBuFrMvY/gCffkdN
YrpRevxBeBYcQF5gRo1tWs0=
=piVD
-----END PGP SIGNATURE-----

Evan Carew wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Try PNG. None of the limitations of gif, decent lossless compression,
> and no artifacts like jpeg when displaying line drawings.
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.1 (GNU/Linux)
>
> iD8DBQFEgFZvpxCQXwV2bJARAqJBAKCSYZnG3L/N5WAseL3fBBuFrMvY/gCffkdN
> YrpRevxBeBYcQF5gRo1tWs0=
> =piVD
> -----END PGP SIGNATURE-----

I did that for a while but got a lot of flack about "unrecognized"
file formats. Maybe it's mroe common now?

But you are right about png's properties.
Very nice way.

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

cavelamb wrote:
> Evan Carew wrote:
>
> Try PNG. None of the limitations of gif, decent lossless compression,
> and no artifacts like jpeg when displaying line drawings.

> I did that for a while but got a lot of flack about "unrecognized"
> file formats. Maybe it's mroe common now?

> But you are right about png's properties.
> Very nice way.

Older versions of Microsoft browsers had this problem. Those of us who
switched to Mozilla or Thunderbird years ago don't experience that
problem either. In other words, there's really no excuse, if you have
problems viewing image formats, either upgrade your browser, or , better
yet, get a different one. Complainers should be told as much.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)

iD8DBQFEggZ9pxCQXwV2bJARAoznAKCUX1fAGWoJuhlua0Tvj9 aahtjdZACfWo6O
myNDY+IsEfaLROVTM9gmVtk=
=yzOq
-----END PGP SIGNATURE-----

In article >,
Evan Carew > wrote:

> Older versions of Microsoft browsers had this problem. Those of us who
> switched to Mozilla or Thunderbird years ago don't experience that
> problem either. In other words, there's really no excuse, if you have
> problems viewing image formats, either upgrade your browser, or , better
> yet, get a different one. Complainers should be told as much.

Wrong. It is best to use open source formats for universal
acceptability. Using MicroSoft proprietary formats is an invitation to
complaints.

john smith wrote:

> In article >,
> Evan Carew > wrote:
>
>
>>Older versions of Microsoft browsers had this problem. Those of us who
>>switched to Mozilla or Thunderbird years ago don't experience that
>>problem either. In other words, there's really no excuse, if you have
>>problems viewing image formats, either upgrade your browser, or , better
>>yet, get a different one. Complainers should be told as much.
>
>
> Wrong. It is best to use open source formats for universal
> acceptability. Using MicroSoft proprietary formats is an invitation to
> complaints.

That too.

Best I've seen is program called ACDSee.
I run v 3.1.
Later versions try to be a little TOO helpful for my tastes.


Richard